White Balance and RGB Consistency in a Studio Photography Setting
In studio photography, achieving accurate color is essential. Photographers often work with tools like grey cards, calibrated lighting, and advanced camera software to ensure proper white balance and exposure. This report explores how white balance and RGB consistency behave in a controlled studio environment, focusing on the use of Profoto studio flash systems and Westcott Flex Bi-Color LED panels with a Canon EOS R5 camera and Capture One software. We will discuss the role of 18% and 50% grey cards in exposure and color calibration, the physics of light and camera sensors as they pertain to white balance, and why different grey tones might register slight color imbalances even under the same lighting. We also examine whether such RGB inconsistencies stem from the calibration targets themselves or from genuine white balance shifts at different exposure levels. Finally, specific observations related to the Canon R5’s sensor behavior and the differences between LED and flash illumination on neutral targets will be addressed. The goal is to provide practical insights for studio photographers working on color correction and consistency.
Grey Cards for Exposure and White Balance
Grey cards are standardized neutral references used to assist in setting exposure and white balance. A traditional 18% grey card reflects 18% of the light falling on it, which corresponds to a middle-tone grey in photographic exposure. In fact, this 18% reflectance grey is equivalent to about a “50% grey” brightness in a digital image (in 8-bit terms, roughly RGB 128,128,128). The terminology can be confusing, but 18% reflectance and 50% digital brightness refer to the same middle grey point – one describing physical reflectance, the other describing image tone. Camera light meters are typically calibrated so that if you meter off an 18% grey card, the resulting exposure will render that card as a mid-tone in the image (around 50% brightness).
Grey cards serve two primary purposes: exposure calibration and white balance calibration. For exposure, an 18% grey card placed in the scene under the same lighting as the subject can be metered to set a baseline exposure. This helps achieve a well-balanced exposure because the camera’s reflective meter sees a neutral mid-tone instead of being fooled by an overly bright or dark subject. For white balance, a grey card provides a neutral reference that ideally reflects all colors equally. Because the card is neutral, it should appear without color cast when properly illuminated – making it an excellent target for white balance adjustments. Photographers often include a grey card in a test shot and later click that card with the white balance picker in Capture One (or set a custom white balance in-camera) to remove any color tint from the lighting.
It’s important to note that not all grey cards are created equal. High-quality photographic grey cards (or white balance cards) are spectrally neutral – meaning they reflect red, green, and blue light equally across the visible spectrum. A truly neutral grey card will take on the color of the light source without imparting its own tint. Using such a card, if the studio lights are a bit warm or cool, the card will appear warm or cool by the same amount, and the camera’s white balance can be adjusted so that the card registers as neutral grey in the final image. Once that adjustment is made, all other colors in the scene should then be accurately balanced relative to that neutral point.
While 18% grey is a standard, some photographers also use lighter “50%” grey targets or white balance cards that have higher reflectance (often around 30–70% reflectance, which is a lighter grey). The reason is that a lighter grey card can improve accuracy in white balance by providing a stronger signal to the camera sensor. An 18% card under modest lighting might register somewhat low in the exposure (especially if the lighting is dim or if low ISO is used), which could introduce more noise into the measurement of color balance. A lighter grey (closer to white, but still neutral and not clipping) gives a higher exposure value for the camera to sample, resulting in less noise in the R, G, and B channels. This is why some commercial white balance targets are not 18% reflectance but something higher – they are optimized to produce a good signal-to-noise ratio for color sampling without requiring a very bright light or high exposure. For example, one popular white balance target in the ColorChecker system has about 60% reflectance for this reason – it ensures that even in lower light, the camera gets a clean read of neutral grey. In practice, whether using an 18% grey card or a lighter grey card, the key is that the card must be truly neutral in color. If it is, the specific reflectance mainly affects exposure and noise, not the actual color balance.
In summary, grey cards (whether “18%” or “50%” grey) are invaluable tools in studio work. The 18% grey card is traditionally used to set exposure because camera meters aim for that mid-tone. Meanwhile, any neutral grey card (including lighter ones) can be used to set white balance by providing a color-neutral reference. The choice may come down to convenience: an 18% card can do double duty for exposure and color, whereas a lighter grey/white balance card might be used when precise color neutrality and low noise in measurements are paramount.
Light Physics and Camera Sensor Interpretation
To understand white balance and RGB consistency, we need to delve into some light physics and how camera sensors interpret light. Light is composed of a spectrum of wavelengths, and the spectral distribution of a light source determines its color. Our eyes and cameras perceive light color in terms of color temperature (in Kelvin) and tint (green–magenta bias). A “neutral” white light, such as midday sun or flash, is around 5500–6500 K and has a balanced spectrum across visible wavelengths. Warmer light like tungsten bulbs (~3000 K) skews toward longer wavelengths (reds and oranges), while cooler light like overcast sky (~8000 K+) skews toward shorter wavelengths (blues).
Most real-world light sources are not perfect blackbody radiators, but we describe them by correlated color temperature – e.g., a flash might be rated ~5600 K to mimic daylight. In practice, studio photographers encounter two broad types of lighting technologies: incandescent/flash (broad spectrum) and LED (or other solid-state, often spiky spectrum). Flash units (such as Profoto studio flashes) use gas-discharge tubes (typically xenon) that emit a broad spectrum of light. They produce light that, when passed through a frosted dome or diffuser, approximates daylight-balanced output. This broad spectral content means they contain a mix of wavelengths from blue through red, which tends to render colors in a full and natural way.
LED panels, like the Westcott Flex Bi-Color LED, work differently. Bi-color LED panels contain an array of LED emitters of two different types: one set of LEDs is tungsten-balanced (warm) and another is daylight-balanced (cool). By mixing the output of these two sets, the panel can be tuned to a desired color temperature (for example, 3200 K or 5600 K or anything in between). High-quality LED panels have improved greatly and often boast high CRI (Color Rendering Index) values in the mid-90s, indicating they render colors accurately under many conditions. The Westcott Flex panels, for instance, are rated around 97 CRI (and similarly high TLCI, the Television Lighting Consistency Index, which is a metric more geared toward camera sensors). This means the light output is very well balanced across the spectrum for most colors – an important factor for photography. However, even a high CRI LED is not a continuous spectrum source – it typically has distinct spectral peaks (for example, a strong blue spike from the blue LED die and a broad hump in mid-wavelengths from phosphor, in the case of daylight LEDs). The warm LEDs in a bi-color panel will have their own spectral profile (strong in red-orange). When the two are mixed (for an intermediate color temperature like 4000 K), the resulting spectrum is a blend of two peaks.
Camera sensors capture color using an array of pixels covered with color filters (usually a Bayer pattern of red, green, and blue filters). Each filter only lets certain wavelengths through. The sensor’s interpretation of color depends on how the incoming spectrum aligns with these filter sensitivity curves. When we set a white balance, either in camera or in software like Capture One, essentially we are applying gain adjustments to the R, G, B channels so that a neutral reference in the scene comes out with equal R=G=B values (which would appear grey). For example, if the illumination is warm (excess red), the white balance will reduce the red channel’s relative gain or boost blue to compensate, making a neutral target balanced. White balance has two main adjustment axes: temperature (blue–amber axis) and tint (green–magenta axis). These correspond to balancing the ratio of blue to red (color temperature) and adjusting green vs. magenta (which balances the green channel relative to red/blue).
Even though a light source might be labeled “5600 K”, the camera may still need a tint adjustment if the spectrum has an imbalance in green vs. magenta. Flash tubes, for example, can sometimes have a slight green or magenta bias depending on design or power level. LEDs and fluorescents often require a magenta/green tweak because their emission spectra can cause the camera’s green channel to respond differently. Capture One’s white balance tool allows for both temperature (in Kelvin) and tint adjustments to nail down neutrality.
Light and Sensor Interaction: The crucial point in white balancing is that a camera’s sensor doesn’t measure color the same way the human eye does. The eye has its own three kinds of receptors, and what looks neutral to us is a result of our brain’s adaptation. A camera’s RGB sensitivities are designed to imitate human vision, but they are not identical. This is why sometimes a light that looks white to our eyes might still produce a color cast in photos – the sensor might be more sensitive to a part of the spectrum that our eyes compensated for. For instance, many LEDs have a strong narrow spike in blue light. Our eyes perceive the overall mix as white (after adaptation), but the camera’s blue pixel responses could be disproportionately high, resulting in a cooler image if left uncorrected. Proper white balance adjustment accounts for this by scaling down the blue channel or boosting red, etc., until neutral objects photograph as neutral.
In essence, the physics of light (spectral output of the source) combined with the spectral sensitivity of the sensor determines how an image’s colors record. White balance correction is the process of reconciling those factors to achieve neutral tone where it should be neutral. However, if the light’s spectrum is unusual, a single white balance setting might not perfectly neutralize every tone – which leads us to the nuanced issues of RGB consistency across different grey patches.
Profoto Flash vs. Westcott LED: Spectral Characteristics
In our scenario, we have two types of lighting in use: Profoto studio flashes and Westcott Flex Bi-Color LED panels. It’s worth comparing their characteristics, as they each interact with camera sensors in slightly different ways.
Profoto studio flashes (such as the Profoto D1/D2 or B-series) are engineered to produce a daylight-balanced output (~5600 K) with high consistency. In standard operating modes, these flashes are very stable in color from shot to shot. For example, a studio flash might advertise color temperature consistency within ±100 K or even ±50 K over its power range (when not in special “freeze” mode). This means if you set your white balance once, the flash won’t suddenly shift color on you as you vary the power for minor adjustments. Flash tubes emit a broad spectrum. If you look at the spectral output of a typical photographic strobe, it has energy in ultraviolet through visible into some infrared. There are often some spikes (from ionized gas spectral lines), but with a diffuser or protective glass dome, the spectrum is smoothed out. The result is an output similar to sunlight, perhaps with a tiny bit of bias (some flash tubes run ever so slightly cooler or warmer, and older flashes might drift). Profoto in particular designs their gear for color consistency – they even have modes to prioritize color stability. In a normal studio use (not the extreme short-duration mode), their flashes will deliver a very neutral light. In sum, flash is a near full-spectrum, stable source. When you set a white balance for flash (often around 5500–5600 K, tint near neutral), a neutral grey card should appear neutral at various brightness levels, at least in theory, because all parts of the spectrum are present to illuminate each color equally.
Westcott Flex Bi-Color LED panels, on the other hand, while extremely useful and versatile, have a different spectral profile. They allow adjusting color temperature by blending warm and cool LEDs. Let’s consider what happens at two extremes and in between:
At daylight setting (e.g., 5600 K), predominantly the daylight-balanced (cool) LEDs are on at near full power and the tungsten LEDs are dim or off. The light output will have a strong blue LED spike (around ~450 nm, typical for white LEDs) and a broad emission from the phosphor that covers mid and some red wavelengths, but possibly not as much deep red as a true daylight spectrum. The CRI being ~97 means they’ve formulated the phosphor mix to cover colors well, but often the most challenging area for LEDs is the far red spectrum (CRI’s R9 value for deep red is a known weakness in many LEDs). The camera’s red channel might thus receive slightly less signal relative to green and blue under this LED than it would under a flash.
At tungsten setting (e.g., 3200 K), the warm LEDs dominate. These likely have an LED that natively emits in the violet or UV and a phosphor that produces a warm output, or they might literally be separate LEDs with different phosphors. The spectrum here will emphasize reds and oranges, with less blue content. The camera’s blue channel will be the one needing a boost in white balance.
At mid settings (e.g., ~4500 K), both sets of LEDs are on. So the spectrum is a mix: there will be significant blue from the cool LED side and significant red-orange from the warm side. However, there might be a dip in some part of the spectrum that neither LED type covers strongly (possibly in the cyan region or in deep red).
For a high-quality panel like Westcott’s, the designers try to cover these gaps as much as possible to achieve high CRI/TLCI. Still, in practice, an LED’s spectral power distribution is not as continuous as a flash tube’s. This can lead to subtle color balance complexities: one white balance setting might perfectly neutralize a mid-grey under the LED, but perhaps a very bright highlight or very deep shadow might show a hint of a cast because the camera’s color calibration might not perfectly line up at those extremes for that light spectrum.
Another difference is how these lights behave when dimmed or used at different intensities. Flashes typically maintain color temperature fairly well across their power range in normal mode. Some portable flashes have a known behavior: at lower power, the flash duration shortens and the color can shift cooler (because the tube isn’t sustaining the amber part of the glow as long). Profoto’s high-end units mitigate this, but certain modes (like a “Freeze” mode for ultra-short flash duration) deliberately allow color to shift bluer in exchange for that speed. In a studio scenario, if you keep your flash in a consistent mode and within a moderate power range, you likely won’t see a significant color change between, say, a flash at low power vs. higher power – it’s minor and usually not visible in practice. The spec sheets often quote something like “within ±50 K throughout the range” for color constancy, which is negligible.
LED panels, when dimmed, usually maintain color balance (the ratio of warm/cool) if you’ve set a specific Kelvin, because the LED controller will dim both sets proportionally. Good bi-color LEDs have feedback to maintain the color even as you adjust brightness, but extremely low brightness might introduce a slight imbalance if one set of diodes turns off earlier than the other. However, in practical terms, you set the color temperature on the LED panel and it stays at that as you dim – the main change is just lower overall output (which for the camera means a darker exposure if settings aren’t changed).
In summary, from a spectral standpoint, the Profoto flash provides a broad, even illumination that typically makes it easier for the camera to maintain consistent white balance across various tones. The Westcott LED is also designed for color accuracy, but due to its inherently peaky spectrum, it might present more of a challenge for the camera’s white balance to be “perfect” for all shades with one setting – especially if the camera’s color calibration isn’t tailored to that exact light spectrum.
RGB Consistency Across Different Grey Tones
After setting a white balance using a neutral reference, one would expect all neutral objects in the scene to register neutral (i.e., their R, G, B values should be equal, yielding a grey with no color cast). However, photographers often observe that grey cards or patches of varying brightness (light grey, medium grey, dark grey) in the same image do not all show perfectly equal RGB values in Capture One or other editing software. For example, you might take a test shot of a multi-step grey chart under your studio lighting. You click the middle grey patch with the white balance tool, and indeed that patch now reads R=G=B. But then you check the lighter grey above it and the darker grey below it. Sometimes, the lighter patch might show something like R=242, G=240, B=245 (a slight bluish or reddish tint), or the dark patch might show R=50, G=52, B=48 (a slight greenish tint, for instance). Why is this happening, given that all these patches are supposed to be neutral and lit by the same source?
There are a few potential reasons for such discrepancies, and it’s important to dissect whether the cause lies in imperfections of the target patches or in actual white balance variation due to exposure level or capture process. Here are the key factors to consider:
Spectral Neutrality of the Patches: Not all “grey” patches are perfectly neutral. High-quality targets like the ColorChecker greys are designed to be very neutral, but even they can have extremely subtle biases. In fact, earlier versions of some color charts had slight color casts. For instance, the classic ColorChecker’s medium grey patch (“Neutral 8” on the old 24-patch chart) was found to have a slight coloration due to the pigments used – it wasn’t perfectly flat spectrally, meaning it reflected a bit more of certain wavelengths. Such a patch might look grey to the eye but under certain lights it could lean slightly warm or cool in the camera. Newer grey cards and custom white balance targets have addressed this by using special coatings that achieve truly flat reflectance across the visible spectrum. If one grey patch in your chart isn’t as neutral as another, that could explain an RGB mismatch. The medium patch you used to set white balance might have been truly neutral, so the white balance is correct for that. But a darker patch might be made with a different dye that, say, absorbs a bit more red relative to green and blue, causing it to appear cooler (more bluish) under the same light. In that case, the discrepancy is in the chart itself, not the light.
Sensor and Software Calibration (Profile): When you shoot raw and open in Capture One (or any raw processor), the raw data from the sensor is converted to visible colors using a camera profile or calibration matrix. These profiles are typically derived from shooting known color charts under standard lights and finding a matrix or LUT that maps the sensor’s RGB to standard color values. It’s optimized to make neutrals neutral and colors accurate. However, most profiles are an approximation and might be more accurate in midtones than at extremes. If the profile perfectly neutralizes mid grey under a given illuminant, it might still leave a residual tint in very dark greys or very bright near-white greys. This is because of how the sensor behaves at low vs high signal, and how the color calibration might apply tone curves. Some camera profiles even have a “look” or tonal response that is slightly non-linear per channel. Capture One’s default profile for a Canon R5, for example, aims for a certain rendition – it might have subtle channel differences in the shadows or highlights to optimize overall colorfulness or contrast. These could manifest as slight neutrality shifts at the extremes.
Exposure and Dynamic Range Considerations: Different grey patches mean different brightness levels, which exercise different parts of the sensor’s response curve. A dark grey patch (near black) will be recorded with very low numerical values in each channel. At such low levels, two things happen: the signal approaches the camera’s noise floor, and any fixed pattern noise or bias in one channel can become significant. Many sensors have slightly higher noise in the blue channel, for instance, or a higher readout offset in one channel. After white balancing (which might involve multiplying the blue channel more if the light is warm), that noise can be amplified and result in a slight color cast in the deepest shadows. Photographers often see this as a tint in the blacks when they really crank up exposure or shadow recovery – sometimes shadows go a bit green or magenta. In the context of a grey patch test, the darkest patch might register a off-neutral because of these noise and calibration quirks. It’s not so much that the actual light had a different color for the dark patch, but rather the camera+software didn’t record it as neutrally due to signal being low.
On the other end, a very light grey patch (near white) could be flirting with the sensor’s saturation or the upper non-linear region. If one color channel saturates slightly before the others (imagine the light has a lot of blue, and the blue channel clips while red and green are just below clipping), then that patch will skew in color. Even if not fully clipping, sensors sometimes have a “shoulder” in their response – for example, highlights might compress differently per channel depending on the color. Raw converters also often apply a tone curve that could potentially differ by channel if not carefully designed, which might lead to slight hue shifts in highlights. Ideally, raw processing is done in a scene-referred linear way up until white balance and color matrix, and only then a common tone curve is applied, which would preserve neutrality. But any channel-specific highlight roll-off could introduce a cast in near-white patches.
Lighting Uniformity and Angles: It’s worth ensuring that the grey patches truly were under the exact same illumination. In a studio setup, it’s common to assume everything is evenly lit, but subtle differences can occur. Perhaps the dark grey patch was on a part of the target that angled slightly differently or was farther from one light, receiving a bit more of one light source than the other in a mixed lighting scenario. If you have both flash and LED on together, or multiple lights, a slight position difference could change the ratio of those lights hitting a given patch, which in turn changes the color of light on that patch. Even reflection from nearby objects (like a colored wall or outfit) can contaminate a patch. However, in a carefully controlled test with one type of light on at a time and a flat target, this is less likely. Still, a minor consideration: ensure the grey card or chart is facing the camera and lights properly to minimize any shading or angle-induced differences.
Given these factors, one can deduce whether the problem is mostly with the target or the camera/lighting by a simple approach: try using a truly neutral reference for white balance and see how far off the others are. If possible, use a dedicated white balance card (those typically lighter grey, spectrally flat cards) to set the white balance, then check all the greys including the one used. If the dedicated card and one patch on the chart disagree, it suggests the chart patch is imperfect. Indeed, photographers have found that using the large neutral grey card from something like the ColorChecker Passport yields perfect neutrality, whereas the smaller greys on the ColorChecker Classic might show slight bias – confirming that the older chart’s greys weren’t 100% neutral. Manufacturers have even explicitly stated that their grey balance card is “spectrally neutral… equal amounts of R, G, B in all lighting conditions,” which underscores that not every grey patch meets that bar.
On the other hand, if all patches consistently show, say, a tiny shift toward a certain tint as they get darker, that points to a camera/sensor characteristic. For example, suppose under LED light you notice the darker the patch, the more it shifts magenta. This could hint at the LED spectrum plus sensor causing an issue – possibly the blue channel noise (which often has a yellow/blue effect) or some non-linearity. If under flash the effect is less, it further supports that it might be the spectrum interplay with sensor at low light.
In practical terms, these differences are usually small – a few RGB points here or there – and they might not visibly affect a normal photograph once the white balance is set. But for critical color correction work, understanding them is useful. It might guide you to, say, always white balance using a midtone grey (to ensure you balance where the camera is most linear), and not worry if the extreme ends are one or two points off neutral, as that could be within tolerances. If needed, one can create custom camera profiles for each lighting type which might slightly correct such residual tints across the range.
Imperfections vs. Exposure-Induced Variations
Let’s drill down on the question: is the phenomenon of different grey tones showing different RGB balance due more to patch imperfections or to actual white balance variation due to exposure levels?
From the discussion above, it’s clear both factors can play a role. However, their contributions can often be distinguished:
Patch Imperfections: If you observe irregular behavior, such as one medium patch being off while both lighter and darker ones are neutral, or each patch having a different random small tint, the patches themselves are suspect. Ideally, a neutral scale should all be made of the same paint/pigment just in different concentrations. But if, for instance, the darkest patch uses a mix that includes more carbon black (which might reflect infrared differently) and the lighting or sensor is sensitive beyond visible, weird things could happen. Or maybe the brightest “white” patch of a card has optical brighteners (some paper whites do) that fluoresce under flash UV content – causing a blue cast. These are patch-specific issues. High-end targets try to avoid such issues by using stable pigments.
Exposure/White Balance Variation: If the tints seem to change in a consistent direction as brightness changes (for example: progressively more bluish in highlights and progressively more yellowish in shadows), that might indicate an exposure-related white balance effect. One scenario is “metameric failure” in the system: The camera’s color correction is optimized at a certain mid-level. Off at the extremes, the combination of light spectrum and sensor response might not perfectly cancel out. This kind of systematic shift is not due to individual patch materials, but due to how the imaging system is handling different intensity regions.
In modern digital cameras like the Canon R5, the sensor is largely linear and well-behaved across the range, so pure linear physics says a neutral should stay neutral regardless of brightness, as long as it’s not clipped or buried in noise. Deviations therefore come from either sensor quirks or raw processing quirks. Sensor quirks could include slight differences in black level calibration per channel. For example, if the camera sets a slightly higher black level for the red channel, very dark neutrals might end up a bit red-deficient (showing green/blue). At normal exposure, that offset is negligible. On the top end, if the green channel saturates a tad earlier (since green pixels usually outnumber others and might hit voltage limits sooner), very bright neutrals could lean magenta (losing some green). These are subtleties often below noticeable levels, but measurable with precise charts.
White balance variation due to exposure can also refer to the fact that extreme underexposure or overexposure changes the effective color temperature captured. If you were to intentionally shoot a grey card very underexposed and then brighten in post, you might see a color shift because the signal was so low that color noise took over. Similarly, if you overexpose and recover, you might see color shifts if one channel clipped. However, within a single properly exposed image containing multiple grey tones, those extreme conditions aren’t really separate exposures – it’s one exposure, and the differences are more about tone response.
In the context of our studio setup: It’s likely that imperfections in the patches are a primary cause of any observed inconsistency, especially if using a standard color chart. This has been evidenced by the introduction of specialized white balance cards that replaced using a grey patch from the old chart. If the old chart’s grey was perfect, people wouldn’t need a separate white balance card – but they did, because the separate card was formulated to be better. That said, actual white balance variation due to exposure levels can happen subtly, particularly under LED lighting. Under flash, a neutral card at different brightness levels is very close to neutral all through (provided the flash power and spectrum is consistent). Under LED, you might find the darker patches come out a hair different, possibly indicating the camera’s white balance calibration for that spectrum isn’t one-size-fits-all.
For a Canon R5 specifically, there isn’t strong evidence that it has any unusual color non-linearity under normal circumstances. The R5 is praised for its color rendering and “Canon color science.” However, users have noted that under certain artificial lights, they needed small tint adjustments. For example, under some LED lighting around 4000 K, some photographers found the R5 images had a slight magenta bias that they corrected by adding a bit of green in the white balance tint. This implies the sensor + LED combination had a slight deviation that auto white balance or a preset didn’t fully account for. In RAW editing, these are easily fixed. It’s less a sensor flaw and more the reality of LED spectra not always matching the camera’s expected model. In very deep shadows, if one were to push the R5 files, there have been observations of color shifts (e.g., shadow noise having a tint), but in a well-exposed image of a grey chart, that would be minimal.
In conclusion on this point, both patch neutrality and exposure-related factors contribute to varying RGB readings on different grey tones. If forced to choose, one might say: If the equipment (lighting and camera) is high-quality and consistent, any significant neutral inconsistency points to the target. If the target is known high-quality (and the inconsistency is very subtle), then it could be minor sensor/calibration effects. In practice, it’s always good to use a high-quality grey reference and expose it properly for white balance checks, to minimize both issues (ensure the reference is neutral and well-exposed for low noise).
Canon R5 Sensor Behavior and Examples
The Canon EOS R5, being a modern full-frame camera, has an excellent sensor with a high resolution (45 megapixels) and a wide color depth. Canon’s color science is generally trusted for producing pleasing and accurate colors out-of-camera. Some specific notes relevant to our discussion:
Custom White Balance Usage: The R5 allows custom white balance by taking a photo of a grey card and registering it. This is the recommended way to get the most accurate color in a controlled lighting scenario. The camera then applies that white balance to JPEGs (RAW files always allow re-adjusting later). When shooting RAW with Capture One, the in-camera WB is just a starting suggestion; you can refine it in software. The R5’s implementation simply measures the average color of the grey card area and shifts WB until that average is neutral.
Auto White Balance (AWB): Users moving from older Canon models to the R5 sometimes reported that the R5’s AWB behaved differently (some said it was less consistent shot-to-shot under certain lighting). This is only tangentially related, but it underlines that the camera is making “best guesses” and sometimes they vary. In studio, AWB is usually turned off in favor of a preset or custom value, to avoid any inconsistency.
Color Cast in Extreme Conditions: As mentioned, if you drastically underexpose and then push the R5’s files, you might see the shadows go weird in color (some have noted a tendency toward blotchy colors when extreme shadow recovery is done – a scenario outside normal shooting). This is due to internal noise reduction or the sensor’s readout amplifying tiny differences. However, in proper exposures, the R5’s sensor yields very neutral greys from black to white. There is no known issue of, say, “mid greys calibrate but highlights go off” specific to this model beyond what we’ve discussed generally.
Dual Pixel Raw / Dual Gain: The R5 has dual-pixel CMOS AF but not dual gain like some sensors. It doesn’t have a feature where different halves of the sensor handle bright and dark differently (some cameras like certain Sony or Nikon sensors have dual conversion gain that kicks in at a certain ISO – but that affects noise, not color much). The R5 at base ISO uses one conversion gain across the range, so there isn’t an obvious breakpoint where color accuracy would suddenly shift. The consistency should be quite good.
Anecdotal Example: Suppose we test the R5 under two scenarios: one with the Profoto flash and one with the Westcott LED, using the same grey chart. In Capture One, we set the white balance by clicking the 18% grey patch under flash and under LED separately (since they require different WB settings). Under the flash shot, likely all the grey patches from dark to light will show very minor variance, maybe within 1-2 points of each other in R, G, B. Under the LED shot, we might find the darker patch shows a 3-4 point discrepancy (maybe a hint of green or magenta). If that occurs, it would illustrate the point that the LED’s spectral qualities plus the sensor’s response at low luminance produce a slight cast, whereas the flash (with more total spectrum and stronger signal per channel) did not. If both shots show one particular patch off, then it’s the patch. For instance, if in both flash and LED, the darkest patch is always a little off, then possibly that patch pigment isn’t perfectly neutral (could be the material has a non-linear reflectance or picks up IR).
One specific finding from earlier technical evaluations: the ColorChecker Passport (a product often used with Canon cameras for calibration) includes a large neutral grey target for white balance. That target is around 60% reflectance and extremely neutral. Using it tends to give very consistent results on the R5. People noticed that if they instead white-balanced off one of the smaller greys in the chart, the result wasn’t as clean. So for critical work with the R5, many will shoot a frame with that Passport’s grey card under the studio lights, set the custom white balance from it (either in camera or later in software), and then proceed with the actual shoot. This ensures the camera’s raw files have an appropriate WB that Capture One can read, and minimal adjustment is needed thereafter.
In summary, the Canon R5’s sensor behaves in a very standard and reliable way: neutrals stay neutral when properly calibrated. There are no glaring idiosyncrasies beyond the common ones all sensors have (noise in darks, potential slight channel clipping in highlights). So any anomalies in grey patch consistency on an R5 are more likely attributable to the factors we’ve discussed (chart and lighting) rather than the camera itself. It’s nonetheless useful to be aware of how the R5 handles color so one can have confidence in using it for demanding studio color work.
LED vs. Flash: Interaction with Greyscale Targets
When comparing LED and flash lighting with regards to greyscale (neutral) targets, we touch again on the concept of spectral differences and metamerism. Metamerism, in this context, refers to the phenomenon where two light sources of different spectral makeup produce the same apparent color (to a human observer or even to a camera when white balanced on a certain object) but might render other colors differently. With a greyscale target that is ideally perfectly neutral, one might think metamerism doesn’t apply – grey is grey. But if the target or the sensor has any twist, it can.
Spectral distribution impact: As noted, a flash’s broad spectrum means any given colored object in the scene will reflect some portion of most wavelengths. A neutral grey object reflects all wavelengths equally (in proportion to its reflectance percentage). Under flash, since all wavelengths are present in roughly balanced amounts, the grey object reflects a balanced mix – and the camera’s three channels each get their expected share. Under an LED, the grey object still reflects whatever light hits it equally – but if the light itself lacks certain wavelengths, there’s nothing in that range to reflect. The camera’s color perception is then entirely based on the wavelengths that are present. If, for instance, the LED light had very low output in the 600-650 nm range (orange-red), then even a neutral grey that would reflect that range can’t reflect what isn’t there. The camera’s red filter might primarily pass wavelengths from, say, 580 nm up to 700 nm. If the LED has a gap around 610 nm, the effective “red channel” content is slightly altered relative to what a continuous spectrum would give. The white balance might correct overall neutrality based on an average, but maybe the balance of what falls into the red filter vs green filter is a tad different for bright vs dark reflectance.
A concrete hypothetical: imagine the LED light has proportionally more energy in the deep red end at high intensities (maybe the warm LEDs influence more in highlights because they might behave non-linearly). A dark patch might be lit mostly by the lower-intensity part of the LEDs’ output where the spectrum skews a bit. This is somewhat speculative – high-end LEDs are usually linear (dimming changes magnitude, not spectrum shape, aside from any heat-induced color shift). However, there’s another angle: Color profiles and metameric mismatch. Camera color profiles (like the one used by Capture One for the R5) are typically derived under standard illuminants (daylight and maybe tungsten). LED lighting, if its spectrum deviates from those, can introduce errors. The camera profile assumes certain relationships – if those aren’t met because the illuminant is different, you get small color errors. Those errors could manifest as certain tones not being perfectly neutral even if theoretically they should.
We should also consider that LED and flash interact differently with materials beyond just visible reflection. Many flash tubes emit some UV, which grey card materials might absorb or not. Quality grey cards often have UV inhibitors to avoid fluorescence. LEDs emit virtually no UV. If a grey target were fluorescing under flash UV (emitting a bit of visible light), it could appear slightly different under flash vs LED. This is more relevant for “bright white” targets with optical brighteners (which absorb UV and emit blue). A grey card typically doesn’t have brighteners unless it’s a white side. But it’s a subtle consideration: a grey fabric or paint might behave differently if the light includes UV or IR. Infrared is another factor – flash emits some IR, LEDs very little. Most camera sensors filter out IR with an IR-cut filter, but not perfectly at the extreme end. A dark grey patch might reflect IR more relative to visible (especially if it has carbon black, which sometimes is reflective in IR even if black in visible). Under flash, that IR could sneak through the sensor (the R5’s IR filter will catch most, but if any passes, it likely affects the red channel). Under LED, no such IR is present. So the dark patch might appear truly neutral under LED (no IR contamination) but slightly reddish under flash (if IR reflection was interpreted by the red channel). Again, these are very marginal effects, but they illustrate how different spectra can cause differences in neutral reproduction. It’s often at the extremes (very dark or very bright) where these show up, since those extremes emphasize either the noise floor or potential sensor non-linear response regions.
Summation of LED vs Flash with neutrals: In practical testing, photographers generally find that flash photography yields very clean, neutral results with standard grey targets, and white balancing is straightforward. With LED lighting, results can also be excellent, but one must be mindful of white balance fine-tuning and possibly profiling. If you notice that after white balancing on a grey card under LED panels some grey shades still aren’t perfect, you might create a custom ICC color profile for the camera under that LED light using a ColorChecker. This would calibrate the camera to that specific spectral condition and likely iron out those last small variances. Indeed, this is a technique to deal with metameric failure: you shoot a known color chart under the given lighting and use software to generate a camera profile. That profile will adjust not just overall white balance, but the color matrix so that multiple patches (including neutrals at various levels) match their reference values. Essentially it teaches the software, “under this light, if something is supposed to be neutral across bright and dark, apply these channel corrections.” Once such a profile is applied, you’ll find all grey patches become more perfectly neutral. The need to do this is more common under tricky lighting (mixed LEDs, fluorescent, etc.) than under flash or daylight, which camera makers and software already tune for.
Practical Applications for Studio Photographers
From a practical standpoint, what should a studio photographer take away from this discussion? Here are some actionable insights and best practices:
Use a Quality Neutral Reference: Always include a neutral grey reference in your setup when shooting in controlled lighting. Invest in a reputable grey card or color calibration target. Ideally, use the dedicated grey balance card that comes with products like Calibrite/ColorChecker if you have one. These are designed to be spectrally neutral. By doing so, you eliminate one major source of error – you know the reference is truly grey, so any color cast you measure from it is from your lighting/camera, not the card.
Expose the Grey Card Correctly: When using the card for white balance, ensure it’s neither underexposed nor overexposed. Aim to put it in the mid-tone region of your histogram. This might mean taking a test shot with the card and adjusting lights or camera settings. The goal is to have the card’s RGB values somewhere comfortably between the noise floor and saturation – often around 50% to 70% on the histogram. This yields a clean read for white balance. If needed, you can take a shot just of the card filling the frame with the appropriate exposure for it, set white balance from that, then revert to your shooting exposure (especially if, say, you purposely underexpose a scene for effect, you’d still want a properly exposed reference shot of the card).
Set Custom White Balance or Use Raw Tools: In the studio, the lighting is consistent, so it’s wise to set a custom white balance in camera from your grey card shot. This ensures your camera JPEGs or previews are neutral and it gives a good starting point for RAW. If shooting tethered into Capture One, you can simply use the picker on the grey card in the first shot and then apply that white balance to the entire session. Capture One also allows setting up recipes or styles; you might have one for “Profoto flash at 5600K” and one for “Westcott LED at 4800K” etc., saved from prior sessions.
Check Multiple Neutrals: It’s a good practice to sample more than one neutral if available. In Capture One, you can set up multiple sample points (color readouts) on different patches of a test chart. After balancing on one, look at the others. This will quickly tell you if there’s any significant issue. If one patch is off by a noticeable margin (say one of the RGB channels differs by more than, for example, 2–3 from the others), you might adjust strategy: perhaps use a middle grey for balance instead of the brightest one if the brightest is prone to slight clipping. Or note the direction of the cast – if, for instance, all darker patches trend a bit green, you might slightly tweak the tint to compromise so that mid and dark are equally balanced (though mid might go a hair magenta, you distribute the error). Usually this isn’t necessary unless doing extremely critical reproduction work.
Profile Your Camera for The Lights: If you frequently use the Westcott LEDs for important color work (like product photography where exact hues matter), consider creating a custom camera profile under those lights. Tools like X-Rite/Calibrite ColorChecker software or third-party software can make an ICC or DNG profile by analyzing a shot of a ColorChecker under your LED panel illumination. This profile, when applied in Capture One (via the ICC profile for the camera), can correct nuanced color issues that a simple white balance cannot. This includes ensuring neutrals are neutral across all levels. The result is often subtle but can improve overall consistency, especially in mixed lighting or unusual spectra. For flash, the standard profiles are usually fine, since flashes emulate daylight well.
Understand Limits but Aim for Consistency: Recognize that small variations (a value or two in R, G, B) are often below visual significance. Don’t chase absolute numerical perfection if it’s not affecting the image visually. The goal is to remove obvious casts (skin looking too pink or background grey looking off). Whether the dark corner of a vignette has a slight tint when eyedroppered might not matter if it’s unnoticeable. However, knowing these effects exist helps you avoid misinterpreting them. For instance, if you see the phenomenon where your deep shadows aren’t perfectly neutral, you won’t panic – you’ll know it might be a normal sensor noise issue rather than something wrong with your lights.
Match Lighting in Mixed Setups: If you use both Profoto flashes and Westcott LEDs in the same shoot (perhaps flash as key light and LED panels as fills or accent lights), be careful. Mixed lighting can introduce real white balance complexities because you now effectively have two different spectra lighting the scene. A grey card in one area might not catch that another area lit by a different mix has a slight cast. The ideal solution in such cases is to spectrally match the lights as much as possible – for example, set the LED panel to the same color temperature as the flash (around 5600K) and perhaps use a custom calibration or gels if needed to align them. Still, even when matched in theory, the LED vs flash spectral difference could cause slight multi-illuminant issues. Some advanced workflows might do a dual-illuminant profile or simply avoid mixing by using all flash or all LED for critical color shots. If you must mix, take test shots and examine neutrals in various parts of the frame. You might find, for example, the side lit by LED is 1 or 2 points off in tint from the side lit by flash. In Capture One, you could correct this locally if needed (with localized color adjustment) or globally fine-tune to compromise.
Monitor Calibration: As a side note, all the careful white balance in the world won’t help if your monitor is not calibrated or if you’re judging by eye on an uncalibrated display. Ensure your editing monitor is calibrated to a standard (such as D65 white point) so that when you see a neutral grey in Capture One, it actually appears neutral grey to you. This is crucial for color correction work.
By following these practices, a photographer can achieve very consistent color results. The combination of Canon R5 + Capture One is a powerful one – Capture One is known for excellent color handling and providing robust tools for calibration and correction. With the stable output of Profoto flashes or the flexible tuning of Westcott LEDs, one can create lighting setups that are both creative and colorimetrically controlled.
Conclusion
Achieving accurate white balance and consistent RGB neutrality in studio photography is a matter of controlling variables and understanding the tools at your disposal. Grey cards (18%/50% grey) act as reliable anchors for both exposure and color balance, but only if they are truly neutral and used properly. The physics of light reminds us that not all “white” light is equal – spectra differ, and our cameras may see colors differently under flash vs LED illumination. High-end equipment like Profoto flashes and Westcott bi-color LEDs are designed to produce quality light, yet the camera sensor and processing pipeline still need to translate that into an image. We learned that different grey tones in the same scene can sometimes display minor RGB mismatches due to either the target’s neutrality or the sensor’s response at extreme brightness levels (or a bit of both). In practice, these effects can be mitigated: by using well-made neutral targets, by exposing them optimally, and by calibrating the camera for the specific lighting conditions.
For the Canon R5 in particular, we can trust its sensor to deliver solid results as long as we feed it good input (i.e., neutral references and appropriate white balance settings). The differences between LED panels and flash heads in how they render neutrals boil down to spectral content – a domain where careful profiling and testing can iron out surprises. Ultimately, consistency in studio color comes from a combination of using the right reference tools, setting custom white balances, and understanding your lighting. With these in place, Capture One’s software can faithfully reproduce colors so that a grey is grey at every tone, and skin tones or product colors remain true to life.
Color correction work becomes much easier when the foundation – neutral balance – is solid. By applying the insights discussed, photographers can ensure that their studio shots have a trustworthy neutral baseline, from the deepest shadows to the brightest highlights, regardless of whether they flash a strobe or turn on an LED panel. The result: more accurate colors, less time fixing casts in post, and greater confidence that what you see in the studio is what you’ll get in the final image.
Bibliography
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Cambridge in Colour. (n.d.). Understanding White Balance. Retrieved April 16, 2025, from https://www.cambridgeincolour.com/tutorials/white-balance.htm
Grey, T. (2021, April 5). 50% Gray versus 18% Gray. Ask Tim Grey. Retrieved from https://asktimgrey.com/2021/04/05/50-gray-versus-18-gray/
Myers, R. D. (2010). ColorChecker Passport Technical Review (Rev. 3) [White Paper]. Retrieved from https://chromaxion.com/information/ColorChecker\_Passport\_Technical\_Report.pdf
Profoto AB. (n.d.). Profoto D1 Flash – User Manual and Specifications. Retrieved from https://inside.cad.rit.edu/wp-content/uploads/2014/10/Profoto-D1.pdf
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