Chasing perfect color, and common myths about white balance

The previous article on the inexact science of color and emotion dealt with why color was important, and how we can use it as a tool to alter the mood and emotional response of the viewer of our photographs. This article explains how we get there.

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Sandwiches. Did you know greens are heavily affected by the yellow channel? Nikon D700, AFS 60/2.8 G Micro

Although highly saturated color is visually striking, and B&W images are timelessly classic and elegant, there are a lot of times when neither is appropriate or an accurate representation of the scene. I’ve recently realized that I like accurate color above everything else – saturation control then becomes a matter of seasoning to taste. Color accuracy is actually quite critical when it comes to things like food – if the color of cheese or lettuce is off, it just looks moldy or unfresh. This is definitely NOT good for commercial work! My recent work is what I’d call in a ‘natural’ style – the color, saturation and hues are as close to my perception and remembrance of the scene as possible. I’ll do some shifting of white balance to make things warmer or cooler as required, but not a huge amount because it can do some very strange things to tonal accuracy.

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Scarlet Ibis. The red in is plumage is due to pigments in the shellfish that forms the majority of its diet. Leica V-Lux 3

Skin tones are perhaps the most difficult to replicate accurately; this is because skin is both reflective of ambient light (easy for the camera to capture) and emissive – we’re warm, and there’s some passive IR radiated by warm objects. Although modern cameras have very effective UV/IR blocking filter packs, they also produce (in my opinion) slightly dead-looking skin tones. I actually liked the skin tones from the Leica M8 for this reason, which was notorious for having perhaps the weakest UVIR filtration of any camera on the market – to the point that to get accurate blacks you’d have to use a UVIR filter on your lens.

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Black fabrics in the sun are notorious IR-emitters. Leica M9-P, 28/2.8 ASPH

Other objects that are notoriously difficult to reproduce accurately are flowers, some animals, and some fabrics. Again – this is because of the way they interact with the near-UV and near-IR spectra, which affects the way our eyes perceive color (though we can’t see UV or IR directly unlike some animals). To date, there is no camera that accurately reflects the spectral response of the human eye – and I suspect it might be very difficult to make one, because the filter pack would have to be calibrated to transmit or cut out a certain amount of each wavelength. It’s much easier to make a filter that cuts out everything above and/or below a certain wavelength. Throw in the added complication of mixed light sources, and you’ve got a minor nightmare.

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Colors. All of them. Which one do you balance for without shifting the others? Answer: focus on your subject – in this case, skin tones and blacks. Olympus E-PM1 Pen Mini, 45/1.8

So what can we do to achieve perfect color?

First clarification: we are not trying to achieve perfect spectral reproduction; we’re trying to achieve perfect perceptual reproduction. It’s not quite the same thing. Basically, you want to get to the starting point of being as close to what you remember seeing as possible, then work from there. That way, you know that all of your tweaking isn’t going to create some strange shifts in certain parts of the tonal spectrum.

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Chilis. Nikon D700, AFS 60/2.8 G Micro

White balance is inextricably linked to color. And there are some important things one has to bear in mind:

1. You have to get it right first time if you’re shooting JPEG. There just isn’t the tonal headroom in 8 bits to be able to make anything other than minor channel adjustments and not encounter posterization or weird hue shifts.

2. Manual white balance and a piece of paper are your best friends.

3. If you’re shooting RAW, white balance is less critical, but if you blow a channel, you’re not getting it back. Usually reds and yellows are the first to go. With earlier cameras, you might have to underexpose by as much as two stops to maintain tonal detail in the reds. I think it’s something to do with IR-sensitivity, the effectiveness of the filter pack over the top of the sensor, and how the red pixels respond very strongly to IR pollution.

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Cigars are one of the most difficult colors to get right. I don’t know what it is about the tobacco leaf, but that rich, deep brown hue requires a lot of work to perfect. Nikon D700, AFS 60/2.8 G Micro

4. White balance does affect exposure. This isn’t immediately intuitive; the reason is because if you get it very, very wrong, you’ll find that after correction, the dominant colors in the shot will shift, and the sensor may not have gained up enough at the extreme ends (red or blue) resulting in underexposure – most likely. You can to some extent recover this in post, but the bigger problem is that you’re going to land up with a very noisy image – the blue channel is generally holds the most noise for most cameras as it is the least sensitive due to the laws of optics, photon energy and filtration…but I won’t go into that here; complex quantum mechanical formulae are beyond the ability of my blogging software to input and display. 🙂

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Prayer wheels, Nepal. Nikon D700, 24/1.4 G

Bottom line: shoot raw, and get in the right ballpark. Small adjustment are fine, and you can never get it 100% right all the time with a manual balance because ambient light is always changing. AWB works reasonably well on most cameras these days, but you have to watch out for the very warm light sources. I was told by several people in the camera industry that it was a conscious choice to leave the yellow/red components in the tungsten AWB because people expect the light to be warm (back to perception) – and having pure whites just looked odd to most consumers. I can attest to that as a lot of my students have asked me why the color is so blue when shooting indoors! Although I can’t say whether it’s a visual expectation on the part off the photographer, or whether inaccurate white balance is something they’ve come to expect because it was inadvertently dictated by the industry.

I’ve been playing with a handy little tool recently called a WhiBal. Basically, it’s a very, very accurate neutral gray card. I’ve found there are two ways to use it – one, take a shot under AWB with the card in the frame, and use that as your reference frame; eyedropper tool WB from the card in ACR, then sync white balance between the remainder of your files. Note that these two methods only work when your lighting is consistent from frame to frame, i.e. under studio conditions. The other option is shoot the card under the lighting conditions you’re going to use to set the preset in camera; I find this works better because all of your frames are automatically synced from the shoot. And if you’re using the same setup – as I do for watches – I can basically do it once and just leave one of my manual presets to match my flash and diffuser combo.

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If any of you have shot purple flowers, you’ll know they’re notorious for shifting towards blue: that’s because of the UV reflectance. Flowers have UV and IR reflective pigments to signal to other animals – in this case pollinating insects and birds – that can see UV and IR.
Nepal. Nikon D700, 24/1.4 G

Next, make the tweaks – in your RAW converter, (I use ACR 6) perfect your white balance. Use the eyedropper tool on various gray areas in the scene until, it looks close to what you remember. (This is another reason why I like to process as close to immediately as possible: you might forget what the originals scene looked like, or any processing ideas you might have had at the time). Don’t worry if the eyedropper tool doesn’t get it right; you can shift the color temperature and hue sliders a little until you do.

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This blue is one of the most difficult colors to get right. What makes it so appealing as a car color – the fact that it changes a lot under different lighting conditions – also makes it a royal pain to photograph and represent accurately. The honest truth is that I have no idea what RGB value this actually is, because it’s both reflective and in many spectra. Nikon D700, 28-300VR.

Open your file, make whatever contrast adjustments you need to – curves/ levels – then only use the Hue/Saturation tool to adjust the individual channels. Using curves inevitably shifts the saturation and hue slightly – there’s no way out of that – so you’ll need to bring back the individual channels. For instance, if it’s predominantly red and you used a curve that darkened the image, you’ll have to compensate for that by reducing saturation and increasing lightness slightly in the Hue/Saturation tool. There is no exact science to this – it’s all about experience, perception, and having the most accurate monitor you can find.

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Remember what I was saying before about shellfish and birds? Nikon D700, AFS 60/2.8 G Micro

Each camera has a different filter pack and spectral response. Even though manufacturers try to keep the color output consistent from model to model, there will be differences. The D3100, for instance, has a crappy color gamut that I was never happy with – much like the NEX-5 – however, the D700, D5100 and D7000 are all pretty similar. The D800 is close, but even more accurate and with a wider supported tonal range out of the box. The M8 with UVIR filter, M9 without and S2 are almost identical. Since I use a whole bunch of cameras – at the last check, Leica, Nikon, Olympus and Ricoh – I’ve created individual color profiles for each camera in ACR and saved them as camera defaults. The look I like is somewhere between the tonal richness of Leica and the warmth of Olympus – perhaps Olympus + Zeiss glass describes it best. Oh, and different lenses have different spectral transmission characteristics too, just to make life more interesting. Your personal preferences will almost certainly be different because each individual perceives color differently. But I suggest that if you have the time, this is a worthwhile exercise.

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The challenging pale but saturated lightness of macaroons. Nikon D700, Carl Zeiss ZF.2 2/2.8 Distagon

One important final note: all of this is in vain if your final output use is extremely limited gamut or highly compressed (*cough*FACEBOOK*cough*) – all of the additional tonal information you tried to save is going to be lost and compressed to hell. Some browsers (Safari) and photo sharing sites (Flickr) are better than others because they are color profile aware and don’t compress images, but the issue then becomes monitor accuracy. So unless you know the final output method and have some control over it, it’s very tricky to ensure that everybody is seeing the same thing. And printing is a whole separate blog on its own…MT


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Images and content copyright Ming Thein | 2012 onwards. All rights reserved