No tricks Bob, just what I wrote in my first response to this thread, that is :

I also assume you know how to adjust the white balance so that your image does not have a colour cast. For birds with neutral white or grey parts this is easy; the RGB values for these parts should be approximately equal and can be fine-tuned using the DPP white balance adjustment tools. In other cases it can be difficult and you will need to rely on the pre-set white balance appropriate for the lighting, that is, Daylight, Shade, Cloudy, Flash, etc. Even then you may not be satisfied with the colour in which case you may resort to making adjustments to the Blue–Amber and Magenta–Green sliders or the Colour Temperature slider but you should only attempt to do this if you have a properly calibrated screen otherwise you may make the colour adjustment worse.

Cheers, Ian

In regards to your question David, the aim is to produce an image of an object so that it looks like it has the same colour no matter what the lighting used or what camera + lens was used. Furthermore, the colour should be accurate, for example, if you are photographing a Coca Cola product the colour of the label is important and will be specified by a Pantone colour with a certain RGB equivalent. The use of a colour checker will enable you to produce images of the label having the correct RGB values when photographed using your studio lighting using your camera + lens. Hope this helps.

David raised the question is the aim to standardise the colours in each image to a reference set of conditions regardless of the light conditions at time of capture (in which case all of the final images would look the same)?
In his response Ian wrote In regards to your question David, the aim is to produce an image of an object so that it looks like it has the same colour no matter what the lighting used or what camera + lens was used. Furthermore, the colour should be accurate, for example, if you are photographing a Coca Cola product the colour of the label is important and will be specified by a Pantone colour with a certain RGB equivalent. The use of a colour checker will enable you to produce images of the label having the correct RGB values when photographed using your studio lighting using your camera + lens. Hope this helps.

I have no argument with what Ian has written; in fact it is the standard practice in all forms of commercial product photography.
It is also probably fair to say that the majority of photographers will set the White Balance to reflect the ambient lighting, e.g cloudy, shade, etc. But is this appropriate to bird photography?

I remember a debate that I had with the late Ken Simpson (Co-author of the Simpson and Day Field Guide) in 2005 when we were establishing the BOCA Photography Special Interest Group. If my memory is correct, Ken was the Past President of BOCA (Bird Observers Club of Australia) and I was the President of the Photography Group (PhotoBOCA) at the time. Ken was taking me to task over the necessity for our images to ensure that our colours were accurate and that a new bird observer could confidently rely on the image to assist in identifying the birds they observed. His main argument centered on the fact that whilst the actual colour does not change, the perceived colour as we see it does change.

Without wishing to start a scientific debate, if a bird is in bright sunlight, the intensity of the light reflected from its plumage will be high and the colours bright and vivid. However if the same bird is photographed on a heavily overcast day, the intensity of the reflected light will be lower and the colours less bright and more subdued. Without recanting the full discussion which extended for several hours, Ken was urging us to edit our images in a manner which preserved the perceived colours as observed under differing light.

Ken’s final comment on the debate was something like – If it is important to capture images depicting the changes in the plumage (such as breeding plumage), then why would you not wish to record the perceived changes in the colour of the plumage resulting from different lighting conditions?

15 years ago, I could not come up with a valid reason to not accede to Ken’s proposal: I still can’t today. So over to you. I will be interested in your comments.
Bob

Bob, my understanding of human vision and colour perception is different to what you state. This is an extract from the American Academy of Opthalmology website "Your past visual experiences with objects also influence your perception of color. This phenomenon is known as color constancy. Color constancy ensures that the perceived color of an object stays about the same when seen in different conditions. For example, if you looked at a lemon under a red light, you likely would still perceive the lemon to be yellow."

By contrast, an object in different lighting conditions (different colour temperature) will differ in the spectrum of light physically reflected from it. This is inevitable. If the light hitting an object changes, then the light bouncing off it must change also.

So the statement, attributed to Ken Simpson that 'His main argument centered on the fact that whilst the actual colour does not change, the perceived colour as we see it does change', is actually the reverse of the way I'd describe it. Human perception tries to keep the colour the same regardless of the lighting. A camera records the actual reflected light colours and this changes depending on the lighting conditions. That's why the same object photographed under different light can look so different in an image.

Human vision is remarkable in its ability to achieve colour constancy - seeing the same colour no matter what the light is like.

The same should be true of a photo viewed on a computer monitor. Your vision will automatically adjust to the white balance of the screen's backlight so that any image should look the 'correct' colour, that is the colour we expect it to appear. A conflict arises when the camera image does not have its white balance corrected. We will still see an odd colour cast in the photo. What I think is happening here is that our vision system sees other objects on the screen and in the surrounding area which tells it what the right colour should be for those other objects. It gives priority to those, not the odd cast in the photo.

I hope that's not totally confusing but what it means is that it's critical to correct for casts caused by different lighting conditions as the camera will record these differently to how our vision would remember them at the time.

Thanks all for contributing to this interesting debate.

I am definitely no expert but I wonder if the perceived colour changes in different environments have less to do with brightness and more to do with different colour temperatures. Eg we might perceive a bird as 'glowing' in morning or evening light which probably has as much to do with the warmer colours rather than the brightness of the light. However, perception of colour could also have to do with the amount of reflectance (is that a word?) in feathers, which would change depending on the direction and brightness of the light. A classic example would be hummingbirds in the US, where the colour can be quite drab in some lights and vivid in others. (NB I had written this sentence before I saw Ian's most recent post so it might have been overtaken by that.)

I suppose the difficulty with what I could call the 'perceptive' approach is that there is no absolute - it becomes about what the photographer wants to depict (perhaps based on some vague 'memory of the scene'). This has the potential to lead to a high variation in colour, and also the use of colour for dramatic effect (as seems to be routinely happen with landscapes these days). If we think of bird photography from a 'creative' perspective perhaps this doesn't matter - the image impact, drama, mood, message might be the main consideration. However if we think of bird photography more from a 'scientific' perspective (ie a record of the species) we might give more credence to 'accuracy', however determined. Overall, I tend to prefer a more subdued look, but accept that sometimes it doesn't make for a particularly interesting or dramatic photo.

Part of the challenge the 'non-expert' photographer faces is the different approaches taken by different post processing software, in their default approaches. I did a quick check of three different software programs on my computer using a particularly difficult type of photo, the male Australian King Parrot. This photo depicted the bird sitting on a greyish brown branch, with dark green foliage as the background, so there was not really a decent target for setting the white balance using the eye-dropper. I used 'neutral' in DPP as the baseline (with things like sharpening turned off, and had the white balance set to 'daylight' (5200K) in all cases purely to enable consistency across products. I compared this to using RawTherapee 5.8 (using their 'neutral' settings) and DxO Photolab 3.2 using the 'No Correction' preset which sets all sliders to 0. Obviously this isn't a scientific test in any way. However in each product the rendering was visibly different. DxO rendered the bird a warmer red; while there is obviously quite a bit of variation between the RGB values pixel by pixel, it had reds about 250-ish, but greens typically about 20 points higher than blues. DPP had about the same value in the red, but with the greens and blues with relatively equal values - a bit more green than blue. The bird appeared, to my eye, a cooler red, with a bit more pink on the screen. RT measures values as a percentage rather than on the 0-256 scale, but again the green and blue values were reasonably similar (close to 50%) with a little more blue than green. The actual appearance on the screen was different from either of the others, being much greyer. I would have liked to compare the RGB value for a specific pixel but unfortunately DxO does not appear to allow me to pick a particular pixel on the x/y matrix. My screen is a Dell, calibrated with Spyder 5 Pro. I have an old version of Lightroom, but I didn't bother looking at that. If nothing else, this illustrates the difficulty the typical photographer will have is simply operating 'by eye' on the screen using different software products in isolation. I find it very difficult to decide how, exactly, to set the red for these birds, and it can change perceptively in different lights.

Perhaps, at least for Canon, one option might be to use DPP neutral as a visual guide to help set the starting point for other software, given that it has been shown to be reasonably accurate.

Simon

I'm not expert either, Simon. There are a few points I'd like to make from your post.

First, brightness should not affect colour: the colour reflected should be the same for different brightness levels. Direction, polarisation and other factors may affect things though. One factor, I understand, is that for birds, quite a few generate colour by diffraction rather than pigment dyes in the plumage. Diffraction is going to be affected by light direction and possibly polarisation; not just brightness. However, that's going to complicate this too much. Let's work on the situation where the light is differentially absorbed and reflected by pigments in an object with the result that the object has a colour that is not white. In that case, colour temperature of the source light is going to be a major influence on the colour a camera will record. Remember, for this discussion a camera can be thought of as a simple machine that records the colour in three colour channels (Red, Green and Blue) to generate a colour image. It simply measures these values precisely at each pixel and has no knowledge or intelligence about what the object actually looks like or what its colour is. Let's compare two light sources. The first has equal red, green and blue output levels (if you took a photo of the light source, it would render white or grey depending on the exposure). A second light source has a red output that is half the green and blue outputs. Now consider an object of a particular colour that reflects 20% of the red, 80% of the green and 70% of the blue. You should be able to work out that the absolute amount of light reflected by the object under the two light sources is going to be different. For the R=G=B light, the amount of red light reflected will be twice that under the light source that has half the red output: the absolute amount of red light hitting the object will be half so the amount reflected will also be half. The green and blue light reflected will be the same for the two light sources. This will result in a different colour recorded by the camera.

As for your 'perceptive' approach, perhaps you could clarify what you mean by this? Are you suggesting that the colour in a photo is simply adjusted based on how you remembered it? I'm not suggesting that be done. It is possible to precisely render colour using knowledge of the colour temperature of the light source and how the camera has recorded a particular colour. An example is a carefully generated colour card like the type Ian mentioned very early in the discussion. Most of the time we won't be using those. We can rely on other tricks. For example, if a bird has an area of white (and is exposed in the RAW file so it's not over-exposed and clipped), the red, green and blue values of that area should be identical. If they are not, the colour balance needs adjusting. The reason different RAW converters will produce different results is a bit beyond this discussion but in the end it comes down to how carefully they manage colour and how much time and effort the developer has put into adjusting for variance between different camera sensors and brands. Not all cameras are not all the same. Suffice to say the world is not perfect and the result is variation between converters. That's even assuming the developer of the RAW converter is aiming for accurate colour. They may not be. It's possible they are trying to create images that will sell their RAW converter to their target market, for example to average consumer. That might involve making the colour inaccurate such as over-saturated or warmer than it actually is.

Where does that leave me? SImply, use a trusted RAW converter like DPP that can produce accurate colour. Next, use the correct white balance setting for the lighting situation. Finally, fine tune this as sometimes, the lighting can not completely match one of the presets or be thrown off by light reflected off a nearby object like green foliage etc. Use whatever areas of known colour that you can in your scene or subject (like a patch of white on the bird). I think I've just repeated what Ian said in his initial reply to your post starting this thread.