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Monday, 22 December 2008

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I hope this is not a too pedantic restating of above.

Using a grey card or expodisc gets you to a "pseudo-real" neutral colour base. It does not give you the REAL colour.

The 'REAL colour - outdoors' changes with the seasons, time of day and weather conditions (cloud).

If you colour balance using a card/device it removes the "seasonal" "time of day" and "weather" colouration.

Example: A photo at sunset if colour balanced using a device/card will end up looking as if it was taken (in colour terms) like a mid day scene.

A card/device tells you what to do to get an image back to a neutral "pseudo-real" colour base it does not give you what the light colouration was at the time you took the photo (it does not tell you what to adjust the colour by to remove (a)the camera colour bias and (b)the colour of the outdoor light.

Notionally you could calibrate your camera using a known light eg 5500K but that is only part of the story as it can be that your camera needs different calibrations measured with a range of lighting eg tungsten, sodium, flourescent etc etc.

Nitpicking is mostly a waste of time because you most often can't control the colours when your viewer sees it.

The factors will be the colour of the light they are viewing under, the paper the image is printed on, the fidelity of the reproduction by the printer (machine/person) or simply the monitor calibration/quality.

All you can aim is to be in the ballpark using the grey card/device and the ADJUST back to the light colour at the time the image was taken (assuming you liked/want to show what the light was like at that time e.g. sunset, sodium light etc.)

A question.

Has anyone used a standard set of adjustments to change a neutrally balanced image to a sunset/tungsten etc.(or are the ACR adjustments just perfect ;-) )


Two+ adjustments!
Beware Photographing people on lawns or under trees or anywhere that the light is reflected off a non neutral surface.

You will find that under chins /arms etc are a different adjustment to the face. This is because (I presume) you take your reading (from device/card) pointed from the face back to the camera position.(a fill-in flash might be helpful).

You need to know what colour you want at the time of shooting and be aware of what is hindering you from getting what you want.

Carl,

Excellent investigation of a complex topic.

Michael Tapes

Carl,

The pictures you selected do an excellent job of demonstrating your point, but I'm not sure that I fully understand your technique for getting something that approximates your subjective view of a more appropriate rendition of overcast or stormy light.

(1) First you set a "neutral" white balance using the eyedropper/gray card settings from your reference picture.

(2) You adjust the temperature slider until the picture looks about right.

(3) You check with the RBG sampler to see if the G is about 5 points above R and B is about 5 (or 10) points above G.

I'm not sure I understand why (3) is really necessary, if you are satisfied with your result from step (2). Assuming you get pleasing/subjectively appropriate lighting out of step (2), but that the results don't match your expectations in step (3) with regard to the relative RGB values, would you then ignore the result of step (2) and keep adjusting the white balance to get a result that satisfies step (3), or would you stick to your step (2) result? I'm not trying to be provacative, this is a sincere question. I'm trying to understand how you value the subjective step (2) vs. the somewhat more objective step (3).

In a related question from the other side of the coin, is there any way to go directly from (1) to (3)? If you save a custom white balance setting in your RAW converter, it just saves the actual color temperature setting, right? If you just apply the same color temperature to other pictures in slightly different light, I would expect the results to be "off". What you need is some sort of macro or action that takes a "neutral" result and then adjusts the RGB values relative to eachother to match your preferred ratios. Is that possible?

Last question: it looks like you are using the keychain version of the WhiBal card. Is there any benefit to using a bigger card (or any disadvantage to using the small card)? In theory I suppose that if your card is big enough, you could use it to set a custom WB in the camera, but that seems like it would be impractical in most situations, since the card would have to be pretty big. Are there any other advantages I'm missing?

Best regards,
Adam

Yip. Another subject where WB'ing becomes problematic is sunsets/-rises - one really doesn't wnt to correct them towards neutrality. A grey card should look anything but neutral under these circumstances.

This holds true for all photos in which the [strange] light is the actual subject, from modern functional architecture, like subways [British usage!] or railway stations, to mixed lighting, coloured lights and night shots.

Bottom line: It's your decision, not the environments.

Carl,

thanks for this informative articles.

"Accurate, or Convincing?" that's the real question.
Here my thoughts about it.

We can neutralize certain sources of light by selecting the WB for neon light, lamps, shade etc. Or with a white balance on a suitable medium exactly on Kelvin, we can prevent the light dyeing its environment after own liking.

But what the heck with it? What is the reason for our neutralization illusion?
Naturally, our eyes have the ability to see white as white in each color of light. The experience library of our brain makes it possible. Even mixed light situations we adjust on a perfect way.

Only the view from our illuminated living room window outside into the dawn, permits us, to see the blue hour, or to look from outside into warmly illuminated dwellings.

But already briefly after we entered the pure area of a wafer-producing company we see nothing more from the intensive-yellow lighting, which prevails there.

What do we make now? Do we place the yellow light neutrally? Do we let the employees carry white or yellow work clothes? Does a the Blue Hour become a Grey Hour?

I make an experiment for some time: if I photograph outside with daylight, I set the camera on 5400 Kelvin, in artificial light to 3400 Kelvin. And actually, in the light ambiance swings again, sometimes coldly, sometimes warm, sometimes blue, sometimes green.

I make exceptions with flash photographs and mixed light. Because my experience is, that in these situations the AWB of the camera supplies more plausible results. Perhaps, because electronics makes better of a shady business than I could do.

Honestly, if we see a photo, in which the natural lighting effect is conserved, we do not offend as an avoidable technical lack.
On contrary! If I often regarded neutral colors within my own photos as a relating to crafts, I could regard the pictures of colleagues more relaxed and notice, that not only light and shade, but also “ambience” set accents.

Courage for ambience!

(Please excuse my bad english)

"Has anyone used a standard set of adjustments to change a neutrally balanced image to a sunset/tungsten etc."

No reason not to, as long as you realize that the idea is to get a quick starting point to deal with future pictures. The article mentions my starting points for overcast and stormy light. Another example is fluorescent where I find the sense of the light is often best if I get the r and g perfectly matched but with 5-10 points higher b reading. I want to get rid of the green cast, but find a cold look feels like the actual light. For some reason I never seem to shoot under tungsten lights but for anyone who does, a bit of experimenting could find a custom starting point. I suspect it would be neutral r/g with a lower b reading.

Adam wrote: "(2) You adjust the temperature slider until the picture looks about right.

(3) You check with the RBG sampler to see if the G is about 5 points above R and B is about 5 (or 10) points above G."

In the example, these are not two separate steps, even if I didn't make that clear. I'm watching the picture thumbnail and the numerical readout both as I adjust the WB sliders. The visual clues and the numbers are a sort of reality check on each other. So this is a single step. The next step is to switch to a full screen view of the actual picture and make the final fine-tuning as a purely visual judgment (in this case I didn't make any further changes). The weirder the light or the stranger the subject colors, the more valuable the "abstract" numerical values obtained from the test card will be.

"Last question: it looks like you are using the keychain version of the WhiBal card. Is there any benefit to using a bigger card (or any disadvantage to using the small card)?"

The benefit of the keychain card is that it's always there in one of your pockets. The disadvantage is that it can be difficult to get a nice big image of it with a short lens without bringing it within inches of the camera. I actually use the shirt-pocket size more often.

White balance is something I struggle with. I'm often tempted to pick up some neutral device (all of which promise to make WB easier). For situtaions where you just want to reproduce acurate color, I get it.

However, for lots of other photos where perfectly neutral color isn't what you're shooting for, why use it at all? If you're fiddling around with the color balance until it looks right, how does starting with a neutral point help with that? If possible, can you explain the "reverse-engineering" stage a bit? What are you gaining from having a neutral reference point?

Thanks!
Aaron

Carl,

I just do not agree with using a white balance target under natural light, wether sun or cloudy. The grey balance tool has just one function: make the color of the lightsource disappear from the picture. That is fine if you wont to reprooduce the colors of a painting under whatever light, or make a portrait there.

But when I take pictures outdoors, there is always the color of the light that I wont to see in my pictures because that is what produces the feeling for the place or the weather.

So I never use the AWB,m it is never right.
I use the presets of the camera, for daylight most of the time. The cloudy setting is to warm mostly, but for any camera make but Canon one can change this setting to a more blueish color.

Of course, as we are all shooting in RAW, we can make presets in the RAW conversion software to do basically the same. I use the same white balance setting for all my outdoor pictures, unless its late in the evening. This also solves the sunset sunrise colorproblem, the colors just come out right.

When film users deployed filters or gels to balance the light or get the effect they wanted, they actually had quite a range of implements to either screw on their lens or cover their lights with.

I wonder it WhiBal or some other lighting group could come up with a set of virtual filters -- just a set of RGB numbers -- that you could apply after using the Whibal card to get a neutral position. In other words, all your photos would be neutral, but then with a figurative flip of the wrist, you could get sunrise/shadow, sunrise/open, sunrise/stormy, midday/shadow...etc., with the conditions described in words, rather than in temps. It does seem to me thatthere is some value in starting with a neutral position all the time... I could see the possibility of dozens of virtual filters -- maybe even , a sort of Tiffen color drawer, based on degrees kelvin, that would get you very close to the actual (subjective) light, starting from a neutral position.

Say...could this be a big moneymaker?

JC

Aaron and Eduard,

If sensors reacted to changes in ambient light in a way that mimicked our senses we could leave the white balance at daylight and be done with it. But they don't.

Individual perceptions will vary on this, but in general light that varies substantially from neutral sunlight will be recorded in a way that looks exaggerated when we view the picture. We sense that open shade is cool, but not as cool as the camera records it at a 5000K white balance.

This is a subjective call, and "struggle" is an excellent term for what happens when a picture taken under unusual light "looks wrong" and we try to find the right WB for it by just diving in and playing with the sliders. This is especially true when both the temp and tint sliders need substantial adjustment--how much of which to use? This can turn into a real whirlpool. A test card exposure gives a helpful starting point and primarily makes it quicker and less frustrating to find "convincing" color.

As several have noted, one exception is when the light itself--not something illuminated by the light but literally the light itself as when photographing a sunset sky--is apt to look just right if the camera is set to manual daylight WB.

The LAB color space offers some advantages, both in evaluating color and in applying a similar shift to different images with a different starting white balance.

Since LAB separates color from luminosity, you can see patterns, casts, etc. in the values and ratios in the A and B channels more easily than in RGB. Plus, even in the absence of neutral reference points you can infer (or sometimes guess) the color of ambient light source(s) and respond as you like. You can see LAB readouts in the Photoshop Info palette without changing the color mode of a picture to LAB.

You can also apply color shifts across the luminosity of an image (if that's what you want) with curves on the A and B channels. If you want that same shift in multiple pictures, you can copy the curves layer from one image to another.

(If you don't want the color shifts applied uniformly across luminosity, curve in RGB or CMYK instead.)

JC,

The problem I see is that unless individual camera calibration is perfect, all those virtual filters will be inconsistent. My K20 and my E1 are a couple hundred degrees Kelvin and, more dramatic, nearly twenty points of "tint" different in clear sunlight. Apply a "cloudy day" virtual filter that really just sets 6000/0 and...oh, Adobe already has half a dozen of these in the White Balance pulldown menu .

Add to that the fact that interpretation of convincing color is subjective--your notion of deviation from neutral rgb to convey a sense of overcast light could be quite different from mine--and it seems more sensible for users to do a little experimenting and make their own set of virtual filters (for each camera they use) which can be saved as custom subset->white balance, in ACR.

"If you are in light that is likely to fool the camera's AWB and you plan to use the camera's histogram for exposure evaluation, it's a good idea to select a manual balance or attempt a custom white balance to get the color closer. Even though you can correct the raw file for white balance based on your exposure of a test target, the camera histogram, based on a badly color-balanced camera JPEG, may be so far off that color correction will end up clipping one or more channels. If the WB is set close to accurate color, the histogram will be a much more accurate exposure indicator, and you can still fine-tune the raw files for color using the test card exposures. Note, changing the white balance setting in-camera doesn't have any effect on the raw data, but making the JPEG-based histogram more honest can avoid mistakes based on a faulty histogram."

Carl, it's been bothering me that I'm told to pay so much attention to the histogram when it's actually based on the jpeg image and not the raw. You clearly state why and how we should be doing this. Thank you.

My head is spinning.

**note to self** Study Black and White photography and edit exclusively to B&W on every image for the rest of my life.

**note to readers** I'm color blind. I can see color......just not like a non-color blind person. I can't tell the difference between red, green and brown in most situations.

B&W could free me from the shackles of color angst.

Superb column. I have some thinking to do.

Interesting article! I have struggled with this, particularly with overcast. Finally I shoot raw+jpg and leave Daylight WB set almost all the time, that way I have a jpg reference that while sometimes exagerated, does show the 'mood' of the light. Being neutral is so far off at times that I wouldn't recognize the picture I took.

I loathe residential lighting, and I dont mean as a photographer, I really hate artificial lighting. While my eyes might 'adjust' and see normal color at home, I'm still QUITE aware of the odd lighting. Making an indoor photo neutral freaks me out! Sometimes I'll neutralize it (if it seems sensible), but often I'll leave it at/near daylight orange cast and all.

I hadn't realized I was cheating myself with the histogram though, thats a great point. Anyway, my view of reality (after chasing accuracy/neutrality) is that Daylight WB is most realistic.

JC/Carl,

Actually, I think JC's idea would work, I just think that it probably wouldn't be necessary. Here's why:

If I understand correctly, John is suggesting that the filters be applied AFTER a "neutral" white balance has been set using, for example, a WhiBal reference shot. This step should eliminate the impact of white balance differences between cameras. What John is suggesting is that you should then be able to apply virtual "filters" that would adjust the white balance for shade, open sun, etc. In theory, these would just be adjusting the temp/tint values BY a fixed amount, not TO an absolute value. So for "Cloudy Day", the filter wouldn't just set 6000/0, it would set X+1000/Y+0, where X is the temperature and Y the tint of the picture AFTER a neutral white balance has been set.

I think that some programs can already do this (Ctein has been supportive of Picture Window Pro, which I believe has virtual filters named after their real-world Wratten counterparts, and Tiffen has produced Dfx Digital Filter software, which I imagine does something similar). These programs surely include more extensive filters and capabilities, but for the kind of thing John is suggesting, it seems to me like it should be easy enough to just enter the correct value in the raw converter directly. So if you have a "neutral" temperature of 5639, it seems like it would be easy enough to just enter 6639. Of course, you would have to experiment first to see if +1,000 is actually the value that you think best brings the neutral setting up to an accurate representation of a "Cloudy Day". But once you find an increment you like - whether +850, +976 or +1,147 - you should be able to use it for all other pictures that you want to have the same atmosphere.

I think.

I'm sure somebody here will correct me if I have just demonstrated my complete ignorance of this subject...

Best,
Adam

Thanks for the post. Very well written and easy to follow. Unfortunately, you need a WhiBal card to get your technically accurate starting poin and they are not available where I live (not anything like it).
I figured an alternative method and it would be great if you could validate it for me. I could photograph an object that I think is neutral grey in colour with direct flash (and no other light source) and the camera set to flash white balance. In ACR I then click with the eye droper on the object and if it gives me the same colour balance as the flash white balance, then the object is neutral grey, a different colour balance means its not. I will try different objects until I find one that works. I understand this will only work if the flash colour balance is set to exactly match the colour of the light emitted by the flash, but you would think that's what manufacturers would do, right?
Thanks for you help,

Tom K, I commend LAB to you. I'm in the same boat and learning about LAB has made all the difference to me. I'm much more confident with color now (and my hairline has stopped receding and I have friends now!) and also understand my color deficiencies. I can't color correct as well as the experts, but I can certainly outperform what I used to do.

The great thing about being color blind is that you can ignore things like monitor calibration and ambient viewing light color.

The not so great part is that you have to try stuff and see how normally-sighted people react ...

Adam, I had a hunch about your latest suggestion so I played around with an overcast WhiBal shot. It looks like the correction factor can't be applied in a linear fashion. This shot at neutral was 5850/-8. To get my "stormy light" r/g/b ratio measured on the card took -600 Temp and +3 Tint. But the shot used in the article illustrations, which began with a neutral of 8800/+4, required -1350 Temp and no change in Tint to get the same r/g/b ratio. There may be an arithmetic handle for the non-linearity, but I suspect it's easier to just jiggle the sliders to get the desired r/g/b ratio on the card.

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