Now I'm confused. What is Auto WB based on?

[leicaglow]

I was shooting some very warm colored landscapes today. I normally manually change the white balance for the

lighting. I accidentally had my D200 on Auto WB and the results were horrible. They were very bluish, and I can't

describe the look, but I can't really get a decent image in PhotoShop. I already got back my negatives taken with

a Leica and they look beautiful.

 

Another series was of a car in the same scene, and the car looks purple (it's midnight blue).

 

So what is Auto WB based on? How does it really know what is white? Would the warmth of the golden leaves and

sunlight against trees in the shadow, throw it off? The images were mainly shot with sunlight streaming through a

shady forest. I'll manually choose the WB for now, but it would be good to really understand it. Thanks for any

ideas.

[davidsimageline]

I would suggest you reset the camera by holding down the two buttons with the green dot beside them and try again

because something is off.

 

Did you try to find the black and the white point in photoshop? If you don't know how to I can explain how.

[Matt Laur]

A reminder that if you shoot in RAW, you make the WB setting in the camera a completely non-issue. It's very hard to torture a JPG back into the right balance if it's off, but a RAW file has all the latitude you could want. The WB settings (auto or otherwise) are still recorded by the camera and come along for the ride in the RAW file (and that can greatly easy batch conversions to JPGs if it's correct), but you can ignore them with no cost to the quality of the output image.

[rnt]

I believe the auto WB settings are based on what it takes to bring the overall color of the image back to a 'neutral' average (success depends on the smarts of the camera, scene type recognition, etc). As you note, this can cause some unexpected results.

 

The purple/blue car color may be due to something else- I've noticed that there are certain shades of blue (often found in flowers, btw) that cameras simply can't render properly- probably out of gamut.

[john schroeder]

Auto does not mean perfect. It never did and it never will. Your camera corrected for the yellow and everything else went blue. Not a big deal really. It is very simple to adjust the color tone of your images in Photoshop. Film lab techs have to adjust for color shifts all the time. We just never notice it unless they do it wrong.

[leicaglow]

Yup, I did try the white point but all the other colors were off. I guess I'll just make sure I don't do it again. I don't even shoot JPEG anymore. Maybe I will do a reset. I was making a lot of changes recently, so maybe it's something else. Thanks all!

[studor13]

Perhaps the LCD was too bright to see what you were getting but I find that under incandescent lighting any WB problems are immediately noticeable.

 

Fixing it in CS3 isn't that difficult. You can set in the preferences so that all JPEGs go through ACR. There you can adjust the WB. It's not perfect but it's a good start.

 

Or you go into CS3, and in Curves, pull one (or two) of the channels to get a fairly good and quick result.<div></div>

[leif_goodwin8]

I find that using the pop up flash set for fill -2 stops ensures good auto WB. I believe the pre-flash allows the camera to determine the true colours of the scene and calculate an accurate WB. The explanation is supposition but it works, at least on the D200.

[albertdarmali]

Now still in the same topic of white balance, I always wonder, when we are doing custom white balance and shooting a white sheet of paper for example, do we have to cover the whole viewfinder with the white sheet or it it enough to just say, cover the area of the focus point and a bit more?

[costas_h]

Every camera has its own algorithms for calculating white balance, but in general there two basic ways:

 

1) The camera looks for the lighter parts of the images and assumes they are white so it can calculate the WB

setting that would make them white.

 

2) All pixel color values are averaged (think of it as mixing all colors of a painting) and that is assumed to be neutral

(grey).

 

Of course modern cameras also include databases of usual scenes so if the camera recognises the scene it can do

additional adjustments.

 

Anyway, Nikon cameras have one of the best auto WB systems and they are rarely fooled.

Check in case you had dialed any compensation for the WB that you forgot to change.

 

If you really need very accurate in-camera WB you should buy a grey card and use it before shooting (or just use a

white piece of paper).

 

 

Changing WB in post processing isn't that difficult, neither for RAW nor for jpeg, as most people think.

Photoshop can also open jpgs in Camera Raw and you can then change the JPEG's WB easily.

All you have to do is enable it in Preferences.

[frank_skomial]

I was hoping someone would explain how the Nikon's huge built-in database of shooting scenarios is used? or not

used ? to come up with correct color balance and exposure.

[costas_h]

Those scenarios are mainly for exposure determination.

 

Don't expect to find exactly how Nikon or Canon or ... implement their versions of WB determination, these are

corporate secrets.

 

Here is a possible scenario: the camera checks, say, for light and dark areas. If a small area is much darker than

the rest of the frame then the odds are that you are shooting something backlit, perhaps a person. Now, if that area

resembles skin tones then the camera "concludes" that you are photographing a portrait of somebody and

compensates for the right exposure and WB.

 

Basically all of the information the 1,005-pixel RGB sensor (for the Nikons) carries (brightness, color etc) can be

compared to the in-camera database, which consists basically of thousands of professionally taken photos, and the

best match will probably be really close to the shooting situation.

 

That is just a guess, but I suppose first of all the camera breaks down the scene in bands or smaller areas, then

tries to determine the origin or direction of light (light-dark areas), then the light type (from the color of the source)

and then uses the rest info to compare to the photos in memory.

[leicaglow]

Sounds like I'm not the only one who has or will be bit in the butt by selecting AWB.

[leif_goodwin8]

Michael: As mentioned, since you are shooting landscapes, and time is on your side, just use a grey card to generate a preset WB. And shoot RAW. That way you will get excellent results.

[walterh]

Michael there is a trend that I dislike. The trend is for more computing power in cameras that is used to

generate "better" images. We all profit from this development to a different degree. Unfortunately the mass

market dictates the trend and define what exactly is a "better" photograph. With all this computing power in the

camera automatic exposure and WB are getting more and more complex and are important factors for camera sales.

This in turn results in more and more secrecy about the processes involved and the people who would be able to

understand (and use this understanding to generate "better " images in their own definition ^^) are as much in

the dark as any other mass market customer.

 

The same thing happens with photoshop. If you look there you find the most powerful features used as black boxes

and their function is unexplained. You get cookbook recipes how to "improve" your images but explanations of the

image processing behind is not available.