white balance in camera raw CS3

windoze

quick question about correcting white balance.....
if i use the eye dropper and i find something in the image that has the same RGB values ex R=145, G=145, B= 145 can that be used to help color correct? And if thats ok then anytime you have the same RGB values that = a neutral grey ( I dont think so )?


troy

arodney

windoze wrote:

quick question about correcting white balance.....
if i use the eye dropper and i find something in the image that has the same RGB values ex R=145, G=145, B= 145 can that be used to help color correct? And if thats ok then anytime you have the same RGB values that = a neutral grey ( I dont think so )?


troy

R=G=B is a neutral in some color spaces (all RGB working spaces: sRGB, Adobe RGB (1998), ProPhoto RGB etc).

Use the WB tool on non specular whites in a Raw converter like CR or LR. something like the 2nd white in a Macbeth color checker.

pathfinder

I think a light,light gray - lighter than 128,128,128 and less than 230,230,230, will do the trick, Troy --

Kind of what Andrew was calling the second white on the MacBeth color checker. You do not want to use a specular reflection for white balance.

I use this technique for white balance every day, along with looking at the image on a calibrated monitor, to verify that the changes with the WB eye dropper look acceptable.

windoze

pathfinder wrote:

I think a light,light gray - lighter than 128,128,128 and less than 230,230,230, will do the trick, Troy --

Kind of what Andrew was calling the second white on the MacBeth color checker. You do not want to use a specular reflection for white balance.

I use this technique for white balance every day, along with looking at the image on a calibrated monitor, to verify that the changes with the WB eye dropper look acceptable.

Yikes!!!! I think im doing something right for once.

Thanx Path and Andrew!
highly appreciated......


troy

pathfinder

The ability to open jpgs and tiffs in RAW in Adobe RAW convertor 4.1 means you can do this WB trick for them also

arodney

pathfinder wrote:

The ability to open jpgs and tiffs in RAW in Adobe RAW convertor 4.1 means you can do this WB trick for them also

Not all that well, not anything like doing WB on a Raw file.

Vizhon

pathfinder wrote:

The ability to open jpgs and tiffs in RAW in Adobe RAW convertor 4.1 means you can do this WB trick for them also

Actually, that doesn't work. It tries and it may look better after such a correction, but a jpg simply does not hold the data necessary to adjust white balance. The color data in a jpg has already been adjusted for white balance when it was made into a jpg, and to then white balance that is white balancing an already white balanced image. It's like correcting filter caused discoloration by adding another filter. RAW data on the other hand is just what is claims. It is RAW and straight from the sensor, pre-WB correction. Any WB corrections put into the picture by the camera is simply 2 values - a temperature and green-magenta adjustment. These values are then applied by your RAW developer to the RAW data as offsets to give the White-balanced image. You adjust the WB sliders on a RAW image and you are really adjusting the WB on the RAW data. Really, white balance adjusting a jpg reduces the quality of the image and the accuracy of the data and can cause banding similar to turning contrast up too high on a jpg.

colourbox

Vizhon wrote:

Actually, that doesn't work. It tries and it may look better after such a correction, but a jpg simply does not hold the data necessary to adjust white balance. The color data in a jpg has already been adjusted for white balance when it was made into a jpg, and to then white balance that is white balancing an already white balanced image.

One of the reason that's true is that a JPG or TIFF may have already been clipped at the highlights or shadows during the original conversion from RAW. Automatic/eyedropper white balancing is often not as accurate (or sometimes, not accurate at all) if some of the original highlight and shadow channel data has already been chopped and dropped forever.

Still, having a White Balance slider for a JPG has saved a few JPGs already. They just would have been higher quality if my friend's camera had been able to shoot raw in the first place.

pathfinder

Vizhon wrote:

Actually, that doesn't work. It tries and it may look better after such a correction, but a jpg simply does not hold the data necessary to adjust white balance. The color data in a jpg has already been adjusted for white balance when it was made into a jpg, and to then white balance that is white balancing an already white balanced image. It's like correcting filter caused discoloration by adding another filter. RAW data on the other hand is just what is claims. It is RAW and straight from the sensor, pre-WB correction. Any WB corrections put into the picture by the camera is simply 2 values - a temperature and green-magenta adjustment. These values are then applied by your RAW developer to the RAW data as offsets to give the White-balanced image. You adjust the WB sliders on a RAW image and you are really adjusting the WB on the RAW data. Really, white balance adjusting a jpg reduces the quality of the image and the accuracy of the data and can cause banding similar to turning contrast up too high on a jpg.

Vizhon,

I shoot RAW routinely, but occaisionally I am given a poorly shot jpg that is under exposed or has a cast, and I find ARC 4.1 helpful in wrangling the image into a more acceptable appearance. Correcting the image in Photoshop is going to exact a price also, is it not? Is it really less damaging to the jpg to rebalance in Photoshop rather than RAW?

I agree that this is not the best thing to do for a first class, well exposed and color balanced jpg for the reasons mentioned. But it seems there is an almost endless supply of jpgs, that have a bad cast, that folks want improved even if just a bit.

As I said, I shoot RAW routinely, even with my point and shoot.

If you try to color correct a jpg with a strong cast, using curves or other methods, rather than ARC 4.1, you still may harm the image also, are you not? I just find ARC easier to use for color balancing than curves, I guess.

MarkR

pathfinder wrote:

Vizhon,

I shoot RAW routinely, but occaisionally I am given a poorly shot jpg that is under exposed or has a cast, and I find ARC 4.1 helpful in wrangling the image into a more acceptable appearance. Correcting the image in Photoshop is going to exact a price also, is it not? Is it really less damaging to the jpg to rebalance in Photoshop rather than RAW?

I agree that this is not the best thing to do for a first class, well exposed and color balanced jpg for the reasons mentioned. But it seems there is an almost endless supply of jpgs, that have a bad cast, that folks want improved even if just a bit.

As I said, I shoot RAW routinely, even with my point and shoot.

If you try to color correct a jpg with a strong cast, using curves or other methods, rather than ARC 4.1, you still may harm the image also, are you not? I just find ARC easier to use for color balancing than curves, I guess.

Thank you, Pathfinder! I feel validated! Validated!

To my previously-secret shame, I have been running my Jpgs through ACR 4.1 because I found the white balance so much easier than juggling curves, and I thought I was getting better results with less effort. I'm glad to see I'm not the only one.

pathfinder

You could shoot a MacBeth Color checker or a neutral gray card in a frame of your jpgs,( not an 18% grey card for exposure) and use the WB eye dropper in ARC 4.1 also - but if you are going to do that, why not just shoot RAW in the first place?

Or even RAW + jpg - that way if you are satisfied with the jpg you're golden, but you still have a RAW file if needed for color balancing? I must say though, that I have given up on jpgs - the camera almost always puts the white point on a specular reflection, rather than a white point in in-camera jpgs.