White Balance and RAW

[amanda_accamando]

Hi All,

 

I am extremely new to this site and to photography in general! I was hoping

someone could help me with some basic answers regarding shooting in RAW, white

balance and converting.

 

My situation is basically this: I am interested in measuring animal color. I use

a Canon Rebel 400 and shoot in RAW. I do not have Photoshop CS2 so I use the

camera's software (Digital Photo Professional)to convert RAW images to TIFF. I

also use the GretagMacbeth ColorChecker and inCamera software in Photoshop 6.0

to create and apply profiles to my images.

 

As I am trying to measure the color of an animal's skin/hair, accurate color

values of hue, saturation and brightness are most important to me (not

aesthetics of the image).

 

I have read a lot about white balance but I am unsure how setting the white

balance is going to affect my color measurements. If I shoot in RAW, does my

camera's white balance setting matter at all? For example, I shoot animals in

both indoor and natural settings; should I adjust my white balance settings

dependent on the location? The images appear very different in the RAW converter

depending on the white balance I have used. I am wondering if this will carry

over to Photoshop when I apply a new profile and later when I measure the HSL.

 

Any insight for a beginner would be extremely helpful and appreciated!

 

Thanks so much!

[steve_dunn2]

<cite>If I shoot in RAW, does my camera's white balance setting matter at all?</cite>

 

<p>If you're shooting RAW, the WB setting you choose in the camera has two effects. It is used for the embedded preview JPEG image within the RAW file, and it can be used as a default if your RAW converter chooses to do so. The actual image data in the RAW file are not affected by the camera's WB setting; they come straight off the sensor and are not processed for things like WB or picture styles.</p>

 

<p>Imagine that you take two pictures of the same scene. You're shooting RAW. For one picture, you choose WB of 3000K; for the other, you choose WB of 7000K. When you look at the embedded preview image, the two pictures will look very different due to the different WB. Now let's say you convert both of them, choosing 5000K as the WB for the conversion in each case. Your two final images will look the same; both will have been converted at 5000K, ignoring the 3000K and 7000K settings you chose when you took the pictures.</p>

[geoffs1]

In order to get anything near a correct colorimetric analysis from a digital image, you'll almost need to have a copy of the test-chart in every shot. You might be able to get away with taking a photo of the chart separately if your lighting conditions are absolutely consistent. You may also want to do some reproducibility tests to see how much the sensor and readout electronics drift over time (although I'd guess that's a small effect).

 

To answer you camera WB question: I've heard rumors that the camera WB setting will affect RAW files from some cameras, but it seems unlikely. To be safe, I'd probably set the camera WB to the same value for all your shots.

 

Other things to think about: the color characteristics of lenses are not the same. If you need to use different lenses, you'll probably want to characterize each one separately. Also, it seems unlikely, but the spectral response of he sensor might change with different ISO settings (ex. if the RGB amplifiers aren't perfectly matched), so you might want to check that if you need to shoot at different ISOs.

 

Good luck; sounds like an interesting project.

 

Cheers,

 

Geoff S.

[mike_earussi1]

If you want accurate color balance, and if indoors under fixed lighting, you will need to have at least one shot of the color chart taken under the same lighting conditions as the animals, then color balance to the card not to the animal and apply that color balance to the rest of your shots. If outdoors under changing light, the color card should be in every shot.

[sknowles]

This is getting confusing from these posts. Are you saying a camera with the variety of WB

setting, average (selected by camera), daylight, shade, cloudly, indoor lighting of different

types and so on, the raw files will all be the same from the camera or just the file from the

camera converted to the WB setting you selected? Isn't that saying the camera does actually

process raw files into the WB setting you select? And doesn't this mean the WB setting, and

even picture style and exposure metering is critical for raw files?

[digitmstr]

>>I am interested in measuring animal color...I am unsure how setting the white balance is going to affect my color measurements<<

 

What do YOU mean by "color measurements"? How do you measure animal color?

 

White Balance has to do with the light hitting the subject relative to the film/sensor, NOT the color space/saturation/contrast/etc...

 

Very simply put, the light source must match the film/sensor in order for the colors in the subject to be rendered as they were in reality.

 

If there is a mismatch between the light source and the film/sensor you will have a color shift.

 

It gets more complicated with mixed lighting etc... Just do a Google search for Color Temperature Chart, find one you like and print it. Hang it next to you photo computer so that you can see it often. That will take care of the WB issue.

 

As for calbrating your entire workflow, that's a different issue.

 

When you load images in DPP it 'reade' the WB setting at the time the shot was taken. You can then, re-adjust if needed to balance the picture. In that sense, it doesn't matter what you camera settings were at the time you took the picture. However, I STRONGLY advice everyone NOT to use RAW as a crutch for exposure and/or white balance.

Without a strong knowledge of both you won't be able to advance as a photographer, period. There is not substitute for knowledge. If you are in a shooting situation in which there is mixed lighting, etc... you will have to make decisions, possibly in front of your client (if you are a pro...). Without a solid understanding of the issue at hand you will NOT be able to make ANY decision at all. Same for exposure.

[amanda_accamando]

Thank you everyone for your helpful suggestions. Just some follow up comments...In an indoor (and more controlled) situation I have been custom setting my WB (using an 18%gray card) on my camera before taking the shots of the object and colorchecker, so I imagine that should take care of that problem. However, in natural settings I am unable to custom set the WB before hand, so depending on the cloud cover, etc. I would use the most appropriate WB setting? As I said earlier, I am interested in measuring hue, saturation and lightness of an object as it would be in reality.

 

One last question: Wouldn't a "shift in color space" caused by an inappropriate WB result in inaccurate meausres of hue, saturation and lightness?

 

Thanks again, this has been immensely helpful!

[chrispy]

Hi Giampi, you said:

 

"I STRONGLY advice everyone NOT to use RAW as a crutch for exposure and/or white balance"

 

When shoting in RAW, other than placing gels over your flash, the only place the white balance setting gets used is the default setting in your raw converter, what other decisions do you need to make in regard to white balance?

 

Would the white balance setting also affect how the flash meters during the shot?