Confused about RAW, WB and 18% Grey card

[herb_sims]

Guys and Gals,

The more I read about RAW, CS2 and WB the more confused I get. My question is this:

I have a 18% grey card. The grey card is in the first photo that I take for any given lighting situation. I take all the photos of interest (in the same lighting conditions), then go to CS2/Bridge. I then use Bridge to bring up the first photo. Now here is where I get confused: Where/How do I tell Bridge that I am using the 18% grey card (using the eyedropper I would assume) and to color correct to the 18% grey?

Thanks,

Herb

[jimsolt]

Guys and Gals,

The more I read about RAW, CS2 and WB the more confused I get. My question is this:

I have a 18% grey card. The grey card is in the first photo that I take for any given lighting situation. I take all the photos of interest (in the same lighting conditions), then go to CS2/Bridge. I then use Bridge to bring up the first photo. Now here is where I get confused: Where/How do I tell Bridge that I am using the 18% grey card (using the eyedropper I would assume) and to color correct to the 18% grey?

Thanks,

Herb

First when you are shooting this card in RAW, you can just have it as PART of the scene . . . you can just prop it up, ask someone to hold it . . . it doesn't have to fill the screen as in setting a custom white balance. It's just an extra shot to help you out.

When you click the eye dropper on the card, it adjusts the white balance . . . BUT . . .

Lets start from scratch. White Balance tells the digital camera the color temperature of the light that is illuminating the scene. Based on that "knowledge" the camera adjusts for proper color rendering. You can use one of the preset white balances including automatic though when shooting RAW that doesn't do much to help you out. It shows up as the original "suggestion" for white balance in the "as shot" box. It is possible to modify the "as shot" settings to reflect which of your many cameras you are using that day, but that gets complicated.

In shooting jpeg if you don't wish to use one of the preset White Balances, you must do a custom white balance -- shooting a white or 18% gray card and following your camera's instructions to set a custom balance. It must be done in advance of the shots taken in that light. After that is set, the card shot does nothing. That's the only way it works.

In shooting RAW you may shoot a white or gray card in the same light as the subject at any time in the shooting sequence -- first, last, in the middle. Then when adjusting the RAW image prior to conversion you can use the eyedropper on that card and apply the result to all the images shot in that light OR just the one image -- your choice. You could in fact use any white or gray object in the picture to do the same though the chances of the card being more appropriate are pretty good.

It really does NOT color correct to the 18% gray. It tells the camera the color temperature of the light falling on the scene. I think of color correction as pertaining more to other adjustments.

Unfortunately (for those trying to understand it) the same gray card can be used for setting exposures, but this is a different proposition and should not be confused with white balance.

If you come from a film background, White Balance is the digital equivalent of changing from daylight to tungsten film or using filters to achieve the same effect.

Does this help?

Jim