Some white balance and color questions from colorblind newbie.

I'm red-green colorblind so I have to really rely on the camera to handle getting the colors right since any color-changing post processing I do would likely make a mess of things. What looks great to me can be quite, well, odd would be a generous way of putting it. This makes wb settings pretty critical. Plus I have a powershot a620, which does not provide raw format images, which I gather would give me more leeway for post processing (if I were up to it, that is).

I have read about using neutral gray cards for setting the custom wb. I also encountered mention somewhere of just using a white sheet of paper. Since I don't have a neutral gray card, is the white paper a reasonable approach? I'll get a gray card when I can if it is necessary, but already always have the white paper in my notebook with me.

I ask this next one with the goal of getting proper prints regardless of having just a cheap and old monitor combined with poor color vision. Please keep that in mind since I may be asking the wrong question:
Is there a way to include a reference card in photos, or better yet, in a separate photo under the same lighting conditions, and use it to adjust colors (not just wb)? I'm looking for something that doesn't require expensive monitor calibration tools that can handle it in some manner that takes the "hmmm, those two colors LOOK the same to me" part out since I fail that test. I can always grab the color values and compare that way I guess, but I don't know how to approach the problem.

How do auto WB vs custom WB work? I would think auto took some sort of measurement of the scene and performed a best guess, but seems it must do so at the time the picture is taken since it doesn't fire the flash (if set to fire). Custom does fire the flash (if it is set to fire) when setting the WB. Any suggestions on when to choose each one, or when to use one of the pre-set, like tungsten? I know I'd use tungsten under tungsten light, etc. but is custom likely to give better results for any situation (if given a proper reference like a gray card, or white if that works as well)?

One more: exposure compensation adjustment in various modes... what does it adjust? There is shutter speed, aperture and ISO that can be adjusted, but I'm not clear which this actually adjusts.

Long questions, sorry, but this will really help - Thanks!

As far as white balance, it depends on how anal you want to be about it. White paper or fabric will usually get you close enough, unless there's some reason you need pinpoint accuracy. The main thing to be careful of is to not overexpose the target. Fill the majority of the viewfinder with the white target so the camera's metering system exposes it to gray.

There are reference targets available, but I don't see a need for one in your case, nor do I think it would help. But I may be misunderstanding your question.

Auto WB is the camera's best guess. Most cameras can guess fairly close outdoors and do a rather poor job indoors. I do suggest you use a custom WB whenever you can. If you can't do a custom WB, one of the presets (sun, cloudy, shade, tungsten, etc.) might work better than auto WB.

As for exposure compensation: In Av mode the camera will adjust the shutter speed. In Tv mode it will adjust the aperture, and in P mode it may depend on the conditions. The camera is programed to behave different ways in different lighting.

Curtis has (as always) given a very good answer. Here's my £0.02 to add: I don't think it necessarily matters if you're colour-blind when it comes to getting the WB right. What you need is a software app that allows you to use an "eye-dropper" tool to select an area that you want to be a neutral colour (i.e. pure white, or grey, but with no colour). Then just select an appropriate point on your image and hey presto you've got the WB right. If you're taking a lot of photos under the same lighting conditions, then you could take a picture of a white or grey card, get the WB adjustment from that, and apply it to all the photos in the set. How easy that is depends on what software you use (and I'm not an expert on the pros and cons of different packages).

Gray Card…White Paper. What’s best?

Best if (1) it's really white, not yellow-white or blue-white, & (2) it doesn't have little blue lines running through it.

IMO, Auto doesn't work so well. You may not be able to see the differences here: Gray card: Why your meter may be lying to you!

In PS you could use an Adjustment Layer to correct the "separate photo under the same lighting conditions". Then just drag that layer into the next pic that you need to correct.

Sorry this is so long, but I'm trying to get my head to work...

No RAW option cause I have an A620 I gather this means I have to do a better job taking the picture since I have much less leeway in PP.

Curtis N wrote in post #2168876
.Fill the majority of the viewfinder with the white target so the camera's metering system exposes it to gray.

There are reference targets available, but I don't see a need for one in your case, nor do I think it would help. But I may be misunderstanding your question.

Ah, never would have thought to expose the custom WB "picture" so the white paper is gray. You are not misunderstanding my question, and are no doubt right about it being good enough for my purposes. I want to be reasonably sure that the colors are decent, which is hard due to my vision. I don't need perfection, just don't want my dog to be green. Ok, maybe a little better than that... should say I don't want people to see my photos then turn to me and say "Are you colorblind?" but rather "Wow, cool photo!" (WB is far from my only hangup, of course, but it is a low hanging fruit in a tree full of fruit).

StewartR wrote in post #2171280
What you need is a software app that allows you to use an "eye-dropper" tool to select an area that you want to be a neutral colour (i.e. pure white, or grey, but with no colour). Then just select an appropriate point on your image and hey presto you've got the WB right.

Got it, sorta...
I have gimp, but currently don't have photoshop. Just not sure what to do with the eye-dropper selection to set the balance in the picture. Can you give me a hint how it is done in PS (or gimp or any other) so I have an idea what to look for? PhotoGuy's post after yours seems to cover how to apply the results to other pictures taken under same lighting - combining those two (if PhotoGuy's can be done in gimp)... just what I need. I'll go play around and see if I can figure it out in gimp, as well as hunt down a gimp forum (bet I'll need that as much as I need POTN!)

PhotosGuy wrote in post #2171717
Gray Card…White Paper. What’s best?

What a great resource! I need to reread it before really groking it but it was a good start. I'm not clear on the chimping concept... It was summed up in another thread (which refered to that one) as, to paraphrase:

"It is unlikely that any highlights (other than chrome or such) will be brighter than the white paper, so by adjusting the exposure so it is just left of the right edge you make the most use of the sensor while not blowing the highlights."

Does that capture it ok? Is that what chimping means??

Now, I think I was confused by the separate but mingled (?) issues here involving the white card: WB and exposure level. The chimping (if I understood) is for exposure. You actually want it to look gray when doing the custom WB, two seperate steps? Best reread it I guess.

I don't see that in gimp, which does do things differently at times (of course). I'll have to post somewhere to ask about that cause that would be perfect.

Again, y'all are great!

chimping is checking your photos in the camera via the screen on the back after you have taken your photo. real chimping is when you go ooooh ahhhh when you are viewing it. hence making you sound like a monkey. hence chipping. no ever says they that do it of course

not to sure about your camera tho but some have a histogram which you can use to get a photo just right.

how colour blind are you. I am also slightly red-green colour blind, but I trust myself to see the colours right. I just can't name them correctly.

Yes. If you take a reading of just the white paper for WB, it will/should come out gray in the pic. To set exposure, you need to change the settings so it hits the right of the histogram.

There's a good one, as well as a LOT of .doc & tutorials that you can download.

That from a guy in CA!