White Balance

[Leukeh]

One thing I never learnt how to use in my photography class in school is what white balance is and how to use it. I'll probably learn it next year at college but I'd rather not have to wait till then... so could somebody please write an in-depth "article" on white balance? I'm sure it'll be useful to a lot of other people, not just me...

[MLlanes]

heres an article that i found.
http://www.cambridgeincolour.com/tutorials/white-balance.htm

[purplerose]

Yepp, that article pretty much says it all.

However, rules are meant to be broken though. I like using white balance settings that aren't meant for my light source. I've turned some things green/blue or pink/purple by doing this.

So, learn the rules and then learn how to effectively break them. :)

[Leukeh]

Thanks for that guys! Really helpful. One thing I'd like to know now is how to actually change the white balance once it's on my computer in RAW format... Apparently Photoshop CS had a plug-in for Canon RAW format, CS2 came with it built in and I have CS3 so in theory it should work. I open up the photo, with a .cr2 file extension but it opens as a jpg... is this what's supposed to happen?

Once I get past that... where's the white balance function? I've been using Photoshop for years and never actually seen it... there's levels, colour balance and all that sort of stuff but no white balance. Changing any of those things won't get me any different results than if I shot in .jpg format... So yeah. Just wondering where to go from here. Also, does iPhoto have a white balance function hidden somewhere?

[carolupus]

I also have Photoshop CS3 and it works great. I just drag and drop the cr2 files into ps and the camera raw dialog box opens. white balance is right on the first page on top then.
adobe help says that it's a plugin, so maybe you don't have it or it's deactivated? check your preferences!
and maybe this site will help: http://livedocs.adobe.com/en_US/Photoshop/10.0/help.html?content=WSD040CF04-C176-4ecb-8A8E-155FBA26AA77.html

[Leukeh]

Oh ok cool - I opened it a different way before and it didn't work, but this did! Thanks.

One other thing... I've been told it's often better to shoot a tad over exposed because you can always darken an image. Underexposed images tend to go grainy when you brighten them so I guess that makes sense, but is it true? Obviously it can't be too over exposed.

Sorry for all the questions, I'm doing my first try at model photography in a "studio" on Saturday and really don't want to waste the opportunity...

[carolupus]

I've read that, too. Better a little overexposed than too dark. although it's also hard to darken highlights that are too bright, which happens especially if you use the built-in camera flash. but there's a function called 'recovery' in this camera raw dialog box, which seems to adjust that a bit.

model photography in a studio sounds great - have fun!

[purplerose]

Well, I was taught differently.

It's better to be slightly underexposed if figuring out exposure is going to be a pain. Overexposing causes you to lose detail in your highlights. It's better to brighten your highlights than to burn/darken them. Burning/darkening your highlights makes them stand out... a LOT.

Personally, I've only had grain show up if I was using a really high ISO or working with film.


Of course, the best option is getting proper exposure while shooting... ;)

[MacStian]

I recommend trying to hit the perfect exposure...

Overexp. images I have found to be harder to "save" than underexp though. Noise from brightened images I feel is kind of an outdated problem, todays CCD´s and CMOS are getting quite good, but shure.. too much either way will cause problems.

[Jabo]

What Leukeh has heard was probably Expose to the right, (http://www.luminous-landscape.com/tutorials/expose-right.shtml) which means "expose as bright as possible without loosing a lot of detail in the highlights".
This is not overexposing though, but "not quite overexposing".

In analog photography, brightening underexposed images was a better way to achieve good values in post processing (i.E. dark room).
This is because the chemicals on the film reacted differently than digital sensors and A/D-converters.

In digital photography, it's the other way around. The A/D-converter in the camera processes the image data from the top to the bottom,
beginning at the brightest parts. When you read the article above, it's clear what this means.

A 12 bit image is capable of recording 4,096 (2^12) discrete tonal values. One would think that therefore each F/Stop of the 5 stop range would be able to record some 850 (4096 / 5) of these steps. But, alas, this is not the case. The way that it really works is that the first (brightest) stop's worth of data contains 2048 of these steps — fully half of those available.

So, most detail in a digital image is in the brightest fifth of the histogram and from there downwards, the data amount is halved.
That's why noise appears in the darks first when you mess with the levels in Photoshop.
In the darkest parts, where shadows usually lie, only 384 levels of grey are available.
Compare that to the 2048 that live in the brightest f-stop and you know why it's important not to underexpose in digital photography.
It's not just noise (which could be outdated in a few years, right), but it's the amount of color/greyscale-information stored in the lower part of the histogram.
There's nothing to "push up" there, so saving the darker tones in a digital image is a lot harder to accomplish than saving the bright parts.