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FORUMS Post Processing, Marketing & Presenting Photos The Business of Photography 
Thread started 13 Apr 2006 (Thursday) 10:08
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How to ensure WB on RAW Post-processing is spot on?

 
Benji
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Apr 21, 2006 09:47 |  #16

For studio work my lab sells a 'Zebra Card' that you place into the first image and shoot it then when you bring the images up in Adobe Bridge you can click balance for perfect whites, blacks and very accurate color balance. It is black and white striped with an 18% gray strip right down the middle.

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DesignVHL
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Apr 21, 2006 09:50 |  #17

that sounds very conventional! Is this accurate though? Or will it throw the balance off? I thought you had to have solid block of color....wouldn't any reflecting light throw it off? Just a thought....but if this works, I might consider getting one of these! Would this work in the field - say concert photography? Would it be worth my time to put the card up on stage and shoot it for correct WB balance?


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Benji
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Apr 21, 2006 14:54 |  #18

You need an 18% grey card for white balance. You can't use a 'white' anything because what is white (actually I guess you could use a piece of photographic ink jet paper, I never thought of that!) Is a wedding dress white? Yes. but so is snow, clouds, typing paper, toilet paper, most ceilings, T shirts and the list could go on and on, but there is only one 18% grey card. Someone makes a plastic one that has no sheen like the Kodak 18% cardboard cards have so you don't have to worry about reflections.

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DesignVHL
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Apr 21, 2006 15:04 |  #19

thanks benji...makes perfect sense! :) I didn't know that most cards had a sheen to them...I thought they were made of cardboard (or some paper type matte material)...at least for the companies I've worked for IME I've never seen a shiny grey card...seems stupid...lol

Would it be helpful for me (shooting raw) to bring one of these for concert photography? Take a shot or two up on the stage - say during sound/lighting check? Or is that pointless?


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Benji
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Apr 21, 2006 15:50 |  #20

Yes I believe it would as it would tell the camera what is 'white' according to the light source on the stage (which I assume is a mixture of tungsten and colored lights with some carbon arc thrown in for good measure.

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PhotosGuy
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Apr 21, 2006 19:13 |  #21

You need an 18% grey card for white balance. You can't use a 'white' anything because ...

Sorry Benji, not true. White contains all colors, just as gray does. Underexposed white = gray.
Gray Card…White Paper. What’s best?


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4jallday
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Apr 22, 2006 07:26 |  #22

I shoot raw but and have a grey card. My question is if I take a shot of my grey card and use it as my custom wb setting will it work with raw or is that just for jpg?


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PhotosGuy
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Apr 22, 2006 08:44 |  #23

It will work for both.

In this cases I would select the white picker and click on the white dress. In many cases when I do this I tend to mess up other colors. Or atleast that is what I think is happening.

You could make 2 conversions, one for the dress & one for the rest. Then blend them with a layer mask. It takes less time to do it than it does to tell you about it.

This is blending exposures, but the proceedure is the same when it comes to using a layer mask to show/hide changes.
Make 2 exposures in RAW conversion.
1 is "normal".
2 is dark to hold the highlights. (Or you could make it a lighter conversion to hold the shadows.)

Open 1, then Shift-drag 2 on top of it. (Shift-drag keeps everything registered.)
Layer>Add Layer Mask / Hide All. (Layer Masks allow you to make non-destructive, reversable, changes)

As long as the mask has a double line around it (may have to click on it to get one) you can use a light colored brush to paint on the pic which removes the mask effect from the 2 layer. I might start with white @ 40% opacity.
Layer masks are non-destructive. If you make a mistake, just paint over it with a dark brush.
NOTE: all Layer> Adjustment Layers have a built in mask, & this works just great with them, too.

There's an example in post #6 here. Look for more info in the processing stickys. ;)

...my question is this: I shoot concerts. Say I bring a white (or grey) card w/ me and put it up on stage and shoot it a few times (Wouldn't the lighting change the cards white balance use -adding color)?

Good luck with that! You're going to have to guess. Maybe start out with the custom Tungsten setting, & then post-process. Keep in mind that the correct WB isn't always the right WB for any shot. You get to make it look good to you.


FrankC - 20D, RAW, Manual everything...
Classic Carz, Racing, Air Show, Flowers.
Find the light... A few Car Lighting Tips, and MOVE YOUR FEET!
Have you thought about making your own book? // Need an exposure crutch?
New Image Size Limits: Image must not exceed 1600 pixels on any side.

  
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Benji
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Apr 22, 2006 09:09 as a reply to  @ PhotosGuy's post |  #24

PhotosGuy wrote:
Sorry Benji, not true. White contains all colors, just as gray does. Underexposed white = gray.
Gray Card…White Paper. What’s best?

I guess my lab and their digital experts need to update their information as they said to use a grey card.

Benji




  
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PhotosGuy
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Apr 22, 2006 09:16 |  #25

There's nothing wrong with using a gray card. My issue is with your comment "You can't use a 'white' anything because ..." Properly exposed white will work just as well. Did you even look at the link I posted?

EDIT: Possible confusion over what "Properly" means in this case. See post #29 below.


FrankC - 20D, RAW, Manual everything...
Classic Carz, Racing, Air Show, Flowers.
Find the light... A few Car Lighting Tips, and MOVE YOUR FEET!
Have you thought about making your own book? // Need an exposure crutch?
New Image Size Limits: Image must not exceed 1600 pixels on any side.

  
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Curtis ­ N
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Apr 22, 2006 09:59 as a reply to  @ DesignVHL's post |  #26

DesignVHL wrote:
Would it be helpful for me (shooting raw) to bring one of these for concert photography? Take a shot or two up on the stage - say during sound/lighting check? Or is that pointless?

If you could get the lighting guy to remove all the gels from all the lights, and turn them all on 100% so you can shoot your grey card, well, maybe. Good luck. ;) Lighting technicians usually have more important things to do.

The whole point of white balance is to give the camera or RAW conversion software the information it needs to approximate the adjustment that our brain makes automatically when we view a scene under a certain light source.

But the software was not designed to work in the conditions created by color gels used in concert & theatre photography. It's a bit pointless to try to get the correct white balance when the light isn't white to begin with. Additionally, different elements used on the stage will create different color temperatures, even without gels, and the color temp will vary as they are dimmed. So the effect will depend on which elements are used, at which power setting, at the moment the shot is taken.

Whenever I'm shooting under stage lighting, I just set the camera to tungsten and concentrate on other things. The colors you get in your pictures will never seem quite the same as when you saw it in person. If you want to make adjustments later with your RAW converter, that's fine, too.


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DesignVHL
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Apr 22, 2006 13:23 |  #27

Good thing I DO know the lighting guy for this one particluar band and he would totally do that for me...

:)

HOWEVER your points about the lighting are spot on, and I could see why it would be pointless...


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valerie
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Canon EOS 350D / Digital Rebel XT
EF 28-135mm f/3.5-5.6 IS USM
EF 50mm f/1.4 USM
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---------------
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jc1350
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Apr 25, 2006 12:11 as a reply to  @ DesignVHL's post |  #28

I'm considering buying the WhiBal (until now I've been using my brain to guess the WB in PP).

I have read that cameras today actually meter for a 12% gray. Is that why there are 2 shades of gray with WhiBal? When should I use which? With the newer model of WhiBal (the G6) - there's only one card, so are my questions moot?


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PhotosGuy
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Apr 25, 2006 12:53 |  #29

I may have thrown you off by saying, "Properly exposed white will work just as well."
In THIS case, "Properly exposed" means to meter the paper & shoot AT the meter reading. That will result in a somewhat gray image which is what the cam needs to calculate WB. It would also work for WB in PS or RAW software, but not for exposure at that setting. (But you could use it as a starting point & open up a few stops after taking the WB shot.

there's only one card, so are my questions moot?

As far as the software is concerned, there's no difference between 12%, 18%, or even 50% gray. It looks at the relative RGB values & tries to make them equal.


FrankC - 20D, RAW, Manual everything...
Classic Carz, Racing, Air Show, Flowers.
Find the light... A few Car Lighting Tips, and MOVE YOUR FEET!
Have you thought about making your own book? // Need an exposure crutch?
New Image Size Limits: Image must not exceed 1600 pixels on any side.

  
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jc1350
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Apr 25, 2006 17:56 as a reply to  @ PhotosGuy's post |  #30

You weren't the first. The manual states that about CWB and, not really using it, never learned if they meant "proper exposre" according to the meter or according to what should produce a white color. Thanks for the clarification.


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How to ensure WB on RAW Post-processing is spot on?
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