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FORUMS General Gear Talk Flash and Studio Lighting
Thread started 03 Oct 2009 (Saturday) 21:52
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Gray card? what are they used for?

 
Muskydave22
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Oct 03, 2009 21:52 |  #1

I have been reading a lot of posts around here and people advising to use gray cards to get white balance correct? what exactly is a gray card and how does one use one? A little confused, is this something you purchase?

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jeromego
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Oct 03, 2009 22:51 |  #2

a gray card is 18% gray. Scroll down to the bottom and you'll find more topic about this.


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TMR ­ Design
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Oct 03, 2009 22:57 as a reply to jeromego's post |  #3

A gray card is used to set a custom white balance. Any source used for white balance (gray card, WhiBal, ExpoDisc, etc.) is completely neutral in that it has even amounts of red, green and blue. If you were to look at an RGB histogram showing the spike you would have perfect alignment of all three channels. If white balance is not set correctly you'd see the individual channel spikes out of alignment.


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Oct 04, 2009 00:26 as a reply to TMR Design's post |  #4

I'm no expert, having just learned it. But I'm puzzled by your claim that after you read so much you still couldn't find the answer. Are you after some issue other than just how to use a gray card, or why people use a gray card?

If not, maybe you can go to Youtube and search for a video on how to use a gray card. There are plenty. PhotoVision has some, too. It may be easier to learn by video than by reading.



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Muskydave22
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Oct 04, 2009 00:33 |  #5

i guess my main reason what what makes a gray card gray... i figured that out. Also, do you always need to use one of these? why not just let camera settle on Auto WB? or shoot Raw and fix later?

dave


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ByTheBrooke
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Oct 04, 2009 01:13 |  #6

I suppose that's true, but isn't the goal to achieve perfection straight off the camera? To need no or little post processing? That's what has always been "beaten" into me.

I will admit that I'd heard about a gray card back when I started courses through NYIP about a year ago (which I never finished) but never knew what it was. Now I think I should learn to use it :)


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alphonsis
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Oct 04, 2009 03:01 |  #7

The one thing that confused me for a while is that there are two types of gray cards. One for exposure and one for white balance.

Walking into my local photography store and asking for a "gray card" got me a mix of both types.

unless of course, I'm still confused, in which case someone should correct me. ^_^


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colormaniac
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Oct 04, 2009 11:10 as a reply to alphonsis's post |  #8

In reply to some of the questions, as far as I know,

1. using a gray card can reliably determine the white balance. Checking it on the screen is not reliable.

2. but then, of course, it depends whether you need to get THE right white balance. (The right one isn't always the one that pleases your eyes most.) That's why some people think it's important and some people don't.

3. the same gray card can be used to set the white balance and brightness. At least, this is what I found many experts suppose in their discussion here, and I successfully do both of them with the same gray card.



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Oct 04, 2009 12:42 |  #9

Grey Card who uses one and which one ??


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wyofizz
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Oct 04, 2009 12:54 |  #10

Muskydave22 wrote in post #8756407external link
i guess my main reason what what makes a gray card gray... i figured that out. Also, do you always need to use one of these? why not just let camera settle on Auto WB? or shoot Raw and fix later?

dave

I always use one when shooting indoors.
My experience is that AWB doesn't work that great inside.
Fix later: Sometimes easier said then done and achieve exact colors.
(However I'm no PS expert)

Dave


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Oct 04, 2009 15:58 |  #11

1. Some gray cards are for setting WB only, as they are not 18% tonality and therefore not suitable for a reflected light reading for setting exposure.
2. Some 18% gray cards are for setting exposure only, as they are not neutral in R-G-B balance and therefore would lead to falsely balanced photos for WB
3. Some gray cards are tonally balanced (same value for R-G-B) and also 18% tonality, so can be used for both exposure and WB setting.
4. You can take a shot with a gray card filling the viewfinder, and set Custom WB in the camera to shoot photos with correct WB setting. This is particularly the better way when shooting in-camera JPG files only, or...
5. You can shoot a shot with gray card in the scene and later use that during PP to set the correct WB setting. This works fine when processing RAW files in RAW convertors, or shoot in camera WB photos (a superfluous activity if shooting RAW and using a RAW convertors with easy batch processing tools, but a reasonable technique to use with captured JPG)


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Gray card? what are they used for?
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