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01-23-2011, 06:37 PM   #1
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Using gray card for WB on K-x

I'm just not getting this. I'm pretty sure I understand the theory behind using the neutral grey to adjust the white balance setting to compensate for taking pictures where there are larger than usual very dark or very light areas. But when it comes to setting the needed WB on my K-x using a grey card, the operating manual is not helping me.

Once I'm in the White Balance screen, I select Manual. But on page 185 the manual tells me to use a white sheet of paper, NOT a grey card. Surely it's not a matter of either/or. Am I getting mixed up between two different procedures?

And once someone points out what is probably as plain as the nose on my face, maybe you can also tell me what I'm supposed to do on the K-x to keep that WB setting for the rest of the shoot.

Thanks

01-23-2011, 07:17 PM   #2
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WB is not about large parts being light or dark. It's about the color cast of the light.

You can use a piece of white paper (some have a bluish tint), or a gray card that has no color bias. It does not matter. Some people use a white coffee filter squished in or between filter rings (or just hold it around the lens).

I don't have the K-x but I think it will keep the setting until you turn it off. Or, go into the custom settings where it allows you to itemize the settings to save when powered off.

Last edited by SpecialK; 01-24-2011 at 06:31 PM.
01-23-2011, 09:27 PM   #3
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When you set the Manual WB (pg 184), it will stay there until you change it. Even if you go to a different WB (such as auto) and then go back to Manual WB.

I'm not seeing Anywhere, in the K-x manual, in the manual WB setting instructions where it says Not to use a gray card. As noted, White Paper may have tints, even those you do not perceive. As long as used in the same lighting you intend to shoot in, the gray card will give your camera a color-less, tint-less target. Just fill the frame with it when making your test shot per the instructions. Pick a non-shaded area of the card to set your WB from.

During a photo shoot of any sort, I'll sometimes drop a gray card in the first frame so I have a post processing target. I can then copy that WB to the rest of the photos done in the same lighting.

01-24-2011, 12:27 AM   #4
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QuoteOriginally posted by Yukoner777 Quote
I'm pretty sure I understand the theory behind using the neutral grey to adjust the white balance setting to compensate for taking pictures where there are larger than usual very dark or very light areas.
Not really sure what 'larger than usual' means, but you sort out the correct exposure for pictures that are darker or lighter than usual by using the histogram feature. Not sure how it works on the K-x, but on the K7 you press the replay button and then the Info button cycles through a variety of displays on the LCD including one with the histogram.

01-24-2011, 01:20 AM   #5
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QuoteOriginally posted by JeffJS Quote
I'm not seeing Anywhere, in the K-x manual, in the manual WB setting instructions where it says Not to use a gray card. As noted, White Paper may have tints, even those you do not perceive. As long as used in the same lighting you intend to shoot in, the gray card will give your camera a color-less, tint-less target. Just fill the frame with it when making your test shot per the instructions. Pick a non-shaded area of the card to set your WB from.
When I said, 'NOT', I just meant that the grey card wasn't mentioned; only the white sheet was mentioned.

So, you're saying I can use either white OR neutral grey to set the WB? Makes no difference which one? I thought that if I took a picture of something that is only white the camera would see it as neutral grey. Hmmm, I think maybe I'm getting mixed up between exposure compensation and color temperature.

Sorry for being so thick. Obviously I don't understand all this as much as I thought.
01-24-2011, 02:12 AM   #6
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QuoteOriginally posted by JeffJS Quote
When you set the Manual WB (pg 184), it will stay there until you change it. Even if you go to a different WB (such as auto) and then go back to Manual WB.

I'm not seeing Anywhere, in the K-x manual, in the manual WB setting instructions where it says Not to use a gray card. As noted, White Paper may have tints, even those you do not perceive. As long as used in the same lighting you intend to shoot in, the gray card will give your camera a color-less, tint-less target. Just fill the frame with it when making your test shot per the instructions. Pick a non-shaded area of the card to set your WB from.

During a photo shoot of any sort, I'll sometimes drop a gray card in the first frame so I have a post processing target. I can then copy that WB to the rest of the photos done in the same lighting.
Would you tell me how you do it Jeffs, I need to learn how to do it . Thanks in advance .
01-24-2011, 07:00 AM   #7
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QuoteOriginally posted by Yukoner777 Quote
When I said, 'NOT', I just meant that the grey card wasn't mentioned; only the white sheet was mentioned.

So, you're saying I can use either white OR neutral grey to set the WB? Makes no difference which one? I thought that if I took a picture of something that is only white the camera would see it as neutral grey. Hmmm, I think maybe I'm getting mixed up between exposure compensation and color temperature.

Sorry for being so thick. Obviously I don't understand all this as much as I thought.
You are confusing colur balance with exposure. You can use anything that's neutral (though black wouldn't work!) for colour balance, which affects how blue or red a picture is. Exposure that affects how bright the image is.

Color balance - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Exposure_(photography)

Wikipedia might be able to explain it better.
01-24-2011, 08:58 AM   #8
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QuoteOriginally posted by Ken T Quote
Would you tell me how you do it Jeffs, I need to learn how to do it . Thanks in advance .
See This for setting WB on a JPG.

The way I really prefer to do it though is with ACR using Adobe Bridge. See the Cloning section in my dust removal article.

https://www.pentaxforums.com/forums/pentax-dslr-camera-articles/121739-those-...ur-photos.html

The White balance is one of the settings you can copy to other photos.


QuoteOriginally posted by Yukoner777 Quote
When I said, 'NOT', I just meant that the grey card wasn't mentioned; only the white sheet was mentioned.

So, you're saying I can use either white OR neutral grey to set the WB? Makes no difference which one? I thought that if I took a picture of something that is only white the camera would see it as neutral grey. Hmmm, I think maybe I'm getting mixed up between exposure compensation and color temperature.

Sorry for being so thick. Obviously I don't understand all this as much as I thought.
The gray card will get you both your centered meter for exposure as well as your color balance.



01-24-2011, 10:01 AM   #9
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QuoteOriginally posted by JeffJS Quote
When you set the Manual WB (pg 184), it will stay there until you change it. Even if you go to a different WB (such as auto) and then go back to Manual WB.

I'm not seeing Anywhere, in the K-x manual, in the manual WB setting instructions where it says Not to use a gray card. As noted, White Paper may have tints, even those you do not perceive. As long as used in the same lighting you intend to shoot in, the gray card will give your camera a color-less, tint-less target. Just fill the frame with it when making your test shot per the instructions. Pick a non-shaded area of the card to set your WB from.

During a photo shoot of any sort, I'll sometimes drop a gray card in the first frame so I have a post processing target. I can then copy that WB to the rest of the photos done in the same lighting.


I try to make sure I shoot something slightly gray and use that as a clone point - set the WB in a test frame, and then copy it on to the other images. Jeff's method.

If, as sometimes happens, I forget to shoot a reference frame, I've had good luck with pushing vibrance all the way up, then finding something white in-frame. You will see when you push vibrance up that white objects turn yellow, magenta, blue or green. Then you adjust the white balance sliders till it looks white again. Drop the vibrance back down, and you'll be very close to correct white balance. These all only really work if you're shooting in RAW, though. If you're in JPEG you'll have to set it right in-camera.
01-24-2011, 10:06 AM   #10
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Much appreciated . Thanks a lot Jeffs .
01-24-2011, 03:16 PM   #11
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QuoteOriginally posted by JeffJS Quote
The gray card will get you both your centered meter for exposure as well as your color balance.

Now I remember hearing/reading about both those uses . . . I'll bet that was why I got my wires crossed. Thanks for clearing it up for me.

I managed to find some stiff, matte finish, near neutral grey paper for 45 cents a sheet and a big piece of foam core for $3 at Walmart, so I'm going to make a 12" x 12" grey card for home and a smaller one to put in my camera bag. A lot cheaper than buying them!
01-24-2011, 04:03 PM   #12
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QuoteOriginally posted by Yukoner777 Quote
Now I remember hearing/reading about both those uses . . . I'll bet that was why I got my wires crossed. Thanks for clearing it up for me.

I managed to find some stiff, matte finish, near neutral grey paper for 45 cents a sheet and a big piece of foam core for $3 at Walmart, so I'm going to make a 12" x 12" grey card for home and a smaller one to put in my camera bag. A lot cheaper than buying them!
It is probably close enough for government work. Have fun with it..

01-24-2011, 05:23 PM   #13
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Interestingly, the best material I have found for manual white balance setting is a Bounty paper towel. I distrust gray cards because the gray colour is dye, and it is prone to fading/oxidizing, and I just figure that if I am setting white balance, I should probably be using something that is white.
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