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02-18-2018, 04:03 PM   #1
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gray card

I am enjoying my new KP. I am curious about use of a gray card or other methods of setting up the camera for accomplishing the same thing. What is the best way to set up the camera for using a gray card? Any tips on setting custom white balance and adjusting temperature settings?
As I understand it the card is meant to help with color rendering not simply exposure but any further clarification would be appreciated. Is it an accurate statement that a light meter or the camera's meter only detects light generally, not the coolness or warmth of the light?
I have not found a good tutorial on the forum but I certainly could have overlooked it. One you tube video I found somewhat helpful described simply taking a picture of the card and locking the exposure or setting the camera manually to the exposure settings shown on the camera display but it does not identify the setting to use when taking the picture. Should that matter?
What about using a light meter with the card? We are metering with the camera after all correct? Again, metering is about light not necessarily color.
What about the green button?
So much to learn.
Thanks for any help.

02-18-2018, 04:24 PM - 1 Like   #2
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QuoteOriginally posted by A H Thompson Quote
What about the green button?
Read the manual. In general not needed but in some cases very useful particularly with all manual vintage lenses
QuoteOriginally posted by A H Thompson Quote
We are metering with the camera after all correct?
Correct. A hand held light meter is rarely needed for general photography. I have used one in the studio for setting up lighting but otherwise not something you need.
QuoteOriginally posted by A H Thompson Quote
I am curious about use of a gray card or other methods of setting up the camera for accomplishing the same thing.
99% of the time for general photography the camera's automatic white balance will be good. However if you are in challenging lighting conditions they can be handy. I always shoot in RAW so if I suspect the camera's white balance is not going to be accurate I'll snap a few shots of my gray card for reference. I have never used it to set a specific WB in the camera. If you are shooting jpegs that might be needed on occasion but with RAW and a reference shot I can set all images to the correct WB on the computer.

But if you are just starting out, not something to be concerned about. Yet. Many other things to learn that will make a bigger difference in your results at first. Just my opinion.
02-18-2018, 04:50 PM - 1 Like   #3
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QuoteOriginally posted by A H Thompson Quote
Is it an accurate statement that a light meter or the camera's meter only detects light generally, not the coolness or warmth of the light? .
The light meter does measure light in the red, green, and blue channels and thus could compute the coolness or warmth of the light that it sees. But the meter, by itself, does not know whether that measured color is due to the object in view or the light source.

For example, a white room lit by a cool light source would look identical to a pinkish-orange room lit by a warmer light source. And as far as exposure goes, the meter can't tell if it's looking at a white room with a dim light or a black-painted room with a bright light.

The point of using the gray card is to have something with known reflectance and known color-balance. Metering off a gray card (and setting white balance off a gray card) ensures the camera knows the true brightness and color of the light source and is not fooled by the color or darkness of the painted room or objects when estimating exposure & white balance.
02-18-2018, 10:15 PM   #4
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QuoteOriginally posted by photoptimist Quote
The light meter does measure light in the red, green, and blue channels and thus could compute the coolness or warmth of the light that it sees. But the meter, by itself, does not know whether that measured color is due to the object in view or the light source.

For example, a white room lit by a cool light source would look identical to a pinkish-orange room lit by a warmer light source. And as far as exposure goes, the meter can't tell if it's looking at a white room with a dim light or a black-painted room with a bright light.

The point of using the gray card is to have something with known reflectance and known color-balance. Metering off a gray card (and setting white balance off a gray card) ensures the camera knows the true brightness and color of the light source and is not fooled by the color or darkness of the painted room or objects when estimating exposure & white balance.
I think he is also asking what to do with the gray card shots when you have them, I hear people say, "use the dropper" and things like that but I would like to know the proper way to do so. With my house being lit by LED bulbs I have spectral peaks that do not follow a curve to get their rated K rating. I use mostly 5000K but have some warmer white at 3200K and even a few 2700K mixed in. It confuses my K-50 so I just shoot Daylight most of the time and adjust in DXO. Cards and droppers....Help a fellow out. You are tech savvy so maybe you should write a "How To" article for the forums.

02-19-2018, 04:55 AM   #5
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Thanks for your comment SSSGGeezer. Additionally, the KP is reported to excel in jpeg and I would prefer to take full advantage of its capabilities and not use RAW editing at all if possible.
02-19-2018, 08:43 AM - 1 Like   #6
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QuoteOriginally posted by SSGGeezer Quote
I hear people say, "use the dropper" and things like that but I would like to know the proper way to do so.
I've no idea about 'proper' but this is what I do:
1) I only shoot RAW
2) During a shoot I snap a few shots of the gray card while it is reflecting the same light as the subject. Don't hold it up close and shade the light with your body, it has to be reflecting the light as the subject sees it.
3) In Lightroom develop module, select the gray card image and in the basic panel use the eyedropper to pick the gray card. Check the results. Sometimes a different spot on the gray card will end up with a different result. Depends on how the light hits it. Find a result you like.
4) Now select all images from that shoot and 'sync', select only the color temp (white balance) unless you know that all other settings are the same.
5) All images should now have the same, corrected WB

Notes:
1) You can also select all images in the develop module and use the 'autosync' function if you prefer
2) If you do not have a gray card or forget often you can find something with a neutral gray in the image that will work almost as good in a pinch
02-19-2018, 11:45 AM   #7
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QuoteOriginally posted by jatrax Quote
I've no idea about 'proper' but this is what I do:
1) I only shoot RAW
2) During a shoot I snap a few shots of the gray card while it is reflecting the same light as the subject. Don't hold it up close and shade the light with your body, it has to be reflecting the light as the subject sees it.
3) In Lightroom develop module, select the gray card image and in the basic panel use the eyedropper to pick the gray card. Check the results. Sometimes a different spot on the gray card will end up with a different result. Depends on how the light hits it. Find a result you like.
4) Now select all images from that shoot and 'sync', select only the color temp (white balance) unless you know that all other settings are the same.
5) All images should now have the same, corrected WB

Notes:
1) You can also select all images in the develop module and use the 'autosync' function if you prefer
2) If you do not have a gray card or forget often you can find something with a neutral gray in the image that will work almost as good in a pinch
Thanks for the response,
Since I am not an Adobe user, and have been staying in DXO with forays into Darktable and Raw Therapee, I figure that there is similar functionality in those PP software programs. Or if not, I can look and see what I have as a K value and use that for the remainder of the series of images taken at that time.

I need to dig and practice for accuracy rather than what I feel looks best. Then I can go for what I think would look best.
02-19-2018, 01:01 PM - 1 Like   #8
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Gray card articles tend to be too abstract. Following article illustrates quite beautifully using simple language. You can start from the paragraph ""All in-camera light meters have a fundamental flaw: ....."
Understanding Camera Metering and Exposure


Additionally see this picture from Wikipedia
Gray card - Wikipedia
Gray card - Wikipedia picture

02-19-2018, 04:19 PM   #9
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QuoteOriginally posted by SSGGeezer Quote
I need to dig and practice for accuracy rather than what I feel looks best. Then I can go for what I think would look best.
If your monitor is calibrated what you feel looks best, is best. I only use Lightroom, no time to learn something else, but I feel confident there is a similar functionality in most software. It is pretty basic. What I really appreciate about Lightroom is the quick ability to sync something over hundreds of images, like a new WB setting. Maybe the others have that as well I've never checked, but for my workflow that one feature says me hours of processing.
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