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Author Topic: What is the Kelvin white balance adjustment for  (Read 3042 times)

sunshine1234

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What is the Kelvin white balance adjustment for
« on: January 05, 2014, 02:39:01 pm »

In the menu of my Canon 5D Mark II there is a way of adjusting white balance in 100 degree Kelvin increments. What does this actually do and what are some of it's applications?
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Jim Kasson

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Re: What is the Kelvin white balance adjustment for
« Reply #1 on: January 05, 2014, 03:10:06 pm »

In the menu of my Canon 5D Mark II there is a way of adjusting white balance in 100 degree Kelvin increments. What does this actually do and what are some of its applications?

I'm assuming that you're shooting raw. If not, tell me, and I'll give you a different answer.

Setting the WB in the camera does not affect the raw image data, but does affect what's written into some fields in the metadata. That information is used by the raw processor, when it's in "as shot" WB mode, to set the white balance for the image. If the white balance is set manually the raw processor ignores the metadata that specifies the WB.

So what's in-camera Kelvin WB good for? If you have a color temperature incident exposure meter, you can take a reading of the light falling on your subject and enter the information into the camera's WB settings. Then the camera will pass that information to the raw processor via the metadata. Those meters were common in studio settings in the film era when they were used to find the right color-balancing filter pack, but aren't used much these days, when it's so easy to include a grey card in the first shot, white balance to it in the raw processor, and synch that WB to all the other images made with the same lighting. The advantage is reduced WB work in post.

You work with hundreds of images a day, the labor savings might be worth the expense of buying a color meter and the trouble of using it on the set. If you want to do that, I use and recommend the Sekonic PRODIGI C-500 Color Meter. It's not cheap, though. Also, since it's meant to pick the filter pack to give you the desired color temperature, using to find the color temperature of your source is a little convoluted. There may be meters that give you the illuminant color temperature (and offset from the black-body line, which I imagine that your camera might also accept -- if that means nothing to you, and you want to understand it, let me know; it's not exactly a simple discussion) more directly.

Jim

« Last Edit: January 05, 2014, 03:35:04 pm by Jim Kasson »
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Jim Kasson

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Re: What is the Kelvin white balance adjustment for
« Reply #2 on: January 05, 2014, 03:25:12 pm »

In the menu of my Canon 5D Mark II there is a way of adjusting white balance in 100 degree Kelvin increments. What does this actually do and what are some of it's applications?

OK, what the heck. I'll answer the question assuming you're shooting JPEGs. My first question would be "Why?" But I'll assume you have a good reason and press on. Unlike with raw, the camera's WB setting affects the data in the image file, and there is every reason to want to get this right in camera because of the limited bit-depth of JPEG files. You can do a better job than the camera's internal auto-WB algorithm by doing one of two things: you can auto-WB to a grey card or, even better, a light diffuser made for the purpose. Or you can take a reading with a color meter and enter the data into the camera. Either way will give you good results with spectrally-smooth light sources. With peaky light sources, the situation is murkier.

Jim
« Last Edit: January 05, 2014, 03:48:41 pm by Jim Kasson »
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stamper

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Re: What is the Kelvin white balance adjustment for
« Reply #3 on: January 06, 2014, 05:14:34 am »

It essentially colour balances for "accurate" rendering of an image. I put the word accurate in apostrophes because that is a subject that has been discussed endlessly. Personally I do it visually and sometimes not at all. You can - as Jim suggests - get into the fine detail and nitty gritty or make a personal visual assessment of an image in a "artistic" way and adjust to suit. If you show the final result to someone then they won't know - or care - what adjustments you made to make the original look like the final rendition.

sunshine1234

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Re: What is the Kelvin white balance adjustment for
« Reply #4 on: January 06, 2014, 07:44:16 am »

Thank you for weighing in on this topic.

I usually work with RAW files.

I've read the users manual on the topic, tried using the K feature in the field (thinking I might be missing something) and now I've read your very helpful comments; it sounds like I'd need a Colour Temperature meter to use it effectively.

It seems like the 'manual K' setting has limited use for me.

many thanks for your time
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stamper

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Re: What is the Kelvin white balance adjustment for
« Reply #5 on: January 06, 2014, 08:09:17 am »

Personally I wouldn't rush out and buy something like what you suggested. In thirteen years of shooting I have yet to see anybody using one. Concentrate on using your Raw converter to set WB.

JeanMichel

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Re: What is the Kelvin white balance adjustment for
« Reply #6 on: January 06, 2014, 09:23:21 am »

A simple solution is to use a device such as the ColorChecker Passport. I find that most useful. I think that there may be even a report or review on this site about it.
Jean-Michel
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digitaldog

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Re: What is the Kelvin white balance adjustment for
« Reply #7 on: January 06, 2014, 10:49:15 am »

I usually work with RAW files.
Then as Jim stated, it does pretty much nothing at all (nothing useful). The values are used on the back of the LCD to show you what a JPEG would look like with said settings. But the settings have no effect on the raw data. You can set any WB you please and the raw data isn't affected. It's a suggestion.

Lastly, CCT Kelvin values define a range of colors. So futzing around with a 100K setting seems rather pointless certainly if raw data is involved.

The Passport is a slick tool for WB and building DNG camera profiles if that need arises.
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Raw shooter

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Re: What is the Kelvin white balance adjustment for
« Reply #8 on: January 06, 2014, 12:26:45 pm »

Then as Jim stated, it does pretty much nothing at all (nothing useful). The values are used on the back of the LCD to show you what a JPEG would look like with said settings. But the settings have no effect on the raw data. You can set any WB you please and the raw data isn't affected. It's a suggestion.

Lastly, CCT Kelvin values define a range of colors. So futzing around with a 100K setting seems rather pointless certainly if raw data is involved.

The Passport is a slick tool for WB and building DNG camera profiles if that need arises.

The truth. Always listen to digitaldog on these subjects.
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