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10-10-2011, 11:23 AM   #1
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Purple Displays Blue

I took pictures over the weekend of a soccer team wearing purple uniforms. I used a K-7. These uniforms were a solid deep purple ... there was no mistaking the color for blue in any way. But, on the K-7 rear screen, the uniforms displayed blue. And, when I got the pictures home, they displayed blue on the screen. The blue wasn't even close to purple ...

What would cause such a descrepancy between the actual colors on the field and the color stored in the camera?

Note that the other colors on the field were reasonably fine ... the grass was an accurate green, and the other team wore gold/white uniforms, and those looked reasonably accurate too.

It was just the purple ... which as I said, displayed as blue.

Chuck

10-10-2011, 11:42 AM   #2
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Any chance of posting one of the offending images? That would help us make more than wild guesses.
10-10-2011, 01:14 PM   #3
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Hi

The white balance on Sun or Auto usually leans towards Blue, I always use either Cloudy or Shade when outside for a warmer color cast. This will give you Purple
and not Blue.
You can easily fix it with Picasa auto white or other similar programs.
I also have Olympus and Sony cameras and they all have the same problem.
Remember that when the cam adjusts for the white balance it is compromised because the scene is reflecting a lot of different colors.
If you really want the right white balance it has to be done pointing at the light SOURCE and not reflected light.
10-10-2011, 05:07 PM   #4
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Some colours just don't reproduce the same way we see them. This is especially true for man made fabrics and dyes.
This link will take you to an old Kodak publication from the film days that might shed some light on the subject for you.

http://www.kodak.com/global/en/professional/support/techPubs/e73/e73.pdf


Last edited by Wheatfield; 10-10-2011 at 06:22 PM.
10-10-2011, 06:14 PM   #5
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Assuming you took photo's in camera raw--look for a white or neutral grey area (e.g., the white in the other team's uniforms) to sample for your white balance. If there are no obvious white or grey areas look carefully at for example 100%--and you likely will find some. I am not saying white balance is the cause (purple is a problematic "fugitive" color), but it is hopefully the reason, and the first area to investigate.
10-10-2011, 10:09 PM   #6
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Posting Images

Thanks for the quick reply from all of you.

Here is one of the pics I mentioned:




You can see the purple uniforms appear sort of dark royal blue.

As a comparison, I found an image online that more represents the version of purple I was seeing that night with my eye, which you can see here:



Generally speaking, I'm pretty happy with the colors coming out of this camera. This is the first time I've been suprised at a color inaccuracy on this level.
10-11-2011, 06:31 AM   #7
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Your colour looks awful. Have you calibrated your screen recently?
I took your file and futzed around with the colour a bit. It isn't perfect, but it's better.
These were shot under either artificial light or else very late in the day?

10-11-2011, 06:51 AM   #8
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Thanks for the reply.

These were shot in a dark stadium at night under stadium lights.

cm
10-11-2011, 07:22 AM   #9
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No surprise you can't get the colour quite right then. Artificial light, especially those big stadium lights are often deficient in some parts of the spectrum. It makes it impossible to render some colours correctly.
10-11-2011, 10:01 AM   #10
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It's probably the artificial light in this case. You should be able to see a color temperature in the EXIF, which is the camera's choice. If you used RAW you can adjust and see if the purple gets better.

When I started using Photoshop CS5 with my K-7 files, I had something similar under daylight. Adobe's camera profile is much different than Pentax's for purples. In my case, the rear LCD color was accurate but the color would change in processing. The Pentax software showed something closer to the original color, so I switched camera profiles in ACR and was happy.
10-11-2011, 12:49 PM   #11
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You have to realize that color is a cmplex subject. An object that you think of as purple will look very different depending on what colr the light is. Our eyes and brain do the equvalent of an AWB adjustment to try to account for the color of the light and see colors as they would appear if the light were "pure white" (itself a pretty complex topic). But the eye and brain is much more sophisticated than the AWB system on a camera. Luckily, the camera gives you a couple of "outs" - manual WB, or shooting RAW and adjusting in PP. It may or may not be possible to fully correct the color when starting from JPEG if not shot with the proper WB. But whether you shot RAW or JPEG, he first thing to try is going into a PP application that offers a WB tool and setting the WB to make the white jerseys white. Many offer an "eyedropper" that can be used to select a white area, but don't select one of the blown out highlights. The picture is overexposed enough that it might not be possible to find a white area that contains enough color information to be useful, especially if you don't have a RAW file to start from, but try to find the an area of a white jersey that shows some detail.

Again, starting from JPEG, the camera may have already thrown away so much of he ed channel info as part of its attempt at doing WB that you won't be able to easily get it back to purple, but most PP packages would also offer a way to simply add more red to to the whole image, which should have more or less a similar effect - just not with the same degree of control.

Purple / violet (the terms aren't necessarily interchangeable) is a color that tends to expose these issues, and be hard to represent well even when the WB is nailed in camera, because it's a pretty weird color in terms of its actual wavelength distribution.
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