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02-11-2024, 05:59 AM   #1
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Pentax DSLR green colour cast

I've noticed that many of the Pentax DSLRs I've had, including the K3iii, tend to put a green colour cast on a lot of images. In defence of the colour science in the cameras, I think that the problem may be how my brain perceives the colours of a scene as opposed to how it is in reality. The photo I was just editing was taken after sunset (so there's a shift in natural light for a start) in an area surrounded by trees, so there is a lot of green light around. I think my brain is performing the equivalent of white balancing when viewing the scene at the time, so seeing a photo looking very green seems wrong. I'm curious what others think.

02-11-2024, 06:58 AM - 1 Like   #2
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What white balance setting(s) are you using?

You can check for actual color casts by including a white or (true) gray card/sheet of paper in a frame, and then looking at the color histogram for that part of your image in Photoshop or equivalent. If the white balance is correct, the RGB values should lie pretty much on top of each other. If there is a truly greenish cast, the green histogram will extend farther to the right trhan either red or blue.
02-11-2024, 07:09 AM   #3
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Could it be your monitor needs recalibration ?
02-11-2024, 07:11 AM   #4
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I watched a YouTube review comparing K3III, Canon 90D, and Nikon D500, and I believe the reviewer also commented on a green color shift from the Pentax. I havenít noticed it, but the only sample I have is a K50.

02-11-2024, 07:38 AM   #5
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I agree that our brain does lots of autocorrections....and a camera is more neutral, at least initially..
Except that you can influence a lot with whitebalance and modes (bright, natural, landscape, portrait, ....) : bright would up the colours, portrait is bit warmer and hence skintone friendly, landscape favors greens, ....etc....and there is a night or sunset mode on some models.
So maybe check your settings?
02-11-2024, 03:11 PM - 1 Like   #6
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It's not just Pentax cameras, but all cameras tend to display a greenish cast when there is a lot of green around like trees and grass. If you are sitting in the middle of a field of yellow tulips then the camera is going to display a yellow cast. The white balance in our eyes does a great job in neutralizing the cast, but cameras see things differently. One thing about the sensor in Pentax cameras is that they are very sensitive to color hues. You have to be very careful when you adjust the color hue in-camera. I once forgot to change the small adjustment I made from blueish cast to more yellow and all my pictures about 300 of them, came out too yellow the next time I used the camera.
02-11-2024, 03:36 PM   #7
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The WB question is probably critical. If it is set to AWB then the camera adjusts the WB to get an ideal image ... but as far as I know, nobody knows what that image is, colour histogram-wise. So what you get is what the camera sees, not what you see.
Colour issue - Page 2 - PentaxForums.com

When I used to shoot on film and get it processed & printed (as cheap as possible) by a machine at a local chemist, my dad (who used to work for Ilford Ltd) told me that the automatic print-machine assessed white balance on the basis that it was probably a family picnic on a lawn, so should contain a fair bit of green!

02-11-2024, 04:38 PM - 1 Like   #8
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QuoteOriginally posted by Andy58 Quote
The WB question is probably critical.
One of the first problems is what is the correct white balance?
If was to use a WB card, how I place that card in the scene there would be numerous WB readings you can obtain.
If you are going for accuracy for the temp of the light source then the WB for that source would only be correct for any white or color object that is perpendicular to that light source. Any object that is not perpendicular will have a color cast introduced from surrounding objects.
02-11-2024, 07:23 PM   #9
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With some Pentax DSLR models over time, I have noticed a tendency more for a magenta cast, more in reviewing test report shots- but not true in all models.
02-12-2024, 01:00 AM   #10
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QuoteOriginally posted by Ian Stuart Forsyth Quote
One of the first problems is what is the correct white balance?
If was to use a WB card, how I place that card in the scene there would be numerous WB readings you can obtain.
If you are going for accuracy for the temp of the light source then the WB for that source would only be correct for any white or color object that is perpendicular to that light source. Any object that is not perpendicular will have a color cast introduced from surrounding objects.
That's true, the camera can only deal with one WB. So (simplistic example) if you were taking a portrait of someone inside their house and lit by tungsten lamps, but looking out of a window at their sunlit garden, you would have to choose which WB to use. In post-processing, I guess you could divide the image into two areas and separately adjust their WBs.

More complex interactions of different light sources with different colour temperatures would be harder to deal with.
02-12-2024, 01:47 AM   #11
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QuoteOriginally posted by Andy58 Quote
That's true, the camera can only deal with one WB. So (simplistic example) if you were taking a portrait of someone inside their house and lit by tungsten lamps, but looking out of a window at their sunlit garden, you would have to choose which WB to use. In post-processing, I guess you could divide the image into two areas and separately adjust their WBs.

More complex interactions of different light sources with different colour temperatures would be harder to deal with.
Actually a couple of Pentaxes can produce JPEGs with different WB applied in different areas of the picture.

With RAW, the processing software applies one WB to the whole, but I created two copies as different layers in photoshop, set different WB and blended them to get the result I want

At one time I did use a grey card and manually set WB but I haven't done that for 15 years or more, auto is close enough most of the time and I can adjust in post. When it's wrong it doesn't seem err in the same direction (where exposure, when it's wrong, is almost always 'defensive under exposure')
02-12-2024, 03:24 AM   #12
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Capture One Pro also allows WB setting for local adjustment layers.
02-12-2024, 04:21 AM   #13
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I've noticed that but only where there actualy was green lighting and not very bright...otherwise no (on K1ii)
02-12-2024, 03:43 PM   #14
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QuoteOriginally posted by James O'Neill Quote
Actually a couple of Pentaxes can produce JPEGs with different WB applied in different areas of the picture.
I did wonder if any advanced models could do that (not my K30!). Are the areas defined before shooting or is this all in-camera post-processing?

QuoteOriginally posted by Ian Stuart Forsyth Quote
what is the correct white balance?
I think it is whatever looks good to the photographer - whether that's one WB applied to the whole image or something more complex.
02-12-2024, 04:40 PM - 1 Like   #15
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QuoteOriginally posted by AstroDave Quote
What white balance setting(s) are you using? You can check for actual color casts by including a white or (true) gray card/sheet of paper in a frame, and then looking at the color histogram for that part of your image in Photoshop or equivalent. If the white balance is correct, the RGB values should lie pretty much on top of each other. If there is a truly greenish cast, the green histogram will extend farther to the right trhan either red or blue.
I wish I knew where my grey card was! I've changed most of the wildlife settings from AWB to Daylight.

QuoteOriginally posted by pschlute Quote
Could it be your monitor needs recalibration ?
No. It's apparent on multiple monitors.
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