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11-15-2014, 03:34 PM   #16
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Just to throw in another couple of variables for consideration ...

- the use of noise reduction - particularly chroma NR - can have a visible impact on colour rendering, particularly reds.

- JPEG settings (compression level, color metric, colour-subsampling etc) can change colour rendering too.

11-20-2014, 04:50 PM   #17
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hey guys,

I now see this even in raw image. so it can't be WB or other JPEG settings. I'm going to do a test shot with a different lens today to see if I still get the same result.



In reality this is just a red neon light
11-20-2014, 05:50 PM - 1 Like   #18
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The neon sign is a typical problem for metering. Most of the shot is quite dark, while the neon is pretty bright. It won't match a scene in the matrix meter database. The camera chose to raise exposure, most likely overexposing just the very bright, solid reds.

The sensor doesn't treat all colors equally. It has a filter on it that creates twice as many pixels for the green channel as either red or blue. Mostly this is a good compromise, but when large blocks of red or blue are very bright in the image and green is a middle tone, the reds or blues are in danger of overexposing. The matrix meter often recognizes a blue sky pattern so that is less of a problem. The K3 metering looks at each channel so it might have done better.

I think the K-5 IIs is different than my other Pentax DSLRs in handling red. I have been looking for similar shots to test it. I'm used to seeing solid red with no detail from the other cameras. I have at least one shot with strange reds. Too many variables here, because it was sunrise and ISO 1600, but that car is not the right color and Lightroom claims the red channel is OK except for some tiny reflection spots.

11-20-2014, 06:27 PM   #19
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Thanks Just1MoreDave,
that was very helpful.

11-21-2014, 02:45 AM - 1 Like   #20
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QuoteOriginally posted by Samwise.Gamgee Quote
hey guys,

I now see this even in raw image. so it can't be WB or other JPEG settings. I'm going to do a test shot with a different lens today to see if I still get the same result.

In reality this is just a red neon light
Yes, that's a common issue with reds, the red channel blows quite easily.
It's the overexposure which is shifting the color towards orange.
11-21-2014, 07:02 AM - 1 Like   #21
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There are whole threads devoted to the 'what the hell is it with red' phenomenon. General consensus is the CMOS sensors are highly sensitive to red.
11-21-2014, 11:29 AM   #22
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I took some test shots this morning and I can show something odd with reds. I'll have to read one of those threads for more information. I took some shots with my K-5 IIs and a Pentax-F 50mm f1.7 to establish an exposure. That was f8, 1/1000, ISO 200 (because that's base ISO on the DS), two stops underexposed from the matrix meter suggestion. Then I switched the same lens to my *ist DS (CCD sensor), used the same settings and took the same shot. Both were RAW. Then I imported them to LR4 to set the white balance to the same numbers and crop them to the same area. The K-5 IIs has more pixels so its crop is bigger.





The K-5 IIs reds look overexposed because they are missing detail, but LR says the red channel is below 50% for this crop. Notice that the DS shot is nowhere near as sharp but shows detail in the car.
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