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12-09-2009, 07:15 PM   #1
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Blues get washed out (K-X), especially lights

Any reason why the K-X would hate the color blue so much?

This still is from video mode with my 135mm f/2.8 lens. It happens with the stock lens, too.



Is this a problem with the camera in general or just mine?


Last edited by greenless; 12-10-2009 at 11:16 AM.
12-09-2009, 08:39 PM   #2
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What area(s?) of the image have an issue?

The image you've supplied isn't a very good one to show what I think you want to show. How about shooting and posting a photo of a colour spectrum chart or something like the Photodisc test image?

Also perceived/actual colour rendition can be influenced by many things on a per-camera basis.

You know all of these things no doubt, but maybe some of these things are influencing what you are getting and may be worth looking into:

- camera settings (eg Custom Image settings that alter color tone, saturation etc, or the colour space chosen for the camera to use) ;
- lens coatings and filters (eg UV filters);
- monitor colour calibration;
- image processing options (JPG conversion, RAW engine).
- lighting conditions at the time of the shot.

etc.
12-09-2009, 09:43 PM   #3
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I'm talking about how portions of the blue LED light in this image are jet black.

This has happened since the first day I opened up the box. I'm not using any altered settings in-camera and it's not something that's happening in post - the vibrant blues get blacked-out on the live view LCD, too.
12-09-2009, 10:32 PM   #4
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How weird, that black area in the middle of the blue glow. I'll do a mirror test like that with my K-x (white model also)

Though, here's a photo with some extreme blue light in a darkened lobby (you can view full size):
IMGP1051 on Flickr - Photo Sharing!

I suppose you can't get a better sample than that, the glowing cube, and the light casting on near by objects. Though, the blue cube was actually very smooth in real life, while in the photo, you ended up with a more solid blue with a harsh transition to the hotter areas. But I don't see any spots that turned black.

Same thing with the bright spots having more of an edge instead of a smooth transition to the vivid color in this purple background: Flickr Photo Download: IMGP1050

And this face lit by bright red had less contrast, making it look more flat than it really was:
IMGP1041 on Flickr - Photo Sharing!

But I'll do a test with that particular LED color and mirror. Who knows, it could be a side effect the mirror is causing. Don't know if mirrors have any special coating. Or could the LED glow, refresh rate, or whatever, have an odd effect during the exposure? Maybe try different exposure lengths.


Last edited by TimothyB; 12-09-2009 at 10:39 PM.
12-09-2009, 11:55 PM   #5
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I've only noticed this so far when in video mode (my primary use for the camera).

It happens with the blue LED on my stereo in the living room and also when I shoot vibrant royal blue objects like a plastic dogfood bowl. I've only noticed it during low light situations - I'll try some with better light.

I'd hate to have a location with a cool glowing blue cube (like in the photo TimothyB posted) and not be able to use it.

If there's something wrong with my camera's censor or something I'd like to find out now!
12-10-2009, 03:17 AM   #6
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Conveniently, my PC monitor has a bright blue on/off LED. FWIW, I just tested the K-x against it and it rendered the blue LED as it should, colour correct, in video and still pictures, using a DA 40 and AWB setting.

I also reviewed a batch of videos I did a while ago of some musicians on stage, at night, with blue stage lights all over the place illuminating the performers and the set, using the tungsten light AWB setting, and shot with the DAL 18-55 kit. Everything looked OK there too. No weirdness was on display, except from some of the performers. ISO for some of these would have been up to 6400, and one maybe even 12800.

Is there any pattern (eg using a particular lens, or particular lighting - you mention low-light but what about bright daylight, or an AWB setting) to your experience of the issue?
12-10-2009, 05:31 AM   #7
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QuoteOriginally posted by greenless Quote
I'm talking about how portions of the blue LED light in this image are jet black.

This has happened since the first day I opened up the box. I'm not using any altered settings in-camera and it's not something that's happening in post - the vibrant blues get blacked-out on the live view LCD, too.
- There is not only one type of "blue LED". At least this one looks more like violet with possible some close UV component. Combined with some vivid setting could oversaturate sensor or could not be rendered being stopped by lens or filter, like sometimes in a sunset where you see black spots in over-bright areas (but it's steep transition in this case). I'll bet that TimothyB's cube with clean, true blue it'll be fine.

Last edited by silverflower; 12-10-2009 at 05:46 AM.
12-10-2009, 05:45 AM   #8
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QuoteOriginally posted by greenless Quote
Any reason why the K-X would hate the color blue so much?


Is this a problem with the camera in general?
Isn't it kind of poor style to make a statement like "Blues get washed out on K-x" by a single observation from a LED? Before I would make such a statement in public, I would be sure to run a lot of tests.

If the bright LED is disturbing you, just disable it. As a side effect, this will very likely improve battery performance.

Stefan

12-10-2009, 07:19 AM   #9
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So this is a still frame from a video...are the frames before/after like this? Is it alternating in any sort of pattern, or always show up this way? I am going to guess that it is a product of the video framerate and saturation, some sort of combination is causing this wavelength of the color spectrum to distort...my best guess anyway. Is that a focus limiter of some sort you have attached to the lens, or something you've made for fine focus? I am intrigued by that little handle!
12-10-2009, 11:13 AM   #10
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Yes, this is a still frame from a video and it appears on all frames before and after. It also happens on vibrant blue objects like my dog's plastic bowl. It happens in video AND still mode with the stock lens and my 135mm f/2.8 lens.

@16N64 -- It's not the fact that the blue LED is there that disturbs me, it's the fact that the color information is not being registered in the image. I've tested this on several different blue LED lights (Wii, stereo system, camera's light) as well as a couple of household objects (dog's bowl and blue mailing box) and it's the same no matter which mode I'm in or which lens I use. It does, however, only seem to happen in low-light situations.
12-10-2009, 11:34 AM   #11
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Throw in some stills of different objects, including exif, to clear things up, because in this image it is not blue that is not being registered. The blue is still there, in the middle of the spot and around it, but the blackness and weird gradient is caused by the lack of other colours actually.

What is the cause of this i'm yet unsure, but last time someone was asking for help with similar black spot (not sure if in this forum, i think it was a P&S), the conclusion was defective sensor and it got replaced and the problem was gone. Still more DIFFERENT pictures are needed to tell for sure (some with the defect and some with similar blue shapes and without the defect).
12-10-2009, 11:35 AM   #12
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Since I don't even know where the LED is in the picture (is it part of the camera?), and since I don't know if LED's, like fluourescent bulbs, have a natural wavelength shift over the course of a normal 60Hz AC cycle, I'd post the pictures of your dog's bowl. If what you're seeing is not unique to LED's, then might as well factor that out of the equation right now. And might as well make it a still, not a video frame.

Last edited by Marc Sabatella; 12-10-2009 at 05:37 PM.
12-10-2009, 12:32 PM   #13
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QuoteOriginally posted by ytterbium Quote
Throw in some stills of different objects, including exif, to clear things up, because in this image it is not blue that is not being registered. The blue is still there, in the middle of the spot and around it, but the blackness and weird gradient is caused by the lack of other colours actually.

What is the cause of this i'm yet unsure, but last time someone was asking for help with similar black spot (not sure if in this forum, i think it was a P&S), the conclusion was defective sensor and it got replaced and the problem was gone. Still more DIFFERENT pictures are needed to tell for sure (some with the defect and some with similar blue shapes and without the defect).
If there's a problem with the sensor will Pentax replace it for me or will I have to pay for it?
12-10-2009, 12:34 PM   #14
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Given that it only happens in video and low light, I think it is likely a product of the wavelength of the color/video framerate, and a high gain/ISO due to the low light (as you described when this occurs). I will have to give this a try later and see if I can mimmick the results.

Mark - the LED he was referring to is the 'on' LED on the Kx, right behind the shutter button - in the shot you don't see the LED itself, but its reflection on his hand.

Greenless - have you tried changing the saturation or other image/video settings under the same circumstances?
12-10-2009, 01:12 PM   #15
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I did a video test in a mirror similar to the original poster.

At times there appears to be a ring that's a darker blue or turning black. At a few points I can start to see what the poster sees. I want to do the video again to try and get the effect with my hand further away like the posted image. Though, I've been distracted with a new lens that arrived last night.

The blue was hard to capture with a photo, just wasn't there.

EDIT: Here's the first video I took. I cropped into it, but still 100%. The odd crop ratio might effect playback speed. Though, at 25 seconds, you can see something similar to the poster's image.
http://www.youtube.com/watch?v=sHGj7K66OCo
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