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07-08-2012, 01:52 PM   #1
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Noise stripes on high-ISO shots

Hi,

When I shoot in low light/high ISO situations (typically ISO 3200-6400 which I often use for concerts), the photos often come with horizontal stripes of what looks like noise artifacts. They are very noticeable, for example on this photo or this one.

I shoot raw (DNG) and the stripes do not seem to depend on the raw converter I use (I usually use RawTherapee and I tried UFRaw with similar results). They are more obvious when I raise exposure compensation in PP, and they tend to disappear when I raise the black level in RawTherapee.

I can't swear these stripes have always been there, but I see them in photos taken at the end of april (I bought my K-5 new at the end of february).

Are they a known artifact of the K-5, or do I have a problem with my sensor?

07-08-2012, 02:26 PM   #2
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I have had the same problem with mine as well.
07-08-2012, 02:28 PM   #3
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That is not good. Did you make RAW (I think)? Did you put incamera noise reduction for hi-iso on or off?

Did you update firmware?
07-08-2012, 02:45 PM   #4
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Shoot Raw, noise reduction is on AUTO, Have not updated latest firmware but up to the last one.
shows up in 6400, 12800.

07-08-2012, 02:51 PM   #5
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I shoot raw (DNG), no noise reduction, no high lights or shadows compensation, color space is sRGB if that matters. I have firmware 1.12; AFAIU 1.13 only fixes GPS-related bugs. I will upgrade to 1.13 anyway, just in case.
07-08-2012, 02:56 PM   #6
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Looks to me like a high-ISO RAW processing issue that may be dependent on the RAW engine you are using and your processing steps, at least to a degree..

What happens if you use the supplied Pentax Digital Camera Utility to process your RAW's into JPG's? That should be your starting point to diagnose any issues since it is the 'official' RAW processor.

And what happens if you shoot RAW+? Do the in-camera processed JPG's display the same patterns?
07-08-2012, 03:04 PM   #7
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Or develop such a RAW in-camera to a jpg. If the banding is gone, then it is coming from an outside source.
07-08-2012, 03:05 PM   #8
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Send me a RAW: info@iamphotographer.nl with a link or wetransfer.

07-08-2012, 03:50 PM   #9
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I have played a bit with the two photos I linked to in my first post, converting them in-camera still shows the banding but it is much less obvious. It also appears on the camera screen. I am currently uploading both DNG files and two JPEG versions each (one each at 0EV and +2EV, everything else left untouched) to Index of /k5stripes.

I tend to process my concert photos quite heavily as I often have to work with bad light, so I guess this makes the issue much more obvious.
07-08-2012, 04:11 PM   #10
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I downloaded the two files you provided and used my normal raw processing routine on them. I can see the horizontal banding on the pianist faintly. This may be a spectral response of the sensor to LED stage lighting. If so, not much to be done about it.

Jack
07-08-2012, 04:43 PM   #11
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I briefly looked. The singer with the mic is underexposed and I would say that that is maybe one off the things. I would say at least a full stop of underexposure. Then you used 1-500th for shutter, so you could easily go to 1-200th and have a descent exposure with iso6400.

I took one of my own images and gave them the same treat
+ 100 fil light and + 4 EV light compensation in Light Room 3

https://dl.dropbox.com/u/20195454/aa1.jpg

https://dl.dropbox.com/u/20195454/aa2.jpg

https://dl.dropbox.com/u/20195454/aa3.jpg

Too soon too say that something is wrong, but it is not good. For testing you should need more then just one shooting.
07-08-2012, 05:28 PM   #12
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That is typical banding noise.

Digital Camera Image Noise: Concept and Types
07-08-2012, 05:29 PM   #13
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QuoteOriginally posted by RonHendriks1966 Quote
I briefly looked. The singer with the mic is underexposed and I would say that that is maybe one off the things. I would say at least a full stop of underexposure. Then you used 1-500th for shutter, so you could easily go to 1-200th and have a descent exposure with iso6400.

I took one of my own images and gave them the same treat
+ 100 fil light and + 4 EV light compensation in Light Room 3

Too soon too say that something is wrong, but it is not good. For testing you should need more then just one shooting.
Like you said it's really pushing it and you lose a lot of data when you underexpose with high ISO, you cant recover that like you do with low ISO photos.
07-08-2012, 07:16 PM   #14
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EXIF says imgp2416 (girl with mic) is -1.3 EV, ISO 6400, f2.8, 1/50. That's quite a bit of underexposure, and means you are running an ISO more like 12800. The white balance is also really off and dominated by reds, which may also be a factor. Finally, EXIF says that the camera body temperature was a little above 30 deg C, and while that may not be super-hot, heat means noise.

A bit of banding isn't such bad news. One can still do something useful with an image like that with some adjustments for white balance, noise, a little contrast boost and shadow tweaking etc.
07-08-2012, 09:28 PM   #15
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I sometimes see this at ISO 12800+, under some conditions, and therefore I would also expect it sometimes at ISO 3200/6400 with a pushed underexposed image.

I think it's normal.
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