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Forum: Pentax DSLR Discussion
06-03-2008, 02:28 PM
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Thanks for that link... that table pretty much answers my question.. the pattern on that ISO 2200 shot in my original post is visible because the blacks aren't clipped high enough.. no bad sensor, etc...
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Forum: Pentax DSLR Discussion
06-03-2008, 01:22 PM
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Yes, 40D has some banding, but it is of consistent intensity across the frame. Not sure about D60.
The E-510 has very bad, very structured horizontal banding, and the bands are in different, random places on each color channel. This just happens to be why I am switching systems (can ruin shots at ISO 800 + incandescent, even where shadows are not that deep)
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Forum: Pentax DSLR Discussion
06-03-2008, 12:52 PM
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Every shot, taken on different days in different places/situations... same pattern.
Yes you did, and thanks! I have it right here, WB set to the extreme left and boosted +3 EV so the pattern is obvious:
Your camera's pattern is slightly different (as are each of the 3 K20D's I have dark frames for) but they all generally have a lower level near the vertical center and higher near the top and bottom with a bit of horizontal banding.
It is obvious that the K20D sensor has a noise pattern, that question is moot to me.. I'm just trying to figure out at what point it ruins a typical incandescent lighting shot by answering a few questions:
1) Is the RAW converter to blame for making it so obviously visible? (I am thinking the answer to this one is yes)
2) Do in-camera JPGs exhibit the problem as badly as I am seeing it from RAWs? If so, what makes the difference? Is it the level at which blacks are clipped? The same shot with in-camera JPG next to a RAW conversion would really help.
3) Are some sensors just worse than others? I don't have a dark frame shot from the camera that took the original patterns I posted, but the other 3 I have are all about the same in terms of intensity... just can't compare them in a real situation since they are just dark frames.
I am moving away from a different system precisely because of noise pattern, so this is a very important consideration for me.
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Forum: Pentax DSLR Discussion
06-03-2008, 10:36 AM
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The same pattern shows up on every shot, it is not light from the scene. The slice on the right (incandescent WB) shows some detail from the scene as there was no completely blacked out slice in the shot, but the color cast and luminance pattern are from noise.
I am very interested to see others' K20D high ISO shots with significant areas of deep/clipped shadow across the frame, particularly WB to incandescent light. (more than just dark frames) If you have camera JPG vs RAW conversion, even better.
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Forum: Pentax DSLR Discussion
06-02-2008, 11:39 PM
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I've been considering moving to the K20D from a different system, but there is something bothering me.
I have an acquaintance with a K20D that took it to Disneyworld not too long after getting it. On the "dark rides" (i.e. Pirates of the Carribean), he took full advantage of high ISO with his fast primes to get some really fun shots. By their nature, these types of shots have a lot of deep/clipped shadows (similar to say.. shooting a dimly lit concert) and they exhibit a strong noise pattern across the frame.
At a local level there is some large grain pattern in the shadows, but that's not the problem, it is the noise pattern across the entire frame that is the problem. At the vertical center of the frame (landscape composition) the noise levels are very good, but they get progressively worse toward the top and bottom of the frame. (and slightly worse at the bottom than the top)
I don't want him to get angry with me for posting his shots, so I'm just going to post vertical slices. The following are vertical slices of 2 different shots (NOT 100% crop, but rather resized) that he converted from RAW using Lightroom. I intentionally cropped to show areas of mostly just clipped shadows.
The left is ISO 4500 with a warmer white balance, and the right is ISO 2200 and white balanced to incandescent (blue channel torture test). I put them against a black background so the pattern stands out:
To be clear, the pattern comes from the noise only, these should mostly just be clipped shadows.
I had him send me a few of his RAW files, and the only way I've found to ensure consistent black levels throughout the frame is to clip the blacks to the highest luminance level of the shadow pattern (top and bottom of the frame), thus giving up a whole lot of dynamic range. Is this the only workaround?
Also, I'm wondering a few things: first, I've had a few members of this board send me RAW dark frames from their K20Ds, and I've also taken a few of my own at a local camera shop, and while I am seeing distinct patterns for each sensor tested, I can't produce a file with a pattern as pronounced his camera seems to have. This makes me wonder if he's got a bad sensor?
But then, they were also converted from RAW. Most of the high ISO K20D shots I've seen online so far have been camera JPGs, and they don't seem to have as much or any pattern visible. So does the JPG processing engine just clip the black level enough to make it invisible or is something else going on? Am I completely missing something else?
So.. how do your K20D shots that have a significant amount of deep shadows look? Particularly under incandescent light as the blue channel will always be the noisiest. In his shots, the pattern started to become obvious at ISO 1600 for incandescent, and nearer to 3200 for warmer white balances.
Thanks for your input...
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Forum: Pentax DSLR Discussion
05-25-2008, 04:33 PM
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Thanks much.. I'm not looking to judge the noise in any real life sort of way, just want to look at the pattern.
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Forum: Pentax DSLR Discussion
05-24-2008, 08:02 PM
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I'm looking for a K20D owner willing to take 3 shots with the lens cap on @ 1/30th sec for ISO 800, 1600, and 3200 and send me the RAW files. I'm curious to check out the noise patterns. Please PM me if you will help. Thanks!
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