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Old Sep 28, 2006, 8:39 PM   #11
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The lens test certainly looks different with 'long exposure noise reduction' on.




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Old Sep 29, 2006, 2:16 AM   #12
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Funny I did the same thing with my D50 and had a similar "purple spot problem" on the top
Also my bands seem to be horizontal, And well they don't actually show up in my pictures.

heres 2 sample pics at ISO 400 and 1600 With the levels equalized (30 second shots F3.5)
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Old Sep 29, 2006, 6:23 AM   #13
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I don't think I'd really worry about the quality of images a camera produces during a long exposure with the lens cap on and an iso of 1600:G. I've never been in a situation where this was needed to capture an image.All kidding aside, this is such an extreme example, there are bound to be issues. Typically long exposures are done with lower iso to avoid some of the issues that occur from the increased amplification of the sensor at higher iso's like hot pixels, etc. Since you really don't need higher shutter speeds (you don't need to stop action) try reducing the iso to 200 or 400 when shooting these types of images. That coupled with using long exposure noise reduction will likely take care of your banding issues.
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Old Sep 29, 2006, 6:23 AM   #14
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doesnt every camera have this?
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Old Sep 29, 2006, 9:28 AM   #15
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rjseeney wrote:
Quote:
I don't think I'd really worry about the quality of images a camera produces during a long exposure with the lens cap on and an iso of 1600:G. I've never been in a situation where this was needed to capture an image.All kidding aside, this is such an extreme example, there are bound to be issues. Typically long exposures are done with lower iso to avoid some of the issues that occur from the increased amplification of the sensor at higher iso's like hot pixels, etc. Since you really don't need higher shutter speeds (you don't need to stop action) try reducing the iso to 200 or 400 when shooting these types of images. That coupled with using long exposure noise reduction will likely take care of your banding issues.
But how can I win the Lens Cap Photo Contest with shots like that?? :lol: Normally you're right, I have used lower ISOs for star shots, but at lower ISO even at 30 seconds it doesn't gather enough light to see the milky way and only the brightest stars show up, the Big Dipper for example comes through clearly at ISO 100. Maybe 800 would do it, I haven't tried that yet (one more shot to experiment with!).

If I hadn't been able to see the band in the first shots I wouldn't have tried the extreme test of shooting the inside of the lens cap at all, but if it's normal and not a damaged/broken/bugged sensor, and can be pretty much removed by lowering the red channel I can certainly live with it, especially since I've seen absolutely no sign of it in the far more common sub second exposures.

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Old Sep 29, 2006, 2:45 PM   #16
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I am glad what I am seeing is normal. My shot was taken at ISO 400, 30s.*It is a bit worrisome for night shots, not that i do them frequently. I wonder if cooling the camera would work (put in fridge). That is what is done on scientific CCD cameras with a Peltier element behind the CCD.
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Old Sep 30, 2006, 9:40 AM   #17
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I would think if you tried cooling the camera you'd have problems with condensation on the lens and/or sensor when you took it out. The same thing that happens to a can of pop when you take it out of the fridge would happen to the camera. Around here the humidity gets up in the 80-90% range at night, maybe cooling it would work if you lived in the desert?

John

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Old Oct 1, 2006, 4:30 PM   #18
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There are camera's out the designed specifically for astrophotography. Cooled and everything. dSLR's are not the ideal solution if that is what you are doing.

If you must use a dSLR for this purpose, get your hands on a Canon 20Da. It has some modifications to the 20D sensor that help it in regards to photographing the stars.
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