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DPChallenge Forums >> Hardware and Software >> Dead Pixels? or pain noisy Pictures? (Olym C3040)
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Olympus C-3040Z
 11/09/2003 02:28:11 AM · #1
Recently I went ard at night taking photos on a tripod and in alot of situations, used long exposure. However, when I uploaded the photos, there were a green dot (and some blue ones somewhere) that were consistantly present, I took some long exposure pictures that were very noisy b4, but this few are okay cep the annoying dots, I was wondering if it is because of a fault in the camera's CCD or it is pain noisy picture generated by my old C3040? Please help, thank you all.
Pentax K10D
Pentax DA 18-55mm f/3.5-5.6 AF
 11/09/2003 02:47:58 AM · #2
Longer exposure may cause noise in the picture. High ISO will also cause noise.

Try adjusting the EV + (up) and lower the exposure. It may help.

If this is happening when using normal exposure there could be a problem with your camera.
Canon EOS-7D
Canon EF 24-70mm f/2.8 L USM
 11/09/2003 03:02:22 AM · #3
I would guess you have a hot pixel - they show up much more clearly on a long exposure. Try taking a picture for two seconds exposure with the lens cap on. If it is there in the same place, it is hot!
Olympus E-510
Sigma 50-500mm f/4.0-6.3 EX APO RF HSM for Olympus
 11/09/2003 09:32:31 AM · #4
I found this to be a real big problem with my Olympus C3000. I sent it back and had the CCD replaced (under warranty of course) and it acted better. I found when I did a couple photos at a longer exposure, they ended up okay, maybe a couple dots here and there. The more photos I took, the more dots kept showing up until eventually, I looked like I was in outer space. I didn't realize it at the time I took the photos. But when I got done, They really showed up on the computer. I pretty much just stayed away from the long exposures after that, or only took a couple at a time.

I solved the problem once and for all by buying an Olympus C5050. They have C5060's out now, which is the same thing with 4x zoom instead of 3x. I thought I was just getting a 2MP upgrade in resolution. I was way off. It's leaps and bounds above the C30xx's.

Good luck - I wish there was an easier solution than sending the camera back. The cost of the repairs if you don't have a warranty are around $200, which I would put toward a better camera if it were up to me.

Bob

Edit: Does it look like this? //www.pbase.com/image/23129061


Message edited by author 2003-11-09 09:37:56.
Canon EOS R5
Canon RF 24-70mm f/2.8 L IS
 11/09/2003 11:37:56 AM · #5
Virtually all cameras will show hot pixels with along-enough exposure. If it becomes a real problem (there are too many to clone out) then subtracting a "dark frame" exposure is an easy way to minimze the effects of the problem.
Take a photo under the same conditions with the same exposure settings (shutter speed & ISO) but with the lens cap on. Subtract this exposure from the "real" exposures, and the hot pixels will be compensated for.
This does not work for random noise which is also a problem for long night exposures. For that, use multiple exposure stacking.
Combning the above techniques can produce images that are dramatically better than a sngle image taken with the same equipment under the same conditions. The multiple-exposure technique obviously has limitations as far as recording scenes with motion. Also, neither technique is currently DPC-legal.
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