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Photo Forum / Digital Photography / DSLR Cameras / March 2006Strange Dots -- Help?
These two photos were taken just a few seconds apart: http://homepage.mac.com/christopherjcampbell/Problem%20Photos/ The first was at f/6 and 1/6 second; the second at f/22 at 5 seconds. Both photos were taken with a tripod and no adjustment has been made for color balance, sharpening, or anything else. They are just JPGs taken straight from the raw files. The lens is the 12-24mm AF-S Nikkor. The scene is a night photo of Heritage Street in Vigan City in the Philippines. I can understand how stopping down might cause the star filter effect seen in the second photo, but where did the strange dots come from? > These two photos were taken just a few seconds apart: > [quoted text clipped - 9 lines] > I can understand how stopping down might cause the star filter effect > seen in the second photo, but where did the strange dots come from? A longer exposure increases the visibility of partially defective pixels. Repeat the shot with "dark frame subtraction" enabled (or whatever its called on your camera). David > > These two photos were taken just a few seconds apart: > > [quoted text clipped - 13 lines] > Repeat the shot with "dark frame subtraction" enabled (or whatever its > called on your camera). Awfully big pixels! Actually, both shots were taken with Nikon's NR set the same; in this case, it was on. A few shots later I turned it off, but there was no change. >>> These two photos were taken just a few seconds apart: >>> [quoted text clipped - 18 lines] > set the same; in this case, it was on. A few shots later I turned it > off, but there was no change. Oh, I thought you meant the single pixel on the right-hand side. The dots round the lamp look like rain or moisture somewhere. Filter on the lens? David > >>> These two photos were taken just a few seconds apart: > >>> [quoted text clipped - 23 lines] > The dots round the lamp look like rain or moisture somewhere. Filter on > the lens? ACK! What pixel? No, no filter. >>>>> These two photos were taken just a few seconds apart: >>>>> [quoted text clipped - 27 lines] > > No, no filter. OK, so on the front element, then. David > Oh, I thought you meant the single pixel on the right-hand side. Taking a look at that pixel, it is the only frame of several dozen that shows it. The raw file shows it more clearly and it is still too large to be a pixel. What it looks like to me is a small light leak through the metal doors of the closed shop. Actually, if the shop had still been open, I would have thought it an LED on the ceiling. >> Oh, I thought you meant the single pixel on the right-hand side. > [quoted text clipped - 3 lines] > through the metal doors of the closed shop. Actually, if the shop had > still been open, I would have thought it an LED on the ceiling. OK, the images are so small it's difficult to tell (about the single pixel). David >> Oh, I thought you meant the single pixel on the right-hand side. > [quoted text clipped - 3 lines] > the metal doors of the closed shop. Actually, if the shop had still > been open, I would have thought it an LED on the ceiling. The images do not have exactly the same view, the second being slightly wider. The bright dot on the second image is just visible at the edge of the first.  SignatureMåns Rullgård mru@inprovide.com Hi Christopher, It seems dustparticles on the chip to me. The way to check this is to take a shot of the bright blue sky (or white paper) with f=22. If than you see these spots than you have dust on the chip and need to clean it. Regards, Harry > These two photos were taken just a few seconds apart: > [quoted text clipped - 9 lines] > I can understand how stopping down might cause the star filter effect > seen in the second photo, but where did the strange dots come from? > Hi Christopher, > > It seems dustparticles on the chip to me. > The way to check this is to take a shot of the bright blue sky (or white > paper) with f=22. Not dust. Already tried that. >>Hi Christopher, >> [quoted text clipped - 3 lines] > > Not dust. Already tried that. Are you sure? I vote for sensor dust. (or gnats) > These two photos were taken just a few seconds apart: > [quoted text clipped - 9 lines] > I can understand how stopping down might cause the star filter effect > seen in the second photo, but where did the strange dots come from? Maybe a cloud of out of focus gnats attracted to the light? |
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