What caused this striping on the photo?

Discussion in 'Pentax' started by steve_t.|1, Jul 19, 2009.

  1. [​IMG]
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    Hopefully it is plainly visible to you too, the upper left to lower right diagonal striping/banding across the photos, in particular the sky. Blown up on the computer, the striping does not seem to run across the buildings, just the sky. Other than the cropping, the photo is presented as captured by the camera. Shot a couple photos like this, the only difference between them is the time open of the shutter. Any ideas on what is happening here?
    Shooting info- about 45-50 minutes post sunset last night, looking westerly over the Mississippi River and downtown Minneapolis, MN. K20D. Sigma 10-20mm EX F4-5.6. F/11, 16mm, 25 second exp., expanded ISO 200 (expanded dynamic range mode), highest quality jpeg. Clear glass Hoya filter on front of the lens.
    My first thought is the filter, second thought is the expanded ISO range, but I did not see this until I was home and had the photos downloaded to the computer.
    Help/ideas/thoughts are most welcome and appreciated.
    p.s. Hold the presses- I just looked at all 4 photos I took, the only differences being exposure- 8 sec, 13 sec, 20 sec, and finally 25 sec (to let in lots of light and keep noise controlled) which is what you are looking at. None of the others have this striping. Thoughts as to why?
     
  2. Looks like detector ("sensor" in photgraphy talk) pickup noise. Can happen if a (rather strong) microwave or VHF/UHF radio emitter (details dpend on the setting of the detector readout, like clocking) is close to the readout electronics. Nothing serious, doesn't do any damage, just spoils that particular picture
     
  3. I had this happen once with my cell phone that went off during a longer exposure. I would suspect Thomas is correct and if you were near a cell tower or transmission line, You got this. Try it somewhere wher you know the area is clean of electro-radio interference.
     
  4. PS: You see it clearly in the lower left dark parts as well, this runs all over the chip with a few ADU amplitude, you just don't see it in the buildings becuase the local dynamics over the same pixel-distance scale is higher than the amplitude of the noise.
     
  5. Thomas-
    Guess what was right over my head? High voltage power distribution lines. Guess what was a couple hundred feet to my left? Yep, a coal-fired power generation plant. Here's a shot of those lines (nine lines all together) taken during daylight, just upstream about 200 yards or so. But why only at the longer exposure time and not the shorter time?
    Damn power lines- they always mess up my favorite views![​IMG]
     
  6. Hi Steve,
    Pickup noise is very "unreliable". Anything can change it, like orientation of camera, even you yourself being in a slightly different position wrt. camera and noise source.
    The way it works it not on the image sensor itself. Sensors, both CCD and CMOS have a single bottleneck though which every pixel passes, namely the gain amplifier. This is the point where pickup noise acts: When the pixel is going through the amplifier while the electromagentic wave going through the camera is in one state, say high, it is altered by adding, say 5 ADU. Less than a nanosecond later the next pixel is amplified, but now the electromagnetic wave is in a slightly different stare, altereing the pixel with a different ADU. So the stripes you see is really the time-pattern of the wave, modulating every single pixel on the way as it is going through the amplifier.
    As I say, the way the EM wave goes through the camera is very sensitive to external conditions, and usually camera electronics is shielded well enough to keep the effects out. Exceptionally, however, you get it.
    The 50Hz of power supply should be no problem, the EM wave must have MHz to GHz to disturb the readout. Although power plant may create that sort of EM waves as secondary effects, a better guess would be a cell phone or radio tower nearby, or an actual cell-phone right next to the camera.
     
  7. Thanks, Thomas.
    You must be in Europe, yes? Here in the USA the frequency is 60 hertz, but I now get the idea. I'll be at my dentist's office in a couple weeks, I'll see if they have any spare lead x-ray blankets laying about!
    Well, my cell phone was on and in my pants pocket, camera was at head level, but no cell activity at that time, from me, and nobody nearby. Either way, I'll stay alert to such conditions, thanks very much.
     
  8. Born German, but I live in South America, Chile, since 2005. They have a 50Hz 220V system here as well.
    Regards, Rivi
     
  9. Even if you weren't actively talking on your cell phone (or sending or receiving a text message), the phone is still communicating with the towers. As an experiment, place your cell phone next to your computer speakers and turn up the volume. Every now and then, you'll hear some funky noises coming through your speakers -- this is the result of your cell phone communicating with the cell tower.
     
  10. A friend of mine asked me about this for his k20d. I had no idea, but now I'm wondering; Why has this happened to the k20d? With all the other cameras (k10d, k100d/s k200d, etc.) there never was a problem. I'm licensed for and experiment with all different radio frequencies from 100Hz to 5GHz, and I have never had this happen with my k10d, k200d, or k100ds. But come to think of it, I've never been transmitting while I was taking a picture.
    I'll try transmitting while I take a picture, and see what happens to the picture. I'll post the results.
    -Jon
     

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