anton_nieuwint Posted October 26, 2005 Share Posted October 26, 2005 For several months I have been getting small circular dark spots in the sky on pictures taken at F16+ & Shutter speed 1/60. I have cleaned the sensor in line with the handbook and the camera has been back to the UK KM Servicing Centre twice within the last 6 weeks for cleaning. They tell me the sensor is clean but the spots remain but not always in the same position. I have changed lenses only once since it was cleaned and the spots show up when using both lenses. They show up more in a rich blue sky and when using a circular polariser. Has anyone else had this problem and any suggestions how to overcome it. I am now concerned that it may not be a dust problem afterall. Perhaps it is something I will have to live with when working at F16+ ? Thanks AK NIEUWINT Link to comment Share on other sites More sharing options...
edward_h Posted October 26, 2005 Share Posted October 26, 2005 Clean the sensor yourself. Buy a soft, soft, soft nylon artist's brush from your local hobby store. Clean the brush thoroughly and then start swiping your sensor until dust levels are under control. Your sensor will never, ever become dust free but the problem can be controlled with brushing/swiping until clean(er). Personally I never see dust because I sit at f2.8 all day. :) Link to comment Share on other sites More sharing options...
clinton_abe Posted October 26, 2005 Share Posted October 26, 2005 What differences does it make what aperture the lens is set for, if the dust is on the sensor? To me the dust, or spot, must be in the lens, somewhere before the light passes thru the aperture, more towards the front of the lens. As the aperture is closed down, the depth of field causes the spot to come into focus. Also, as Anton says it occurs more when using a circular polariser, maybe the polarised light reduces the scatter of light passing thru the lens which causes the spot to stand out more. Link to comment Share on other sites More sharing options...
dw fletcher Posted October 26, 2005 Share Posted October 26, 2005 Aperture makes a big difference, trust me. I don't remember why but I've seen it explained before. You've never experienced this? Link to comment Share on other sites More sharing options...
dw fletcher Posted October 26, 2005 Share Posted October 26, 2005 Too bad I can't edit my post because I have something to add. I don't think you're ever going to get rid of all the dust. Working at tiny apertures you'll see some most of the time. As far as I can tell, it's just the way it is. But if someone has better advice, I'd like to hear it because sometimes it can be a pain in the ass to photoshop out. I'm not much of a technical photographer so I can't explain this either, but polarizers seem to make it worse. Seems like any kind of anomoly sticks out when its against a dark blue. Noise is even worse in blue. I think that must have something to do with it. Anyway, I had this problem printing negatives, too. The slightest speck of dust on a neg will be very noticeable in the sky, especially when you used a polarizer. Link to comment Share on other sites More sharing options...
andrew robertson Posted October 26, 2005 Share Posted October 26, 2005 Clinton, you are so dead wrong. You could try it yourself if you had a DSLR - dust that is invisible at f/2.8 is very noticeable at f/16. Link to comment Share on other sites More sharing options...
greg_erker Posted October 26, 2005 Share Posted October 26, 2005 The dust is likely on the cover glass of the sensor. So it is a small distance above the actual pixels. When shooting wide open the light comes from a big source so the dust speck only blocks some of the light. Stop down to f16 and the light source is much smaller, so the dust speck blocks most or all of the light reaching a pixel. You can see this effect by making a shadow with your finger by holding it an inch or two above a table. If the overhead lights are fluorescent tubes (a big source) the shadow will be not very dark. But if the overhead lights are small pot lights then you will have a very sharp shadow that is quite dark in the center. Greg Link to comment Share on other sites More sharing options...
clinton_abe Posted October 27, 2005 Share Posted October 27, 2005 Greg- Thank you for your answer, it makes sense to me. Too bad, KM can't come out with a DSLR with a sensor cleaner like that found on an Olympus E-1. Link to comment Share on other sites More sharing options...
orensztajn Posted October 27, 2005 Share Posted October 27, 2005 Totally truth what Greg says, if you shoot on small apertures then you will see more effects of the dust, inverse if you shoot wide open. It is a big difference. Link to comment Share on other sites More sharing options...
chris_harley1 Posted October 27, 2005 Share Posted October 27, 2005 Got the same problem, spent ages cleaning lenses until I realised it was the sensor. Kept thinking I had sorted it until I changed to smaller aperture. Let me know how you get on cleaning your sensor. Link to comment Share on other sites More sharing options...
phule Posted October 27, 2005 Share Posted October 27, 2005 << Buy a soft, soft, soft nylon artist's brush from your local hobby store >> An artist's brush may look like the same brush that VisibleDust sells but they're not the same and they don't behave the same way. Get yourself a proper sensor cleaning tool. Link to comment Share on other sites More sharing options...
anton_nieuwint Posted October 31, 2005 Author Share Posted October 31, 2005 Thankyou for the feedback. Minolta have agreed to replace the sensor free of charge under the 12 month warranty and the camera is now on route to the UK service centre.Anyone with similar problems should contact their local service centre. I will keep you posted. AKN Link to comment Share on other sites More sharing options...
julien_aubert Posted November 3, 2005 Share Posted November 3, 2005 As far as sensor dust is concerned I found out that the best solution (by far) is to use those "sensor swabs" with eclipse cleaning fluid. http://www.photosol.com/swabproduct.htm Ok it's not cheap. However, you should not follow the vendor's advice and throw away every swab after one single use. My experience is that they're 4-5 times reusable without loss of efficiency. So a box of 12 will cover all your DSLR's life. Link to comment Share on other sites More sharing options...
ilkka Posted November 20, 2005 Share Posted November 20, 2005 The problem is not 'loss of efficiency' but the risk of picking up a hard piece of debris and then subsequently using that to scratch the sensor (or actually the protective glass on top of the sensor). Link to comment Share on other sites More sharing options...
jiri_kolar Posted December 16, 2005 Share Posted December 16, 2005 Do not take dust on the sensor as an answer.I had same problem with my camera.For the first time when I send my camera for the rapair I was told it is a dust problem and same sensor cleaning will solve this--wrong!!!!I was sending the camera for rapair couple times finaly they told me there must be something wrong with my lenses and I was asked to send the lenses with camera body so they can find wher the problem is,in a week I had body and lenses back with a letter-same lens cleaning was done and everithing is OK-it did not help.I asked for replacing camera---I had new body with same problem and it hapend two more times now I do not have camera but got my money back,Iwas told it may be the problem camera was bilt with they can not send my another body because all of the cameras send to US have same problem and they need to spoke about this issue whit KonicaMinolta in Japan.good luck and Iam sorry for my english I did my best Link to comment Share on other sites More sharing options...
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