HELP Please!Is this expected level of noise? Or should i get my EM5 checked

Discussion in 'Astrophotography' started by ajPhoto, May 28, 2014.

  1. ajPhoto

    ajPhoto Mu-43 Rookie

    May 27, 2014
    Hi, I recently captured a few night sky shots at relatively high ISO (1600 - 3200) range 20-30 sec exposures using Oly 9-18 at 9mm and f4.0. I processed the images in LR5, and used Noise reduction etc. to make these images "acceptable". [​IMG]

    Can any of you please help me determine, if I am doing something wrong in processing or do I need to take EM5 in to the dealer and have the sensor checked. From reading this forum I know the EM5 is supposed to perform very well at high iso and longer exposure. You can see larger size image here. Thanks for your help.
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  2. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia
    In the menu there are 2 options: Noise Reduction and Noise Filter. They are different. You want to turn Noise Filter off (it's the one which does what Lightroom calls "noise reduction" and it isn't applied to RAW files anyway) and do that sort of noise reduction in Lightroom.

    You want to turn the Noise Reduction menu item to "on" or "Auto"—I use Autio. What this option does is what is called dark frame subtraction. Noise gets increased in long exposures and some of that noise is generated by the sensor in a repeatable manner. What dark frame subtraction does is to take a second exposure after the image exposure. This second exposure is for the same length of time so it effectively doubles the time required for your shot but the shutter is kept closed so no light falls on the sensor and anything captured during the second frame is only the repeatable sensor noise pattern which is then digitally subtracted from the image file. Noise Reduction is applied to both RAW and in camera JPEG files and it does reduce noise during long exposure without affecting image sharpness. The Auto setting only applies it to long exposures which is why I just leave it set to Auto.

    You haven;t said what your settings are but if you have both Noise Reduction and Noise Filter set to off, then turning Noise Reduction to on or auto may well help a lot.

    The EM5 has an automatic sensor cleaning system which works when you turn it off or turn it on, can't remember which. It's rare for the EM5 to need sensor cleaning.

    Apart from that it appears that the noise is in the darkest parts of the frame and that's what you would expect with noise, especially in a long exposure. While the EM5 does perform quite well at ISO 1600-3200, the test images you see showing performance at those settings are normally at exposures in the handheld exposure shutter speed range, not long exposures like 35s. There is always going to be more noise in an exposure like the one you show here than in the sorts of exposures you see in test images because you're giving the sensor a much more demanding task with this sort of exposure and it is the sort of situation which is far more likely to generate some noise.
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