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11-29-2011, 02:12 AM   #1
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noise

Ive been using my istdl for long daylight exposures of 30-45seconds @ f8-f16 with nd filters. My resulting images have a kind of speckled noise on them and im wondering if this is a result of the sensor getting warm ? I have mirror up facility on the camera but i think this is for cleaning purposes...not really sure. Any advice ? Thanks.

11-29-2011, 02:45 AM   #2
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indeed, it can be because of warm.

You can turn On noise reduction, it will take another picture with mirror down (so no light will go trought the sensor), and it will delete the corresponding noise from the black picture to the picture you took before.

See : Page 140 of the manual, in the grey part of the "bulb mode"

manual here : http://www.pentax.jp/english/support/man-pdf/istdl.pdf
11-30-2011, 02:20 AM   #3
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thanks Aurele, let me try and understand ( im new to dslr )............are you saying i take one shot without NR and then shoot another with N reduction on ? Please forgive my ignorance and be patient as i am new to photography and having a hard time grasping all that requires taking good photos as opposed to snapshots. Thanks for the link to the manual...i only wish it was easier for this novice to understand.
11-30-2011, 02:41 AM   #4
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Turning NR on effectively means 2 exposures. The first one is the one you activate. When that exposure has finished, the camera then takes a "dark frame" exposure of the same duration and at the end of the dark exposure, it is subtracted from the original frame to remove thermal and electrical noise. The downside of using NR is it effectively doubles the time to complete 1 exposure. A better solution may be to shoot darks seperately and then subtract the dark frames in photoshop, or what ever your favourite poison is.

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