Old 05-02-2012, 08:55 PM
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Carl is offline
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DSLR iso setting fo bad pixel frames

Hi all
I'm using Nebulosity2 and the manual advises that when creating a master bad pixel file you should "combine several frames taken at the longest exposure duration you expect to use".

This all makes sense, but what iso setting should i use? Do the RAW bad pixel frames need to have matching iso settings of the light frames?

Plus supplimentary question:
If i create a library of bad pixel masters for how long can they be used, ie
best before date!

It appears that one of the benefits of bad pixel mapping is that you don't have to spend extra time after each session shooting dark frames.

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Old 06-02-2012, 06:50 AM
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I don't quite get this one, if taking dark's eliminates the problem why not stick to that without creating libraries of (Bad Pixels)

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Old 06-02-2012, 08:47 AM
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Terry B
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Location: Armidale
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The bad pixel file is good to use. Some hot pixels are not consistent in their response. By taking a long dark frame and selecting the hottest pixels you create a "bad pixel map".
IRAF and other professional reduction programs use this feature.

As for the original question, use the ISO you always use. I used 800 for my 40D as this gave the best dynamic range. There is an optimin ISO to use with each DSLR.
All changing the ISO does is to change the "gain" that the value each pixel reads is multiplied by. You want to use the full dynamic range of your camera. If the ISO is turned up too high you will lose the brighter parts of your image ie stars. The data for the dimmer parts of your image is still there at lower ISOs but needs enhancing using curves etc to bring it out.
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