I'll be going to the mountains/D800E/nightsky photography advice request

Started Feb 12, 2013 | Questions thread
Robin Casady Forum Pro • Posts: 12,898
Re: I'll be going to the mountains/D800E/nightsky photography advice request

Judy Stone wrote:

- I didn't know about taking dark shots!. So I would use PS to "subtract" the noise from each still? Any description on how is this done, I mean, I will have say 10 so dark shots, I stack them to add all the noise and subtract this from each image?

Open the image and the dark frame in Photoshop. From the dark frame window select Duplicate Layer. In the dialog that comes up select the image file. This will place the dark frame as a layer above the image in the image file.

If the layer palette select Difference for the blending mode.

Chris Limone has a web page about it.

TheRidgeback wrote:

you then need to take some bias frames, this is normally the fastest shutter speed again take 5-10, these images only contain the readout noise from your sensor.

What do you mean by "fastest shutter speed"? 1/8000?? And taken with the cap on?

I have no idea what TheRidgeback is suggesting. I typically use only one dark frame with an image. What is important is that it was taken at the same shutter speed and temperature as the image you wish to use it with.

If temps are changing during the night (I'd be surprised if they weren't) you should take a dark frame periodically. Then use the dark frame that was taken closest to the time of the image.

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