Can A Dark Frame Library Get Too Big

[CapturingTheNight (Greg)]

Hello,

When I started out imaging I created a folder on my computer for dark frames and divided it up into seperate sub folders for different ISO speeds and exposure lengths. Now I am getting quite a collection in some of the folders. My question is- is there a downside to collecting and using dark frames from different imaging sessions (as long as they are the same ISO and exposure length) or should I only use the dark frames from that particular imaging session? As I understand it, hot pixels are generally always the same ones but if they are not and I have a multitude of them over the entire library could it start 'eating' my images?

Cheers

Greg

[leon]

It is always best to do the dark's at the same evening as your lights, with as close as possible temp range.

However some do have a library of dark's, but i think most don't keep them forever, so to speak.

Leon

[rogerg (Roger)]

Sounds like you're dealing with a DSLR so I agree with Leon that you would be best using dark frames from close to the time the light frames were taken, due to temperature variation of the camera. As such your possibility library size of useful frames is quite limited.

If you were working with a temperature regulated camera then you can more effectively build up an extensive library of dark frames to use over many months or years. Even then I find the darks change slightly over time and so I prefer to take new ones each year or so and stop at a reasonable number like 30 dark frames for a given set of camera settings.

[CapturingTheNight (Greg)]

Originally Posted by leon

It is always best to do the dark's at the same evening as your lights, with as close as possible temp range.

However some do have a library of dark's, but i think most don't keep them forever, so to speak.

Leon

Thanks for that Leon I'll start ditching some of the oldest ones. I always take darks as soon as I have finished imaging

Originally Posted by rogerg

Sounds like you're dealing with a DSLR so I agree with Leon that you would be best using dark frames from close to the time the light frames were taken, due to temperature variation of the camera. As such your possibility library size of useful frames is quite limited.

If you were working with a temperature regulated camera then you can more effectively build up an extensive library of dark frames to use over many months or years. Even then I find the darks change slightly over time and so I prefer to take new ones each year or so and stop at a reasonable number like 30 dark frames for a given set of camera settings.

Yes I'm using an uncooled DSLR Rodger. Thanks for the clarification. I probably got the idea for a dark frame library from someone who has a cooled CCD camera and thought it would be a good idea for a DSLR. I'll just use the ones from the same night from now on, or until I take the next step and upgrade the camera to a CCD

[tlgerdes (Trevor)]

Ideally you want to take them each session but, on the other side of this, you only need the master dark from each session, not the 10-20 subs that make up the master.

[CapturingTheNight (Greg)]

Originally Posted by tlgerdes

Ideally you want to take them each session but, on the other side of this, you only need the master dark from each session, not the 10-20 subs that make up the master.

Thank you very much Trevor I've started just using the ones from each session, although as you say I might hold on to the master darks for maybe future use.

[Terry B]

There are ways of scaling darks from other sessions with different temperatures if you don't get darks at the time of your data aquasition. "Iris" has a process to scale darks that is independent of the exposure time.
However, with an uncooled camera it is easiest to take the darks at the time.

[CapturingTheNight (Greg)]

Originally Posted by Terry B

There are ways of scaling darks from other sessions with different temperatures if you don't get darks at the time of your data aquasition. "Iris" has a process to scale darks that is independent of the exposure time.
However, with an uncooled camera it is easiest to take the darks at the time.

Thanks for that Terry

[mswhin63 (Malcolm)]

Has anyone done a trail to test whether age of the camera may affect darks?