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troypiggo
30th of September 2008 (Tue), 17:10
I've never shot long exposures before, but I've been shooting RAW since first started out. I have never noticed this before, but when shooting for 30secs, 90 secs etc, after the shutter has closed again, the camera takes nearly the same amount of time the shot took to write it to memory (didnt' actually measure the time, but roughly). So for a 30sec shot, it takes around another 30secs to write to card, doubling the time.

I'm worried if/when I start attempting 30min star trails etc, they're each actually going to take an hour each and so on.

Haven't tried shooting JPG to see if it's the same thing.

Do you all shoot RAW? If not, is the above the reason or something else?

Main reason I have always shot RAW is better control of exposure and white balance etc, and also treat those files like negatives. But with astrophotography, maybe exposure and white balance aren't as much a factor due to the subject? Not sure. (Of course exposure is important, but what I mean is it's not like someone's face is underexposed, we're talking about white dots on a black background anyway - that make sense?)

Johnny9s
30th of September 2008 (Tue), 17:30
I only shoot in Raw at the moment. Do you have long exposure noise reduction on? If you do then that is why it takes so long. You should turn this off and do the noise reduction in post processing. Your card write speed can play a roll in the length of time it takes as well. You should try to get the fastest card you can afford.

troypiggo
30th of September 2008 (Tue), 17:36
Thanks for the tip on long exposure noise reduction. I don't remember setting it myself, but I'll check to see what it's set on. The card I have is pretty fast.

Jeff
1st of October 2008 (Wed), 09:55
Long Exposure Noise Reduction was probably set to AUTO by default so you didn't actually do anything to turn it on. In AUTO any shots longer than 1 sec it will have LENR applied.

hollis_f
2nd of October 2008 (Thu), 09:22
Your card write speed can play a roll in the length of time it takes as well. You should try to get the fastest card you can afford.

The time difference in writing a single raw file will be negligible unless you're using a really, really slow card. Anything like a Sandisk Ultra II or better will suffice.

le_R
3rd of October 2008 (Fri), 07:50
I confirm for the Long Exposure Noise Reduction. To have better result in thermal noise reduction, disable it, and do yourself several dark frames. between 10 and 20, you should build a good dark frame. Use Iris (http://www.astrosurf.com/buil/us/iris/iris.htm) or DSS (http://deepskystacker.free.fr/) for example.

troypiggo
3rd of October 2008 (Fri), 09:39
Yep, Long Exp NR was set to auto. Have disabled and will check to see the benefits. Thanks.