Night photos and camera processor time

[acer0001]

A question for all of you night shooters...

I have been doing night shots that last from 10 sec to 90 sec at F16 at ISO 100 on my Canon Rebel XT. I have noticed that after a longer shot, the camera's processor can take a long time to create the image and write it to the card. Sometimes it can take even longer than the total exposure time. Is this normal and is there a way to reduce this time? I would like to make images that last 30 mins or more, but the camera processing time might take another half hour or more!

Also, I know that long exposures chew up battery life. So, how do you guys manage? Just swap out batteries frequently, or do you buy a grip with multiple batteries in it? Let's say I want to a few hours exposure, How can I be sure that a full battery will last that long?

Thanks everybody...

John

[Daniel Bates]

Are you using in-camera noise reduction? That feature can dramatically increase processing times (especially if the camera is using a second exposure to subtract noise from the original picture - I'm not sure if the XT does this or not).

[Imagebuffet]

I take lots of night exposures, and, yes, the longer the exposure, the longer the processing time on my Canon 20D. I don't remember the longest exposure I've made. I've never run out of battery life, though, from just a few exposures. I have a spare battery if I ever run low.

[kenmyers70]

There is a custom function on your XT to turn off "Long Exposure Noise Compensation"

[trahanw]

My suggestion in to raise your ISO reading to 400 or greater and caculate the time and grain noise to your perfection, with my D300 shooting in the same senerio you mentioned at ISO 100 takes some time in comparison to ISO 3200. Just a tought, then use Noise Ninja if needed to reduce grain. Hope this helps.

[Wes]

My D70, D200, and D3 all take a long time to process images - relatively speaking. I believe that the processor in the D3 is faster than that in the D70, which would explain why a 20sec shot on the D3 takes less time that the same length shot on the D70 and D200. Shoot RAW and your noice processing setting won't really matter. If you shoot at a low enough ISO I doubt that you'd have enough noise in the image to worry about in post anyway.