Camera Processing of Long Exposures

Russ77

Russ77

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Russ
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I noticed while taking some long exposure shots of fireworks, my 400D seems to take as long to process the image as the exposure.

For example, using the bulb setting, ISO 200 and f8 I'd hold the lens open for around 3-6sec, it would then take a similar amount of time after the shutter closed before I was able to take the next image.

I was using a sandisk III 8gb card and just wondered if this was to be expected (and if so what's the reason as the file size doesn't seem to be significantly bigger) or if there's a problem with my camera and/or memory card.

Cheers in advance

Russ
 
This is long exposure noise reduction working as designed.

What it does is take a second frame with the exact same time as the first just with the shutter closed - this is then used in camera to remove the noise form the first frame.
 
It's a result of how many cameras reduce long exposure noise. They tend to do this by making another exposure of the same duration as the first but without opening the shutter. The result of this dark exposure is then subtracted from the original leaving only the planned image. To stop the camera being out of action for this period, turn off any in camera long exposure noise reduction and deal with the noise in PP using Noise Ninja, Noiseware or similar.
 
before you turn it off though it's worth thinking that the in camera long exposure NR gives results that are at least as good as using NR software. Unless it causes you issues I'd leave
 
TBH, it was more out of curiousity than necessity.

Seemed to take FOREVER while I was trying to capture some fireworks so I changed tactics in the end and went by the music that was accompanying them i.e. guessing that there were likely to be bigger bangs at certain parts during the tracks played.

At first I was getting caught out on the little low level stuff and the camera was already processing when the bigger high level stuff was going off.

May change the settings for 5th November next year but other than that I think I'll let NR do it's funky thing :lol:
 
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