noise with long exposures

[ballroom_boy]

Hi there

I've been playing around with long exposures lately (typically 1-15 seconds). I am finding in the "dark" areas of the shot that there is a lot of "noise" - typically for the exposures from 1 - 5 seconds. At about 10 seconds, I don't see it anymore. BTW, I am using ISO 200 and 400 for these shots.

Is this "normal"?

[Andre]

Originally posted by ballroom_boy
Hi there

I've been playing around with long exposures lately (typically 1-15 seconds). I am finding in the "dark" areas of the shot that there is a lot of "noise" - typically for the exposures from 1 - 5 seconds. At about 10 seconds, I don't see it anymore. BTW, I am using ISO 200 and 400 for these shots.

Is this "normal"?

Are you using JPG or RAW?
I find with higher ISO the noise is worsened with JPG.

[ballroom_boy]

I am shooting JPEG... I know at ISO 800/1600 there is quite a bit of noise, but I didn't expect that at ISO 200!

Is this a problem with JPEG or has anyone else experienced this?

[Andre]

Originally posted by ballroom_boy
I am shooting JPEG... I know at ISO 800/1600 there is quite a bit of noise, but I didn't expect that at ISO 200!

Is this a problem with JPEG or has anyone else experienced this?

It's not so much of a problem with JPEG. It is that JPEG latches onto the noise and during its compression, it makes it worse.
Try the same thing in RAW and you'll see that it's better.

[puglover]

This image was shot in low light - ISO 400, F2, 125s, 50mm 1.4 Nikkor... this is the blue channel only at 100%.

I have outdoor shots also at ISO 400 that don't have this problem at all - and also shots from this same series at ISO 200 that don't have the blue channel noise... but the ones in the church at 400 or higher the blue noise is horrible - is this a problem with my camera or is everyone else experiencing this??

[puglover]

And the above was slightly sharpened - however it looks almost as bad with no sharpening at all as I always turn it off in the camera... also, this was shot as a JPEG.

[szszsz]

I'm a newby on this forum ... without having introduced myself before.
Therefore I'm now trying to do a good start with a picture.

In this forum I've already learned many interesting details about my camera and the processing of images - thanks guys.

Now to the thread.
I was positively surprised by the low noise on long exposures!
I shot the attached image at midnight in London!
ISO 200, 2' (minutes not seconds), f8.0, raw, default processing (LE software)


I did a similar shot with different settings:
ISO 1600, 15", f8.0, raw, default processing and this image has heavy noise.
I guess it comes from the ISO setting (basically what I expect) - I'll have to do further tests.

Regarding puglover's "blue channel" comment:
I read somewhere that the individual channels seem to have heavy noise and the software then fixes it with mixing the channels - or so.