Noise and colour banding in night photography help

Psilonaught · 16 Jan 2006 at 09:45

I finally got some time to take my kit out for some night photography, and went to the South Bank last night - it was a full moon and I was pretty happy with my results (will post them in a seperate thread).

The problem is that post RAW processing is showing quite a lot of noise and worse, some blotchiess and colour banding in the sky.

The noise I can fix in Noiseware but the banding looks bad in some of them and will almost certainly be rejected by istock

I always shoot ISO 100 and I have noticed the same noise and banding at 4sec and 30sec, so exposure time seems to make no difference

I've tried playing around with CS2 RAW settings and luminous smoothing set to 99% seems to help but not much.

The original raw image when viewed in the preview pane (pre-processing) doesn't seem to exhibit the same noise and banding??

Any tips, suggestions??

Psilonaught · 16 Jan 2006 at 11:07

on most of the shots I underexposed in the shot, and increased slightly in CS2. I also cooled down most of the images to reduce the orange glow from junk light in the clouds

Are you saying that using post processing to increase exposure can cause these issues?

Psilonaught · 16 Jan 2006 at 11:18

ok will take another look at the RAW images tonight and play around with the ones with higher exposures.

Don't worry, I always bracket night shots, and I have a copy of each at a higher exposure

Psilonaught · 16 Jan 2006 at 12:46

guys what about mirror lock-up? Should I always be doing this when out at night with my tripod? Normally I set the camera to 10sec delay, focus, click and wait for the exposure.

Thanks

Psilonaught · 16 Jan 2006 at 15:30

I found some more info about this on istock forum

CCDs on most cameras will overheat and get qwirky grain problems on long exposures in low very light.

the camera retains MORE information in the right side of the histogram than the left side. The rightmost one-third or one-quarter contains something like 3/4 or more of the image information. So you want to make sure that your mountain range is weighted to the right side, in effect. The histogram should look lopsided to the right side. Your subject, hopefully, should be as much as possible on the lighter side of middle tones

interesting. Looks like my mistake was to use a high F stop and hence longer exposure, when in fact i should have been using a low F stop and shorter exposure.

I also need to overexpose night images so the graph is right-sided

Psilonaught · 16 Jan 2006 at 18:06

yep that all makes sense - I did everything right apart from the over exposure part :rolleyes:

WIll post the pics when I get home