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Jpeg artifacts on a night sky?

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ngannet
 
Posts: 12

Jpeg artifacts on a night sky?

Post Thu Dec 23, 2010 2:57 am


Hello. I took some pictures of the lunar eclipse the other night and after uploading to my site, I noticed horrible blocky jpeg artifacts (I guess that's what they are). Any way to get rid of these other than reducing noise and using the brush tool to black them out? Ugh...the pictures were nice til I uploaded them. Here's an example: http://www.pbase.com/ngannet/image/131311047 and an even worse one here: http://www.pbase.com/ngannet/image/131311049 Any tips would be appreciated. Thanks.

dw_thomas
 
Posts: 481

Re: Jpeg artifacts on a night sky?

Post Thu Dec 23, 2010 3:10 am


Hmm - on this monitor I don't see what I would call artifacts -- the second shot looks like there was some sort of internal reflection in the lens elements, and maybe a bit of flare forming a slight halo along the bright side (although that could be atmospheric haze or slight condensation on the lens too).

My equipment is woefully inadequate to such a task, but I'm glad to see I wasn't the only one freezing behind my 40D the other night! :D

ngannet
 
Posts: 12

Re: Jpeg artifacts on a night sky?

Post Thu Dec 23, 2010 3:13 am


I should have mentioned that I don't really see the artifacts when looking at the image straight on. Stand up and look down at the image on an angle and perhaps you'll see what I mean. Hahaha, yeah, it was FREEZING out there. A beautiful still clear night, but bone-chillingly cold! I stayed up for the duration of it!

dw_thomas
 
Posts: 481

Re: Jpeg artifacts on a night sky?

Post Thu Dec 23, 2010 4:56 am


Hmmmm - I see a difference in the flare looking from way up high, but that's about it. Have you looked at it on another monitor? Since I don't exactly know what you're seeing, this is all speculation, but I'm wondering if it's some aliasing or Moiré effects from file pixel pitch vs screen pixel pitch. I wonder if anyone with eyes way younger than mine has checked it out?! :shock:


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