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DPChallenge Forums >> Tips, Tricks, and Q&A >> Artifacts and Is My Camera Broken?
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AuthorThread
 03/05/2006 02:09:57 PM · #1
Hi all,

I am hoping you can help me out. I have been taking a lot of landscape pictures with my Rebel XT. I have noticed in many of the pictures that there seem to be artifacts or noise in the sky. At first I thjought it was because of the JPG processing, but I have taken some pictures in RAW mode and I get the smae thing. Funny thing is it doesn't always seem to happen, but oit does happen often. Next, I thought I was shooting at too high of an ISO, so I cranked it from 400 down to 100, still getting these artifacts (or whatever they are). I didn't think it was a lens problem, but I switched from my Canon 17-85 to a Canon 100-300 L lens and still have the same problem. I am starting to think it is a problem with my sensor. I really am new to all of this, so I don't know a whole lot about things. Can anyone look at the picture I ahve attatched and help me out?

Thanks.

--Lit

large image

Message edited by langdon - large image.
 03/05/2006 02:15:03 PM · #2
Originally posted by Litl:
Hi all,

I am hoping you can help me out. I have been taking a lot of landscape pictures with my Rebel XT. I have noticed in many of the pictures that there seem to be artifacts or noise in the sky. At first I thjought it was because of the JPG processing, but I have taken some pictures in RAW mode and I get the smae thing. Funny thing is it doesn't always seem to happen, but oit does happen often. Next, I thought I was shooting at too high of an ISO, so I cranked it from 400 down to 100, still getting these artifacts (or whatever they are). I didn't think it was a lens problem, but I switched from my Canon 17-85 to a Canon 100-300 L lens and still have the same problem. I am starting to think it is a problem with my sensor. I really am new to all of this, so I don't know a whole lot about things. Can anyone look at the picture I ahve attatched and help me out?

Looks to me like just regular electronic noise. Get a noise reduction software or, if you have built-in noise reduction in your image editing software, use that. Should easily take care of that.

When working with jpeg files you only have 8-bit color which has a limited color space and you will see discontinuous pixel differences where there should be subtle shade variations, 8-bit color does not have the in-between shades. This usually shows up most in skies.

Message edited by author 2006-03-05 14:18:45.
 03/05/2006 02:23:17 PM · #3
I see a large image spanking coming on....

Litl it is better to post a link and a file size warning as there is handful of dialup users here that get grumpy (prolly cause they are still on dialup)

Don't see much artifacts, maybe some noise... is this your first dSLR? there is a lot of Post-P that you could do to this shot.

Andy

ED: been fixed...

Message edited by author 2006-03-05 14:23:51.
 03/05/2006 02:24:44 PM · #4
I see one spot on the far right of the picture, in the sky, about 25% down from top that appears to be sensor dust. Nothing other than that. Search the forums for Sensor Cleaning and you will find many threads with links, techniques, etc. on just how to clean it and what not to do.

EDIT: Very nice image by the way. It definitely looks better larger. I just downloaded the image and ran it through Neat Image, auto profile. It cleaned up the sky nicely although there wasn't much noise there. A few adjustments to the image and it really gets a Wow! factor. The sensor dust spots are not very dark and would probably easily blow off with a blower (nasal syringe) - don't use canned air.

Message edited by author 2006-03-05 14:47:41.
 03/05/2006 03:46:33 PM · #5
If you're talking about the couple darkish blotches, those appear to be sensor dust. It looks like your sensor needs to be cleaned. Could you take a photo of the sky, stopped down to f/22, and post it back here?

Thanks,
Terry
 03/05/2006 08:25:01 PM · #6
Thanks all, adn I am sorry about the large picture size. I thought I needed to keep it big so people could more clearly see what I was talking about.

These answers are very helpful. Thanks for the comments about the dust on the sensor. I will get that cleaned off. My main worry was about the sky in general having the uneven texture. The RAW looks like the JPEG. I will try running some noise reduction on it. I have PhotoShop CS2, so I can play with it or look into getting a plug-in. AS for processing, I really didn't do any on it. I saved in from Camera RAW without any attempt to improve the image. I have jsut seen problems with my sky pictures, so I was worried I might have a sensor problem. My camera is just over six months old, so I figured if I had a faulty sensor, I better get it fixed, but it seems like no one feels that is the problem.

Terry, I will take a ski shot and post it on here.

Thanks again everyone - you are terrific.

--Lit
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