Advice on strange exposure problem causing banding on bright photos

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spitfire1942

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Hi,

I've got a Canon 300D with the stock 18-55mm lens. It's just over 2 years old now and has done me great service while travelling Oz & NZ last year. Towards the end of the trip I started to notice exposure problems in bright outdoor photos, particularly when there were no clouds and the sun was shining well. A few examples from my flickr collection are -

http://flickr.com/photos/mlbm/1108675080/
http://flickr.com/photos/mlbm/1107827253/
http://flickr.com/photos/mlbm/1108673872/
http://flickr.com/photos/mlbm/1108672174/


These are the original images, I have not altered brightness, contrast etc. They are all shot in same place, the difference between shots being that I stopped the exposure down in 'PIC 003' and 'PIC 004'. Hopefully you will be able to see banding from top to bottom on the landscape shots. The banding is curved, bending toward the right side of the shot. The portrait shot does not seem to exhibit the effect.

Photos not shot in such bright conditions do not appear to exhibit the problem.

The CCD has been inspected by a technican, and I have taken a look myself. I have never touched it. I have not been able to test with a different lens as I do not own a 2nd, and do not know anyone with one (or had a nice bright day to test on in the uk ;) ).

The only explanation I can think of is that there is a problem with the apeture parts. When the light is plentiful is closes up nice and small, but there is a crack or flaw in it meaning that light gets through, causing the brighter bands. This would account for the curved nature. When there is not as much light the apeture stays open and so any flaws would not come into play.

That is just my best guess though, and I don't really understand the finer details of my camera. Before I go out and buy a new lens I would like to know if anyone has any thoughts at all. I'd really appreciate some help, or to hear from anyone who has seen anything like this before. I could throw lots of money at having the camera & lens tested, but I can't really afford to do that.

Thanks in advance, matt.
 
Doesn't look like an aperture blade issue to me (but it could be of course), it looks more like shutter blade troubles. Where the blinds that make up the shutter aren't travelling across the frame smoothly.

I don't know if the shutter on a 300d goes from side to side over the frame or top to bottom. If it's vertical travel, then it's not your problem.

Tis an odd one though, some testing might be in order to see if you can narrow down when it happens and when it doesn't.
 
The shutters on pretty well all modern DSLRs travel vertically these days as it enables a sightly faster flash sync speed, so I don't think it's shutter related.

Beats me tbh and the fact that it's curved makes me think it might be a lens issue, but I'm wildly guessing. Were you using a lens hood? Did you have any filter(s) fitted?
 
The curves were what made me think it's the lens. I would have thought if it were the shutter blade 'stuttering' I wouldn't see dark areas of similar exposure, with brighter areas in between. I'd expect a gradient across the image as one side was exposed for longer than the other.

I did have a lens hood fitted, and a clear filter. I haven't got shots online but I did test without either and got the same results so I did at least eliminate them as a problem.

It's worth noting that in Oz particularly I encountered a lot of dust as I travelled through the remote outback. I was cleaned professionally once and then I was very careful about taking it out in dusty conditions.
 
The shutters on pretty well all modern DSLRs travel vertically these days
Click to expand...

Showing my era eh...... :embarrassed:

Well that's me lost too then. :shrug:
 
I would have thought if it were the shutter blade 'stuttering' I wouldn't see dark areas of similar exposure, with brighter areas in between
Click to expand...

I got a very similar effect for a couple of frames just before the shutter shredded itself on a eos the other week. Only going the other way of course. ;)

My gut feeling is still that it's mechanical rather than a ghost in the machine. That could well be completely wrong too. :lol:
 
I've been into camera stores before but not had a great deal of help. I'm torn at the moment because I have friends coming over from the states in 2 weeks and they've offered to get me a new lens.

I had another thought as well. If it was the shutter or CCD I would expect it to affect all photos, not just brightly lit ones. In the same way that dust spots are visible on nearly all shots (expect night ones). Or it is possible that light is entering the lens through a gap between the moving part of the barrel and the outer grip ?

I know the only way to really diagnose the problem would be to send it away, but I'd rather buy a new lens and then if it turns out to be the body upgrade that too ;) It seems that it is a very rare and obscure problem, and that it would cost a fair bit in labour to figure it out.
 
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