Light Leaking?

S

Steelmagnet

Messages
284
Name
Steve
Edit My Images
Yes
Hi all

My friend has a problem with his 1D and I wonder if someone might give me an idea what is causing the problem.

As you'll see from the attached image there's a fairly large flare and it's on every shot. It's not a fault with the lens (Sigma 120-400) as we've tried it on his 5D.

My guess is that light is leaking in somewhere, and although it looks like there might be a hair somewhere, we can't find one.

Many thanks
Steve

33orzn8.jpg
 
Show us another shot, in different light, with a different lens.

You can only guess at these things, but I would say could be lens related, light reflecting off summat shiny like a filter thread, or some internal reflection from the strong side lighting.

I've also seen shutter faults with a similar pattern. The blinds run down in a curve like that.
 
Thanks for your reply.

The only alternative I can show is the same lens on the 5D MKII, taken on the same day, with no hint of the fault.

o6xs06.jpg


I think that rules out the lens, especially considering that the fault shows on the 1D regardless of the amount of light. It's also not visible through the viewfinder so my guess is that it's light leaking onto the sensor, or shutter related as you say.

I'll get him to chuck his 70-200 on the 1D at the weekend to try and prove that it's the camera at fault. Of course, there's the chance that it's the combination of that lens and the 1D. In that case, he's got all the excuse he needs to buy a shiny new lens and body...
 
That's not conclusive though. If it is a lens/light issue, it will vanish when the bright side lighting of the first pic changes to overcast in the second.

I think I'm going for a shutter fault though. Come back and tell us when you get to the bottom of it, just for future reference :)
 
Shutter count is 133k, which I guess is quite high, but certainly not screaming 'worn out' at me.

The problem is manifesting itself on the less brightly lit shots, but nowhere near as obviously.

I'll post further investigation results in due course.

Thanks all.
 
Any sign of a scratch on the mirror (towards the hinge at a guess)?

Bob
 
Steelmagnet said:
A scratch on the mirror wouldn't appear on the image though would it?
Click to expand...

It wouldn't appear sharp on the image. The mirror is around 40% transmissive (40% of the light passes through it). When the mirror flips up, it effectively blocks any light progressing from the eyepice and through the pentaprism to the mirror chamber. 40% of any light heading this way will get in but it only becomes an issue on longer exposures....hence the little cover for the eyepiece. If the transmissive coating is scratched away then there's a small fissure where 100% of the light can get into the mirror chamber.....causing a slight fogging on that portion of the image.

Hope that explanation worked for you.

Bob
 
I don't think it is shutter. There would be black edges, no a bright streak.

It can't be hair or dust - that would show up darker. Perhaps the sensor is smeared around the bright spot and needs a clean. Lock up the mirror and have a look.

Take a photo WITHOUT the lens, then with a different one. Still there?

A general light leak would more likely cause overexposure and loss of contrast.

The sensor isn't scratched by any chance? In theory this should sharpen up towards f/22 to a bright thinner line.
 
Last edited:
Canon Bob said:
It wouldn't appear sharp on the image. The mirror is around 40% transmissive (40% of the light passes through it). When the mirror flips up, it effectively blocks any light progressing from the eyepice and through the pentaprism to the mirror chamber. 40% of any light heading this way will get in but it only becomes an issue on longer exposures....hence the little cover for the eyepiece. If the transmissive coating is scratched away then there's a small fissure where 100% of the light can get into the mirror chamber.....causing a slight fogging on that portion of the image.

Hope that explanation worked for you.

Bob
Click to expand...

Bob, the mirror is opaque backed. The only light getting though when the mirror is up, via the viewfinder, is through any gaps around the edges or the sealing around the piggy-back AF mirror.

Almost zero except in extremes, eg 10-stop ND, that don't apply here. Unless there's a fault. Or unless I'm misunderstanding your meaning ;)
 
HoppyUK said:
Bob, the mirror is opaque backed. The only light getting though when the mirror is up, via the viewfinder, is through any gaps around the edges or the sealing around the piggy-back AF mirror.

Almost zero except in extremes, eg 10-stop ND, that don't apply here. Unless there's a fault. Or unless I'm misunderstanding your meaning ;)
Click to expand...
That's it in a nutshell Richard. Now, if the coating were to be 'nicked' near the hinge (outside the region of the sub mirror), it would be feasible to get a small leak that would be oblique to the sensor.
I'm not saying that this is the cause of the problem, just putting an idea out there.

Bob
 
I'm with you Bob :) Be interesting to see how it turns out.

There was a similar thread, prolly a couple of years ago now and I can't find it. That turned out to be a shutter fault. Not unheard of with Canons apparently.
 
You must log in or register to reply here.
Back
Top