5Diii light leak, or what

[Horwig]

I decided that I should do a better process of some widefields I recently took, and apply a dark, so took the following dark image:

trouble is, I don't see the red streak on my lights:-

camera was in a dark room, lens cap on and light tight box for the dark, exposure details for both, 30 seconds at ISO 25600, lens on manual focus. and as far as I can recall, all other settings identical.

 

I've read that some 5Diii cameras suffer from leaks from the top LCD, but then it would be in the light as well.

 

Anybody with any ideas?

 

Huw

 

[wxsatuser]

5DMK3 is known to have ampglow issues at high ISOs

[Horwig]

14 minutes ago, wxsatuser said:

5DMK3 is known to have ampglow issues at high ISOs

Agreed, the corners look particularly bright in the dark, but why don't I see the red curved streak in the light?

 

H

[michaelmorris]

It could be a light leak through the viewfinder. Did you cover the viewfinder with black tape when taking the darks?

[Horwig]

good point, will try with the viewfinder covered.

[Alien 13]

I would question the need for dark's on higher end Canon cameras I find a bias frame is ok and some flats to eliminate optical/sensor errors.

Alan

[Horwig]

No luck I'm afraid, same as before. What is interesting is that the streak is not identical on each exposure, very slight differences, but not much.

 

Huw

[Alien 13]

Are you running the camera with a grip or std, the battery's can produce a lot of heat.

Alan

[Horwig]

It's a standard battery, I'm stumped. My brother's friend has a 5Diii, I'll ask him if he has anything similar on his.

[Alien 13]

The reason I asked about a battery grip is that they place the batteries, normally two away from the camera internals  so any heat generated is not picked up by the sensor. An in camera battery can generate localized hot spots depending on the contact resistance, you have to remember that the 5D 111 is very sensitive.

Alan

[Horwig]

I'm still playing with this, and lo and behold, one of the 30 second darks I've taken has no red smear on it. Now I really am confused, there was no difference in the way I took the exposure from all the others I was taking.

[Horwig]

I think I've found it! The difference between the lights and the darks was the LENS CAP. Remove the lens cap, and replace with a black cloth, and the artefact goes away.

 

Live and learn

 

Huw

[wimvb]

Lens caps are not (IR) light proof. I used to cover my lens with aluminium foil when I did darks, and stopped the lens down to highest f/ just to make sure.