Canon 6d modified purple light leak with certain lens

[Rowancummins]

Hi there look for some help with my canon 6d it has been modified by astrononmiser ha modified I’m a wide angle Astrophotography guy most of the time but I wanted to capture a shot of comet/2022e 3 the only longer lens I have is a Tamron 70-300 f4-5.6 however something weird was going on the more I zoomed in the of a light leak I got it’s a c shaped purple pink I know that Astro modified 6d have a light leak in live view so it wasn’t that then I tested inside a dark room with the lens cap on and zoomed out two 70mm it’s a dark image as expected but wen I zoom to 300 there’s a massive pink light leak so my guess is it’s a lens issue I haven’t had this on any other lens for Astrophotography all my other lenses are primes so maybe it’s a zoom lens issue but it get worse the closer you get to 300mm

Edited January 31, 2023 by Rowancummins

[michael8554]

Could you post a jpeg of the problem ?

I have a Canon 6D Mk I, and I've never noticed a light leak in LiveView mode.

You have the viewfinder blanked off, though that shouldn't matter in a dark room ?

Weird.

Michael

[sharkmelley]

Without seeing example pictures it is impossible to diagnose.  But many lenses do have an internal IR LED that leaks IR light:

https://www.infraredcameraconversions.co.uk/copy-of-tamron-lenses

https://kolarivision.com/canon-mirrorless-rf-lens-internal-infrared-led-fact-or-fiction/

Mark
 

[Rowancummins]

Yeah here’s the jpegs I increased the exposure as they are quite dark but in the field and take images it’s quite obvious at 300mm one is at 70mm which looks fine the othe is at 300mm where light leak is apparent 

[sharkmelley]

3 hours ago, Rowancummins said:

Yeah here’s the jpegs I increased the exposure as they are quite dark but in the field and take images it’s quite obvious at 300mm one is at 70mm which looks fine the othe is at 300mm where light leak is apparent 

That would appear to be consistent with an IR source internal to the lens.

[Rowancummins]

3 hours ago, sharkmelley said:

That would appear to be consistent with an IR source internal to the lens.

Thanks for your help 👍

Edited February 2, 2023 by Rowancummins

[michael8554]

I stretched the image further

 

R=75

G=64

B=110

Is this consistent with an IR source, or just light leak ?

Michael

[sharkmelley]

Generally speaking if the artifact appears purple when white balancing has been applied (e.g. in the in-camera JPG) then the cause is an IR leak.  The question is whether the IR source is inside the camera or the inside the lens.  For the Canon 6D, if you have the camera live-view switched off then the lens is the most likely origin of the IR.

Mark

[Rowancummins]

These were shot in raw with a custom white balance they were converted to jpgs when I uploaded them when I was testing the camera i covered  the led on the side of the camera next to the sd card and covered the red light on my intervalometer and this still happened they are also not shot in live view and this doesn’t happen with other lenses so I think the Tamron 70-300 has a ir light source inside it

Edited February 2, 2023 by Rowancummins