Canon EF 24-70mm Exposure Issue on RED Epic

[Elwin van Alst]

Came across this issue last week and its baffling us... wonder if anyone has some insight.

When I zoom using the Canon 24-70mm lens on our RED Epic (and also our FS7) the image exposure drops 2-3 stops, however the camera indicates that the lens aperture has remained constant. However, when I throw the lens on our Canon 5Dmkiii and try to replicate the issue it captures a constant exposure the full length of the lens.

The RED is using the EF Mount, while the FS7 utilizes a speed booster.

Let me know if I need to provide more info.

Thanks for the help.

[Simon_G]

Came across this issue last week and its baffling us... wonder if anyone has some insight.

When I zoom using the Canon 24-70mm lens on our RED Epic (and also our FS7) the image exposure drops 2-3 stops, however the camera indicates that the lens aperture has remained constant. However, when I throw the lens on our Canon 5Dmkiii and try to replicate the issue it captures a constant exposure the full length of the lens.

The RED is using the EF Mount, while the FS7 utilizes a speed booster.

Let me know if I need to provide more info.

Thanks for the help.

Hey Elwin,

I have been using this lens for years and it does loose light through the zoom.

My guess is in photography application it doesn't because the shutter might accommodate?

But it certainly falls off some on my c100 & Raven. I just tweak the shots to match.

Canon are pretty slippery with their products and are not full honest with specifications.
I am hoping to move away from Canon this year for more motion aligned lenses.

[Kris Tait]

This is a well known issue for all their zoom lenses. It drops approx. 1.5 stops of light between 24 and 70mm. The 24-105mm suffers from it most. Really bad lenses for digital cinema. Excellent for photography.

[Grzegorz Gill]

The light loss drove me nuts, look into cn-e 18-80mm. I bought 2x of them and love them, no light loss, manual aperture and IS. Strong lens with a zoom rocker, plus the zoom is internal. Lot's of budget cine lenses out there, no need for stills glass anymore.