RF100-500 ISO maxes out at f/8

[Yvita]

hi, 

i have an issue with my RF100-500 (on a canon r5)  and I hope someone can help me:

When it is all zoomed out to max, and f7,1 nothing is wrong, but when I add one stop to f8,0 and I want to shoot, ISO goes to the max and screen gets dark because of that. Same with higher aperture.

Tried another lens, no problem (ef 24-105mm plus adapter). Tried to lower max ISO, same problem but not so dramatic because of the lower iso.. When I zoom a bit back to for example 460 mm. no problem at all. Weird right?

I have filmed it but can not upload it here?

[Waddizzle]

How old is the lens?  If the lens is under warranty, have you contacted Canon Support?

https://www.usa.canon.com/support/service-and-repair 

[Yvita]

Thanks for your answer, the lens is over a year old, had a crack in the inside half a year ago, they repaired it as warranty.. maybe something went wrong there? can not recall I had this problem before that

[shadowsports]

Greetings,

What shooting mode are you using?  I agree with @Waddizzle,  If this is not happening with other lenses, it would seem to indicate a problem with your 100-500.

What happens if you shoot in Av?  Set the aperture to f7.1, zoom to 500mm, half press shutter or press DOF preview, confirm f7.1.  Add 1 stop, press DOF Preview, does your aperture jump to f22?  

[Yvita]

Hi! I allways shoot in manual mode.. i tried av mode like you said, same problem.. the image gets dark, i do not see the iso value or aperture value change though.. in 7.1 no problem, 8.0 problem. And not when i zoom back in a bit…

[ebiggs1]

"... had a crack in the inside half a year ago, ..."

That warranty is still good. Call Canon 1 (800) 652-2666