topic Re: R6mk2, I can't get the flash to allow slow shutter speeds. in EOS DSLR & Mirrorless Cameras

R6mk2, I can't get the flash to allow slow shutter speeds.

adam461 — Fri, 04 Jul 2025 20:37:04 GMT

My flashgun (EL-10) is acting in a way that I don't want it to, there must be a setting I can change but I can't seem to find it. I've had my R6mk2 for around five months now after upgrading from a 1DX, there's been a few things I've had to learn with mirrorless and I've got most of it sussed, apart from one issue; I noticed that some my pictures taken indoors with flash were very under exposed and I couldn't work out why, today I discovered what the issue is, but I can't seem to fix it.

Whenever I take a picture (AV mode) with the flash (EL-10) switched on, the shutter speed won't drop below 1/60th of a second. Even if the correct exposure is 1/30th of a second, the camera won't drop below 1/60th and the picture is slightly under exposed. Back with the 1DX, I could shoot in AV mode, take pictures at 1/15th, etc and everything would work fine, but with the R6mk2, it stops at 1/60th.

I've scrolled through the menu settings but I can't seem to find anything, the safety shift is switched to off, I'm guessing there's some sort of flash sync exposure setting I can change somewhere, but I for the life in me, can't find it. Obviously there's a maximum shutter speed that the flash will sync to, but I've never known there to be a issue not syncing with a slow shutter speed.

TIA for any help you can give.

Re: R6mk2, I can't get the flash to allow slow shutter speeds.

adam461 — Fri, 04 Jul 2025 20:44:30 GMT

Just to update, the flashgun is always in HSS mode and I'm shooting in Elec. First Curtain mode on the camera. I've just asked Google my question, and it says 'electronic shutter mode, it might not be compatible with flash below 1/60s. This is because the electronic shutter exposes the sensor by scanning across it, which can interfere with the flash synchronization.'

So I'm assuming it would work ok in mechanical mode. Will it not go below 1/60th in electronic shutter mode? I will try it tomorrow when it's light again.

Re: R6mk2, I can't get the flash to allow slow shutter speeds.

deebatman316 — Fri, 04 Jul 2025 22:12:42 GMT

Electronic First Curtain Shutter has restrictions. Also check the flash sync in Av Mode setting. Also the flash algorithm works differently on the EOS R series. DSLRs defaulted to 1/60th F/4 ISO 400. The EOS R series will push the ISO up very high depending on the lens.

Re: R6mk2, I can't get the flash to allow slow shutter speeds.

p4pictures — Fri, 04 Jul 2025 23:48:21 GMT

EOS R series cameras work differently to DSLR when it comes to flash with Av mode.

I wrote about this on my blog back in 2018, though it’s still the same for the current R-series cameras.

https://www.p4pictures.com/2019/03/fill-in-flash-different-eos-r-rp/