Why does my EOS R5 keep going to auto ISO?

[comolfa2]

Can you help me? I have done some shoots recently with my R5 (with battery grip) in Manual mode and the Lock button engaged. I am using a Godox transmitter for lighting. However, it keeps jumping into Auto ISO. What am I doing wrong?

[shadowsports]

Greetings ,

Under your custom functions menu settings, please look at Safety Shift.

[johnrmoyer]

I hope some of this might be helpful.

There are several places in the camera menus that might cause the ISO setting to change automatically.

https://cam.start.canon/en/C003/manual/html/UG-03_Shooting-1_0070.html#Shooting-1_0070_2 

Note

• The [Minimum] and [Maximum] settings will also function as the minimum and maximum speeds for ISO speed safety shift ().

https://cam.start.canon/en/C003/manual/html/UG-03_Shooting-1_0070.html#Shooting-1_0070_2 

https://cam.start.canon/en/C003/manual/html/UG-08_Custom_0030.html#Custom_0030_1-7

Note

• Safety shift overrides any changes to [ISO speed range] or [Min. shutter spd.] from default settings in [ :  ISO speed settings] if standard exposure cannot be obtained.
• The minimum and maximum limits for the safety shift with the ISO speed are determined by [Auto range] (). However, if the manually set ISO speed exceeds the [Auto range], the safety shift will take effect up or down to the manually set ISO speed.
• Safety shift will take effect as necessary even when flash is used.

Auto lighting optimizer enabled might cause the ISO to change.

Having a flash attached changes some of the behaviors. I do not use a flash often, so others could give a better answer.

I use Fv more than M, and some of the behaviors differ between the 2 modes even when none of the settings are auto in Fv mode.

Some of the interactions among camera settings have changed with firmware updates. The version of firmware in your camera might matter.