EOS 5D Mark IV Auto ISO keeps ISO too low

[Aurel8]

Hello,

I'm having a very annoying problem with the auto ISO behavior of my 5D Mark IV : it is very reluctant to climb in ISO and tends to stay in rather low settings while compromising the speed, and even setting a slower speed than the minimum speed that I set (1/125). For instance, when it should go to ISO 800 and 1/250, the camera choses ISO 200 and 1/80 (The max ISO value in ISO AUTO is set to 3200)

Anybody ever had this problem ? 

[Waddizzle]

How can we reproduce your issue?

What shooting mode setting are you using on the top dial?  

Do you have “Safety Shift” enabled?  If so, disable it.

[deebatman316 · Accepted solution]

Also what lenses are you using. I noticed that the camera likes to use 1/ focal rule. To avoid camera shake. Lenses with stabilization will allow slower shutter speeds too. Is a speedlite being used. If one is being used the camera usually uses ISO 400-800 in Auto ISO. It won't go higher than that. I would also check the firmware version too. I've never had the camera set my shutter speed lower than what the set minimum is. This sounds like safety shift is turned on. Usually the camera will use a wider open aperture ie F/1.4 instead of F/4. Instead of using a higher ISO. Using a wider open aperture reduces noise.

[Aurel8]

Thanks for your answer ! 

Indeed I had a flash mounted, but it was turned off. Apparently it still causes the ISO auto range limitation ! There is no way to bypass this flash induced reduced ISO range ? 

However, the speed getting slower than the one I manually set as the minimum speed is something that happens often (with both the 6D mark II and the 5D mark IV)

The lens I was using is the TAMRON 24-70 G2

[Anonymous]

As Demetrius mentioned, check if safety shift is turned on in the custom functions. This will override your settings if needed to cause a correct exposure if not disabled.

 

[Aurel8]

Thanks a lot ! That answers the minimum speed overide indeed

[Aurel8]

Hi, 

I finally checked my camera and the safety shift was turned off ! So it's strange that the minimum speed is sometimes being overriden 

[deebatman316]

I can't duplicate your problem with a speedlite attached but off. What brand speedlite are you using. Also what brand of lens are you using. 

[Aurel8]

It's the canon EX430II. The lens was a TAMRON 24-70 G2 

[deebatman316]

When is the last time you changed the batteries in the speedlite. I've seen a similar problem on this website. When the batteries get low. The speedlite doesn't communicate well with the camera. I tried to replicate the problem with a 600EX II-RT, 430EX III-RT & 470EX-AI. But it wouldn't happen. The camera didn't allow the shutter speed to be set faster than x-sync. Which is 1/200th because the speedlite wasn't set to high speed sync. Check and see if Safety Shift is turned on. @5DIV/ Bob said that this custom function. Ignores your minimum and maximum shutter speeds set. Check this Custom Function to see if it's enabled.