Why my camera always sticks to ISO 400 when using external flash in AUTO ISO?

[Hjalmarg1]

I don't normally use speedlites because I do a lot of school sports and landscape but recently I was shooting family pictures at a family ceremony and I left the ISO in AUTO and later realized that the camera always set the ISO to 400 regardless I was indoor or outdoor or at any different level of ambient light. It resulted in many overexpossed outdoor pictures and many underexpossed indoor pictures. Shouldn't the camera increase or decrease the ISO automatically to match the ambient conditions for overall exposure?
I have tried to find information on the users manual and couldn't find why my camera does that and how to improve this situation. My camera body is 5D Mark III

Support is very appreciated.

 

[AvTvM]

Unfortunately ISO 400 in auto-iso with on camera flah is an age old limitation of canon's implementation of auto-iso.

Several workarounds available (mode P, mode M, high speed sync on/FP, safety shift off, etc.), nine of them really satisfactory. Only, real solution: Nikon (higher level cameras, like D810) havre a far superior auto-iso algorithm. canon 1dx also handles it better.

 

[JohanCruyff]

I didn't knew one could hope for a different ISO algorithm.
I'm used to it: when I shoot with my 70D, after half-pressing the shutter button, the viewfinder shows me if it expects a underexposed or overexposed picture and this allows me to set the flash_exposure_compensation level accordingly.
It's a bit anooying but it should work with other bodies too.

 

[9VIII]

I still baffles me that so many huge multinational corporations can get basic menu and firmware functionality so wrong.
If there's anything people should be in an uproar about it's stuff like this.

 

[AvTvM]

I still baffles me that so many huge multinational corporations can get basic menu and firmware functionality so wrong.
If there's anything people should be in an uproar about it's stuff like this.

we have had many discussions re. Canon's poor implementation of Auto-ISO on many/most of its cameras. Every time the topic was downplayed and led Off-topic in the usual way by assorted Canon fanboys around here. I have given up expecting anything from Canon. Especially when it is something really simple and really useful that could be implemented really easily by way of a firmware update.

 

[Hjalmarg1]

I still baffles me that so many huge multinational corporations can get basic menu and firmware functionality so wrong.
If there's anything people should be in an uproar about it's stuff like this.

we have had many discussions re. Canon's poor implementation of Auto-ISO on many/most of its cameras. Every time the topic was downplayed and led Off-topic in the usual way by assorted Canon fanboys around here. I have given up expecting anything from Canon. Especially when it is something really simple and really useful that could be implemented really easily by way of a firmware update.

It is sad and disappointing to hear that situation that could be easily solve remains, as others have mentioned, not yet solved by Canon. My P&S camera does increase or decrease the ISO based on the environment light, even using flash for better exposure.