1DX ii Minimum shutter speed in AV mode

[settysphoto]

When using the AV mode on my canon 1dx ii with the 500mm f4 it determines the shutter speed based on the focal length used for hand holding which means it usually aims for around 1/1000th of a second but while it aims for this said shutter speed it ramps up the ISO to maintain the shutter speed at 1/1000th. The shutter speed does not need to be that high, i can quite easily hand hold it at 1/500 of a second which would bring the ISO down too.

If i use the 500mm lens on my 5D iii on AV mode the shutter speed & ISO it decides is much more reasonable because this camera does not determine what the shutter speed should be based on focal length.

Why isnt there a way to just turn the feature off on the 1dx? 

Maybe im missing something obvious?

Id really like to have it how my 5D iii is.

Is there a workaround from this issue?

[ebiggs1]

"I would suggest resetting camera to factory and clearing all custom settings ..."

I advised this a long tome ago.  It is what you need to do next and first off. I have only used a 1DX Mk II a few times but I use my 1DX  all the time. Unless something was drastically changed between the two I don't see what you are. Either that or the ef 500mm f4 is a unique lens and I don't have one to try for you.

The biggest lens I can put on my 1DX right now is the Siggy 150-600mm S.  I set the Av to f16 and ISO to 100.  The camera selected a SS which would be impossible for me to accomplish a sharp picture (1/30, 1/15, etc). Well below the 1/600 you would have expected if your thoughts were correct. 

When I set it to auto ISO (min ISO to max ISO) and had good light the 1DX did seem to try and stay at 1/500 (600mm lens) which you might expect.  However, when I pointed it to a really dark place the SS went very slow as expected. So slow you could not get a sharp picture. Do the reset.