Odd behavior when using flash with Auto ISO

Hello, hopefully someone can help me answer this question. When shooting with auto ISO in aperature priority, the camera does not go above 250iso when ISO is set to 64 AUTO. However when I bump up the ISO to 800, and leave it in AUTO, the ISO will set anywhere from 64-3200(or whatever max value). This is entirely different from how the camera behaves without flash. Is this how it is supposed to work? Shouldn't the AUTO ISO stay in full auto, able to set to whatever value it needs, at 64 AUTO regardless of whether the flash is on or off?

Hopefully that makes sense, and that someone can help me. Thanks!! I am using sb-700 fyi.


  • PB_PMPB_PM Posts: 3,933Member
    Can you tell us which camera you are using? In camera flash settings, etc. Is it a D810, D850? No idea if that's normal to be honest, since I don't have either.
    If I take a good photo it's not my camera's fault.
  • WestEndFotoWestEndFoto Posts: 2,894Member
    Not exactly sure, but this does not surprise me. Most cameras have a maximum synch speed, which is 1/250 second with the better ones. I am sure that your camera is ensuring that you don't exceed your maximum synch speed. Then of course if you push it higher, then it thinks it is intention and permits it.
  • PistnbrokePistnbroke Posts: 1,761Member
    I use this feature all the time ..when you plug in an external flash the iso goes to 4x the base iso . I always use 200 so with the flash it goes to iso 800 BUT if it is very bright say I forget and leave it on outside the iso will go down below 800 .If the flash is not powerfull enough it will go above iso 800. It stays at iso 800 95% of the time .
    When you turn the flash off it goes to normal auto iso mode which I haveset at 200-6400.
  • edawg011edawg011 Posts: 2Member
    Ok thanks. Problem is now I have to remember to raise the ISO when using flash, and lower it when the flash is off, even though ISO is in AUTO which has me wondering what is the point of having auto ISO then?
  • WestEndFotoWestEndFoto Posts: 2,894Member
    I wasn't paying attention. Thought you were talking about shutter speed.

    Auto ISO is handy with no flash. It boosts the ISO when shutter speed is getting low. I use it on my D800/850 all the time.

    This may work a little differently if you have a different model.

    I use SB-910s, but usually shoot them in manual, so I am not really thinking about ISO.
  • retreadretread Posts: 506Member
    Interesting. I am learning to use a Sb5000 with my D500. I shoot in manual and float the ISO. I will have to see how it works when I have a chance to work on it. Just now learning how to set the flash hopping it will do what I want it to do.
  • PistnbrokePistnbroke Posts: 1,761Member
    No NO edawg001 ..the rise to 4x iso is automatic so if you are on 64 iso it will go to 250 iso WHEN YOU TURN THE EXTERNAL FLASH ON and back to 64 when you turn it off .
    Try it in a room with normal artificial light levels and you will see it in the viewfinder.
    Of course if Nikon would aboandon "pro controlls" and give us U1 U2 etc we could change to flash preferance at the flick of a switch.
  • sportsport Posts: 103Member
    Here is a page with information on Auto ISO and Nikon speedlights:

    Auto ISO and Nikon Flash

    Are you changing between using the speedlights and not during a single shoot? For me, manual mode works better.
  • PistnbrokePistnbroke Posts: 1,761Member
    The link above is total out of date rubbish when related to D7100 cameras and later. Prior to the D7100 Nikons did not have the 4x iso lift for flash.I have seen nothing printed by Nikon on the system .
    Get it clear this applies to fitting one flash in the shoes . My limited experience with remotes (yn622n TX) indicates that the iso stays at a fixed base iso when these are in use. Some third party flashes will not work at all with nikon ( D810 and after) ie Meike but I have no problem with YN.
    sport ...please delete your link it will cause endless problems for some readers
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