Nikon D800 & Auto ISO

in
I had an issue with my D800  yesterday afternoon. I shoot in manual with auto-iso. Minimum Iso setting is 100, max iso is set at 2000. I was at the parking lot eagle nest at Magee Marsh. Between shooting the eagle with my D810/600mm I would pick up the D800/300mmF:4 AFS and check how the ISO was behaving and all was good. I later went onto the boardwalk and I went up on the tower. Shooting a Pine warbler the ISO dropped to 100 and no matter what I did it would not change off of the 100. I reset the mode to shutter mode and ISo reset to 1250. Once I got home I changed the D800 back to Auto-Iso with a minimum iso of 100 and max at 2000. I checked the camera on walking to the house and it worked perfectly. Its almost 8PM and I stepped out on the porch and checked it again and it worked perfectly. What gives?? Why did it reset to 100 on the tower and work perfect a few minutes ago?
Yesterday when this happened also I noted the camera and movie switch had been moved to the movie position. I think the movie selection will lock the ISO so it cannot be changed while shooting. When I switched it back to camera auto-ISO worked perfectly. I checked that switch all day today and its stayed at the camera position. I am stumped. Will a 2 button reset (reboot) work here?

Thanks much
Larry Shuman

It likely means that it needed to go to ISO 100 to properly expose with the shutter speed and aperture that you selected. In manual mode with auto ISO, you select shutter speed and aperture and the camera adjusts exposure via ISO only. Also, remember that in manual mode with auto ISO, exposure compensation is active and applies to the ISO setting that the camera choses for the the scenario that you are photographing so make sure that is set where you want it.

I talked to someone at Norman Camera this morning and while on the phone I picked up the D800 w/300mmF:4 and looked at the curtain on the window and the rig worked perfect with compensation at 0. I then looked at the floor under the window at the camera read 1/1000 @7.1 & 2000 ISO. exactly as it was set in the auto ISO menu. So the problem I was having must have been the camera was at its limit and I needed the bump up the menu ISO setting then all would be good. Thanks EJ

cheers

Larry

I used the D800/300mmF:4 this afternoon. While in the parking lot the setup worked fine, however when entering the boardwalk a the autoISO again dropped to 100 ISO. That's it, I changed modes to shutter priority and was off running. I talked to a friend who shots a D5600 and had the exact problem I am having. The shots I got with shutter priority were so good they did not require any changes on ACR screen. So manual with auto ISO is as useless as a bag of hammers and shutter priority bought in the money shots.

Larry

It just means that for the aperture and shutter speed you selected, it required ISO 100 to obtain the shot. If that's not the case then your camera is malfunctioning. It isn't that auto ISO is useless in manual mode. It actually works quite well when set-up properly and your shooting conditions are within the Ev window that you have limited your auto ISO range to.