Sun 05-Jan-14 02:36 PM | edited Sun 05-Jan-14 02:38 PM by mathjak107
i came across some interesting results when the d800 is in manual and you use auto iso in constantant lighting.
my wife and i were shooting macro and i decided to try something i never use in macro, the auto iso.
typically in macro i get a nice exposure but decide i want more or less depth of field. i thought it would be nice to leave auto iso on under the contstant lighting and vary aperture to change depth of field while in manual.
i figured auto iso would self adjust leaving me with the same exposure range only different depth of field since i only changed aperture.
well thats not what the d800 does. however that is just what my wifes d7000 does when in manual, auto iso.
the d800 held the iso at a constant value and adjusting the aperture changed my exposure. it held that iso constant until the lens was just shy of fully open ,then it let the iso fall.
very different results than i am used to getting which is more like the d7000 behaved.
My D800 certainly doesn't behave in the way you're describing yours behaving. In Manual exposure mode with ISO Auto, as the subject darkens the camera increases the ISO up to the maximum set; any darker than that it underexposes. It does not change the aperture or shutter speed at any stage.
It sounds to be working correctly, if you had low light, and the 6400 ISO setting was still too low of the aperture and shutter you selected in that light. That is indicated by it dropping when opening the aperture all the way. Find out what the light level is, either with the internal meter or external light meter and make sure the shutter speed is slow enough to allow keeping the ISO below the level where you would start seeing objectionable noise. 6400 might be pushing it pretty hard for noise. The best way however is forget that lighting and set the shutter and ISO for image conditions and use additional lighting to render proper exposure. Stan St Petersburg Russia