auto ISO and changing f/stops or speed
OK call me dense. I have set the minimum speed to 125th of a second with the highest auto ISO at 6400; however when shooting in aperture mode in low light conditions the f/stop automatically goes to f/2.8 when I want to shoot at f/5.6 even when the ISO is increasing. Should not a higher ISO afford me the opportunity to keep the f stop at f/5.6 and not drop to 2.8 when the ISO is 3200 or even higher? Why is the f stop changing to f/2.8 when the ISO is increasing? I am finding that the speed is dropping or the f stop is becoming wider. What am I misunderstanding; I know that I have lots to learn. Thanks again. Also, I am still getting somewhat noisy photos and I do not think they should be that noisy when shooting at ISO 1500, the inside lighting is not that dark. Maybe I am asking too much of this camera. The D700 is better than the D200 when using a higher ISO but I was hoping for better images than what I am getting so far. I am using matrix metering, the 24-70 f/2.8 and 85mm f/1.4 lens mainly indoors.
#1. "RE: auto ISO and changing f/stops or speed" | In response to Reply # 0briantilley Nikonian since 26th Jan 2003Fri 16-Apr-10 04:21 PM
Are you sure that the camera is in Aperture Priority mode? Is there a big "A" in the top left corner of the camera's top LCD display?
In A mode, the aperture value that you select with the front Command Dial should be what you get - it won't be changed by the camera, whether you have ISO Auto selected or not.
#2. "RE: auto ISO and changing f/stops or speed" | In response to Reply # 1Windy Vision Registered since 01st Jul 2004Fri 16-Apr-10 04:43 PM
Yes, I shoot 95% of the time in Aperture mode. And just realized not to shoot in Aperture mode when using the flash but in speed or program mode. Wow did I have some blown out highlights when using the SB800 in aperture mode with a wide open f stop. I am learning! Are you saying that when I set the aperture to lets say 5.6, the auto ISO is on to max 5600 that the f/stop should remain at f/f.6 and the ISO should kick in and the speed should remain to 125th of a second which is where i have it set to the lowest speed? That is what I am expecting anyway. The noise should not be that bad and there should be little noise unless the lighting is just so poor that 3200 or 5600 ISO has kicked in.
#3. "RE: auto ISO and changing f/stops or speed" | In response to Reply # 2briantilley Nikonian since 26th Jan 2003Fri 16-Apr-10 07:15 PM
>Are you saying that when I set the aperture to lets say 5.6,
>the auto ISO is on to max 5600 that the f/stop should remain
>at f/f.6 and the ISO should kick in and the speed should remain
>to 125th of a second which is where i have it set to the lowest
Yes, that's basically it.
In Aperture Priority, if you set the aperture to f/5.6 that's the aperture you will get. The ISO will start off at whatever value you choose, and the camera meter will choose a shutter speed to give what the meter assesses to be the correct exposure. If the metered exposure results in a shutter speed slower than the 1/125th you have specified, the camera will use 1/125th and raise the ISO to compensate, and will keep doing that if light levels drop, until the ISO reaches your chosen maximum of 5600. At that point the camera has to lower the shutter speed below 1/125th because that's the only option it has.
#4. "RE: auto ISO and changing f/stops or speed" | In response to Reply # 2ScottChapin Charter MemberSat 17-Apr-10 09:19 AM
> And just
>realized not to shoot in Aperture mode when using the flash
That's not true. I am assuming that you are outdoors in bright light when the flash fails to operate as you like. In that case, a maximum ss of 1/250 is selected and is too slow for the lighting conditions. The "HI" indicator will light up,letting you know that is the case.
If you switch to focal plane flash, then higher shutter speeds will be permitted, and you can in fact shoot at your desired aperture in aperture mode.
Powder Springs, GA, USA
Nikonians Team Member
#5. "RE: auto ISO and changing f/stops or speed" | In response to Reply # 2blw Nikonian since 18th Jun 2004Sat 17-Apr-10 05:58 PM
> And just realized not to shoot in Aperture mode when using the flash but in speed or program mode.
Aperture preferred mode works just fine with flash. Your problems are elsewhere.
If you're in aperture preferred mode, you shouldn't get any aperture other than the one you set, no matter what. (Assuming that the lens can actually achieve that aperture.) But if you're in aperture preferred mode, the shutter speed will respond to the ambient light, and/or to the changes in auto ISO. If you really want to be certain of the aperture and shutter speed, you should be shooting in manual, presumably with auto ISO.
The noise can be pretty bad at ISO 2000 or so if you get underexposure. That's not really different from any other camera.
Even on the D700 ISO 6400 produces some noise, it's just nowhere near as bad as some other cameras at similar ISO.
Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!