Dave327 wrote:
Manual: You set the exposure (F stop), you set the shutter duration, you set the ISO, but have the option to leave ISO on auto and have the camera decide the ISO based on the exposure & shutter speed you have set. Auto focus still works fine, unless you want to switch to manual.
Manual is manual exposure... just the way it sounds. With M you make all the settings, the camera doesn't make any. This is a slower process that requires you have some knowledge how to set things up, but it "locks down" exposure so that it cannot vary due to different tonalities in the scene being photographed. Manual exposure might be set referencing the camera's built-in metering system or by evaluating the histograms of test shots made with the camera, or with a separate hand held meter, or even "by eye" if you have learned to do so. Cameras with electronic viewfinders might be able to be set using what's seen on that screen with a form of Exposure Simulation. Similar can be done using the rear LCD screen and Live View on many cameras that have optical viewfinders, instead of EVFs.
Some cameras also have a "B" or "Bulb" setting, which is for fully manual, extra long exposures that you time yourself. Most modern cameras can do as long as 30 second exposures using M.... so B would only need to be used for timed exposures longer than that.
A (or Av) is Aperture Priority AE... You set the ISO and the aperture, the camera automatically chooses what it thinks is a correct shutter speed.
S (or Tv) is Shutter Priority AE.... You set the ISO and the shutter speed, but leave it to the camera to choose what it thinks is a correct aperture.
P is Program AE... You set the ISO and the camera chooses both shutter speed and aperture, based upon info that's been programmed into it.
Manual WITH Auto ISO is a new exposure mode made possible by digital imaging (couldn't be done with film). It most definitely
IS NOT manual. It's just another form of auto exposure (AE). You choose the shutter speed and the aperture, but the camera is allowed to select the ISO it uses. That's auto exposure too!
Because all cameras use a reflective metering system to determine exposure, with
all the AE modes you may need to use Exposure Compensation to "correct for errors". Reflective metering is influenced by the tonality of any subject you're focusing upon. This is because the camera has no idea what's in front of it.... and it can only assume that everything is "18% gray" (or that the range of tonalities being measured average out to 18% gray). But not everything you photograph is 18% gray. For example, if you're shooting a bride in a white gown in a snow storm... an unusually light tone subject and scene... the camera is going to want to under-expose... so when using any of the AE modes you have to dial in some + Exposure Compensation. At the other extreme, if you're photographing a black bear in a coal mine... an exceptionally dark subject and scene... the camera is going to try to over-expose and when using any of the AE modes you will need to dial in some - E.C. in order to get an accurate exposure. (Exposure Compensation doesn't work in fully manual modes... but you have to take these same factors into consideration and skew your setting appropriately, when relying upon the camera's reflective meter for info and the subject/scene aren't "average tonality".)
None of this has anything to do with Auto Focus modes... I don't know why anyone would even mention it because it's not really relevant. Some minor exceptions where exposure and focus [i][atterns[/i] are interrelated include Evaluative/Matrix Metering, which measures the entire scene but places extra emphasis on small areas immediately around the active AF point(s) or some advanced cameras have a means of linking Spot Metering to the Active AF Points to measure
only a small area right around the active AF point. Both of these sort of assume that you are focusing on the primary subject, and therefore that's the most important place to meter.