Is there a mode that lets me set P and A?

Started Feb 3, 2013 | Discussions thread
tom Senior Member • Posts: 2,724
Re: Is there a mode that lets me set P and A?

Has nothing to do with fundamentals.  OP knows that exposure is function of time, aperture, and ISO.  But wants to control DOF (aperture), and freeze motion (shutter speed) and make correct exposure.  So he has 2 fixed parameters and one variable.

In the film days and early digital (mid range ISO = noise) there was nothing to do but compromise (or change film).  Today with sensors having a wide range of useful ISO there is (should be) the option of having the camera auto adjust the third exposure parameter while having the other 2 exposure variables fixed (i.e. if in S-mode with fixed S and I SO adjust A; if in A-mode with fixed A and ISO adjust S; if in TA mode with fixed A and S adjust ISO.)  Apparently, even Sony finally agrees since they put that feature in their top-of-the Alpha line camera.  The question is will they ever put it in lower level cameras?

Example: Photographing a sequence of a bird flying through an area with bright light and shadow.  Distance is changing so AF is needed/useful.  Want a specific shutter speed to freeze motion of wings (S-priority).  Want a shallow DOF (A-priority).  Need both so set M.  Light is changing so just go into menu, set ISO, take shot; bird moves into shadow, go into menu, set new ISO (check exposure scale- oops not enough), go back into menu, set faster ISO, (check scale -ok), bird waves bye-bye and goes around corner.  Well at least you got one or two good shots.  And it beats using film, where you would have to change film to adjust ISO, or...

Set S & A in TA mode.  Focus on bird and track.  Watch for best times (as it grabs the fish) and shoot as desired.  Pick best shots out of the sequence.

There is only one purpose for AF, and auto exposure modes - to allow the user to concentrate on the composition and make the shot at the right time rather than requiring camera manipulation.  When I take a table-top-macro shot I have time to manually adjust composition, focus and exposure, when taking action photos in complex lighting - not so much.  While we got along nicely without them for many years, there is no doubt that auto features have enabled shots/sequences that would have been impossible in the old days.


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