I couldn’t hide my disappointment when I learned AF only works in P mode with the A77. Bummer, who wants to shoot in P mode with a camera like this! Manual controls is where its at and 90% of the time I prefer manual focus. But then there are situations when AF would be nice, even necessary to get the shot. After playing around in P mode and realizing auto focus on the A77 is almost as good as on the Sony FS100 I had to find a work around. It is too good not to be used!
There are a few ways getting around this annoying limitation, let’s start with the lazy version.
Put the camera in movie mode and Auto ISO, program mode will keep the lens wide open (necessary to achieve good AF, the reason Sony disabled manual shutter/aperture control), on the 16-50mm kit lens, it usually sets at f3.5 (at the time of this writing this is the only standard lens worthwhile using in AF mode) and adjusts the shutter speed accordingly. Setting it on Auto ISO is very convenient, since we cannot control the aperture, the two variables left are shutter speed and ISO settings and the program will always try to get close to the ideal shutter speed for your frame rate (and never below your frame rate, i.e. 60p, lowest shutter speed 1/60, 30p, lowest shutter speed 1/30), resulting in very low ISO values (Auto ISO in movie mode 100-1600).
Most of the time the camera picks 1/60 and 3.5 for 1080/60p and you can just hit the AE lock button and be done with it.
But what if you want to shoot at 1/125, you will have to trick the camera, use your Vari filter and point your camera at light or dark objects to obtain the desired shutter speed, then press the AE lock button and you are ready to roll.
If you choose to use higher shutter speeds, let’s say 1/400, its best to select a higher ISO value and watch the program setting, once you see the desired shutter speed appear, press the AE lock button. (If you would like to shoot at a shutter speed lower then your frame rate, manual mode is your only option)
A Vari filter is a must since this will be the only way to control exposure.
Most of them offer a 2 to 8 stop adjustment range which is plenty for most, even very challenging lighting situations.
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