Sony 50mm 1.8 vs Minolta 50mm 1.7

Started Jan 20, 2013 | Questions thread
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Re: Sony 50mm 1.8 vs Minolta 50mm 1.7

from the control system point of view, the minolta uses much more energy to focus accurately and its precision is less than this of sony's. I could see that in my battery's life. plus, sony focuses much faster (but some times visibly less accurate and you can feel that in the jerky micro-adjustments all the time when it gets a bit darker) than the minolta lens.

I had a 50f1.8 minolta for the analogue 35mm 800si(full frame in modern terms) and it was great on it as well as on minolta 7d where the pictures lookes less spherical due to the sensor's crop. sony's 50f1.8 though look even less distorted and I d say a bit sharper on minolta 7d.

the funny thing is that on minolta 7d, the minolta lens on distances from 1.5 to 1.7 m, the minolta lens focuses for portraits better than the sony one, and the sony one on the a57 focuses just bad whist the minolta one does a little bit better but still not as good as with minolta 7d.

it must be something with the pwm pid controller and the inertial errors in the design. a few milligrams of deviation in the mass of the system and the PID controller fails overshooting (control design terminology, not a photographic one) and jerking all the time trying to get to the new target from the feedback loop.

On a57, both lenses without the in-camera correction are ok, but the sony lens has less chromatic abberation (also less in minolta 7d).

as you might expect, a used minolta lens, no matter what people think about build quality, will have accumulated dust and it will probably be a little "detuned". also dust in the rotating parts, not properly lubricated, a bit more weight on one side, some elements slightly displaced (you ll notice the effect of bluring when focusing in the infinite, that one side of the image will start bluring in a sligtly different manner than the other, even in studio symmetrical shots)

so just get a new 50f1.8 lens from sony and enjoy it as much as you can!


if you have a hack for the lens, or any leaked 7d firmware where you can adjust the PID controller parameters, just do it, it will only freak your battery a little.

I do suspect that sony a57 had a change in some lookup tables.

I got some readings using the same conditions from both sony a100 and a57 and a57 has a different data output on the lens' contacts. It might be using some fuzzy logic thing to do calculations on the fly. It has a faster chip anyway, maybe they changed something in the focus control.

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