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11-13-2010, 08:49 PM   #1
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Wide aperture shooting with a fast 50 - AF better than MF?

Hi all -

I have an FA 43/1.9 as well as several manual 50mm lenses - A50/1.2, M50/1.4, ST50/1.4, M 50/1.7. While in most situations I will go for the limited, in very low light I like the idea of the extra speed of the 50s. But I have a terrible time focusing with them because of the illusion of increased DOF in the VF. When I had an F 50/1.7 it seemed to auto focus pretty accurately wide open. Would an FA 50/1.4 with AF be accurate under such conditions? Or should I consider a replacement for my standard focus screen first, to better use the MF lenses I already have?

Thanks for your help,

11-13-2010, 09:21 PM   #2
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Nick, the 50/1.7 is famed to be sharper than the 50/1.4 at f/1.7-2. And the half-stop or so 'advantage' the 50/1.4 may have on the 50/1.7 is negligible. The 50/1.2 is another story - but being MF it has its limitations. We can always ask Pentax for an FA/DFA 50/1.2...

Screen replacement would be up to you, and if you're happy with the 50/1.2 it would be a good choice.
11-13-2010, 10:29 PM   #3
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I have the M50 f/1.7 and bought a Katz Eye split image focus screen just for this lens. I could not judge on my own if my images where in focus or not and the 'In Focus' indicator on my K10D does not respond fast enough when I really need it.
11-13-2010, 10:30 PM   #4
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It's *possible* to MF pretty well with the 50 1.4 and the stock screen, (I'm occasionally forced to when the light source wants to confuse the AF) but you sort of have to practice, cause you can't really see: you can, however, narrow things down to a fairly narrow zone (the apparent DOF and/or where what the electronic aid tells you) and make a pretty decent interpolation.

I'm not entirely convinced, but I'm leaning toward staying with the stock screen because the different metering patterns are handy just often enough.

11-14-2010, 03:41 PM   #5
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More practice with the MF 50s, huh? I can live with that. AF is awfully nice for fast moving kids, but I suspect you are right Ash that if f/1.7-1.9 won't work, f/1.4 is unlikely to as well. Probably should just save my money for that ISO 100,000,000,000 DSLR that is a few years away.

Probably I should use the A50/1.2 more. It's a little hard to get that lens out and subject it to potential trauma, especially when I often misfocus wider than f/4 or so anyway. Would anyone else trade down to a FA 50/1.4?

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