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04-19-2010, 09:36 PM   #16
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I own the f1.4 in question but not the f1.7 I hear optically that the f1.7 is slightly better. There isn't much of a difference in terms of which is better. I love my f1.4 when I'm shooting. but I think that if I had gotten the f1.7 lens I'd be just as happy. In terms of low light performance you'd see very little difference.

04-19-2010, 10:09 PM   #17
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I'm luckily enough to own both.Optically speaking,there is a grain of salt difference between them in my opinion.If you want to see it for yourself,be like me and own both and compare.
04-20-2010, 08:13 PM   #18
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Something else: Aperture and focal length interact in interesting ways. An f/1.4 lens DOES let you shoot at slightly higher shutter speeds in slightly less light, and that higher shutter speed may be the difference between an acceptably sharp keeper and an unacceptably blurry loser. But there's also DOF, the range of distance where the image is acceptably sharp. Many of us prize fast lenses because they provide a thin DOF, which helps in isolating a subject from its surroundings. Faster lenses have thinner DOF, and so do longer lenses. I'll compare wide-open shots on a 50/1.4, 55/1.7, 58/2 and see similar (but different) DOF and bokeh.

--

It is less than one stop.
04-21-2010, 05:26 AM   #19
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How long you been doing this?

QuoteOriginally posted by RioRico Quote
Hey Justin (I can almost remember too!) the reason it's always at f/1.7 is because it's an M-type lens. M-types always stay wide open in the Auto modes. If there were an A setting on the aperture ring, you could control the aperture from the camera, and it would stop down automagically when you shoot. But an M-type *must* be used in M(anual) mode and preferably using the Green button to take exposure readings, in order for the lens to stop down.

In that regard, screwmount lenses on adapters are a little easier to use, except at small apertures. Except in M(anual) mode, the camera goes to Av by default. So you set the aperture ring to whatever you want, and the camera reads the light and sets the exposure. But you might get a better exposure with the M(anual)-mode Green-button trick. Your mileage may vary. All I can say is, try it out. Shooting is free. No film was wasted in the making of this experience. Whew.

Something else: Aperture and focal length interact in interesting ways. An f/1.4 lens DOES let you shoot at slightly higher shutter speeds in slightly less light, and that higher shutter speed may be the difference between an acceptably sharp keeper and an unacceptably blurry loser. But there's also DOF, the range of distance where the image is acceptably sharp. Many of us prize fast lenses because they provide a thin DOF, which helps in isolating a subject from its surroundings. Faster lenses have thinner DOF, and so do longer lenses. I'll compare wide-open shots on a 50/1.4, 55/1.7, 58/2 and see similar (but different) DOF and bokeh.

A 50/1.7 is about midway in there, but still with pretty thin DOF. I may have already recommended (and if I didn't, I should have) that you consider buying a DIRT CHEAP Helios-44 58/2 (still around US$20 on the bay). It's slightly slower but noticeably longer, wide-open sharp yet with thinner DOF, great for closer, more intimate pics than the 50/1.7. And you can use it in Av mode. Just another tool in the kit. (And it WAS the kit lens for zillions of Russian film cameras.)
You don't get out much do you? just kidding I learn a lot here. can't retain it but it's in the jello somewhere.
signed,
on my quest for 2million smackers via 2million posts..thanks pentax!

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