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Old Jul 27, 2006, 10:04 PM   #1
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I have a Pentax istD with a standard 18 - 55mm lens. After reading through some posts I gathered that a really good prime lens would be a smc A Pentax 50mm 1.7. This would be much sharper than my standard lens in addition to having better colour. So, off to eBay I go to get this lens. It arrives in good condition, but the photos are not as sharp as my standard lens and the colours are not as vibrant. I only shoot in raw. On the suface I can find nothing wrong with the 50mm lens. Do older Pentax lenses loose their quality over time. Disappointed.
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Old Jul 27, 2006, 10:17 PM   #2
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This was taken with my 50mm f/1.7, ISO 400, jpg

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Old Jul 27, 2006, 10:28 PM   #3
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I am at a loss :?

I have a 50 f1.7 and a 55 f1.8 and both are unbelievably sharp. Actually every second hand prime lens I have bought including 135/f2.8 and 17/f3.5 are sharper than my kit lens.

I presume your lens is AF, have you tried switching over to MF (focus it yourself) and also dropping your aperture down a setting or two. Not may lenses are their sharpeest wide open.

Maybe you could set your camera on a tripod and take two shots of the same scene with the same settings using both lenses and post up here so we can have a look?

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Old Jul 27, 2006, 10:46 PM   #4
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Use f/2.8 to f/8 and It will show it's true strength's.

1.7 is a last resort I have found.
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Old Jul 27, 2006, 11:13 PM   #5
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I've found thatmy M50mm 1.7 (purchased in 1980)is sharper at 1.7 than the M50mm 1.4 at 1.4 (which is quite soft), however at f8 both are really sharp. I posted a comparison photo and there wasn't much difference between these 2 lenses- the 1.4 seemed to have a bit more color. I haven't actually comparedthem to the kit lens or the 50-200.
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Old Jul 28, 2006, 12:03 AM   #6
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I used Pentax-M 28mm f2.8 SMC to take the picture in this recent thread.

I bought this lens new in the early 1980's so it has not aged too badly

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Old Jul 28, 2006, 7:15 AM   #7
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Check your diopter adjustment. It might be that you're just not focusing the right way.

I doubt that a mint 50mm 1.7 Pentax lens would be soft...

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Old Jul 28, 2006, 7:25 AM   #8
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Even wide open in poor light the old M-series 50mm f1.7 shines. Here is a shot taken wide open at 1/60 sec under one 60W incandescent lamp (the background is Christmas tree lights). Since it was shot at ISO 1600 it is a little "grainy" but I like that in a B&W.

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