Lens for MX

LesDMess · 08-29-2012, 05:14 AM

Originally posted by TomB_tx

I have quite a collection of 50s, including the f1.7, f1.4 and f1.2. In spite of the cost, I think the f1.7 outperforms the faster lenses (except at stops wider than 1.7!).

BTW, how did you qualify your lenses? Since all of my lenses are used - previous owner unknown, I tested all mine using the test chart and my K20D across all major apertures. Unfortunately these results are not very conclusive since they are all limited by the 14.6MP sensor and are almost all the same across the board and only more pronounced due to diffraction at the smaller apertures. Here the much more complex f1.2 clearly leads the pack.

Full res -> http://www.fototime.com/AFA3C6EDB6A663D/orig.jpg

Again, these are my results from used lenses and may not correspond to how they should perform if they were factory fresh but I at least know that none of them are poor performers at least in terms of resolution.

contrabass · 08-29-2012, 06:34 AM

Originally posted by CMG

Thanks very much for that really helpful info! I wasn't aware of his formula...but it does make sense! If I purchased an M 50mm f/1.7 how would I use it on my K-5? I shoot manual most of the time as is, but I know that his lens will not communicate with the camera.

Someone else already showed you the link to using manual K-Mount lenses, and it's not hard to do.

But, if you bought an A 50mm f/1.7, you could use the aperture ring when it's on the MX, and leave it in the "A" setting when it's on digital. Then you can use it like an autofocus lens, only without the autofocus. The M and A f/1.7 lenses have the identical optical formula and are the same size.

The downside is that the A lenses don't have the same wonderful build quality as the M lenses, and cost a little bit more than the M equivalent because people know they're more convenient on a DSLR.

The 31mm on an MX ought to be wonderful, too!

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08-29-2012, 05:14 AM	#16
LesDMess Pentaxian Join Date: May 2011 Location: Santa Cruz, CA Photos: Albums Posts: 3,235	Originally posted by TomB_tx I have quite a collection of 50s, including the f1.7, f1.4 and f1.2. In spite of the cost, I think the f1.7 outperforms the faster lenses (except at stops wider than 1.7!). BTW, how did you qualify your lenses? Since all of my lenses are used - previous owner unknown, I tested all mine using the test chart and my K20D across all major apertures. Unfortunately these results are not very conclusive since they are all limited by the 14.6MP sensor and are almost all the same across the board and only more pronounced due to diffraction at the smaller apertures. Here the much more complex f1.2 clearly leads the pack. Full res -> http://www.fototime.com/AFA3C6EDB6A663D/orig.jpg Again, these are my results from used lenses and may not correspond to how they should perform if they were factory fresh but I at least know that none of them are poor performers at least in terms of resolution.

08-29-2012, 06:34 AM	#17
contrabass Junior Member Join Date: Jun 2010 Location: Pennsylvania Photos: Albums Posts: 44	Originally posted by CMG Thanks very much for that really helpful info! I wasn't aware of his formula...but it does make sense! If I purchased an M 50mm f/1.7 how would I use it on my K-5? I shoot manual most of the time as is, but I know that his lens will not communicate with the camera. Someone else already showed you the link to using manual K-Mount lenses, and it's not hard to do. But, if you bought an A 50mm f/1.7, you could use the aperture ring when it's on the MX, and leave it in the "A" setting when it's on digital. Then you can use it like an autofocus lens, only without the autofocus. The M and A f/1.7 lenses have the identical optical formula and are the same size. The downside is that the A lenses don't have the same wonderful build quality as the M lenses, and cost a little bit more than the M equivalent because people know they're more convenient on a DSLR. The 31mm on an MX ought to be wonderful, too!