To DA 40 or not to DA 40?

Nick Siebers · 05-20-2011, 05:46 AM

The optical design is generally accepted to be the same between the F and FA 50/1.4s, but yet many users have described the F as sharper, especially wide open. I haven't really looked into their methodology, but photodo rates the F version at 4.6 for MTF, while the FA gets a 4.2. (Both are among the highest rated Pentax lenses.)

Here's a link: http://www.photodo.com/browse-lenses/sort-mtf-score-desc

dgaies · 05-20-2011, 06:06 AM

Originally posted by paperbag846

Are they different other than build quality? Sorry for misreading...

No, as Nick said above, they're optically the same (along with the A50/1.4). There is a notion that there was less sample variation among the copies of the F50/1.4 compared to the FA50/1.4, but you would to test quite a few of each to really figure out if that's true or not.

Blue · 05-20-2011, 07:36 AM

In addition to what Nick and Dgaies said, the F is not just the highest rated lens on the photodo tests, but about the 3rd highest lens over all. Some folks have suspected that Pentax had revised their SMC coating after 1991 as well.

On a side note, I have always found it interesting that the FA 43mm ltd didn't do so well in the Photodo tests.

huh · 05-20-2011, 09:52 AM - **1 Like**

What I read somewhere that the F50mm/1.4's has thorium in its rear element glass (either in the glass or the coating), maybe that caused the difference in MTF?

Check out this video showing the geiger reading on the lens

You Tube

asdf · 05-20-2011, 09:14 PM

Originally posted by huh

What I read somewhere that the F50mm/1.4's has thorium in its rear element glass (either in the glass or the coating), maybe that caused the difference in MTF?

Check out this video showing the geiger reading on the lens

YouTube - ‪Radioactive Lens -- Pentax 50mm f/1.4 S-M-C Takumar‬&rlm;

No wonder, Pentax users have superpowers.

05-20-2011, 06:06 AM	#17
dgaies Veteran Member Join Date: Oct 2009 Location: Maryland / Washington DC Posts: 3,917	Originally posted by paperbag846 Are they different other than build quality? Sorry for misreading... No, as Nick said above, they're optically the same (along with the A50/1.4). There is a notion that there was less sample variation among the copies of the F50/1.4 compared to the FA50/1.4, but you would to test quite a few of each to really figure out if that's true or not. Last edited by dgaies; 05-20-2011 at 07:41 AM.

05-20-2011, 05:46 AM	#16
Nick Siebers Veteran Member Join Date: Jun 2008 Location: Madison, WI Photos: Gallery \| Albums Posts: 2,165	The optical design is generally accepted to be the same between the F and FA 50/1.4s, but yet many users have described the F as sharper, especially wide open. I haven't really looked into their methodology, but photodo rates the F version at 4.6 for MTF, while the FA gets a 4.2. (Both are among the highest rated Pentax lenses.) Here's a link: http://www.photodo.com/browse-lenses/sort-mtf-score-desc

05-20-2011, 07:36 AM	#18
Blue Moderator Site Supporter Join Date: Jun 2008 Location: Florida Hill Country Photos: Gallery \| Albums Posts: 17,377	In addition to what Nick and Dgaies said, the F is not just the highest rated lens on the photodo tests, but about the 3rd highest lens over all. Some folks have suspected that Pentax had revised their SMC coating after 1991 as well. On a side note, I have always found it interesting that the FA 43mm ltd didn't do so well in the Photodo tests.

05-20-2011, 09:14 PM	#20
asdf Veteran Member Join Date: Jan 2009 Location: Canada Posts: 1,252	Originally posted by huh What I read somewhere that the F50mm/1.4's has thorium in its rear element glass (either in the glass or the coating), maybe that caused the difference in MTF? Check out this video showing the geiger reading on the lens YouTube - ‪Radioactive Lens -- Pentax 50mm f/1.4 S-M-C Takumar‬&rlm; No wonder, Pentax users have superpowers.