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SMC Pentax-A* 1:4 300mm
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PostPosted: Tue Jan 24, 2012 5:42 pm    Post subject: SMC Pentax-A* 1:4 300mm Reply with quote

Just received a mint copy of the SMC Pentax-A* 1:4 300mm, exchanged for my SMC Pentax-DA* 55mm f/1.4 SDM. Yes, I swapped an AF lens for a MF lens Cool

It does not feature ED glass, but from what I've seen on the web it's very good optically. And apart from the big front element it's actually quite short, so it easily fits in my normal photo bag.



PostPosted: Tue Jan 24, 2012 7:48 pm    Post subject: Reply with quote

I've actually seen an enlarged image taken with the 300/4 at a library show. The image
was pretty large, and yet the crispness was TRULY evident, even in the corners. I hope
this lens gives you the same results. Would love to hear and see how it works for you. Smile


PostPosted: Tue Jan 24, 2012 8:12 pm    Post subject: Reply with quote

Thanks Laurence! Are you sure it was the K-mount version of this lens? There is also the A* 645 300mm f/4 so I'll ask you just in case Smile


PostPosted: Tue Jan 24, 2012 9:28 pm    Post subject: Reply with quote

Congrats! Great design , very short and seems not so heavy also.


PostPosted: Tue Jan 24, 2012 10:06 pm    Post subject: Reply with quote

Very, very small for the spec.
Not cheap either, sadly for me.


PostPosted: Tue Jan 24, 2012 10:43 pm    Post subject: Reply with quote

Thanks!

BTW, Pentax never claimed it but based on the star designation and its very short design I and a few others suspect that the lens actually uses ED elements. It's also fairly unresponsive to CA and PF. What do you think?


PostPosted: Tue Jan 24, 2012 10:57 pm    Post subject: Reply with quote

Spotmatic wrote:
Thanks Laurence! Are you sure it was the K-mount version of this lens? There is also the A* 645 300mm f/4 so I'll ask you just in case Smile


He was using it on one of the Pentax DSLRs...I THINK it was a K5 model, a fairly new model.

Larry


PostPosted: Wed Jan 25, 2012 6:22 am    Post subject: Reply with quote

Go out and use it! This is quite a rare lens, am i right?


PostPosted: Wed Jan 25, 2012 6:48 am    Post subject: Reply with quote

Of course I will use it, thank you! Smile

It's not super common, but not super rare either. There are a few on eBay at the moment, mostly by the usual "golddigger shops".


PostPosted: Wed Jan 25, 2012 7:02 am    Post subject: Reply with quote

BTW, based on this PDF documentation (with lots of K-mount lenses) the M* and A* 300mm f/4 really featured ED glass. In the case of the A* it's even part of the name as shown.

http://fockert.xs4all.nl/~pentax/catalog/05_Objectieven_Filters_Adapters.pdf


PostPosted: Sat Feb 01, 2020 10:23 am    Post subject: Reply with quote

Both the Pentax M* as well as the A* 4/300mm share the same optical construction; they contain three (!) large ED lenses, as one can see in Marco Cavinas article on the lens:
http://www.marcocavina.com/articoli_fotografici/Pentax_M_300mm_4_star/00_pag.htm

Nevertheless, the lens doesn't particularly outperform other similar lenses from the same time: Neither CAs nor resolution are much better than eg the Nikkor 4.5/300mm IF-ED or the Minolta MD-II/MD-III 4.5/300mm IF.




Here's an image of the Pentax M* 4/300mm ED on the Pentax LX.

The next generation of Pentax 300mm lenses, the Pentax F* 4.5/300mm, has clearly a better CA correction, a (removable) tripod socket and, quite useful, IF with an MFD of just 2 m (vs the rather boring MFD of 4 m at the M* 4/300mm). Focusing, however, is very steep and therefore less precise, due to the AF mechanism. The F* has three large ED lenses as well.



While the M*/A* 4/300mm certainly is a very nice collectors item, i would recommend the F* 4.5/300mm for actual use, both on Pentax FF bodies as well as adapted to mirrorless FF cameras. The F* has as little CAs as contemporary 2.8/300mm lenses, but it's much smaller and lighter (1.1 kg without tripod socket). Wide open, it has a pleasant slight softness (but lots of detail); stopped down to f6.7 or f8 the contrast increases to very good levels. I know of only two vintage MF lenses with similar performance: The Canon FL 5.6/300mm Fluorite (with two fluorite lenses) and the Mamiya Sekor C 5.6/300mm. The Canons corners are less sharp at f5.6, but it has slightly less CAs; the Mamiya may be slightly better than the Pentax as well, but it is less versatile (MFD of 4 m as well, no tripod socket).