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12-31-2008, 03:38 AM   #1
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Aspherical Pentax Lenses

Do any of the Pentax lenses include aspherical elements?

12-31-2008, 04:36 AM   #2
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Many Pentax lenses have contained aspheric elements as far back as the K series of the mid 70s. Bojidar Dimitrov's Pentax page documents this quite well:

Pentax K-Mount Lenses and Lens Accessories

Consult his listings for any lens you may be curious about.

Cheers,

Tom G
12-31-2008, 07:26 AM   #3
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I've got the SMC 15mm f/3.5 aspherical...it's a pretty good lens.
12-31-2008, 07:31 AM   #4
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QuoteOriginally posted by mabelsound Quote
I've got the SMC 15mm f/3.5 aspherical...it's a pretty good lens.
and a very rare lens.

12-31-2008, 07:44 AM   #5
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I;ve got that lens too, excellent apart from the massive fungus problem. One day i will investigate but it seems like a pretty big task...
Anyway, as far as i can tell it was one of the first aspherical lenses pentax made and my grandfather paid a lot of money for it.
12-31-2008, 07:46 AM   #6
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Yes, I was shocked when I realized it was the really rare version! You'll hate hearing this, but I got it for $100 on Craigslist from a guy who was switching to Nikon.

It is soft at the corners and exhibits heavy flare. It's also freaking huge. But I love to use it--it's very weird.



12-31-2008, 09:29 AM   #7
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pentax usually do not divulge whether or not their lenses have aspherical elements
one rare exception is the FA31 which has "AL" in the name
12-31-2008, 09:50 AM   #8
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QuoteOriginally posted by mabelsound Quote
Yes, I was shocked when I realized it was the really rare version! You'll hate hearing this, but I got it for $100 on Craigslist from a guy who was switching to Nikon.

It is soft at the corners and exhibits heavy flare. It's also freaking huge. But I love to use it--it's very weird.

I do hate hearing that.. but good for you! lovely photos by the way.

12-31-2008, 10:00 AM   #9
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Mabelsound

I love stories like that. I hope to be able to tell one just like it some day! It would be even better if I could make an identical find to the one you did. The K 15mm is very high on my wish list.

Cheers,

Tom G
12-31-2008, 10:17 AM   #10
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From the lenses I have or had, I do remember the following

FA*24/2 (still have) was advertized as having aspherical elements. If fact, the aspherical element is not glass but some exotic resing.

FA 28/105 aspherical

FA 28/70 f/4

I do have an SMC-A 15/3.5 but I don't think mine is aspherical. I have never seen it and the only versions I know off are the A and non A versions.
12-31-2008, 10:24 AM   #11
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QuoteOriginally posted by k100d Quote
pentax usually do not divulge whether or not their lenses have aspherical elements
one rare exception is the FA31 which has "AL" in the name
As noted above, modern Pentax lenses with aspheric elements generally have AL in the lens name inscribed on the barrel or face.

Here is a short list of the lenses I am aware of:
  • DA 18-55/3.5-5.6 (yes, the kit lens has an aspheric element)
  • FA 31/1.8 Limited
  • FA 35/2
  • DA* 16-50
  • DA 12-24/4
  • DA 16-45/4
  • DA 17-70/4
  • DA 21/3.2 Limited

It should be noted that aspheric elements are relatively rare in older lenses due to limitations in the manufacturing technique. At one time, hand-grinding was required by highly skilled craftsmen and aspheric elements were only found in fairly exotic lenses. Due to modern technology, this is no longer the case. They are relatively common in modern lenses and really have no particular significance except to indicate that the lens "may" have a more sophisticated design or "may" be better corrected than a similar lens from another manufacturer.

Steve
12-31-2008, 10:40 AM   #12
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Unfortunately "aspherical" does not always mean better. It is said that lenses that have aspherical glass have fewer elements and that reduces interior reflection and gives you a lighter lens. It also makes a lens cheaper to manufacture. So in some cases aspherical lens elements do improve the quality of a lens, but in other instances you get a poorer quality lens that is essentially more cheaply made than an older non-aspherical model. You really need to know your lenses! Most cell phone cameras have aspherical lenses and that doesn't make them great.

Great shots above!

Last edited by jeffkpotter; 12-31-2008 at 02:55 PM.
12-31-2008, 11:20 AM   #13
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aspherical elements are sometimes noted to deteriorate the quality of bokeh as well, if you frequent leica forums, they note certain lenses as Pre-ASPH
12-31-2008, 11:24 AM   #14
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QuoteOriginally posted by mabelsound Quote
I've got the SMC 15mm f/3.5 aspherical...it's a pretty good lens.
I think a lot of us will be interested in a head to head test of this lens with the future DA15/4 Ltd. Although I honestly think that 30 some years of technological advances will shaw pretty quickly.

Radu
12-31-2008, 01:26 PM   #15
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I strongly suspect the DA15 will be better. I did test the SMC15 asph against the Sigma 10-20 at 15mm, and the Sigma was significantly better at the corners.

The nice thing about the SMC15, though, is that it's full frame, and I can use it on film, as in the above pics. I'm sure the DA15 will vignette on film...

One other great thing about the SMC15 is the built-in filters. For the second photo above, I had the red filter engaged...really handy for dramatic skies!
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