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03-09-2009, 10:41 AM   #1
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pentax smc fa 100mm f3.5 ?? diopter ??

good day all.........
i just purchased this lens, used, for a good price...
since this version does not have the magnifying adapter,
like the promaster version.... can anyone tell me what
diopter 'strength' i should look for??
i know this is a 49mm thread mount

1:1 Macro Adapter Included - this is from a web seller for the promaster pentax mount lens, 100mm f3.5

also... i've seen voigtlander focar b, c type filters...
does anyone know if and how this translates to diopter strength(s)???????



Last edited by dcmsox2004; 03-09-2009 at 10:47 AM. Reason: new info sought
03-09-2009, 08:28 PM   #2
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Sorry I don't have the answer to your question, but just a couple of thoughts. I believe the Macro Adapter that comes with the Promaster is single element. 2-element or achromatic close-up lenes are known to give much better results. The Sony VCL-M3358 (+3.3) or the Canon 250D (+4) would significantly decrease the minimum focusing distance, but not sure if it would be 1:1 (or even greater?). Don't think these come in 49mm sizes, so step up ring needed. Before spending any more money I would suggest you use the lens for awhile to see if you really miss not being able to get in even closer.

--Mike
03-10-2009, 05:00 AM   #3
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thanks mike....
it's hard to determine the diopter strength of the macro lens provided...
it finally dawned on me, i'll contact promaster directly and see if they
have any info...
i'll post any new info......
dave m
03-10-2009, 06:56 AM   #4
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It is available to purchase directly from Promaster website for $20 plus shipping.

https://secure.promaster.com/newshop/
Part number PL1001

Also, it appears to have two multicoated elments, not one. It's all metal and glass and the quality is much nicer than the lens.

03-10-2009, 08:39 AM   #5
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duh, why did'nt i think of that...
thanks a million!!!
03-10-2009, 09:30 AM   #6
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You're welcome.
03-10-2009, 09:35 AM   #7
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QuoteOriginally posted by clm Quote
It is available to purchase directly from Promaster website for $20 plus shipping.

https://secure.promaster.com/newshop/
Part number PL1001

Also, it appears to have two multicoated elments, not one. It's all metal and glass and the quality is much nicer than the lens.
If it is a meager $20, it is highly recommended if it is the same one that I am using from Cosina. I bought an old Sigma zoom before and the owner gave me a diopter that happens to be the 1:1 matched macro adapter that comes with Cosina/Phoenix/Promaster 100mm f/3.5 1:2 macro lens. That diopter is 49mm in size and it has thicker glass that looks like twice as thick as the regular close up diopter. People noted as achromatic type of diopter that is supposed to work better in close up.

I use this diopter on my Pentax FA 50 f/1.4 and Carl Zeiss Jena Biotar 58mm f/2.0 which share 49mm filter size. I don't have the exact +n ratio, but someone noted as between +3 to +4.

Here is how the adapter looks on my Pentax FA 50 f/1.4


Cosina 1:1 matched macro adapter




#1
with Pentax FA 50mm f/1.4
close up on FA is about 1:6
with the diopter
I roughly gets closer to 1:3




#2
with Pentax A 50mm f/2.8 1:2 macro




#3
with Carl Zeiss Jena Biotar 58mm f/2.0 (m42)
Not a macro or close up lens
just an oldie which can't get close to flowers
minimum focusing distance is 1.65 feet




#4
with Schneider 135mm f/3.5 (m42)
another older lens on 49mm




Last edited by hinman; 03-10-2009 at 10:27 AM.
03-10-2009, 09:51 AM   #8
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Well if the $20 promaster turns out to truly be 2-element, please let us know as I would be very interested in that as I also have the FA 100 f/3.5 and also a 50mm I currently use on extension tubes. Maybe sometimes you get more than what you pay for...
(btw - nice shots hinman)

--Mike

03-10-2009, 10:16 AM   #9
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QuoteOriginally posted by wasupdoc Quote
Well if the $20 promaster turns out to truly be 2-element, please let us know as I would be very interested in that as I also have the FA 100 f/3.5 and also a 50mm I currently use on extension tubes. Maybe sometimes you get more than what you pay for...
(btw - nice shots hinman)

--Mike
Thanks for the comment. I think the Promaster is likely the same as the Cosina or Phoenix. Perhaps the OP should give it a try and report back with a picture of the purchased adapter to share. I have used my 1:1 adapter on many lens that share the 49mm filter size in primes with focal length in 50, 58, 135mm. Using a diopter for close up is the most convenient to use especially for flowers. I bring it along in my camera bag and it comes in handy and results are quite satisfactory. The combo are more prone to PF/CA especially in wider apertures and there may be other caveats such as corner vs center sharpness.
03-10-2009, 10:57 AM   #10
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i'll let you know as soon as i receive the lens from promaster...
by the way mike, how do you like the 100mm pentax f3.5 lens...
i've read that it's essentially a cosina rebadge, but with smc coatings...
and perhaps a little better constructed... i've heard that the promaster and it's
clones can be quite noisy when focusing........
03-10-2009, 10:58 AM   #11
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hinman, i can only say thanks to your many posts here and elsewhere, you've been a tremendous help with your postings...
and, your pics are great, wonderful compositions, artform....
dave m
03-10-2009, 11:14 AM   #12
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Dave, I have enjoyed using my 100 f/3.5 - it is small and light and takes reasonably sharp macros. It is plastic, but doesn't seem any more fragile than most kit lenses. It is noisy and has a long focus throw, usually use MF for macros. I recently picked up a KM for my wife, and am hoping to get myself a more "serious" macro and let her have the 100 f/3.5. Even after I get a new macro lens, it will still be nice to have both the smaller lighter lens and the close up lens as well for those times when I travel light.

--Mike
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