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05-10-2022, 10:01 PM   #1
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SMC Pentax 28mm f/2 minimum focus distance?

According to the Pentax Forums Lens Review Database and the Pentax K-Mount Page reference site, the SMC Pentax 28mm f/2 has a minimum focus distance of .25m. So when my recently purchased copy arrived I was surprised to see it had a MFD of .3m.

Looking around on the internet I've seen only .3m MFD copies. And my circa 1977 Pentax lenses booklet also lists the MFD at .3m.

Were there differing versions of this lens? Does anyone here own a K 28mm f/2 with a MFD of .25m?



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Last edited by .a.t.; 05-10-2022 at 10:20 PM. Reason: fine print
05-11-2022, 03:32 AM   #2
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Mine is marked down to 0.3m but moves very slightly beyond that. I haven't measured the distance though.

It focuses as close as I would expect a 28mm lens to, although some 28mm lenses are marketed as "macro" when in fact they're "close focus" and focus a little closer than the Pentax. It's not something I'd complain about.
05-11-2022, 07:20 AM   #3
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QuoteOriginally posted by .a.t. Quote
According to the Pentax Forums Lens Review Database and the Pentax K-Mount Page reference site, the SMC Pentax 28mm f/2 has a minimum focus distance of .25m. So when my recently purchased copy arrived I was surprised to see it had a MFD of .3m.

Looking around on the internet I've seen only .3m MFD copies. And my circa 1977 Pentax lenses booklet also lists the MFD at .3m.

Were there differing versions of this lens? Does anyone here own a K 28mm f/2 with a MFD of .25m?



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Attachment 572888
The image you posted clearly shows the lens focused beyond the 0.3 mark.
05-11-2022, 09:49 AM   #4
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QuoteOriginally posted by Jonathan Mac Quote
Mine is marked down to 0.3m but moves very slightly beyond that.
. . .
Thanks for checking.


QuoteOriginally posted by UncleVanya Quote
The image you posted clearly shows the lens focused beyond the 0.3 mark.
That's my own lens with the focus turned as far as it will go. At that setting, I measured MFD to be between 30 to 31cm.


Last edited by .a.t.; 05-14-2022 at 11:30 AM. Reason: revised measurement
05-11-2022, 11:17 AM - 1 Like   #5
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QuoteOriginally posted by .a.t. Quote
That's my own lens with the focus turned as far as it will go. At that setting, I measured MFD to be 31cm.
And infinity is set accurately?
05-11-2022, 12:21 PM   #6
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QuoteOriginally posted by UncleVanya Quote
And infinity is set accurately?
Yes. But I had to go double check just to be certain. Thank you for the reminder.

The Pentax K 28mm f/2 is said to be based on the Zeiss Distagon 28mm f/2 :
SMC┬* PENTAX┬* 28mm f

And this source shows the Distagon has a MFD of .24m :
https://lens-db.com/carl-zeiss-cy-distagon-t-28mm-f2-ae-1975/

So if the .25m claim for the Pentax version is wrong, it would be an understandable mistake.
05-11-2022, 07:08 PM   #7
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QuoteOriginally posted by .a.t. Quote
Yes. But I had to go double check just to be certain. Thank you for the reminder.

The Pentax K 28mm f/2 is said to be based on the Zeiss Distagon 28mm f/2 :
SMC┬* PENTAX┬* 28mm f

And this source shows the Distagon has a MFD of .24m :
https://lens-db.com/carl-zeiss-cy-distagon-t-28mm-f2-ae-1975/

So if the .25m claim for the Pentax version is wrong, it would be an understandable mistake.
Very interesting.

05-12-2022, 07:58 PM   #8
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I have an early one like your picture and also a later one, both have identical focus scales to your picture. I think they just rounded it off for the brochure.
05-12-2022, 09:19 PM   #9
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QuoteOriginally posted by dkpentax Quote
I have an early one like your picture and also a later one, both have identical focus scales to your picture. I think they just rounded it off for the brochure.

Thank you.

Again, has anybody here owned - or even seen - a .25m minimum focus distance copy of the SMC "K" 28mm f/2 lens?

The Pentax Forums Lens Review Database is a treasure and I'd like to help Adam & Ole make sure they have accurate data there.
05-13-2022, 01:31 AM   #10
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0.3m is the closest marked setting on my copy too!
05-13-2022, 08:48 AM   #11
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QuoteOriginally posted by LennyBloke Quote
0.3m is the closest marked setting on my copy too!

Thank you, LennyBloke.
05-13-2022, 09:00 AM - 1 Like   #12
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Maybe the is a difference between minimum focus distance and minimum working distance.

Minimum focus is to the film plane minimum working is to the front element.

But aside from that minor distinction, does it really matter in reality, and perhaps this is a copy paste error,
05-13-2022, 03:03 PM   #13
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QuoteOriginally posted by Lowell Goudge Quote
. . .

But aside from that minor distinction, does it really matter in reality ...

Yes, tilting at windmills, perhaps?

But it seems to me a database is more useful if it includes complete and accurate information.
05-13-2022, 10:56 PM   #14
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QuoteOriginally posted by LennyBloke Quote
0.3m is the closest marked setting on my copy too!
Is that on all of them John ?
05-14-2022, 09:19 AM   #15
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QuoteOriginally posted by .a.t. Quote
SMC Pentax 28mm f/2 minimum focus distance?
I have the first 1976 version, same as yours, it has 0.3 as well for the MFD.

Phil.
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