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05-17-2009, 02:46 AM   #1
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Need help IDing a SMC-A 50mm f/1.2

Hello! Which of the following pictures accurately shows the mount of a Pentax-A 50mm 1:1.2 lens?

#1


#2


#3


One has what looks like a single electrical contact while two have three contacts. Are there multiple versions of the A50/1.2?

05-17-2009, 03:13 AM   #2
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Don't know about the contacts, but there is something odd with the first picture: the apperture blades are not centered in the middle!
05-17-2009, 03:23 AM   #3
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QuoteOriginally posted by Charles Hueter Quote
Hello! Which of the following pictures accurately shows the mount of a Pentax-A 50mm 1:1.2 lens?

#1


#2


#3


One has what looks like a single electrical contact while two have three contacts. Are there multiple versions of the A50/1.2?
They are all f1.2 lenses, the single protruding pin is the "A" contact which relays to the body that the lens aperture ring is set in the "A" position. The other contacts are contacts, the Pentax electronic aperture ID system on the "A" series lenses actually relies on insulated areas. If none of the area on the lens mount is insulated the camera assumes a working aperture range of f1.2-f22.
05-17-2009, 08:33 AM   #4
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QuoteOriginally posted by Douglas_of_Sweden Quote
Don't know about the contacts, but there is something odd with the first picture: the apperture blades are not centered in the middle!
I agree that it looks weird, but I think that's just a consequence of shooting down into the glass at an angle.

QuoteOriginally posted by distudio Quote
They are all f1.2 lenses, the single protruding pin is the "A" contact which relays to the body that the lens aperture ring is set in the "A" position. The other contacts are contacts, the Pentax electronic aperture ID system on the "A" series lenses actually relies on insulated areas. If none of the area on the lens mount is insulated the camera assumes a working aperture range of f1.2-f22.
I'm convinced they are f1.2 lenses, but I'm not convinced they are all genuine Pentax A-type lenses. Did the company produce a series of A50mm f/1.2s with just one contact and then another series with multiple contacts?

05-17-2009, 09:32 AM   #5
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QuoteOriginally posted by Charles Hueter Quote
I'm convinced they are f1.2 lenses, but I'm not convinced they are all genuine Pentax A-type lenses. Did the company produce a series of A50mm f/1.2s with just one contact and then another series with multiple contacts?
Apparently there is a variation: Penatax A 50mm 1.2. Could #1 be the LX 2000 special?

Edit: Nevermind - didn't notice the "Chrome" color in the table for the LX 2000 variation.

Last edited by jem; 05-17-2009 at 09:36 AM. Reason: Self-correction
05-17-2009, 09:34 AM   #6
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Here is my Pentax A 50mm f1.2.



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05-17-2009, 10:52 AM   #7
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After looking around a bit it looks like there are (at least) 2 varieties of this lens (excluding the LX 2000 special).

The serial numbers for the lenses in your photos are:

#1: 1400812
#2: 1423617
#3: 1413306

I found another lens like #1 here.

It's serial number is: 1402785.

My guess is #1 is the original f/1.2 A mount and #2 & #3 are a revised mount later in the production run.

Larry, does your f/1.2 serial number fit into my hypothesis? Anyone else care to supply serial numbers vs mount variation?

Last edited by jem; 05-17-2009 at 11:06 AM. Reason: Clarity
05-17-2009, 11:00 AM   #8
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Mine looks like the examples shown in pictures 2 & 3, it's a great lens to get BTW.

05-17-2009, 11:55 AM   #9
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Serial no for my lens shown above is 1417052

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05-17-2009, 12:18 PM   #10
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A lens with aperture range 1.2 to 22 needs no electrical contacts on the mount besides the pin which indicates whether or not the lens is set to A mode.

The lens in first photo is in accordance with this.

The other two lenses have two contacts besides the pin - these better be shorted or else the wrong information is provided to the camera - if the aperture range is 1.2 to 22, that is. An f/1.2 to 16 lens would have two insulated contacts.
05-17-2009, 02:45 PM   #11
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QuoteOriginally posted by Ole Quote
The other two lenses have two contacts besides the pin - these better be shorted or else the wrong information is provided to the camera - if the aperture range is 1.2 to 22, that is. An f/1.2 to 16 lens would have two insulated contacts.
The extra "contacts" are still conductive so the camera will recognise them as the mount hence they would still represent an f1.2-f22 lens aperture range. The absence of a contact would make a difference, ie the area would need to be insulated so that the contacts didn't short to the mount. Trust me I've owned both variants.
05-17-2009, 02:54 PM   #12
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If the contacts are conductive all is good. I believe that was what I wrote...
05-18-2009, 12:10 PM   #13
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Thanks everyone for their information. I'm looking forward to getting this lens.
07-13-2009, 01:39 PM   #14
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I was googling this with a 50mm f2 too 'coz I found this kind of varaition on a 50mm 1:2.
On with just the "A" contacts and another with additional contacts.
I think I might have an educated guess as to why this is.
I am assuming that Pentax makes mounts that are what we might call "generic" and "modular" where they can use the mount for any specific lens they might want to produce, hence the holes for the contacts.
If a particular lens won't need a contact for that particular hole, then they plug it (plastic plug) or short it (metal plug) with another contact so as it would work for that particular lens. Does this make sense?
Anyway, I got to thinking about this 'coz I have read somewhere about third party lenses having contact holes similar to the Pentax mounts and having those holes ready (for plugs or contacts) for whatever lens they actually attach it (mounts) to.
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