[discharged]

Am I correct in the assumption that the Pentax A, Pentax M and Pentax K 100mm F4 Macro lenses have the same optical design and essentially there are only minor changes made to exterior design and ofc the A setting on aperture? My brother recently found the Pentax K version of this beautiful lens on a garage sale and bought it for me thinking it might be something I wanted. He paid ~$6 for it and it is in really good condition, so I guess it is a fair price atleast

[sandbasser]

Great question! I'm looking for a 100mm Macro myself so I'll eagerly wait for answers.

[pete-tarmigan]

Am I correct in the assumption that the Pentax A, Pentax M and Pentax K 100mm F4 Macro lenses have the same optical design and essentially there are only minor changes made to exterior design and ofc the A setting on aperture? My brother recently found the Pentax K version of this beautiful lens on a garage sale and bought it for me thinking it might be something I wanted. He paid ~$6 for it and it is in really good condition, so I guess it is a fair price atleast

Check the specifications in the Pentax Lens database:

Pentax Lenses - Pentax Lens Reviews & Lens Database

[fwcetus]

Am I correct in the assumption that the Pentax A, Pentax M and Pentax K 100mm F4 Macro lenses have the same optical design and essentially there are only minor changes made to exterior design and ofc the A setting on aperture? My brother recently found the Pentax K version of this beautiful lens on a garage sale and bought it for me thinking it might be something I wanted. He paid ~$6 for it and it is in really good condition, so I guess it is a fair price atleast

Check out Pentax Short Telephoto Prime Lenses . The last six 100/4 macros are optically the same, and, except for the first one (a bellows macro), are physically pretty much the same in other respects, although the K versions have (unnecessarily) larger 52mm filter threads, and A version has the extra Ka functionality.

$6 for any 100mm macro (in good shape) is not "a fair price" -- it's an absolute ~steal~. Pentax, in particular, has ~never~ ~ever~ made a mediocre macro lens, whether 50mm, 100mm, or 200mm, IMHO.

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Last edited by fwcetus; 02-16-2016 at 07:07 AM.

[BrianR]

Great deal for the K-version! While the A-version might be a wee bit nicer to use, you'd expect to pay at least $10 for it, and probably closer to $100.

[discharged]

Check out Pentax Short Telephoto Prime Lenses . The last six 100/4 macros are optically the same, and, except for the first one (a bellows macro), are physically pretty much the same in other respects, although the K versions have (unnecessarily) larger 52mm filter threads, and A version has the extra Ka functionality.

$6 for any 100mm macro (in good shape) is not "a fair price" -- it's an absolute ~steal~. Pentax, in particular, has ~never~ ~ever~ made a mediocre macro lens, whether 50mm, 100mm, or 200mm, IMHO.

I'm sure that the little bump up to 52mm (if it is 52) isn't unnecessary, it can't be! there must be some reason why it is there and I am guessing it has to do with either allowing for the same hood as lens X or some other fantastic reason.

[gofour3]

I'm sure that the little bump up to 52mm (if it is 52) isn't unnecessary, it can't be! there must be some reason why it is there and I am guessing it has to do with either allowing for the same hood as lens X or some other fantastic reason.

The K Series standardized on 52mm for filter threads, the M & A Series was 49mm.

The K100/4 Macro used the same lens hood as the K85/1.8, K100/4 Bellows and the K105/2.8. The K version was only in production for a couple years so it's harder to find.

Phil.

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Last edited by gofour3; 02-16-2016 at 11:51 AM. Reason: Added missing K85

[fwcetus]

I'm sure that the little bump up to 52mm (if it is 52) isn't unnecessary, it can't be! there must be some reason why it is there and I am guessing it has to do with either allowing for the same hood as lens X or some other fantastic reason.

The K Series standardized on 52mm for filter threads, the M & A Series was 49mm.

[Thanks, Phil, for helping to clear up any confusion.]

I think my choice of "unnecessary" may have been unfortunate. All I was trying to suggest was that the difference between the filter thread sizes is not significant in an optical sense -- all 6 lenses are optically nearly identical, and the 52mm is not needed to prevent vignetting -- in other words, "the extra 3mm" (so to speak) is an "unnecessary" distinction without a difference in the context of someone having just scored a nice K 100/4 Macro for 6 bucks.

[Venom3300]

The lens is worth 75-100 dollars and is optically rather good. You got a steal.

[discharged]

[Thanks, Phil, for helping to clear up any confusion.]

I think my choice of "unnecessary" may have been unfortunate. All I was trying to suggest was that the difference between the filter thread sizes is not significant in an optical sense -- all 6 lenses are optically nearly identical, and the 52mm is not needed to prevent vignetting -- in other words, "the extra 3mm" (so to speak) is an "unnecessary" distinction without a difference in the context of someone having just scored a nice K 100/4 Macro for 6 bucks.

Actually, I scored it for $0 since my brother gave it to me...

I also understood what you meant in your message about unneccesary, the tone in my reply is mildly sarcastic, something that is hard to convey over the internet.

It is the uncanny logic of technichians... We have to design as compact as possible!

wait this is too compact and the barrel is only 51mm in outside diameter, that means we have to design a new hood, a new front cap and alot of oher things! Not acceptable! We need to make it bigger, like 52mm so we can reuse details from other lenses! Expanding everything means more weight and more cost... Not acceptable!

What if we add a collar here?

PROBLEM SOLVED!

[Ben_Edict]

Actually, I scored it for $0 since my brother gave it to me...

I also understood what you meant in your message about unneccesary, the tone in my reply is mildly sarcastic, something that is hard to convey over the internet.

It is the uncanny logic of technichians... We have to design as compact as possible!

wait this is too compact and the barrel is only 51mm in outside diameter, that means we have to design a new hood, a new front cap and alot of oher things! Not acceptable! We need to make it bigger, like 52mm so we can reuse details from other lenses! Expanding everything means more weight and more cost... Not acceptable!

What if we add a collar here?

PROBLEM SOLVED!

You should also see it from the consumer's point: The K lenses were designed in an era, when black and white film was still pretty standard. You needed filters to make the best of that film and standardizing on a common filter thread for a whole lens series reduced the numbers of filters needed and the necessary expense. All camera makers took that approach, though many settled on 55mm threads. When Pentax introduced the M-series the standard filter thread was reduced to 49mm, which was the result of the race for more compact cameras (Olympus being the other leading contender). But Pentax made (in my view at least) the mistake to value compact over fast lenses. That was alright for consumers, but Pentax lost out in the pro market with these slow lenses and the M-series cameras. And I think, they never recovered from that loss.

Ben

[redrockcoulee]

Ben

The normal filter size of the SMC Takumar was also 49mm so Pentax unstandardized the K series compared to what they replaced and returned to it with the M series. I still have lots of filters from my Spotmatic F days and three of my four lenses used 49mm and today with my digital lenses all three of my primes still do.

[8540tomg]

The K Series standardized on 52mm for filter threads, the M & A Series was 49mm.
Phil.

Hey Phil,

A little additional info. It is true Pentax did make an A 100/4 macro with 49mm threads.

They also made an A 100/2.8 macro and this one had 58mm threads. I own a copy of this lens.

It is one of my favourite lenses I might add. It is highly unlikely you will find this one for 6 bucks. if you can find one at all.

Tom G

[fwcetus]

They also made an A 100/2.8 macro and this one had 58mm threads. I own a copy of this lens.

It is one of my favourite lenses I might add. It is highly unlikely you will find this one for 6 bucks. if you can find one at all.

Believe it or not, ~many~ moons ago, back in The Film Days of Yore, i temporarily had three of 'em...



The thing I remember the most about the A 100/2.8 Macro was the gorgeous blue reflection from the SMC (much like the blue of the K 200/2.5).

(However, I no longer have any or 'em anymore...)

[K-Three]

There is an M 100 in the forum market place with the matched extension tube (to get to 1:1), and hood

I'd consider it if I didn't have that range covered twice over already.