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04-13-2008, 02:09 PM   #1
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Macro F 2.8/100, worth drooling over?

Perhaps someone can help me with this. I'm been looking on a SMC Pentax-F 1:2,8 100mm Macro. Lens reviews appear to be positive. Anyone with personal experience of this lens?

Two specific questions:

What is the difference between this and the FA version? I never really understood this. When the F and FA lenses came I was stubbornly staying with my manual primes refusing to go into autofocus, so I missed reading about the detailed progress.

A probably stupid question: There is a strange knob on the middle of the lens. What is that for?

04-13-2008, 09:27 PM   #2
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F and FA are optically identical. Focus speed might be different, but I don't know which would be faster.

The knob you saw is the focus limiter. Since most AF macro has much longer focus throw than the usual AF lens, they use the focus limiter to help the lens focus faster. Certainly you don't want the lens to from infinity to 1:1 and back just to focus on you subject.
04-13-2008, 11:18 PM   #3
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QuoteOriginally posted by aegisphan Quote
F and FA are optically identical. Focus speed might be different, but I don't know which would be faster.

The knob you saw is the focus limiter. Since most AF macro has much longer focus throw than the usual AF lens, they use the focus limiter to help the lens focus faster. Certainly you don't want the lens to from infinity to 1:1 and back just to focus on you subject.
OK, optical identical, but whatabout the missing "A"? Does the "F" version miss some automatic functions compared to the "FA"? Why would they want to manufacture a lens with automatic focus but manual exposure?

Is this focus limiter seting the range gradually, or is it a switch between two different length focus ranges? The design sort of suggest the former, but I don't understand what use that should be. If it is a switch between a "long distance" range and a "macro range", then why the bulky design. Why not just a small switch as on the one for AF/MF on the new 50-135mm?
04-13-2008, 11:41 PM   #4
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F 100/2.8 Macro

That tells you precisely what the switch does. Basically, if you want to use the lens for "normal" shot, then you wouldn't want to lens to go to "higher magnification" area while it's hunting. I have no comment on the size of the switch. Generally, old stuff tends to be bigger.

Both FA and F have auto exposure. The FA has only one additional thing, MTF info. I heard that the K10D has a MTF program where the camera will set the aperture at which the lens achieves its highest resolution. To most, this is a useless feature, so it's not even worth mentioning.

04-20-2008, 11:44 AM   #5
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no limiter on FA?

QuoteOriginally posted by aegisphan Quote
F and FA are optically identical. Focus speed might be different, but I don't know which would be faster.

The knob you saw is the focus limiter. Since most AF macro has much longer focus throw than the usual AF lens, they use the focus limiter to help the lens focus faster. Certainly you don't want the lens to from infinity to 1:1 and back just to focus on you subject.
I saw someone claim the FA version has no focus limiter, in which case the F would even be preferable on that point.

The price is ~160 US$, and it will be cheep to send it within Sweden. Fair price isn't it?
04-20-2008, 11:54 AM   #6
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both the F and FA have a focus limiter switch. one would think that the FA would have faster auto focus as it is a newer lens but I cant comment on that. if you are just looking at optical formula and focus limiter switch then it really comes down to your personal preference as these two lenses are identical in this respect.

FA 100/2.8 Macro
04-20-2008, 12:20 PM   #7
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QuoteOriginally posted by Douglas_of_Sweden Quote
I saw someone claim the FA version has no focus limiter, in which case the F would even be preferable on that point.

The price is ~160 US$, and it will be cheep to send it within Sweden. Fair price isn't it?
Uhm, from your title, I thought the F 100 macro was $500-$600. If it's at $160, that's definitely a no brainer. I don't think you can find another AF macro with this IQ at that price.
04-20-2008, 12:28 PM   #8
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Thanks for the info. I can't find it now, but I did read someone complaining on the FA that it had no limiter (a different forum of course! and obviously someone missinformed). Not that it realy matter now.

04-20-2008, 12:47 PM   #9
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robbery?

QuoteOriginally posted by aegisphan Quote
Uhm, from your title, I thought the F 100 macro was $500-$600. If it's at $160, that's definitely a no brainer. I don't think you can find another AF macro with this IQ at that price.

I had begun to suspect that myself, but it is good to get it confirmed by someone with your knowledge. Assuming that the lens is OK, I'm almost feeling as I'm steeling it.
Appears that the seller does not know its value. It's on a small Swedish speaking buy and sell forum. Searching for "pentax" gave only three hits, and there it was. Not knowing what F was compared to FA, at the worst suspecting that it had no A connection (why on earth they should make an auto focus lens without that), I did not dare to act at once, and besides, the seller did not reply for a week, not until today. Now I'm sending the e-mail to confirm that I want to buy it and (at the moment at least) forget about the old Paragon lens I'm also been looking at. Not a bad alternative itself, but definitely no A connection (auto focus I care less for).
04-20-2008, 10:26 PM   #10
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QuoteOriginally posted by Douglas_of_Sweden Quote
Thanks for the info. I can't find it now, but I did read someone complaining on the FA that it had no limiter (a different forum of course! and obviously someone missinformed). Not that it realy matter now.
The FA has the limiter, the current D-FA does not. Autofocus is back in the ages of horse and buggy with that switch missing.
04-21-2008, 04:02 AM   #11
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Thanks Rockies! That's probably what I mixed up (or if it was mixed up already at wherever I read it). So why do they drop such a feature? Believing too much in their autofocus?
04-21-2008, 04:35 AM   #12
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Hi Douglas, i have one spare pentax DFA 100mm/2.8 macro in hand which only 2 month old. and now i got my new voilander 125mm/2 macro. so I want to sell the DFA 100/2.8 macro, see if you're interested in it?
Bu
Regards from the UK
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