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04-22-2009, 09:33 PM   #1
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What Do These Lens Letters Mean?

k series. m series. a series. f series. fa series. d fa series.

been pagin' thru the lens reviews...

thanks.

az

04-22-2009, 11:01 PM   #2
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Here's a fairly good breakdown:

Pentax Lenses Explained
04-23-2009, 05:02 PM   #3
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thanks for the link. it has explained alot. in my search for a manual lens, is there any advantage of the 'a' over the 'm'? from my reading, i don't think so, but i could be misunderstanding things.

thanks again for the input.

az
04-23-2009, 05:28 PM   #4
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QuoteOriginally posted by The WideBody Quote
thanks for the link. it has explained alot. in my search for a manual lens, is there any advantage of the 'a' over the 'm'? from my reading, i don't think so, but i could be misunderstanding things.

thanks again for the input.

az
An "A"lens has electrical contacts to communicate with the camera body. This allows you to control shutter speed, and the camera controls the lens' aperture on camera bodies that have the Ka and later K mount versions. Additionally there is a Program Mode, where the camera selects the f/stop and Shutter Speed automatically.

This feature was introduced in conjunction with the Ka mount in 1983, along with the ProgramPlus/Program A (the A3 was not fully enabled) cameras and continues for any Ka mount camera right up to the dSLR's.

(There have been some technical mount changes along the way, and the above is a generally but not universally correct statement.)

M and K lenses and screwmount lenses require that you set the aperture using the aperture ring on the lens itself and metering is less automated.

Rather than thinking of the lenses it might be helpful to learn about the evolution of the K-mount. Here is a link to a description of the evolution, and which lenses can take advantage of each additional feature along the way.

Summary of the K-Mount Evolution, Names, and Features

Here is a link to a detailed article about the features of the Ka mount.

Features and Operation of the KA Mount

04-23-2009, 05:31 PM   #5
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QuoteOriginally posted by The WideBody Quote
thanks for the link. it has explained alot. in my search for a manual lens, is there any advantage of the 'a' over the 'm'? from my reading, i don't think so, but i could be misunderstanding things.

thanks again for the input.

az
The "A" lenses are auto aperture, you can control the aperture directly from the rear (or front if you have one and configured your camera that way) e-wheel on the camera.

The "M" lenses are completely manual, to change aperture you rotate a ring on the lens. The "M" lenses are usually smaller and lighter than the "A" lenses. You also need to push down the green button so the camera can stop down the lens to the selected aperture and meter the light before shooting. But that step is a lot more difficult to write than it is to do. In real shooting conditions, it's mostly "press - click", "press - click".

The "K" lenses you sometimes see mentioned are also known as SMC Pentax or Pentax SMC lenses. These are also all manual lenses like the "M" lenses but are usually bigger and heavier. Some say the "K" lenses are better optically than the "M"s, but I can't offer any input on that, I've never owned any "M" lenses. That's just by happenstance, not a conscious decision on my part.

I own both "A" and "K" lenses and there is no doubt that the "A" series are easier to use, but not by a lot.

NaCl(hope that helps)H2O
04-23-2009, 06:00 PM   #6
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in the meantime since my question was posted and reading your answers, i read some reviews on the 'a' lenses. i am gonna lean heavily towards the 'm' or 'k' series. it seems that other than size, the major difference between the 'm' and 'k' lenses is the coating. does this coating affect the manual/'green button' ttl metering on the 'ist' or k100d bodies?

thanks again for all your input.

az
04-23-2009, 06:37 PM   #7
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QuoteOriginally posted by The WideBody Quote
in the meantime since my question was posted and reading your answers, i read some reviews on the 'a' lenses. i am gonna lean heavily towards the 'm' or 'k' series. it seems that other than size, the major difference between the 'm' and 'k' lenses is the coating. does this coating affect the manual/'green button' ttl metering on the 'ist' or k100d bodies?

thanks again for all your input.

az
You really ought to spend some time reading Bojidar Dimitrov's Pentax K-Mount Page. There is more information there about Pentax K mount cameras and lenses that just about anywhere else.

While the size of the lenses is a major physical difference between K and M, the size change required significant changes in the optical formula for almost every M lens from the K version. M lenses are really quite different from K lenses in tier optical designs - that is the major difference. The coatings change was really more subtle and gradual - it may not have changed much at all at first.

It is a chemical applied to the lens elements to cut down on flare (light reflections on the glass surfaces), thus increasing sharpness and contrast.

The coating allows more light to pass through the glass. While the coating itself has no effect on green button metering (the meter meters the available light), the additional light might allow a user to shoot a stop slower (smaller aperture / higher f/ number) than without the coating.

Here's a link to the K-mount Page section on SMC Coating.

About Super-Multi Coating (SMC)

Over time the coating formula has been improved; later versions of like-focal-length lenses are often considered sharper (all other things being equal, which they rarely are) than the earlier versions. This is illustrated in reviews of the K, M, and A 50mm 1:1.4 lenses (the optical formula of the A50/1.4 was slightly tweaked from the K / M versions, as well).

Last edited by monochrome; 04-23-2009 at 09:12 PM.
04-23-2009, 08:56 PM   #8
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QuoteOriginally posted by The WideBody Quote
in the meantime since my question was posted and reading your answers, i read some reviews on the 'a' lenses. i am gonna lean heavily towards the 'm' or 'k' series.
Why? Some of the K's are optically better than the M's or the A's, but the A's are mostly identical to the M's optically, and having the ability to control aperture form the camera is definitely nice. The only real drawback to the A"s are that some are harder to find and/or more expensive. But also else equal there's pretyt much never a reason to chose an M over an A. Maybe the 135, where the M version is different optically and generally considered better, although slower.

04-24-2009, 08:48 PM   #9
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QuoteOriginally posted by Marc Sabatella Quote
Why?.
nothing against the 'a' series & newer lenses except the price. in my few posts here, i've tried to explain my purpose of trying to go digital and replicate the experience of using my dad's spotmatic, but on the cheap. the digital cameras that i've had in the past were not much better than point-n-shoots (fuji s7000). i don't mind shooting completely manual. i am just trying to educate myself on the subject and make the right purchase for my needs. many will say that i must buy and have a trial by fire experience, but my budget does not allow for that. i might not have the nicest set of cameras, but i don't consider myself completely without a clue.

my goal. buy one of the k or ist kits used with the kit lens and then buy several manual lenses.

thanks for all of your input.

az
04-25-2009, 10:38 AM   #10
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QuoteOriginally posted by The WideBody Quote
nothing against the 'a' series & newer lenses except the price.
Understandable - I interpreted your original comment as meaning you had seen something in a review that suggested they wouldn't be as good. They *are* generally the same optically and better functionally, but correspondingly more expensive, so I too tend to go for the M's.

FWIW, the two A-series lenses that are still cheap enough compared the the M versions to be worthwhile are the 50/1.7 and 28/2.8. Well, the 50/2 too, I suppose, but there's no reason to get that when the 1.7 is not much more. Also, with some lenses, there is no M or K version, like the 50/2.8 macro.

QuoteQuote:
i don't mind shooting completely manual. i am just trying to educate myself on the subject and make the right purchase for my needs.
Oh, I'm all in favor shooting completely manually - I do that all the time, even with my "automatic" lenses. But be aware that the "A" lenses will be more like the Spotmatic than the M's and K's will be, because only the A's will show you a meter reading when using manual exposure mode. M's and K's actually force you into letting the camera choose a shutter speed for you using the Green button - not really manual at all - more like manually-assisted Av mode. Or else you have to hold the DOF preview open while metering, which works, but is kind of awkward compared to how manual lenses work on cameras that *expect* manual lenses and hence can show you a meter at all times.

So that's what I mean about "A' lenses being better - not that they allow you to use automatic modes, but because they allow manual mode to work the way it was meant to work. Still, M/K lenses are perfectly usable once you get the hang of it.
04-25-2009, 04:31 PM   #11
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QuoteOriginally posted by Marc Sabatella Quote
But be aware that the "A" lenses will be more like the Spotmatic than the M's and K's will be, because only the A's will show you a meter reading when using manual exposure mode.
thanks for your input. certainly i will look up prices of the lenses that you have mentioned and re-evaluate my purchase needs.

as i haven't as of yet purchased a setup - this forums has been invaluable in passing along info that i might not have gathered otherwise.

thanks to all.

az
04-25-2009, 05:04 PM   #12
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QuoteOriginally posted by The WideBody Quote
i've tried to explain my purpose of trying to go digital and replicate the experience of using my dad's spotmatic, but on the cheap.
Then you should be looking at the M42 Takumar lenses. They fit the bill of being usable on digital, being cheap, having high quality.....and with the added benefit that you can get yourself a Spotmatic and actually use them on it. I routinely use these lenses and they easily swap back and forth between my modern digital K20D and K100D, as well as my film Spotmatic ESII and SV.
04-25-2009, 08:50 PM   #13
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QuoteOriginally posted by Mike Cash Quote
I routinely use these lenses and they easily swap back and forth between my modern digital K20D and K100D, as well as my film Spotmatic ESII and SV.
i've read about the screw mount to k mount adapter. how many of these do i need? do i get just one and use it for all of my lenses i may buy or do you just leave it on the camera and the screwmount lenses screw into it?

i had thought of this idea but thought that if i had to spend an additional $30 to make a lens forward compatible then that lens might not be cost effective for me to get.

thanks for the great input.

az
04-28-2009, 02:15 PM   #14
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az, from what I've read in these forums (please correct me if i'm wrong) The k mount adapter should first be connected to the m42 lens, then connected to the camera. It's less likely the lens can get stuck this way (I think). This is not condusive to fast lens changing.
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