Is there a definitive guide to Pentex Lenses


Link Posted 23/04/2007 - 13:57

I've just bought a Pentax K10 (actually a Samsung GX10), and am new to DSLR photography. I'm new, but technically minded. It's a been a week since I got the camera, and I've been through 2 books already. I'm after a fast lense, to take fast wildlife photography. The lenses provided with the GX10 go to about f4. There appear to be lots of petax lenses on ebay, and I'm not partiularly after an automatic focus one, but I don't know which can be used with DSLRs and which can't.

I can't find a definitive guide on which lenses can be used with the K10 in general, can any one point me in the right direction?


Drew, a beginner.

George Lazarette

Link Posted 23/04/2007 - 14:51
There are innumberable threads on this issue, if you care to search.

But briefly, all Pentax K lenses fit on all Pentax DSLRs.

The K10D will work with all of them, but has problems metering with the early lenses (M & K), and has to be used in manual exposure mode.

The good Pentax K lenses are marked SMC Pentax, and then there is a suffix as follows:

K - Manual focus, manual aperture
M - Manual focus, manual aperture
A - Manual focus, auto or manual aperture
F - Auto focus, auto or manual aperture
FA - Same as F
D FA - Same as F, optimised for digital
FAJ - Auto focus, auto aperture
DA - Auto focus, auto aperture, digital only

I suggest you stick to F and downwards, unless you are happy with manual focus, in which case try A. If buying a zoom, the more modern the better, though there are one or two good, old zooms.


PS: Please note that by convention the earliest K-mount lenses are called K lenses, but in fact do not say K on the lens.



PPPPS: Of all the Pentax AF long lenses, the best value is the F 1:4.5 300mm

PPPPPS: Look at the roadmap.
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Link Posted 23/04/2007 - 14:53
Perfect. Thank you.

George Lazarette

Link Posted 23/04/2007 - 14:57
See the edited version. Refresh!

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Link Posted 23/04/2007 - 14:59
This post should be stickied for beginners or FAQ


Link Posted 23/04/2007 - 15:01
Be prepared:-

fast + long = expensive

fast + long + high quality = Pentax * lenses (or other makers premium range) = astronomically expensive

. . . but at least you have the advantage of in-camera shake reduction, which might actually mean that you don't need as fast a lens as you think.
Peter E Smith

My flickr Photostream


Link Posted 23/04/2007 - 15:02
How about 3rd party lenses such as Sigma, Tamron etc with Pentax fits. How do they refer Pentax model numbers. For example would it say K equivelant?

George Lazarette

Link Posted 23/04/2007 - 15:07
I was trying to keep this simple, but Peter has reminded me that I should mention the stars.

A star lens (eg: SMC Pentax-F* 1:4.5 300mm) is, indeed, a star. With price to match.

Even more stellar are the Limited lenses (eg SMC Pentax-FA 1:1.8 77mm Limited). The original FA versions are best; the more modern ones are very compact, and relatively slow. Pentax should have given them a different designation, but they are still very well made and very good.

Keywords: Charming, polite, and generally agreeable.


Link Posted 23/04/2007 - 15:08
Most older lenses will be sold as 'Pentax K fit' or 'Pentax bayonet fit'. New lenses will be sold only as Pentax fit, because the Pentax KAF body mount is the current mount. FYI: The K10D actually has the KAF2 mount which allows the use of older power zoom lenses too. As long as the lens you intend to buy has the Pentax bayonet fitting, it'll work.
Some users have had problems with some Sigma lenses, and old Ricoh lenses can get stuck on the camera. Search the forum for more info.
Peter E Smith

My flickr Photostream


Link Posted 23/04/2007 - 15:10
there are 4 basic generations of K fit lenses

1) no electric contacts, manual focus (Pentax K and M series are examples)

2) with electric contacts and A position on aperture ring, manual focus (Pentax A series)

3) more electric contacts, A position on aperture ring, auto focus (F, FA and D FA)

4) more electric contacts, no aperture ring, auto focus (FAJ and DA)

Non Pentax lenses will also fall into these categorys, at least loosely. An old Sigma lens which has an A position on its aperture ring is likely to act like a Pentax A series for example.

One thing to watch out for with non-Pentax lenses is that some of the old ones are actually designed for the Ricoh version of the K mount. These can jam on Pentax bodys and land you with a hefty repair bill, so caveat emptor.


Link Posted 23/04/2007 - 15:10
Third party normally say "Pentax K" or "PK" and "Pentax Autofocus" = "PAF".

Some have said good things about the Sigma EX lenses - but they are not that cheap, especially the f2.8 glass.

To be honest, if you want "fast" telephoto glass then you'll have to remortgage e.g. a 300mm f2.8 won't come cheap

On the other hand, with the ISO being easily usable up to around ISO800, and depending on your subject, something like the Pentax SMC-FA 80-320 will be an excellent lens - expect to pay around 85 second hand.

If I were you, I would start with something like that to master your techniques and then decide what lenses you should seriously invest in - because that could easily end up being a few thousand quid

EDIT: Do note, that fast glass does not necessarily equal top notch photos

(For gallery, tips and links)


Link Posted 23/04/2007 - 15:17
another thing, with the advent of Shake Reduction there is yet another reason to avoid old zooms.

Lenses before the F series do not pass their focal length to the camera, so if you want to use SR you have to set it yourself. This isn't too bad if you use primes, since the menu pops up automatically when you turn the camera on and changing lenses with the camera powered off is good practice. However, with a zoom you will have to manually change the focal length every time you zoom in or out. Not ideal.

also faster is not always better. A 300mm F2.8 lens has an aperture 107mm across. Whatever clever things they do to the design, thats one big chunk of glass and it's going to be HEAVY. The more modest 80-320 zoom is only F5.6 at 320mm. It's a little slow, but you'll still be wandering about taking pictures long after the guy with the 300 F2.8 has died of exhaustion.


Link Posted 23/04/2007 - 20:05
This is a great post. It should be posted permenantely somewhere. So it's apparent that the fast zoom is way out of my league and price range.

I think I'll take Matts advice, and go for a slower lens and set the iso high. I have 2 questions though.

I have my eye on a ...

Sigma 100-300mm F4.5-6.7DL (for Pentax)

that is going for very cheap.

What does the DL stand for? There's no mention of K, PK or PAF, though the seller does say it does auto focus. I've looked at this post Why is the 80-320 better than the 100-300 (other then the extra range).

The other question is 4 .5 to 6.7 isn't fast at all. I saw a superb picture in a magazine of a Kingfisher tossing an insect it had caught, up and into it's mouth. It was taken with a fast lens. Will I realistically be able to achieve such shots (if I ever had the opportunity!) with a slow lens at a higher iso?


Link Posted 23/04/2007 - 21:02
Another thing, there's a good desciption on Wikipedia, says the following:

The "crippled" KAF mount is used on the MZ-30/ZX-30, MZ-50/ZX-50, MZ-60/ZX-60, the *ist series and recent K series digital cameras. The only difference between the regular KAF mount and the crippled version is the removal of the mechanical stop-down coupler/indicator. The result is that most of these bodies can only correctly use lenses which have an "A" setting on the aperture ring or "crippled" KAF lenses. With a K/M (also known as "pre-A" lens, the body cannot tell what aperture the lens is set to with the "crippled" mount. The *ist series and K series digital cameras have a work-around which allows K/M lenses to be used in full manual exposure mode by simply pressing the AE-Lock button to stop down the lens and take a meter reading. While often adequate, in some circumstances this work-around produces problems with metering range, metering accuracy, 3rd party focus screens, and composing shots in changing lighting conditions. The onbody flash only fires at full power, making it useless with pre-A lenses.

Does this mean that all I have to do it press the AE-Lock button if I get an older lense of this type?

George Lazarette

Link Posted 23/04/2007 - 22:17

But, it won't meter very well.

And, you really can't focus quickly enough on wild birds with a manual focus lens. AF is pretty much obligatory, so that cuts out older lenses with exposure complications.

If, despite that, you do buy a K or M lens, then you can use it at full aperture in AE mode, and the camera will set the correct shutter speed. I do that all the time with my old 400mm.

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