Pentax Digital

It’s impossible to count how many times questions like “Which lenses can I use on my Pentax DSLR?”, “Can I use old lenses on my Pentax Digital SLR?” and “How will this lens type function with my DSLR?” have been asked on forums.

Don’t get me wrong, it’s perfectly ok to be new. Heck, only one year ago I was a complete newbie to the whole Pentax and DSLR thing, and I’m extremely grateful to the nice people on different forums who helped me.

It would however, be convenient if these people had a page they could refer to each time someone asks a question like this.

So, here it is

Pentax uses the so-called “K Mount“.

2 links I have bookmarked are: Dimitrov and Stan’s Pentax Photography. Both offer specifics on each of the Pentax lenses.

This page also has some useful information, although more compact.

Wikipedia has an extensive description of the different K-mount types, I will summarize them (I left out a few technical details that are not relevant here), and add how they can function on a Pentax DSLR:

1. K Mount - “K” or “M” lenses:
   

   This is the first, original mount Pentax used on the K-series of film cameras.
   In-house (this is: Pentax made) lenses made by Pentax for this mount are usually labeled “SMC Pentax-M“, “Takumar (Bayonet)” and there are also a few early “K” lenses, labeled “SMC Pentax” (note the -M or -A is missing)
   Third party (not made by Pentax) lenses using this mount are usually just noted as “K mount” or “PK mount”. This mount is identical to the Ricoh XR mount (beware! only XR mount! The “A” mount for Ricoh causes problems on Pentax DSLRs).

   These lenses will only work in the M-mode (Manual) of your Pentax DSLR. Since these lenses were made before Autofocus (from now on referred to as “AF”) was invented, they only offer Manual Focus (from now on referred to as “MF”)
   However, your Pentax DSLR offers ways to use these old lenses in an automatic way:

   - By selecting the aperture on the lens itself, using the ring, and pressing the “AE-L” button (stands for: Auto Exposure-Lock), your camera will select the proper shutter speed for the aperture you’ve selected, giving you a correct exposure.
   You will notice that when you have selected anything else than the maximum aperture of your lens, when you hit the AE-L button, the viewfinder image will become darker for an instant. This is caused by the camera actually stopping down the lens to the aperture you’ve selected (it was keeping it open using the lever inside the mount, to provide enough light for you to focus), and metering the light coming trough the lens that way.

   - When in manual focus, your camera will give you a confirm “beep” and green light in the viewfinder when it thinks you have focused correctl, very useful.
   If your camera does nto do this, check if under Menu>Set-up “Beep” is checked ON. Whether this is on or off, the camera will always give you a focus indication in the viewfinder.

   Things to check when using lenses of this type:

   • Under Menu>Custom Setting, make sure “Using Aperture Ring” is set to “2 - permitted”, this is OFF by default.
   • Also under Menu>Custom Setting, make sure “AE-L bttn on M expsr” is set to “1 - Program Line”

2. KA Mount - “A” lenses:
   

   This mount was a huge step forward, and offers a real advantage on digital bodies.
   It allows the camera to select the aperture, which opens up the other exposure modes.

   In-house lenses of this type are usually labeled “SMC Pentax-A“.
   Third party lenses are usually noted as for “KA Mount” or “PKA mount“. Beware of the Ricoh version of the “A Mount”, because some of these have an extra pin, that gets stuck in the AF-coupling on your camera, not allowing the lens to be taken off again. It’s a time-consuming activity to get it unstuck, so avoid Ricoh A-lenses.

   As said, this type of lens will work in all exposure modes of your Pentax DSLR, since it can “communicate” with the camera. Of course, since AF was still not invented then, they offer MF only.

3. KAF(2) Mount - “F”, “FA”, “P-FA”, “FA J”, “DA”, “DFA” lenses:
   

   This is the mount found on the current Pentax digital SLR range.
   Third party lenses with this mount will usually just be labeled with “For Pentax AF“.
   In-house lenses using this mount have various labels, each specifying a different functionality.
   They can of course be used in all exposure modes and as the name specifies, all of them provide AF.

   • “SMC Pentax-F” and “SMC Pentax-FA“: These are “regular” AF-lenses. The F-lenses were an early range, with the FA-following them. Usually, the F’s are finished in grey/orange, whereas the FA’s are usually all black.
   • “SMC Pentax P-FA“: the “P” in this name refers to “Powerzoom“, a feature Pentax implemented for the professional Z-series of film cameras, and which is now available on the K10D. These lenses, when used on a supporting body (on digital: only the K10D), zoom in all the way by giving a small twist to the zoom ring. They can also automatically keep track of moving subjects. Very nifty.
     On a body that doesn’t support powerzoom, these can be used like regular AF lenses by flipping a switch on the lens.
   • “SMC Pentax-FA J“: these lenses were made by Pentax in an effort to keep them as compact as possible. The aperture ring on these has been removed, and can only be set trough the camera body (something you would normally do). Other than that, they work just like regular FA lenses.
   • “SMC Pentax-DFA“: these lenses were designed for film cameras, as well as for digital cameras. They have an aperture ring and an image circle large enough to fill a full 35mm frame. They work just like FA lenses. (thanks to Ole for correcting this)
   • “SMC Pentax-DA“: “D” stands for Digital, which implies that these lenses were specifically designed for use on Pentax digital SLRs. Use on a non-digital body is not recommended with these lenses, they can only be properly used on a digital SLR!

4. M42 Mount - Screw mount lenses:
   

   Now this is an interesting mount. Before the bayonet mount, this was the mostly used mount of the world! All it is, is a 42mm screw thread, with a small pin to stop down the aperture.
   Pentax was the first to use this mount on its very early film cameras, and because Pentax ensures backward-compatibility with all of its lenses, you can use it on your Pentax DSLR!
   What you do need, is suitable M42 adapter.
   The type of adapter you need is the type that does not have a flange covering the camera contacts! This is very important, because the distance of the K mount to the film(or sensor) plane is the same of that of the m42 mount. Therefore, if you want your M42 lens to focus to infinity, it must be mounted at the correct distance! Using the wrong adapter will make the lens come further away from the sensor, taking away its ability to focus to infinity, much like an extension tube for macro work would do.

   Lenses like this are all over the 2nd hand market. There are too many third party labels to mention, but they will mostly be accompanied by the words: “For Pentax screw” or “For M42/42mm screw“. Manufacturers include Carl Zeiss Jena, Pentacon, Meyer Optiks, Schnieder, etc. all very prestiguous names.

   In-house lenses were made under the name “Takumar“, “Super Takumar” or “Super-Multi-Coated Takumar“.

   These lenses can be used in M mode and Av Mode.
   That’s right Av (aperture priority) mode, since you actually close the lens opening when you turn the aperture ring, the camera can meter the light without the AE-L button having to close the aperture for you.
   M mode works in the same way as the regular K mount lenses, but it’s easier to use Av mode for automatic exposure. Use M mode when you want to select the shutter speed yourself.

   I have noticed that my *ist DL systematically underexposes in Av mode with M42 lenses, so I put exposure compensation on +1.0 by default, that fixes it.

   These lenses are, of course, MF. The camera is able to give you focus confirmation, but, only if you checked the 2nd remark below, and only if you use an f-stop larger than f8. This is normal, because any AF-system will cease functioning at about f8, because there is not enough light.

   Things to check when using lenses of this type:

   • Under Menu>Custom Setting, make sure “Using Aperture Ring” is set to “2 - permitted”, this is OFF by default.
   • Also under Menu>Custom Setting, make sure “FI with S lens used” is set to “2 - Available”, this’ll give you the focus confirmation.
   • Make sure your lens is set to “M” (Manual) and not to “A”. Most M42 lenses will have an A/M switch or button on the side of the aperture ring. You will notice that in the “A” setting, the aperture is not stopped down until you press the small pin. Since your digital camera cannot press this pin, the lens must be set to M to be able to close the aperture.
     Some lenses do not have this switch and only an auto setting. These lenses must be “fixed” somehow to keep the aperture pin pressed.

There, hopefully this page was helpful. If you have any questions or remarks, please let me know

Regards,

Tom