Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-12-2011, 01:08 PM   #1
Pentaxian
mgvh's Avatar

Join Date: Sep 2010
Location: MD
Photos: Gallery | Albums
Posts: 855
How can I tell if a lens is autofocus?

I've been shopping around ($bay, goodwill, etc) for some older inexpensive lens to get a sense of what focal lengths work best for me.
How can I tell if a lens is autofocus or not?
  1. I try to check reviews, especially here on Pentax forums, but for non-Pentax lens, it oftentimes is not clear. Checking manufacturer's websites or googling for legacy lens often still does not turn up the info.
  2. I know that "auto" on a lens usually means auto aperture, not autofocus.
  3. If there is an "AF" on the lens, does that always mean autofocus?
  4. There must be something physical on the lens mount, but I'm not sure what I'm looking for. (I realize that some of the newer focusing methods involve more electronic stuff, but I'm thinking mainly of the older ones with the simpler mechanical autofocus. I think I'm saying that correctly...)
Thanks for any help.

08-12-2011, 01:29 PM   #2
Forum Member




Join Date: Jan 2011
Location: Texas
Photos: Albums
Posts: 90
This might help

08-12-2011, 02:08 PM - 2 Likes   #3
Senior Member
mannesty's Avatar

Join Date: Mar 2008
Location: Totana - Murcia (Spain)
Posts: 127
The flange/lens illustration above is that of a KF mount that was only ever used on one Pentax body, the ME-F, and is not a KAF auto focus mount. AF lenses used on the ME-F had motors etc, inside the lens itself. Pentax AF bodies since the ME-F have had the motor inside the body with a mechanical screw coupling to provide lens motion.

Drawing of the KAF mount from Bojidar Dimitrov's K-Mount web site



Pentax lenses having an F, FA, FAJ, DA, DA* suffix (EG: smc Pentax-F or smc Pentax-FA) are all AF lenses. Pentax lenses having the suffix A, M, or no suffix are manual focus lenses.

Most of the Pentax AF lenses use a screw drive mechanism with the motor in the camera body. The mechanical coupling takes the form of a slotted hole in the lens mount, and a narrow blade in the body mount. Some newer DA & DA* lenses are SDM only and can only be used in MF mode on older bodies.

With no lens fitted to your camera, look at the mount whilst changing the focus switch from AF to MF. You will notice that this pin is retracted in the MF position, and proud of the mount face when in the AF position.

Looking at the lens mount of an AF lens, holding it with it's red dot uppermost (12 o'clock), the slotted hole can be seen at the 8 o'clock position approx.

Finally, if a lens has the letters AF printed somewhere on it, it is likely to be an auto focus lens, but not all AF lenses have AF printed on them. From memory, none of the Pentax lenses are labelled neither AF or Auto Focus.

Hope that helps.

Last edited by mannesty; 08-12-2011 at 02:42 PM.
08-12-2011, 02:11 PM   #4
Pentaxian
mgvh's Avatar

Join Date: Sep 2010
Location: MD
Photos: Gallery | Albums
Posts: 855
Original Poster
Thanks...

... That got me to the right site. It looks like this is the graphic that shows where the autofocus transmission shaft is.





08-12-2011, 02:23 PM - 1 Like   #5
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
QuoteOriginally posted by mgvh Quote
... That got me to the right site. It looks like this is the graphic that shows where the autofocus transmission shaft is.
Exactly right. BUT... that's also where the infamous RICOH PIN is on certain Ricoh (and maybe some third-party) lenses. Search here for RICOH PIN and you'll find numerous threads discussing it.

But basically, Ricoh designed their manual-focus KR-mount lenses to have a pin in that location. (I forget just what it does.) Many KR lenses have a little nub there instead of a pin -- no problem. But a pin CAN and WILL get stuck in the drive socket of a KAF-mount body, causing loud swearing and some application of a feeler gage to unseat it. Aaarrgh...

If you see a round pin or nub in that location, it's a manual-focus Ricoh KR lens. The aperture ring will also have a P or A(P) position, instead of the A on Pentax A-type and AF lenses. (Ricoh call that setting Program; Pentax calls it Auto.) And the lens mount MIGHT have KR or KA/R stamped on it. If you see a pin with flattened sides in that position, that's the AF drive shaft, just what you want.
08-12-2011, 03:47 PM   #6
Pentaxian
mgvh's Avatar

Join Date: Sep 2010
Location: MD
Photos: Gallery | Albums
Posts: 855
Original Poster
I do have a Vivitar P/K-AR lens w/ the Ricoh pin, but it is in a slightly lower (relative to the pics; closer to the contacts) position than the AF drive. Thanks to this forum, I had read about it, and so I fortunately knew to remove it in advance!
08-12-2011, 03:51 PM   #7
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon
Photos: Gallery | Albums
Posts: 10,749
All good information so all I have to add is that ebay sellers many times have absolutely no idea what they are selling. So no matter what the description says always look and if you cannot tell ask for more pictures.

Reputable sellers are usually fine although anyone can make a mistake. Antique and pawn shops seem to be the worst.
08-12-2011, 08:18 PM   #8
Moderator
Site Supporter
Blue's Avatar

Join Date: Jun 2008
Location: Florida Hill Country
Photos: Gallery | Albums
Posts: 17,211
QuoteOriginally posted by RioRico Quote
Exactly right. BUT... that's also where the infamous RICOH PIN is on certain Ricoh (and maybe some third-party) lenses. Search here for RICOH PIN and you'll find numerous threads discussing it.

But basically, Ricoh designed their manual-focus KR-mount lenses to have a pin in that location. (I forget just what it does.) Many KR lenses have a little nub there instead of a pin -- no problem. But a pin CAN and WILL get stuck in the drive socket of a KAF-mount body, causing loud swearing and some application of a feeler gage to unseat it. Aaarrgh...

If you see a round pin or nub in that location, it's a manual-focus Ricoh KR lens. The aperture ring will also have a P or A(P) position, instead of the A on Pentax A-type and AF lenses. (Ricoh call that setting Program; Pentax calls it Auto.) And the lens mount MIGHT have KR or KA/R stamped on it. If you see a pin with flattened sides in that position, that's the AF drive shaft, just what you want.
ricoh af lenses aren't going to work as af on a Pentax body. Nor will Chinon. That was the beginning of the end for Ricoh and Chinon regarding K-mount lenses.

08-13-2011, 03:02 AM   #9
Forum Member




Join Date: May 2011
Photos: Albums
Posts: 61
Just to clarify, SDM is Pentax's new, lens-mounted AF system. It uses an ultra-sonic motor (or something) beneath the focus ring, and has two extra electrical contacts inboard of the mounting flange.


Pic borrowed from here

You'll need a newer DSLR body to use SDM (not sure exactly which ones, I'm sure someone can tell you). Lenses will have SDM (or HSM for Sigma, or USD for Tamron) in their model name. Some lenses are SDM-only, as Mannesty said.
08-14-2011, 10:19 PM   #10
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
If the seller can't tell you, then don't buy the lens. After all, they obviously don't know the first thing about what they are selling. The lens might be broken or for a different camera moint entirely for all they know.
08-15-2011, 02:21 AM   #11
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 42,824
Usually I just look at the focusing ring- if it's small, you're looking at an AF lens, and if it's big and looks like it turns slowly, then it's manual focus. A perfect example is the generic vivitar/bower 85/1.4 lens.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
autofocus, k-mount, lens, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Good affordable autofocus portrait lens? geekette Pentax SLR Lens Discussion 16 06-19-2011 12:51 AM
zoom on an autofocus lens newpentaxman Pentax Film SLR Discussion 10 11-17-2010 01:57 AM
Autofocus with the kit lens? dragonfly Troubleshooting and Beginner Help 22 12-27-2009 02:09 PM
Does this lens autofocus on K-7 and K-x pakuchn Troubleshooting and Beginner Help 20 12-20-2009 04:22 PM
In-Body autofocus vs In-Lens autofocus Gooshin Pentax DSLR Discussion 7 02-05-2008 11:10 AM



All times are GMT -7. The time now is 04:46 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top