KA Mount on KAF/KAF2 Bodies


stevejcoe

Link Posted 26/04/2007 - 14:21
I have a number of Prime KA mount lenses, my question is this. Is it possible to modify the mount in some way, that will allow Aperture information to be displayed in the viewfinder when used with a KAF/KAF2 body ie MZ7 in Manual mode? Any feedback would be much appreciated.

Tyr

Link Posted 26/04/2007 - 15:10
KA mount lenses feature automatic aperture controlled by the body, although you can set it to manual on the aperture ring if you wish. I think that the aperture will appear on the display of all Pentax DSLRs. I can't test this as my K10D isn't here yet... K mount lenses without automatic aperture settings won't show any information and you must set it manually and use the metering with the aperture stopped down.

At least that is my understanding of it having read the manual and looked up various things.

stevejcoe

Link Posted 26/04/2007 - 15:31
Thanks for the reply. I do not have a DSLR so cannot comment.
When I put a F or FA lens (KAF mount) on my MZ7 with the camera set to Manual and the Aperture set manually, the Aperture information appears in the viewfinder. What I was trying to ascertain was whether it was possible to do this with a Prime KA mount lens. I know that it is not possible with a Zoom that has a variable maximum aperture, but what about with a Prime?

MattMatic

Link Posted 26/04/2007 - 15:57
The issue about whether the aperture is displayed in the viewfinder is as follows:

* If you select the aperture manually from the camera with the lens aperture ring in the "A" position - the f-stop will be shown.

* If you manually select the aperture from the lens, then older bodies will display the aperture. Newer bodies (including dSLRs) cannot display the aperture.

On the original KAF mount the select aperture was sent to the body by a mechanical "finger". The body would detect the position of this "finger" and linked it into the exposure system.
Some of the 35mm cameras had this linkage (my old MZ-5 and Z1 both had this) and could display the information.

On the new "crippled mount" bodies, this mechanical linkage is not fitted and consequently the body has absolutely no way of knowing where the aperture ring is. It's physically impossible.

...but then most of those bodies allowed selection of the aperture from the body - at least for A, F and FA lenses.

HTH!
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

stevejcoe

Link Posted 26/04/2007 - 16:58
Hi Matt thanks for the reply. On my MZ7 with a variety of Prime KA mount lenses the Aperture information only appears in the viewfinder when the lens is set to A. With the KAF mount lens (35-80) that came bundled with the camera I can put the camera into Manual and change Speed (via the select switch) and Aperture via the lens at the same time and still see full information in the viewfinder. What I wondered with my original question was whether I could mimic the KAF lens behaviour with a KA lens by possibly changing some of the contacts.
I know the camera already offers lots of options, I guess I am showing my age and hankering after old fashioned manual with modern viewfinder info
Thanks - Steve

johnriley

Link Posted 26/04/2007 - 17:11
Quote:
I know the camera already offers lots of options, I guess I am showing my age and hankering after old fashioned manual with modern viewfinder info

The MZ3 is perfect for combining modern readout and viewfinder with traditional shutter speed dial and, if desired, manual operation. The slightly older MZ5/MZ5n cameras are also very similar.
Best regards, John

MattMatic

Link Posted 26/04/2007 - 17:34
Quote:
...whether I could mimic the KAF lens behaviour with a KA lens by possibly changing some of the contacts.

Not as far as I know

I seem to remember (it was a looong time ago), I had a Tokina lens that would work manually on my Z1 but not on an MZ5 - bizarre! (I did wonder if there are mechanisms for reading through the contacts digitally, but I can only find evidence for the aperture being read through the "finger".
Not that it helps....

There's quite a bit of K-mount info on: http://www.bdimitrov.de/kmp/

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

Mongoose

Link Posted 26/04/2007 - 17:42
If I recall correctly, my MZ-7 behaves the same way, that is it will display the aperture with FA lenses set away from A but not A lenses.

I always assumed the digital contact on the FA series allowed the camera to read the aperture info electronically, but if this is the case I wonder why they don't make use of this ability on the *ist and K series?

Mannesty

Link Posted 26/04/2007 - 17:54
Question:

If you can set all A and newer lenses to A on the lens, and set the aperture on the camera body (depending on camera) and see the information you want in the viewfinder or top plate, why would you want/need to set the aperture ring to anything other than A (other than habit) ?
Peter E Smith

My flickr Photostream

Mongoose

Link Posted 26/04/2007 - 18:17
Mannesty wrote:
Question:

If you can set all A and newer lenses to A on the lens, and set the aperture on the camera body (depending on camera) and see the information you want in the viewfinder or top plate, why would you want/need to set the aperture ring to anything other than A (other than habit) ?

On the K10D and anything else with twin selector wheels, no real reason, other than habit as you say and some people just prefer to change aperture with the right hand. Everything else about the K10D is geared towards letting you work the way you want to, why not this? I'm playing devils advocate there a bit, since the new lenses have no Aperture ring anyway people should probably get used to not using one!

On the MZ-7, because it's faster. The MZ7 doesn't have a proper selector wheel, just a toggle switch which makes going from stopped down to wide open quickly a right PITA, it's much faster to just grab that aperture ring and give it a good twist.

Also its a great way to switch from any mode to Av at the drop of a hat. I've been known to use the Aperture ring to switch to Av wide open nice and quickly even on my *istDL2.
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