No AF with M42 adapter

[slawek_jacek]

I loved using my old Tamron 105/f2.5 MF lens with semi-AF feature from K100D -

when you turn slowly the focusing ring in AF mode until the camera locks focus

and fires.

 

So I decided to get a SMC Takumar 100/f2.8 as a replacement, as I've heard they

are optically somewhat better (and sooo cheap these days).

 

With an m42 adapter that looks very similar to the original Asahi (no flange),

I went onto shooting. How dissapointed I was to find that my newly beloved semi-

AF feature is not working. The focus indicator works OK, but camera does not

shoot automatically.

 

I figure some contacts on the camera mount are not covered by the lens mount ???

 

Is there an adapter that works in that respect?

[stemked]

Slawomir,

 

I think you need to read the manual. No manual lens is going to autofocus in that fashion. There is a rare teleconvertor 1.7X that will allow fast K-mount lenses to autofocus, but that is as close as you will come.

[mawz]

@Douglas Stemke: Slawomir's using the trap focus feature, which only works correctly if the lens shorts out the A contacts on the mount. Thus it will work with K lenses, but most M42 lenses won't work. This is the same reason that preset or preset-modified K lenses can do Aperture priority on the K100D, but M42 lenses cannot.

 

@Slawomir: Try shorting out the A contacts to the lensmount. The camera doesn't think a lens is mounted otherwise.

[slawek_jacek]

I've heard of M42 adapters "with a flange". I would imagine that such a flange could short out contacts. It would likely also eliminate infinity focus.

 

Could somebody with such a "flange" adapter run a test? (not sure if flange covers contacts).

 

And if the infinity focus is gone - how bad is it? (how far can it focus ? )

[andrew_ng7]

"I loved using my old Tamron 105/f2.5 MF lens with semi-AF feature from K100D - when you turn slowly the focusing ring in AF mode until the camera locks focus and fires."

 

Are you talking about when you focus and the MF symbol on the inner display shows you are in focus? When you say locks focus and fires, do you mean it won't fire until it locks? I can't seem to replicate that.

 

Anyway, I just tried my original Asahi Pentax adapter, that I use to use with my LX way back when, with an old Makinon 28-80mm f3.5. The adapter doesn't seem to short any of the contacts but my k10d still manages to show when the frame was in focus. Thinking it was the lens shorting the contacts, I unscrewed the lens so that none of the contacts were touching and still found focus.

[andrew_ng7]

Btw, I'm am strongly leaning towards getting a 3rd party split prism focus screen to use my MF lenses more efficiently. I don't know if I could fully rely on the camera to tell me that the image is in focus.

[slawek_jacek]

Andrew,

 

If you have any old MF, K mount lens (Pentax K, A or M, or Tamron Adaptall) put it on your K100D, switch camera to AF mode, and point camera to out-of-focus object.

Press the shutter fully and hold. The camera will not fire. Now turn the focusing ring slowly, even slower as you approach point of being in focus. The camera will fire when you hear the familiar beep and focus indicator shows up.

 

This trick is not documented (I think) in the manual. The trade-off is that if you do it too quickly (meaning faster than VERY slow), you turn the ring past your DOF by the time the image is recorded.

 

Still, I love it.

If I could only use my Takumar like this...

[andrew_ng7]

maybe it's because of me having a k10d, but I believe it will fire in AF mode when out of focus. I will try it again tonight and let you know.

[azemerov]

Slawomir,<br>

try to place piece of aluminium foil between adapter and contacts on body. It doesn't look like long term solution, but anyway should easily solve the problem.

[mawz]

@Slawomir: M42 adaptors with flanges will work like your K mount lenses. However they will not reach infinity focus because they move the lens away from the mount.

[mc2imaging]

Trap focus has been a documented feature since the PZ-10 at least, as that was my first

AF

camera. Probably goes back further than that... but Pentax doesn't call it 'trap focus.'

<br><br>

 

That said, off the top of my head I'm thinking there is a setting in the custom menu to turn

trap focus off so that with a MF lens it WILL fire in AF mode even if the camera doesn't

think it

is focused on anything.<br><br>

 

<i>when someone stumbles upon this exchange four years from now via a Google search,

they are going to say,</i> 'does anyone on this forum read their manual?'

[andrew_ng7]

Tried again last night and my k10d will fire regardless of focus with a MF lens and set to AF-s and AF-c.

 

I can still 'trap focus' but with the shutter release half pressed only. Pretty much need to hold the shutter and focus at the same time until the indicator on the internal LCD shows lock.

[roland_nicolas]

I believe Matthew is right. In the custom menu of my K100D, I've allowed everything : shooting with Af unlocked, when flash is not ready, and so on... No problem with M42 lenses and Pentax adapter (I must say I always switch the body selector to MF in this case). I HATE being prevented to fire. Those "idiot proof" features are not for me. I don't pretend I'm no idiot, but I've better a bad picture than no picture at all !

[chetan_dighe]

M42 adaptors with flanges will work like your K mount lenses. However they will not reach infinity focus because they move the lens away from the mount.

 

????????????????????????????????????

 

I am thinking of going for an M42 lens with "flange" adapter for my K10D. I am perfectly ok with manual focus. Question is - does it work on k10D? I am interested in infinity focus, cant live without it.

 

I have other K mount lenses, all manual, and they work with the custom setting "aperture ring" permitted. Focussing is, off course, manual. Wont the M42 manual lenses work the same way?

[roland_nicolas]

Chetan - An M42/K adapter with flange won't allow infinity focus ! You need the Pentax type adapter, which goes inside the K mount of the body. With "aperture ring permitted", you can use M42 lenses in both M and Av modes, and the metering is "centre weighted". Of course, you must stop down the lens manually at the desired aperture value. Lenses with "auto" feature will work if they have a Manual/Auto switch (choose "Manual"). Auto lenses without this feature won't stop down. With M42 lenses, you'll get the "focus confirm" too (check this setting in the menus), from wide open to f5,6 or f8... NB : You'll probably get a constant over or under exposure. Some report that the K10D overexposes with M42 lenses. The K100D (I own one) underexposes +/- 1,5 EL. Always check the histogram !

[pinwu_xu]

Any solutions to the lens that don't have the Manual/Auto switch?

I've a lens that is "Auto" only, that I observed that when changing the

aperture settings, the opening doesn't change, only see the change

when I push the small ping at the end.

 

Could this be fixed (I mean to make it "manual")?

 

Regards.

 

Pinwu