K-7 and M-type lenses


myles

Link Posted 20/01/2010 - 21:45
Hi all!

I'm hoping that some of you can help.

I have a K-7 and have just received a Vivitar 135mm lens, thanks to Brooksy69. It's an old K or M style manual aperture without an 'A'-setting. My problem is that I can't get it to stop down on camera. The meter doesn't seem to recognise that it is at anything other than f2.8.

I have tried the green button, the +/- button, the AF and OK buttons and the DoF preview setting, but no joy! 'Use aperture ring' is enabled and the camera will take the picture when the shutter is released (at f2.8, whatever the lens is set to). It is set to Manual mode.

When the lens is put on a P30T, the DoF preview works fine and the meter on that camera shows different shutter speeds as the aperture is changed.

Has manual aperture from the lens been disabled on the K-7, or have I been doing something wrong?

Thanks in advance (and apologies for the long post!),

Myles

Anvh

Link Posted 20/01/2010 - 21:57
never mind me I had it completely wrong
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Last Edited by Anvh on 20/01/2010 - 22:10

iceblinker

Link Posted 20/01/2010 - 22:06
Pentax digital cameras don't have full functionality with K and M lenses due to the "crippled" mount, but still the lens should stop down in Manual mode when the shutter is released, or when the DOF preview or Green button is operated.

However, the meter will not recognise that anything other than the largest aperture is selected at other times.

Is there no difference in exposure and DOF with shots taken at f2.8 compared to f11?

At f11 (or any small aperture), can you see and hear anything happen when you press the Green button in Manual mode?
~Pete

myles

Link Posted 20/01/2010 - 22:08
No, Stefan, it doesn't. The lens appears to remain at full aperture where ever the aperture ring is set. Normally that isn't a problem, of course, as it should stop down on taking the photo, but the meter should recognise that a different aperture is set and give a different indication. And I would expect it to stop down with the preview button. It doesn't seem to, hence my problem!

Myles

iceblinker

Link Posted 20/01/2010 - 22:09
Anvh wrote:
The aperture already closes right when you use the aperture ring so it can't stopdown since the aperture is already there.

That's not the way normal K and M lenses work. They are held open at the largest aperture when mounted.

I don't know about the Vivitar 135mm, though.
~Pete

Anvh

Link Posted 20/01/2010 - 22:13
I stand fully corrected

The preview button stops down the lens but does not meter (at least if they haven't changed that) you need to press the green button and it stops down and takes a metering but it does not read/say the aperture in the display.
You can use M and AV mode.
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Last Edited by Anvh on 20/01/2010 - 22:16

jackitec

Link Posted 20/01/2010 - 22:14
Set the camera to M setting, stop down to your required aperture, set your shutter speed with the wheel, try different apertures till you get the one you want or are happy with.

Jack

iceblinker

Link Posted 20/01/2010 - 22:21
Anvh wrote:
The preview button stops down the lens but does not meter (at least if they haven't changed that)

Yes the DOF Preview lever does meter in Manual mode, but only when the Electronic Level is turned off.

Quote:
you need to press the green button and it stops down and takes a metering but it does not read/say the aperture in the display.
You can use M and AV mode.

The Green button is optional (though recommened). You can meter with the DOF Preview and select the shutter speed manually, if preferred.

Av mode only works with the largest aperture with these lenses (unless the lens is modfied or not fully fitted).
~Pete
Last Edited by iceblinker on 20/01/2010 - 22:22

Anvh

Link Posted 20/01/2010 - 22:26
Thank you Peter

You sure about the Av, I used some M lenses that way on the K10D.
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Last Edited by Anvh on 20/01/2010 - 22:26

iceblinker

Link Posted 20/01/2010 - 22:40
Stefan, I'm sure about Av. Maybe by "M" lenses, you mean M42 lenses that can be held open at the selected aperture?

By M and K here, we mean bayonet K-mount lenses. "M" comes from the Pentax-M series.
~Pete
Last Edited by iceblinker on 20/01/2010 - 22:44

Mannesty

Link Posted 20/01/2010 - 22:43
In Av mode, M series lenses and older will not stop down when the shutter is released. You need to use (M)anual Exposure mode on the camera, and set the 'Permit use of aperture ring' in the custom menu to allow (or whatever it's called in your model.
Peter E Smith

My flickr Photostream

Anvh

Link Posted 20/01/2010 - 22:56
It seems I need to check things again

I know we are talking about those lenses here Pete, but I thought the camera stop down and take a metering also in Av mode... not so sure anymore
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Last Edited by Anvh on 20/01/2010 - 22:58

johnriley

Link Posted 21/01/2010 - 00:22
You can use Av mode and M mode. If you set any other aut mode (such as Tv) you will get Av regardless.

It's not a convenient way to work IMHO, but it does work. Unfortunately the exposure may not be accurate either.

Personally I stick to A series or later lenses.
Best regards, John

myles

Link Posted 21/01/2010 - 00:28
@ Mannesty - My original post does state that the camera is in manual exposure mode and that 'Use aperture ring' is enabled. That was one of the first things I did when I got the camera!

@ Iceblinker - I had the Horizon Leveller option enabled, but not the 'spirit level'. Turning it off did not help any, unfortunately. To answer the questions in your earlier post - when pressing the green button, or using the DoF preview, nothing happens. Viewfinder stays just as bright and there is no sound of blades moving. I tried an old Cosina 50mm from a CT-1 with the same result and photos taken at f2 and f16 had the same depth of field. I also have an A-series Pentax 50mm and there is no problem with that at all (tested off the 'A' setting of course ).

This seems to affect manual-aperture only lenses; those with the auto setting appear to be OK. If this is a 'feature' of the K-7, I am surprised that no-one has commented before now .

Best,
Myles

iceblinker

Link Posted 21/01/2010 - 01:32
myles wrote:
If this is a 'feature' of the K-7, I am surprised that no-one has commented before now .

No, it is not a feature of the K-7. I have a K-7 and two of the type of lenses in question, and I can use them in the way I describe.

I don't know why it's not working for you, sorry. I can't work out if you're doing something wrong or if you have faulty equipment. All I can suggest is that you check everything yet again and experiment yet some more.
~Pete
Last Edited by iceblinker on 21/01/2010 - 01:50
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