How to modify a Zenitar K for stop down metering

[Albert Aguilar]

Hi everybody

If you have a Zenitar with K mount and don’t like to be restricted to shoot in M mode, here’s an easy and non destructive way to convert the lens for stop-down metering.

You’ll need a small flat screwdriver and a small tweezers.

First remove the clear back filter by hand (#1 in the picture below). Then remove the three small black screws on the black plate (#2 in the picture)



Then remove the two silver screws that lock the diaphragm actuator in place. You may have to select a diaphragm of 5.6 or so to center the actuator on the window.



Mount the back plate with their three black screws and finally put back the clear filter.

Now you can use you Zenitar in Av, Tv, TAv, Sv and of course M modes.

Disclaimer: Do it carefully not to lose anything and at your own risk! :-((

Albert

--
Do not take life too seriously; you are not going to end it alive.

 

[Ishpuini]

I guess you are disabling the aperture ring with this? So regardless its position the lens will behave as if it's in A position?

Wim

--
Belgium, GMT+1

 

[John Bean (UK)]

I guess you are disabling the aperture ring with this? So
regardless its position the lens will behave as if it's in A
position?

It does exactly the opposite - only the aperture ring will stop down the lens. Makes it work like a M42 version and usable in Av mode. All modes other than M on the camera will be default to Av anyway.

--
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[LuzArt]

Do i still have to use the metering button to meter or can i change aperture as normal in AV? I assume not so wonder the point of this mod.

Ben
--



http://www.luzartphotography.com

 

[Ishpuini]

I guess you are disabling the aperture ring with this? So
regardless its position the lens will behave as if it's in A
position?

It does exactly the opposite - only the aperture ring will stop
down the lens. Makes it work like a M42 version and usable in Av
mode. All modes other than M on the camera will be default to Av
anyway.

Doh... Thanks John! Of course that's what it does... Forgot to think about it for a moment there... ;-)

Wim

--
Belgium, GMT+1

 

[richardplondon]

Lens permanently closes to the aperture you have selected (iow, viewfinder image darkens like the DOF preview). The lens is already stopped down, so the camera can meter continuously through the final aperture. Camera doesn't know what you have set, so EXIF will probably record an incorrect aperture.

So on positive side, you can use Av priority mode. On negative side, you view and focus through a stopped-down lens.

Personally I would have thought M mode, with green button operation set to "Tv shift", would do just as well as this modification - cunning though it is.

RP

 

[LuzArt]

rendering this combo less versatile and less useful for me.

Ben
--



http://www.luzartphotography.com

 

[jpfisher]

Interesting. I've got a large array of SMCP-M lenses and this would certainly make Av mode a little more robust, but on the other hand it would absolutely kill any resale value I would have in them if I decided to upgrade a particular focal length to a newer DA or FA lens and wanted to sell the old glass to alleviate the cost.

Is there any chance of damaging the lens doing this? I might give it a shot on one of my cheaper ones just to see how it goes, but I'd be scared to death to try it on my 85mm unless I was very confident that I could put it back together... especially after seeing what the last one of those that sold on eBay sold for.

Jim

--
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[jpfisher]

Do you mind explaining to someone who is still learning what the green button would do in this case?

If you are shooting with an SMCP-M lens in M mode on the camera you have to adjust the shutter speed from within the camera and the aperture via the ring on the lens. What does the green button do here?

If you are shooting in Av mode with an SMCP-M lens, the camera will only adjust the shutter speed based on the lens being wide open, no? Is there any way to stop it down and use the AE-L to to save the correct shutter speed? IE, if I'm out on a bright sunny day and I've got a f/1.8 lens on, without ND filters I'm stuck in manual mode, even at 1/4000 shutter speed I need to stop the lens down adjust shutter manually. If I stopped down the lens to f/8, would I be able to do a DOF preview and hit AE-L to set the correct metered exposure for the next 20 seconds and then take the shot that way?

I guess the best way would be to try this, but my camera is not in front of me. I hope my questions are at least making some sort of sense.

Thanks!

Jim

--
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[JensR]

Camera doesn't know what you have set, so EXIF will
probably record an incorrect aperture.

It won't record any aperture info at all (camera says --, EXIF says IIRC 0.0 or so). This is the same for any lens not set to A.

So on positive side, you can use Av priority mode. On negative
side, you view and focus through a stopped-down lens.

The procedure used to be: Focus and frame wide open, stop down for exposure until the desired DOF / shutter speed is reached.

--
'I only trust those photos I have faked myself.' (Me, 2007)
http://www.jensroesner.de/
--=! Condemning proprietary batteries since 1976 !=--

 

[Albert Aguilar]

Hi Jim:

The procedure that I've posted has the advantage of being non-destructive so at any time you can revert to the origin. (Unless you lost the pieces removed!). In some forums someone suggested to simply cut the lever!!!

For Pentax SMC M or K lenses I think it's a little bit mor difficult to remove the diaphragm actuator since the attachment is different and you have to dig deeper into the lens. I'll make some further investigation and will post the results when finished.

Albert Aguilar
--
Do not take life too seriously; you are not going to end it alive.

 

[Flex029]

unless i'm missing something, i don't see any advantage to doing this over just using the green button for metering. as it is, on my DS in M mode, i just set the aperture i want, press the green button and get the proper stop-down reading which automaticaly sets the shutter speed already. this is basicaly stopped-down aperture-priority.
like i said, what am i missing here? what is the advantage of doing this mod ?

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[JensR]

like i said, what am i missing here? what is the advantage of doing
this mod ?

You don't have to (remember to) push the green button.

Jens

--
'I only trust those photos I have faked myself.' (Me, 2007)
http://www.jensroesner.de/
--=! Condemning proprietary batteries since 1976 !=--

 

[richardplondon]

K10d: go into M mode. Then press the green button and an exposure is metered and set:

If you have a recent lens or an A lens with its aperture ring set on Auto, there is a Custom menu item that determines what happens next. Either it behaves like Program, or like aperture priority based on the current shutter speed set in the camera, or like shutter priority based on the current aperture set in the camera. The camera does not need to stop down the lens in order to meter, in this case. In fact it could achieve the same in Av or Tv or P, except that in those cases the metering continues to adjust to the scene until you take the shot. The M mode green button makes a setting and will not further alter anything by itself.

However if you have an M or K lens, the lens ring is on one or another aperture setting and there is no Auto aperture control. So the green button mechanically stops the lens down (to whatever that setting is - the camera can't find out), meters the scene through the stopped down lens, picks a shutter speed, then opens the lens up again.

You can then alter the shutter speed manually, to apply + or - exposure compensation if desired.

RP

 

[jpfisher]

However if you have an M or K lens, the lens ring is on one or
another aperture setting and there is no Auto aperture control. So
the green button mechanically stops the lens down (to whatever that
setting is - the camera can't find out), meters the scene through
the stopped down lens, picks a shutter speed, then opens the lens
up again.

You can then alter the shutter speed manually, to apply + or -
exposure compensation if desired.

Richard,

Thanks. I'm on a DL now, so I don't have this function. This enhanced functionality is yet another sign that I need to upgrade to a K10D as most of my lenses are full manual K-mount. I prefer shooting in Av mode to M for simplicity's sake, but as of now that only lets me shoot at open apertures. Using the lenses as you described on the K10D would take a lot of the trial and error out of getting a good exposure using a manual lens (granted, I'm getting better at "eyeballing" it in most situations).

--
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[JensR]

Thanks. I'm on a DL now, so I don't have this function.

You do. Switch your camera to M mode, press the AEL button to set the exposure time, then correct by turning the dial. Over/under exposure will be indicated in the viewfinder when you use the DOF preview lever.

M mode might seem daunting at first, but as it is "metered manual" it isn't bad at all.

Cheers
Jens

--
'I only trust those photos I have faked myself.' (Me, 2007)
http://www.jensroesner.de/
--=! Condemning proprietary batteries since 1976 !=--

 

[jpfisher]

Jens,

Thanks so much! I think I was trying to ask if I could do that in another post. I'll give it a try tonight and see if I can manage it... still want the K10D, but this might make me happier with the DL for the time being.

Jim
--
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