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Old Engineer Jan 25, 2008 11:01 PM

I have bought a Yashinon DS-m 50mm x f/1.7 lens. It has a screw-mount base. I have never had a lens with such a base. The only protrusion or opening other that that for the lens is a small pin which is spring-loaded, and you can push it in, then it will pop out when released. This pin actuates the aperture leaves. The lens came mounted on a Ricoh Singlex II camera. I bought it for the lens. I have read that this particular lens is a great one. (Digital World, South Africa)

I understand that I must use an adapter, one specially made to allow focusing to occur to infinity, in order to use a screw-mount base on my K10D.

However, I cannot see anything on the camera body which will push in the pin when the camera shoots. Am I missing something?

The little pin does not control the aperture opening size. This is done with the twisting action on the lens barrel's aperture ring.

After a lot of head scratching I have concluded that when the lens is mounted on the camera, using the special adapter, something keeps the pin always pushed in, and that you then twist the aperture ring to the f-stop desired. Am I wrong in that conclusion?

Or. perhaps I just won't be able to use the lens at all. Is that the case?

I need a little of your collective brilliance to throw light on this subject, please.

Old Engineer

philneast Jan 26, 2008 2:43 AM

1 Attachment(s)
"After a lot of head scratching I have concluded that when the lens is mounted on the camera, using the special adapter, something keeps the pin always pushed in, and that you then twist the aperture ring to the f-stop desired. Am I wrong in that conclusion?"

yes that is right, it is called stop down metering.

Usually I set the lens to maximum aperture to focus and then set the aperture for automatic metering in aperture priority mode.


The infinity focus problem only comes from some poor imitations of the proper adaptor.

Phil

jachol Jan 26, 2008 4:03 AM

philneast wrote:
Quote:

"After a lot of head scratching I have concluded that when the lens is mounted on the camera, using the special adapter, something keeps the pin always pushed in, and that you then twist the aperture ring to the f-stop desired.* Am I wrong in that conclusion?"

yes that is right, it is called stop down metering.

Usually I set the lens to maximum aperture to focus and then set the aperture for automatic metering in aperture priority mode.


The infinity focus problem only comes from some poor imitations of the proper adaptor.

Phil
OE,
Some of that type of lens can be switched between auto & manual, if the lens hasn't got that, then it's not usable. In full manual mode on the camera, you need to be able to switch the lens to manual use, focus with the lens wide open then stop down to what aperture you require to use, exposure is then set with the AE-L or the green button. You also need to set aperture ring use in the custom setting menu. There is no way the the lens will stop down automatically. Hope this helps ... Jack

jachol Jan 26, 2008 4:23 AM

1 Attachment(s)
This is the lens switch ... Jack

TDN Jan 26, 2008 8:55 AM

jachol wrote:
Quote:

Some of that type of lens can be switched between auto & manual, if the lens hasn't got that, then it's not usable.
Actually, with lenses like that, all you need to do is glue something over the pin that keeps it down.

The easiest way is to hold the pin down and put a drop of glue in there, of course that takes away the possibility ever using the lens on your Ricoh camera.
I've heard that some people just glue a small piece of plastic over it, which can be removed if you pull hard enoguh later...
This is at your own risk though, god forbid that the plastic with glue residue gets loose inside the mirror chamber...


But most lenses have the M/A switch, or at least a button you can push to stop down the lens. So those can be used like that.

Tom

Old Engineer Jan 26, 2008 9:05 AM

Thanks for the information. I now understand what the problem is, as well as the fix for it. The guys and gals on this site are my friends. I am beginning to know you all.

I don't know what I would do without this forum, so I want also to give my supreme thanks, bowing and nodding, to Steve and the people who made this site possible and are maintaining it. Thanks.

Old Engineer

jachol Jan 26, 2008 9:33 AM

TDN wrote:
Quote:

jachol wrote:
Quote:

Some of that type of lens can be switched between auto & manual, if the lens hasn't got that, then it's not usable.
Actually, with lenses like that, all you need to do is glue something over the pin that keeps it down.

The easiest way is to hold the pin down and put a drop of glue in there, of course that takes away the possibility ever using the lens on your Ricoh camera.
I've heard that some people just glue a small piece of plastic over it, which can be removed if you pull hard enoguh later...
This is at your own risk though, god forbid that the plastic with glue residue gets loose inside the mirror chamber...


But most lenses have the M/A switch, or at least a button you can push to stop down the lens. So those can be used like that.

Tom
I hadn't seen or heard of that trick Tom, Hope it will work OK for OE. ... Jack

robar Jan 26, 2008 11:15 AM

OE,
adorrama & B&H have adapters you can use. all the ones they sell will give IF and they cost about $18 delivered..

roy

Old Engineer Jan 26, 2008 3:13 PM

Robar, I am ordering today. Thanks Robar.

Old Engineer

dvdrom000 May 8, 2008 1:35 PM

how do you engage that "M" switch? do you have to hold it every time you use the camera?


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