adaptor confusion

[RWaldron]

I don't shoot much 35mm anymore, and don't want to invest much financially, but I have a Pentax Spotmatic (my favorite 35mm SLR) that needs a normal lens and I have a Kodak Instamatic Reflex with a clean Schneider Xenon (my favorite 50mm) and I believe the necessary adapter exists to make this combination a reality - at a price. The price is one problem. Again, I don't want to invest too much in 35mm. So the first question is: Are the $35 generic adapters the same as the three figure versions available through Cameraquest? Second question concerns the functionality of the adapters. I assume you end up using the lens purely manually. What stumps me is that when I look at the lens on my Instamatic, the ring for selecting the f-stop is on the camera. Does this mean that the lens would only work wide open on a screw mount body? That would be giving up too much, and I can't believe anyone would even spend the price for the cheaper adapters if this was the case. As the title of the post says, I'm confused. Anyone familiar with these things?
Randy

 

[Mcary]

What usually happens when using a lens/camera combination in which there isn't an electronic and/or mechanical connection between the lens/camera. The lens operates in what's referred as "Stop Down Mode" Which means the aperture blades are stopped down to aperture that the lens is set to, instead being at the lens largest aperture (Wide Open) during focusing then stopping down during the process of pushing the shutter/taking the picture which is the case with most SLR lens.
Note since rangefinder such at the Leica M series don't use through the lens focusing their lens work in stop down mode.

 

[Godfrey]

I don't shoot much 35mm anymore, and don't want to invest much financially, but I have a Pentax Spotmatic (my favorite 35mm SLR) that needs a normal lens and I have a Kodak Instamatic Reflex with a clean Schneider Xenon (my favorite 50mm) and I believe the necessary adapter exists to make this combination a reality - at a price. The price is one problem. Again, I don't want to invest too much in 35mm. So the first question is: Are the $35 generic adapters the same as the three figure versions available through Cameraquest? ...

Randy,

All Kodak Retina Reflex lenses were designed for use with a leaf shutter incorporated into the lens mount, and at least the early ones interchanged only the frontmost elements of the lens, the rear three or four being common to all of them. I'm not sure if this design carried through for all series.

However, the mount register for the Retina Reflex (don't know what series) is listed as 44.7mm and the mount register for Pentax Spotmatic (M42 threaded) is listed as 45.46mm. That makes a direct adaptation impossible while still being able to achieve infinity focus.

You can find any number of excellent M42 mount 50mm lenses for less than the cost of an adapter from Pentax, Zeiss (for Praktica), and others.

G

 

[RWaldron]

Thank's for the replies. I should have known it was too good to be true. I know there is a 42mm thread version of the Schneider Xenon, but it's definitely way beyond my budget. Actually, while the lens the camera came with - the Takumar 1.4 - is full of fungus, I do have a perfectly good Meyers Something-or-other 1.8 lens in screw mount which may do just as well for all I know. It's just that I used to have a number of Retina rangefinders with the Xenon lens and I always loved the look of the photos from those lenses. Again, it's almost a moot point since I do less and less 35mm photography and would probably give the thing little use once the novelty wore off. I keep telling myself to simplify. Appreciate all the help though.