Where should the aperture be located?

[keithwms]

For my homemade apertures, I use developed (but not exposed) E6 film. It is quite nice and black.

[BetterSense]

Do you cut a hole in it, or do you take a picture of a circular spot?

[Mark Fisher]

If it is a symmetric lens and you can get the aperture in the middle, you are all set. The downside is that it will be tough to focus with the small aperture. If it works out, maybe you can come up with an inexpensive old lens with a variable aperture.

[bowzart]

I don't remember the model, but at least one early Kodak camera used a simple lens with the stop in front of the lens to improve performance. Likely a single element lens, but it's a viable option. ...

Examples I've seen in folding Kodaks, and the Ansco Sure Shot box camera, had simple meniscus lenses, convex side forward. With only one element, where else would you put it?

Some of the Kodak folders had real f/stops, starting (if I recall correctly) at f/16 and getting smaller. In front was a restrictive disk which prevented the camera from being able to operate at wider apertures, although the aperture range was there. I imagine that this was to insure that the user would get sharp pix, because the lens is sharp in the center but has severe aberration if it is used farther out to the edges. I have removed this disk to see what it will do; I got the kind of image that was prized by the blurry pictorialist school around the turn of the 19-20th C's. I've got that camera somewhere still. It's kind of fun.

These had no glass in front.

[unclemack]

I don't know a thing about your lens I'm afraid but I can tell you that I have a Mamiya RZ67 and the 180mm. lens has the shutter and diaphragm behind the lens. Was a big surprise to me when I bought it years ago! No glass behind the shutter at all!!

Not sure how much help this is...