Aperture question newb style!

[Socrates]

Catadioptric (mirror) lenses, fax machines, photocopiers, scanners, telescopes and spotting scopes, microscopes...

I've never so much as considered using any of those lenses on my cameras.

 

[Socrates]

The older Holga's had only one fixed aperture, I believe. Now most of them have two - "sunny" and "cloudy."

Those lenses are compatible with what cameras?

 

[Helen B]

I've never so much as considered using any of those lenses on my cameras.

That doesn't mean that they don't exist. They do, and people do use some of them on cameras. Thinking about it some more, apart from the catadioptric lenses designed for use on cameras, there is/was also the famous Zeiss Hologon, a remarkably high quality 15 mm f/8 lens that had no iris. As with most (but not all) catadioptric lenses*, there was nowhere to put a workable iris.

I think that 'fixed aperture' is best left as a description of fixed aperture lenses, and 'constant aperture' is the best description for zooms that hold their aperture constant while zooming. 'Aperture constancy' is the technical name for that property of constant aperture zooms.

Best,
Helen

*Edit: I re-read that and realised that it could be taken to mean that the Hologon was a catadioptric (= reflective and refractive) lens. It isn't. It's all refractive, but there is no gap in the glass to fit an iris into.

 

[intheQ]

Here is an example of a fixed aperture SLR lens currently on the market.

http://www.bhphotovideo.com/c/product/291393-USA/Phoenix_09064_500mm_f_8_0_Mirror_Manual.html

 

[brileyphotog]

Those lenses are compatible with what cameras?

The Holga is actually a toy plastic camera from China. They cost about $25. They are medium format film cameras (6x6 cm) which are notorious for having all sorts of distortion, light leaks, accidental double exposure, soft focus, way too much contrast, and a host of other "problems." They often lend interesting and artistic effects to photos. Photos taken with Holgas and other cheap medium format cameras have been displayed in art galleries around the world. Some people also rip the lenses off of Holgas and modify them to fit on Canon and Nikon mounts.

Also, I was throwing out just one example. Some of the old Polaroid cameras (the big clunky ones) had one fixed aperture of f/42, I believe. Just because a lens is fixed to a camera doesn't make it any less a lens.

And as Helen pointed out, just because you've never heard of it doesn't mean it doesn't exist.