> If you removed just the front element of the lens, the rear element acts as
a
> lens of greater focal length and smaller aperture. If you focused the
camera before
> you unscrewed the front element then the rear element by itself is
> out of focus. Add to that the diffraction limited aperture and you have a
> similar effect, but it is not a true pinhole. Is this not so??
All true enough. The older Symmars are indeed convertible lenses, with (at
least in my experience) pretty awful performance of the rear element used
alone.
But: I'm not sure why that is relevant in this situation. After putting in
the 1mm aperture, I replace the front element, so that the lens is used with
both front and rear elements at its original (135mm) focal length.
> ...but it is not a true pinhole. Is this not so??
Again, true enough; that's why I used the term "pseudo-pinhole." It gives
the extreme depth of field and slightly out-of-focus effect of a true pinhole
but there is of course a real lens forming the image.
Charlie Palmer