Super Anglon 65mm Rear mounting filters

[Greg Blank]

Is it possible to screw in rear mount filters or holder adapters to the 65mm 5.6 Super Angulon. If so, what is the thread size of the "Rear Element"?

[Peter K]

Is it possible to screw in rear mount filters or holder adapters to the 65mm 5.6 Super Angulon. If so, what is the thread size of the "Rear Element"?

With every filter one gets a spherical overcorretion. So the filter should be placed in the direction to the longer distance - front lens to subject if the subject scale is reduced as with "normal image taking" - to minimize this effect.

Also the thread is too short to screw in a filter in a SA's rear element.

Peter

[wfwhitaker]

With every filter one gets a spherical overcorretion...

How is that?

[Peter K]

How is that?

Also a planparell filter is a lens with the two infinite radii, with a certain thickness, refractive index, Abbe's number etc. So it will influence the total correction of the whole (taking-)lens.

Of course a clean gel-filter mounted behind a SA with tape or two small drops of glue the influence is neglectable.

Peter

[Steve Goldstein]

Yes, what Peter said!

All optical glass has dispersion, i.e. the refractive index is a function of the wavelength (color) of the light, which is the source of chromatic aberration. The amount of color separation increases as the angle of the light becomes less and less perpendicular to the glass surface.

With a wide angle lens, the light heading towards the edges/corners of the film can be at a fairly extreme angle. If you mount a filter on the back, it will thus tend to produce much more color fringing at the image edges than if was mounted on the front of the filter where the incoming angles are smaller. The colors separate less as the filter thickness decreases, which is why you can get away with back-mounting a gel - it's so thin the effect is unobservable except perhaps at extreme enlargements.

Sometimes lens designers will take advantage of the dispersion of a flat piece of glass, as in designing the lens for the gigapixel project. See http://www.gigapxl.org/technology-realized.htm about 2/3 of the way down the page. They used a fairly thick piece of plane-parallel optical glass in the lens design.

[Bob Salomon]

Sometimes lens designers will take advantage of the dispersion of a flat piece of glass, as in designing the lens for the gigapixel project. See http://www.gigapxl.org/technology-realized.htm about 2/3 of the way down the page. They used a fairly thick piece of plane-parallel optical glass in the lens design.

A more common example are with the Rodenstock Apo Sironar Digital and HR Digaron-S lenses. When these are used on roll film cameras rather then digital backs a corrector plate has to be used behind the lens as the last element in the lens is the cover plate over the digital sensor on a digital back.