SINAR Norma: Now I get it!

[Daniel Unkefer]

138S posted this over on Phototrio. Good Reading..............

"First let me point that Ronar is not a telephoto lens, a telephoto glass has a well shorter FFL than the Focal, as defined in the Kingslake bibles...

The Sinar Norma + Ronar is battle tested setup !!!

Sin título-1.jpg default_wolf_new_york_exc_03_0706111605_id_41553.jpg

...being Reinhart Wolf a remarkable user crafting impressive works with that !

Personally I'm experimenting that with cambo sc, as I lack a sinar 8x10 back...
https://www.flickr.com/photos/125592...5/27823423611/
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Let me point that Apo Ronars and Claron glasses for graphic work were optimized for close distance. It is possible to optimize those lenses for distant subjects by adding a proper shim in the front cell to increase a bit the inter-cell distance.

Procedure was described in "Internationale Phototechnik" issue 8/1993...

"Focus the center of your ground-glass on fine structures in the distance like leafless trees or high grasses with a strong loupe at wide open aperture.

Shift the rear frame of your camera to the left and the front frame to the right up to the point you can see the structures get blurry.

Unscrew the front group of the lens circa 2 mm (1 line or 0.08 inch) from the shutter or barrel and look for the fine structures, twigs or leafs. Adjust the distance between the front group and the shutter up to the point the structures are as sharp as possible without any coma and blur. Refocus if necessary during the adjustment.

Place a steel or brass shim of the determined thickness between shutter and front group. If the thickness of the shim is the correct one there is no difference in image quality between the center and the edge of distant subjects. For close-up work remove the shim or place a much thinner one."

Additionally when you unscreewed the from cell to its optimal place then you may count the tours (and fraction of a tour) you need to screew again the front cell. If we multiply the number of tours by the thread pitch then we have the thread thickness we need.

That operation mostly optimizes image quality off center, in the corners and mid.

Probably many (or most) long Ronars around have the optimal inter-cell distance for close work, this can be known by checking if the corners in the image improves when the front cell is unscreewed a bit.

For very long focal Ronars that effect should be noticed less as we take more the center of the image circle, still it would be well noticed when shift/rise performed."

[Greg]

Let me point that Apo Ronars and Claron glasses for graphic work were optimized for close distance. It is possible to optimize those lenses for distant subjects by adding a proper shim in the front cell to increase a bit the inter-cell distance.

Many, many years ago remember reading an article (possibly in the rear equipment section of Linhof International Photo Technik magazine) that Repro Claron lenses were also available with shims inserted for optimum focus at infinity. Around 1980 I bought a 210mm Repro Claron from Stu Kay (Lens & Repro) in a shutter that had those shims inserted. As I remember its coverage on 4x5 allowed for limited movements, but the Chromes that I shot with it were amazingly sharp and contrasty. Photographed many waterfalls with it on cloudy days with the images on my Chromes just popping out.

[David Lindquist]

Let me point that Apo Ronars and Claron glasses for graphic work were optimized for close distance. It is possible to optimize those lenses for distant subjects by adding a proper shim in the front cell to increase a bit the inter-cell distance.

Procedure was described in "Internationale Phototechnik" issue 8/1993...

"Focus the center of your ground-glass on fine structures in the distance like leafless trees or high grasses with a strong loupe at wide open aperture.

Shift the rear frame of your camera to the left and the front frame to the right up to the point you can see the structures get blurry.

Unscrew the front group of the lens circa 2 mm (1 line or 0.08 inch) from the shutter or barrel and look for the fine structures, twigs or leafs. Adjust the distance between the front group and the shutter up to the point the structures are as sharp as possible without any coma and blur. Refocus if necessary during the adjustment.

Place a steel or brass shim of the determined thickness between shutter and front group. If the thickness of the shim is the correct one there is no difference in image quality between the center and the edge of distant subjects. For close-up work remove the shim or place a much thinner one."

Additionally when you unscreewed the from cell to its optimal place then you may count the tours (and fraction of a tour) you need to screew again the front cell. If we multiply the number of tours by the thread pitch then we have the thread thickness we need.

That operation mostly optimizes image quality off center, in the corners and mid.

Probably many (or most) long Ronars around have the optimal inter-cell distance for close work, this can be known by checking if the corners in the image improves when the front cell is unscreewed a bit.

For very long focal Ronars that effect should be noticed less as we take more the center of the image circle, still it would be well noticed when shift/rise performed."

Does this article tell you how to go about cutting the shims? Trying to envision a way to do a neat job in the absence of, say, a punch press and a resident tool and die maker to make the custom sized punches.

David

[Conrad . Marvin]

For thicker shims, say .05mm, it might not be so difficult to turn them very easily and accurately on a metal working lathe. The thickness can be adjusted precisely during manufacturing. The thinner the shim, the more difficult it is to accurately produce and I would think one could use a piece of drafting film and a pair of scissors to do a “temporary” adjustment. If you can read a micrometer, you are well on your way.

[r_a_feldman]

Brass shim stock, 3”x6”, 1 each 0.001”, 0.002”, 0.003”, 0.005”, $3.52 at https://www.dickblick.com/items/k-s-...4aAi_nEALw_wcB

[David Lindquist]

Procuring shim stock is easy enough. Cutting a neat circle with simple tools I think not so much.

David

[Tin Can]

Round Rule Dies

I have a large set and used them for decades with a hammer or press

What diameter and thickness and what material

Also leather belt hole cutter, they are safer for beginners as you won't hit your fingers

[Greg]

Procuring shim stock is easy enough. Cutting a neat circle with simple tools I think not so much.

Picked up a small Craftsman Scroll Saw at a tag sale for under $12.00. Used the thinnest blade that I could find. Double stick tape to secure the brass shim sheet between two very thin sheets of hobby store plywood. Wore a Headband Magnifier and cut very, I mean very, very slowly... maybe 5 minutes per circular cut, no kidding. Final shim may not have looked perfect but it perfectly worked. I'm sure manually cutting with a Jewelers Saw would be even a better way to go.

[David Lindquist]

Thank you Tin Can and Greg, things are starting to look possible...
David