Flange Focal Distance for Zeiss LF lenses?

[peegeenyc]

Hi - does anyone know where to track down the flange focal distance for Zeiss old LF film lenses?

I'm thinking specifically of the 2nd Generation 135mm Planar LF lens, the one with 67mm front filter, which had T* coating on last ones, (not the older 58mm one, though I suppose the relevant figure may be the same)

Zeiss seem to be really bad about giving info online of older lenses.

Thanks.

[Bob Salomon]

Hi - does anyone know where to track down the flange focal distance for Zeiss old LF film lenses?

I'm thinking specifically of the 2nd Generation 135mm Planar LF lens, the one with 67mm front filter, which had T* coating on last ones, (not the older 58mm one, though I suppose the relevant figure may be the same)

Zeiss seem to be really bad about giving info online of older lenses.

Thanks.

Do you have the lens? It is easy to determine with a piece of white board.

[Dan Fromm]

135 Planar? Arne Croell (www.arnecroell.com) doesn't give flange-focal distances.

On general principles, if the lens is in shutter ffd should be ~ 135 mm. This because Planars are approximately symmetrical and their internodal distances are small so the rear node should be close to the diaphragm. If the lens is in barrel, the flange can be anywhere on the barrel so general principles will be no help at all.

Why do you ask? What do you want to accomplish?

[ic-racer]

After so many years a lens for sale may not be in the same shutter as when new, so the published value could be of questionable value. If you are making a point and shoot camera, wait until you get the lens & shutter and then measure it yourself as it is almost never equal to the focal length. If you are seeing if the lens will work on your 4x5 camera, I can't think of any 4x5 camera what would have a problem focusing a 135mm lens no mater what the flange focal distance measures.

[peegeenyc]

It's in the original Linhof-Compur 1 shutter, I believe. How do I check the distance with a piece of white board?
In my experience a "135mm" lens might be anything from 132 - 138mm, which makes finding the precise distance hard.

I want to mount it in a helical mount for use on a Digital Tech Camera, and keep it alive as a lens!

Photos here: https://goo.gl/photos/JGURaPvLtTDBVqdv7

[Dan Fromm]

ic-racer wrote:

After so many years a lens for sale may not be in the same shutter as when new, so the published value could be of questionable value.

Please explain what would change the lens' focal length.

peegeenyc wrote:

In my experience a "135mm" lens might be anything from 132 - 138mm, which makes finding the precise distance hard.

I want to mount it in a helical mount for use on a Digital Tech Camera, and keep it alive as a lens

and posted an image. The lens is on a Super Graphic board. If you have a Super Graphic or 4x5 Pacemaker Graphic (Pacemaker Speed, Crown, they accept Super Graphic boards), put the lens on the camera, focus it on the ground glass on a distant object (miles away) and then measure the flange-to-film distance. Front of front standard to GG is what you want.

Why can't you focus the digicam through the lens?

[peegeenyc]

Correct, it is now on a Super Graphic board, it was originally on a Linhof board. Yes I have the SG camera and can check it, but doubt I can do that to accurate within a mm, let alone 0.1mm.

I want to mount it in one of these https://goo.gl/photos/ScWGxr459kE8x2rX7, which is a fixed distance helical mount for an Alpa Tech camera, so I need an accurate mount distance at infinity, for the height of that box to be machined correctly to 1/10mm (it's not really a 'flange distance', my bad)

[Dan Fromm]

Why not machine the mount or too short and shim the helical or lens? Why not farm the job out to SKGrimes, who have tools and expertise?

You need to have some adjustability. Doesn't the helical have an adjustable start point?

Capaul & Weber are crazy but not stupid. How do they solve the problem of using standard helicals bought from Schneider or Rodenstock and lenses whose focal lengths aren't exactly to spec?

Oh, and by the way, 0.1 mm isn't good enough. The AGI F135 camera uses shims to collimate 38/4.5 Biogons to the body. Those shims are made to 0.01 mm.

[Bob Salomon]

It's in the original Linhof-Compur 1 shutter, I believe. How do I check the distance with a piece of white board?
In my experience a "135mm" lens might be anything from 132 - 138mm, which makes finding the precise distance hard.

I want to mount it in a helical mount for use on a Digital Tech Camera, and keep it alive as a lens!

Photos here: https://goo.gl/photos/JGURaPvLtTDBVqdv7

You open the lens, turn off all of the lights in the room and close the curtains so the room is dark. You hold the lens and point it outside by placing it against the window. You point it at a distant object and with the board in your other hand you move the board towards or away from the back of the lens till you see a sharp scene on the board. That is the flange focal distance at infinity.

[Bob Salomon]

You open the lens, turn off all of the lights in the room and close the curtains so the room is dark. You hold the lens and point it outside by placing it against the window. You point it at a distant object and with the board in your other hand you move the board towards or away from the back of the lens till you see a sharp scene on the board. That is the flange focal distance at infinity.

While it may prolong use by mounting on a digital camera it will not give you results that a digital lens would deliver. One major problem is that lens is diffraction limited at f22 but digital is much smaller then 45 and at f22 you will be way into diffraction. It also is not as sharp, has more distortion and inferior color curves to the digital lens. All of which will be evident in a digital file.