Lens, board, and shim: how critical is spacing?

**Embdude** · 30-Dec-2023, 06:55

Yes Linhof is a camera company and one of their lines of cameras was/is the Technika, so a Technika board is still considered a Linhof board. But not all Linhof boards are Technika boards as they have/had many lines of cameras with boards over the last 137 years...

The Technika cameras more often than not had a rangefinder so in addition to internal lens shims to precisely space the cells they often have shims between the shutter and the board to precisely fit them to the rangefinder.

If you have a rangefinder shim and are moving the lens to a new camera without a rangefinder then it is not needed. Rangefinder shims are in behind the shutter and in front of the lensboard. As your shim is aft of the board it is either not a rangefinder shim or it is in the wrong spot.

Generally lens shims are internal but yours is not. However as it is accomplishing the same thing as an internal shim one has to wonder if it was done intentionally, possibly a DIY solution or a field repair that was never properly addressed. As the front cell is stuck fast to the shutter this may also explain why the previous owner came up with a solution with the rear cell.

Really the only solution is to test the lens with the restriction and without it and see if there is a difference. and which one you prefer.

BTW: In days past portrait photographers sometimes gave a lens a couple of turns to make images with less clinical sharpness. Also there were camera designs where the front cells were rotated for focus. There were also soft focus lenses which used this technique as well and were marked with numbers.

If the lens is really glued in place then you may have more serious issues than cell spacing. If it is just over-tight then the best way is constant pressure, not increasing force. Just carry it around with you all day and keep trying to unscrew it with reasonable pressure, gripping it in different spots. Within a day or 2 it will loosen up.

Good Luck

**Doremus Scudder** · 30-Dec-2023, 11:18

Originally Posted by kunlun121

... What I meant by the rear group actuating against retaining ring is that, when screwed all the way in, the barrel of the rear group sits against the retaining ring, not against the end of the thread of the shutter. The distance between the front group and the rear group is therefore determined not by the length of the shutters barrel. I don’t know what’s normal in this respect. ...

The front and rear elements need to seat properly in the shutter for lens focus to be correct. If the retaining ring is interfering with the rear element seating properly, that is a problem you need to remedy. Reversing the ring, making sure the shoulder of the retaining ring sits down into the hole on the board, or getting a new retaining ring are all possible solutions.

I had a Nikkor M 300mm on a board once that prevented the rear element from seating properly. The focus was lousy. Once I identified and corrected the problem, then proper focus was restored.

Best,

Doremus