Replacing 300/4.5 Heliar with 300/4.5 Apo-Lanthar

[Marco Annaratone]

Take a Compound-mounted 300/4.5 Heliar (i.e., a V): can I replace the front cell and the rear cell with those of a 300/4.5 Apo-Lanthar by just unscrewing the Heliar's and screwing in the Lanthar's (Assuming - which isn't a given, at least to me - that they have the same thread.)

I have seen both Apo-Lanthar and Heliar 300/4.5 mounted on Compound V and the distances between front cell and shutter and between shutter and rear cell *seem* to be very similar.

Just curious.

Thanks!!!

[mhayashi]

Marco, here are the measurements of the compound V mounting barrel of the apo lanthar 30cm f4.5.
The last measurement is the front mounting barrel depth to the shutter surface.
231172
231173
231174
231175

[Marco Annaratone]

Thank you for your measurements!

In fact I do not have a Heliar 300/4.5 but I do have the rear and front cell of an Apo-Lanthar 300/4.5. Looking at many pictures on the internet, Compound-mounted 300/4.5 Heliars and 300/4.5 Apo-Lanthars "seem" to have the same distance between the front and rear cell and position with respect to the shutter. So the idea would be to buy a Compound-mounted Heliar 300/4.5 on the bay, unscrew rear and front cell, and replace them with those of the Apo-Lanthar. It is a very expensive experiment that I would not like to make before having done some serious homework.

Getting instead an "orphan" Compound V with the shutter scale starting at 4.5 (if I ever find one, that is) and having it machined for an Apo-Lanthar 300/4.5 is too much of a headache, at least for me.

But your measurements will definitely be useful, thank again!

Cheers

[David Lindquist]

Take a Compound-mounted 300/4.5 Heliar (i.e., a V): can I replace the front cell and the rear cell with those of a 300/4.5 Apo-Lanthar by just unscrewing the Heliar's and screwing in the Lanthar's (Assuming - which isn't a given, at least to me - that they have the same thread.)

I have seen both Apo-Lanthar and Heliar 300/4.5 mounted on Compound V and the distances between front cell and shutter and between shutter and rear cell *seem* to be very similar.

Just curious.

Thanks!!!

There is a repair manual from Compur Week here: https://www.suaudeau.eu/memo/rep/Compur-shutter-repair-manual.html

If you click on "Specifications" and go about 4 pages you'll find the dimensions for the Compound shutters, as of September 1962. The No. 5 came in two tube lengths for an overall distance from the front seating surface to the rear seating surface of either 74 mm or 60 mm. Both are threaded for the same lens cell thread, that is 82.77 mm diameter with a pitch of 40 threads per inch. So one could expect the cells from one No. 5 Compound to screw in to any other No. 5 Compound, but of course you would need the proper shutter thickness, i.e. 74 mm or 60 mm.

I don't know why a shutter otherwise specified in metric units used a thread pitch for the lens cells of 40 threads per inch. This may very well go back to the early 20th Century when Deckel did the original design so the reasons are probably lost in antiquity.;)

Good luck with this project and please let us know how it comes out.

David

[Marco Annaratone]

Hi David,

thank you for the precious info. I will certainly keep you posted about any progress I make.

Best