"Rack and Pinion" focus on LF lens?

[wallpaperviking]

Hi,
Just hoping that somebody has some insight into such lenses... Are they only Petzval lenses? What is the focusing range of such a system?

Thanks, look forward to any information somebody may have..

[Jim Jones]

Some view cameras had imprecise body focusing, so photographers relied on rack and pinion or helical focusing on the lens mount for precision. This created a demand for at some newer or better lenses than Petzvals to be in focusing mounts.

[wallpaperviking]

Thanks for the reply, much appreciated! I have found an old Dallmeyer 2B in my partners Dad's camera collection and it has the little stick out knob thingy on it... Is that the "rack and pinion" focus system? I have tried to turn it but it does not seem to do anything.....

Or am I totally off here?

Thanks!

[Mark Sawyer]

Turning it should move the lens barrel forward and backward in the outer housing. Besides the fine focusing Jim mentioned, such focusing was popular for stereo cameras so you could focus one lens to match the other, and for some magic lanterns which lacked a focus mechanism.

[Tracy Storer]

Don't force it, theory vs practice on 100+ year old lenses. There are a handful of good people doing repair / restoration on stuff like this, I would defer to them.

[Steven Tribe]

Turning it should move the lens barrel forward and backward in the outer housing. Besides the fine focusing Jim mentioned, such focusing was popular for stereo cameras so you could focus one lens to match the other, and for some magic lanterns which lacked a focus mechanism.

This comment about separate focussing for L and R lenses in a stereo pair may be true for a few dodgy sets, but most are matched pairs (focal length) as shown by nearly consecutive serial numbers. As Dallmeyer stock records show, a batch of lenses of a certain were made over a few days - almost certainly from the same source of each component glass type. Variation in production comes from variation in glass, not variation in grinding/polishing. Many stereo lens set mounts are actually provided with a single rack fine focusing
(And even linked iris systems) ex factory!

Wallpaperviking: The rack and pinion system is definitely not fine mechanics and they don’t accept much wear or any of the 2 or 4 mounting screws being loose. Or perhaps just needing a clean after decades of not being exercised!
The development of cameras and the design of possible positions for focusing took place parallel to each other. Some early, lighter and smaller Petzvals (for instance GEM Lenses) never had any adjustment at all - others had simple friction controlled movement of an inner barrel. As the 20th century approached, Petzvals were produced in plain barrels as an alternative to the “traditional” sleeve and pinion. This is a much lighter product - and cheaper to make.
Many non-Petzval lenses - especially the heavier and larger sizes - used the sleeve/pinion design in the 19th C.

[wallpaperviking]

Thanks so much to everyone who took the time to reply, much appreciated!

[wallpaperviking]

Am revisiting this thread from a little while back...

Am just wondering what lenses came in "rack and pinion" and/or helicoid focusing. Am trying to build a "compact" 810 camera and this part of the lens design would really help.

I have seen a couple of people successfully use the Hektor 300mm 2.8 projection lens for this purpose. Any other ideas?

Thanks so much in advance!

[Vaughan]

Am trying to build a "compact" 810 camera and this part of the lens design would really help.

An important part of a compact 8x10 camera would be the shutter and lens: something in a Copal 1, for instance. Any separate focus adjustment would increase size and weight unnecessarily, you'd rely on adjusting the bed extension to focus.

If you mean some kind of fixed-body travel-wide camera: it depends on what you mean by compact. Overall size would be determined by lens focal length or flange distance: a 300mm lens in a Copal 1 shutter will be compact but it will need ~300mm flange distance. A 150mm lens would need only half the flange distance but the lens itself (like a Nikon SW 150mm) will be big and heavy. A single coated Fujinon W 180mm or 210mm is reasonably compact and might be a good lenses.

[wallpaperviking]

An important part of a compact 8x10 camera would be the shutter and lens: something in a Copal 1, for instance. Any separate focus adjustment would increase size and weight unnecessarily, you'd rely on adjusting the bed extension to focus.

If you mean some kind of fixed-body travel-wide camera: it depends on what you mean by compact. Overall size would be determined by lens focal length or flange distance: a 300mm lens in a Copal 1 shutter will be compact but it will need ~300mm flange distance. A 150mm lens would need only half the flange distance but the lens itself (like a Nikon SW 150mm) will be big and heavy. A single coated Fujinon W 180mm or 210mm is reasonably compact and might be a good lenses.

Thanks for the reply, much appreciated! Apologies, I was not clear enough...

I want to try something like what has been done here....

https://www.newsshooter.com/2018/01/...-video-camera/

Am thinking having a lens with Helicoid will make it a bit easier and compact.

Thanks!