Helical Focussing Mounts In Lenses

[Bill Glickman]

I see lots of lenses fitted with helical focussing systems. Obviously these lens es are suited for non bellows type cameras. I am interested in knowing, who mak es the helical focussing systems? I assume only the manufacturer of the lens... and also, can a helical focussing system be used with any fl lens, or only lens es up to a maximum focal length? I never see them on long fl lenses?

[dangal]

Bill, I have a helical focusing mount for designed for (and made by) schneider 150mm apo symmar which I will be using for rodenstock sironar-N 150 mm with my cambo wide camera. Different lens manufacturer have different flange focal distance so if your camera has a fixed distance from your lens panel (ie non-bellows)then you'll have to make some adjustments. Which I will be doing when I receive my sironar-N 150mm lens soon.

Renee

[Bob Salomon]

Rodenstock makes helical mounts ($380.00 list) for their lenses in either 0 or 1 shutter.

[Bill Glickman]

Bob, is this the determining factor for helical mounts? Will Rodenstock helical mounts work on Schneider, Nikor, Fuji Copal 0,1 shutters? Are the helical mounts designed specificaly for one manufacturer? Since the Helical adds glass, any loss in image quality vs. bellows foccussing with non helical lenses?

[Steve Artz]

There is no glass in a helical focus mount. Both Rodenstock and Schneider make helical focusing mounts for most of their wide angle lenses and some lenses up to 150mm. There are many mounts available. They are specific to focal length and come with the appropriate focus distance scale.

[Pete Andrews]

Bill. A helical focussing mount is just a threaded tube inside a double-threaded collar, inside another threaded tube. The threads are opposite handed, and when the collar is turned, the two threads wind the assmebly out or in to focus the lens, exactly the same as on a 35mm, or MF SLR camera. No optical components are involved.These mounts become impractical for very long focal length lenses, simply because of the extension involved, and the leverage of a heavy lens on the threads.

[Jim Galli]

The old Mamiya Universl (1960's-'80's) system basically used small view camera type lenses (Very excellent Tessars) in helical mount to interchange on the same camera body. The Polaroid 600SE being the final version. All of the shutters were Seikosha 0. The 90 and 100mm 3.5 that was the normal for the system are sometimes VERY cheap on ebay and would provide a size 0 helical mount and a useable Seiko shutter if you're in the mood to tinker. The 127 4.7 that the 600SE used will cover 4X5 about the same as a Kodak Ektar of the same length. Just throwing out ideas so I won't be the only guy straying off into weird areas.

[Bill Glickman]

Jim, are you suggesting that any helical focussing mount can be used in any lens that used the same shutter? If so, this opens up a lot of possiblilities...

[Bob Salomon]

"are you suggesting that any helical focussing mount can be used in any lens that used the same shutter? If so, this opens up a lot of possiblilities... "

Of course not there is a tremendous difference in flange focal length between a 35mm Apo Grandagon and a 150mm Apo Sironar S or N all of which are in 0 shutter.

Then there is the matter of the DOF scale on these mounts. Again the difference is dramatic.

Then there is the difference in the distance scales. Infinity comes much sooner for a 35mm focal length.

Bill stop complicating things.

Each focal length lens that fits a helical mount has it's own helicoid.

Each has a dedicated DOF scale and focus scale. Each is at infinity when fully collapsed.

The most common helicoids where a single focus mount fits a wide range of focal lengths is the one for lenses in 39mm or 32mm enlarging lens mounts. These do not have scale, DOF indicators, etc. They do have extension tubes to allow infinity focus with longer length lenses or to extend maginfication.

They can not be used with shutter mounted lenses.

Every current Rodenstock brochure for large format lenses in 0 or 1 shutter includes a section on the helical focus mounts for them. Rodenstock also has a special brochure for enlarging lenses used for macro or CCD work in the Macro Focusing Mount.

Would you like these mailed to you?

[Jim Galli]

Bill, No, I was suggesting that someone that wants to tinker on a budget might start with one of those. I think you'd be married to the Seiko shutter though, a copal probably wouldn't fit. You'd end up with adapted old, not pretty new, but all a helical mount does is move lens glass forward and backward the same as a bellows.

[Kerry L. Thalmann]

Bill,

I'm not sure what your application is for a helical. Are you just looking for s omething that moves a lens backwards and forwards to focus it on a ground glass. If that's the case, things like depth of field and distance scales aren't requ ired. Or, are you looking to make a point-n-shoot camera that you will focus ba sed on guestimated distance (like the Linhof 6x17). In this case you will need a helical with the proper distance and depth of field scales to match your lens focal length, as well as the proper mechanical size to match the shutter. You w ill also need to calibrate the "zero" distance (infinity focus) from the film pl ane.

On the other hand, if you will have a gound glass to check focus, any helical of the proper mechanical size will do. How close you can focus will depend on the fore/aft travel of the helical. By all means, if you can afford one of the nic e helicals from Schneider or Rodenstock get one. They are well made and worth t he price (check places like Robert White and Badger Graphics for the most reason able prices - you should be able to get one in the $200 range). If this is a lo w budget "experiment", there are cheaper (although less elegant) solutions. In addition to the Mamiya helicals, you might want to watch eBay and the used deale rs for a Pentax helical extension tube. This may require a little hacking and w ill only work with lenses with a small rear diameter, but you might be able to f ind one for less than $100. Also, the guy who makes the Granview makes helicals to adapt a variety of lenses to his cameras. I have no idea how much they cost , but you might check his web site (I think it's www.granview.com).

Good luck, Kerry

[Bill Glickman]

Kerry, you are on the right track. My goal was to use helical mounts in 80mm lenses and focus on a gg, so DOF and scales are not the least bit important to me. So I think you pretty much answered my question... i.e. If I find a helical mount that will mechanicaly fit into the lens, then as long as I gg focus, it should work perfect. Unless I am missing something here?

Bob, thanks for the input, and sorry I complicated things, this is what happens when one is trying to learn something in an area they have no experience in. Once I confirm the camera design, I will take you up on your offer for brochures.

[Bob Salomon]

" Unless I am missing something here? "

The most obvious thing.

Infinity focus.

If it is designed for a lens longer then 80mm it won't focus to infinty.

If it is designed for a lens shorter then 80mm extension must be added to reach infinity.

Unless you are not interested in infinity focus.

[Bob Salomon]

BTW,

Wayne at Casey's Camera on Tropicana can easily help you as he is a large format expert and uses large format all the all the time and can also give you instructions on helicoid mounts as well as retail pricing (I gave MSRP not retail).

He is an excellent resource with large format in stock.

[Bill Glickman]

Bob, totally agreed, I should have wrote, any helical mount designed for the same fl lens I plan to use, that would physicaly fit my proposed lens, would work perfectly. I assume this is accurate now...

[Bob Salomon]

The Rodenstock Helical Focus Mounts are only available for 0 shutters. They are not available for 1 shutters.

[dangal]

So Bob (or anybody), how do you check for infinity focus? I will soon receive a second hand sironar-N 150mm and I will use a schneider focus mount for apo symmar 150mm I know it is to do with the flange focal distance for starters......

[Bob Salomon]

Is it or isn't at focus ay infinity when fully compressed?

Don't be sur[rised if it isn't. The Rodenstock lens may have a different flange focal length and/or a different effective focal length. If those don't match the mount won;t focus properly.

[dangal]

I'm almost certain that the flange focal length will be different. The apo symmar is 144.2 the sironar-N is ? When checking focus at infinity, How do you find whether it is in focus? Try focusing on the moon at night? Or something really far?

[Bob Salomon]

142mm.

You simplt focus on something a few hundred feet away to be safe. It sounds like you will need shims to make it work.

[Michael Feldman]

Bob, since we are into the 21st century now, how about getting your company to put these brochures on-line as PDF files?

[Bob Salomon]

Posting literature is Rodenstock's business. As we represent 21 different suppliers it would be impractical for us to post all of the literature from our suppliers.

Some of these brochures total hundreds of pages for just Kaiser.

But we will mail them to anyone in the US at NC. All you need to do is ask or call our 800 # 735 4373.

[dangal]

Thanks Bob, you are right, I have to shim because the apo symmar's (150) flange focal distance is 2.2mm longer. I'll try to adjust the focusing mount first if possible. There are a few screws around.....