Which is the largest format size a lens with a focus ring can cover

NedL · Feb 17, 2020

I really think you should consider a sliding box camera like Dan suggested or like the one I linked to. It can be a simple as two boxes made out of black foamcore, and you can build a working prototype in an hour or two. A lot of fun and great for big paper negatives! I've built a couple of them, but as I mentioned, even when the two boxes are fully nested, FL is not as close as I like for pinhole... I too was originally thinking of a camera to swap lens/pinhole, but without a bellows it's not very practical ( at least if you like WA pinhole like I do )...

Laci Toth · Feb 18, 2020

NedL said:
I really think you should consider a sliding box camera like Dan suggested or like the one I linked to. It can be a simple as two boxes made out of black foamcore, and you can build a working prototype in an hour or two. A lot of fun and great for big paper negatives! I've built a couple of them, but as I mentioned, even when the two boxes are fully nested, FL is not as close as I like for pinhole... I too was originally thinking of a camera to swap lens/pinhole, but without a bellows it's not very practical ( at least if you like WA pinhole like I do )...

So I really want a very simple, lightweight design and because I’m not into large format I thought that a lens with a focusing ablility is existing like what is used for 35mm photography. But as far as I could see now it’s more about bellows rather than a focus ring for long distances and a focus scale marked on it.
The sliding box can be a solution though but it then makes the whole design a lot more complicated compare to a fixed box and a lens with a focusing ability.
Alternatively I can get a cheap large format camera with a good condition bellows so I can use that or something, I’m just thinking out loud.

Bob S · Feb 18, 2020

Or you could just buy a lens from 23 to 150mm mounted into the correct helical focusing mount for that lens. It will not have distance and DOF markings just like your 35mm lens. However, some of these lenses will not cover 45 at infinity. None will cover 57.

NedL · Feb 18, 2020

That's kind of interesting, I never really thought about it before, but are there any helical focusing lenses for cameras larger than 120 film? The old 116 and 122 (postcard) kodak cameras had scale focus, but it was that little lever that moved the position of the lens and relied on bellows. The thing is, to get enough travel to be useful for focusing, the lens needs to move pretty far. On an 8x10 camera with a 12" lens, the lens needs to move 12" to go from being focused at infinity to being focused 1:1 (24" in front of the camera).... If you try to do that focusing in a helical focuser, you will run into geometry problems that will reduce coverage.

Bob S · Feb 18, 2020

NedL said:
That's kind of interesting, I never really thought about it before, but are there any helical focusing lenses for cameras larger than 120 film? The old 116 and 122 (postcard) kodak cameras had scale focus, but it was that little lever that moved the position of the lens and relied on bellows. The thing is, to get enough travel to be useful for focusing, the lens needs to move pretty far. On an 8x10 camera with a 12" lens, the lens needs to move 12" to go from being focused at infinity to being focused 1:1 (24" in front of the camera).... If you try to do that focusing in a helical focuser, you will run into geometry problems that will reduce coverage.

Recent lens manufacturers large format helical focusing mounts are for their lenses in 0 shutter only.

BradS · Feb 18, 2020

Bob S said:
Recent lens manufacturers large format helical focusing mounts are for their lenses in 0 shutter only.

Roughly how much do these cost ?

Dan Fromm · Feb 18, 2020

Laci Toth said:
Alternatively I can get a cheap large format camera with a good condition bellows so I can use that or something,

Yesssss!

Bob S · Feb 18, 2020

BradS said:
Roughly how much do these cost ?

Go to the Omega Brandess web site, go to their Rodenstock page and they should be listed there. Then check with a camera store for the retail price.

ciniframe · Feb 18, 2020

Kodak had a 130mm f7.7 lens on a folder that had front cell focusing. Granted it will only focus to 6 feet and was designed to cover a frame with a 5 inch diagonal but I have it on a homebuilt 4x5 box camera and it will *just* cover the 6 inch diagonal of 4x5.
The same lens, but without front cell focusing was also used and those Kodak folders had focusing of the front standard, but still to only 6 feet.
If the OP wishes to use 8x10 photo paper as a negative and contact print but wishes to get away from excessively long exposures necessary with pinhole aperture then even a +4 (250 mm) close up lens, stopped down to f64 and set to 20 feet will have DoF of 9 feet to infinity with a blur circle of .2mm, good enough for a contact print.
At f64 a sunlight exposure with ISO 6 paper would be between 2 and 6 seconds, much shorter than pinhole apertures of f256 and up.
Otherwise, as noted earlier, big $ to go with real view camera lenses designed to cover 8x10.

BradS · Feb 18, 2020

Bob S said:
Go to the Omega Brandess web site, go to their Rodenstock page and they should be listed there. Then check with a camera store for the retail price.

Ok. It looks like a focusing helical costs about $1000 each ? That seems inconsistent with the OP's stated desire for a low cost do-it-yourself project.

Bob S · Feb 18, 2020

BradS said:
Ok. It looks like a focusing helical costs about $1000 each ? That seems inconsistent with the OP's stated desire for a low cost do-it-yourself project.

How many of these precision helical do you think are sold per year?

Luckless · Feb 18, 2020

Bob S said:
How many of these precision helical do you think are sold per year?

At that price, probably not many...

However for anyone looking for a precision DIY option, consider looking to the Crayford style focus units as used on many telescopes. While they have their faults and headaches, especially if you're trying to point the unit up or down, they can be made to produce highly accurate controls with access to only moderate tools.

Bob S · Feb 18, 2020

Luckless said:
At that price, probably not many...

However for anyone looking for a precision DIY option, consider looking to the Crayford style focus units as used on many telescopes. While they have their faults and headaches, especially if you're trying to point the unit up or down, they can be made to produce highly accurate controls with access to only moderate tools.

And not have accurate distance or depth of field scales for the lens mounted in it. Which the OP wanted.
You can’t take a random lens and mate it to a random helical and get accurate scales.

BradS · Feb 18, 2020

Bob S said:
And not have accurate distance or depth of field scales for the lens mounted in it. Which the OP wanted.
You can’t take a random lens and mate it to a random helical and get accurate scales.

Clearly, the scales on these Rodenstock units are NOT universally accurate.
They are only accurate for specific lenses and for a camera box with very specific dimensions.
They simply cannot be mounted with a box of some arbitrary film to helical distance and be accurate.

Bob S · Feb 18, 2020

There is more to it then just scales. If the lens is to focus at infinity then the lens, mounted on its helical, must have the same flange focal length as the lens without the helical.

Luckless · Feb 18, 2020

Bob S said:
And not have accurate distance or depth of field scales for the lens mounted in it. Which the OP wanted.
You can’t take a random lens and mate it to a random helical and get accurate scales.

Adding accurate scales to a Crayford is totally possible, however it does mean care and attention to detail while setting things up.

Designing it to be scribed to the focus-body after alignment with the camera is probably the easiest DIY option. And if you go with a "Sliding Boxes" design, you offer yourself loads of space to work with. You could even have multiple scales for different lenses on a single focuser.

I would aim for making sturdy scale indicator out of sheet brass or something, and have the 'lens end' box slide into the 'camera/film end' box. This gets your reading points of your scale away from being hidden below the outer box and may make it easier to read.

BradS · Feb 18, 2020

Luckless said:
....
I would aim for making sturdy scale indicator out of sheet brass or something, and have the 'lens end' box slide into the 'camera/film end' box. This gets your reading points of your scale away from being hidden below the outer box and may make it easier to read.

This is actually a really good idea. Given a sufficiently accurate measuring device, the scales could be calibrated by simply measuring the flange to film distance for various spacing and doing the arithmetic. Furthermore, if the box depth were carefully designed, I guess the same same method could also work to calibrate an arbitrary helical too though.

I still think the OP would be far better off with a good used 4x5 Crown Graphic. Seems like a complete working camera with lens (and possibly accurate range finder) could be sourced for around $250.

Bob S · Feb 18, 2020

BradS said:
This is actually a really good idea. Given a sufficiently accurate measuring device, the scales could be calibrated by simply measuring the flange to film distance for various spacing and doing the arithmetic. Furthermore, if the box depth were carefully designed, I guess the same same method could also work to calibrate an arbitrary helical too though.

I still think the OP would be far better off with a good used 4x5 Crown Graphic. Seems like a complete working camera with lens (and possibly accurate range finder) could be sourced for around $250.

Yes, you might be able to jury rig a random adapter, but for what focal length? The helical for a 65mm is much thinner then the one for a 150mm and much deeper then one for a 23mm lens.
As long as you can rig one up so that the depth of focus lies within your film plane it could work. Just remember, the shorter the focal length the narrower the depth of focus is.

Laci Toth · Feb 18, 2020

Thanky everyone for all your input I’m amazed how many ideas have been gathered since I last checked on the thread (a few hours ago).
I found a Goerz Celor 1b lens for dirt cheap. It’s in a very good condition, everything works as it should and the glass is clean. The owner used it for 5x7 and says it can focus from 2.5 yards to infinity. It’s without a shutter but as I’ll use paper negatives instead of film negatives it’s about long exposures anyway so I’ll just remove the front cap. I might check on Ilex shutters, Polaroid MP-4 or something similar. I’ll do some experiment to see where it’ll go and use some of the sources from your advices and thoughts which really make me feel to build not one but two!!!
=)

David A. Goldfarb · Feb 18, 2020

Does the pinhole camera you want to convert have a groundglass for focusing? If it does, you can make your own focus scale with any helical by focusing at various distances measured from the film plane and marking them on the helical so they line up with an index mark on the lensboard. If you're on a budget, there are inexpensive Chinese made helicals available online. They won't have the fit and finish of a helical from one of the major European lens manufacturers, but what they do isn't rocket science, and they're likely to be good enough for this kind of project. If you need a greater degree of precision, then use a system designed for that.

Bob S · Feb 18, 2020

David A. Goldfarb said:
Does the pinhole camera you want to convert have a groundglass for focusing? If it does, you can make your own focus scale with any helical by focusing at various distances measured from the film plane and marking them on the helical so they line up with an index mark on the lensboard. If you're on a budget, there are inexpensive Chinese made helicals available online. They won't have the fit and finish of a helical from one of the major European lens manufacturers, but what they do isn't rocket science, and they're likely to be good enough for this kind of project. If you need a greater degree of precision, then use a system designed for that.

David, it isn’t that easy. He needs a helical that will focus his lens at infinity. To do that the helical can’t change the flange focal length of the lens. Once the lens is mounted to the helical it MUST have the same FFL. Otherwise he won’t be in focus at infinity.

David A. Goldfarb · Feb 18, 2020

Bob S said:
David, it isn’t that easy. He needs a helical that will focus his lens at infinity. To do that the helical can’t change the flange focal length of the lens. Once the lens is mounted to the helical it MUST have the same FFL. Otherwise he won’t be in focus at infinity.

Obviously, it involves some research to find a combination of box camera, lens, and helical that will work, but it’s still not rocket science. There are shops that make these helicals to order at a modest price (I have one), and it wouldn’t take much to be sure the lens has the right amount of offset to focus to infinity, within the limits of the dimensions of the system. If the box camera is too deep, then obviously that would rule out some ultrawide lenses, but it shouldn’t be that hard to figure out which lenses would work.

Bob S · Feb 18, 2020

David A. Goldfarb said:
Obviously, it involves some research to find a combination of box camera, lens, and helical that will work, but it’s still not rocket science. There are shops that make these helicals to order at a modest price (I have one), and it wouldn’t take much to be sure the lens has the right amount of offset to focus to infinity, within the limits of the dimensions of the system. If the box camera is too deep, then obviously that would rule out some ultrawide lenses, but it shouldn’t be that hard to figure out which lenses would work.

But he also wants DOF scales he said.

David A. Goldfarb · Feb 18, 2020

Bob S said:
But he also wants DOF scales he said.

Fair enough, but engraved DOF scales are an order of magnitude more complex than the project merits. If the infinity point is within the range of the helical, ideally close to minimum extension, then measure and mark infinity, 30’, 20’, 15’, 8’, 6’, 4’, and 3’ (or as close as it goes), compute and print out a DOF table and that should be sufficient for a low-cost project like this one.

Bob S · Feb 18, 2020

Or just use a Rodenstock Pocket Calculator.

Which is the largest format size a lens with a focus ring can cover

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