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UltravioletPhotography

Help Needed: Filter Mounting on Steinheil Lens


OlDoinyo

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I have just gotten my hands on a 50/2.8 Cassarit, hoping to use it for UV. But there is a little issue: the lens has no front filter threads at all. My local camera store was flummoxed trying to figure out how one could mount a filter on this little lens; perhaps a slip-on adapter might work in theory, but stores no longer seem to carry those. I would like to step up to a 55mm thread, though I would settle for 49mm. Who among you has used these lenses, and how was the problem solved?
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The filter has a greater diameter than any part of the lens, and putting stuff back there would probably create mirror-clearance issues and other nastiness, even if it would fit.
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Would you show us a photo of your lens?

Sometimes you need to get sticky. I have a Schneider Jsogon 40/4.5 which used light-weight slip-on filters. I found a thin section of PVC in the correct outside diameter, glued that to the inner ring, where you would expect to find threads, and then screwed, and glued, a step ring to the inside of that. The final result is strong and dependable, the PVC isn't even visible. Thin rubber might be used in place of the PVC.

 

Regards,

Reed

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I've made interesting constructions with thin strips of VelcroTM which solve problems like this with some lenses.
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I misidentified the lens; it is actually not a Cassarit but a Cassar S, S/N 1140572. Thank you all for your suggestions, it looks like improvisation is the way to go here. The front barrel diameter is virtually identical with the rear diameter of my Bay 1->55 adapter; it may be possible to join them together with cleverly deployed electrical tape. When I get my M42 adapter, I may try this.
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The standard solution is finding a step ring that fits as tightly as possible inside the front of the lens, and then apply some epoxy glue. Be very careful so as to avoid glue onto the front glass of course.
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JCD- Yes, that is what I have. At first, I thought it had threads, but those turn out to be just anti-glare grooves in the front barrel. The front barrel is of about 32-34mm OD. A slip-on solution might be possible if something of the right ID could be found. The Series-n type adapters are no help because they were designed for drop-in filters and apparently do not provide for a standard screw-in filter thread; also, their rear fitting does not look very light-tight. I am staying away from epoxy or any such thing.
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With your aperture adjustment via the smaller front knurled ring a push on filter may be problematic. It appears that if you glue a step ring inside the front you would be forced to adjust the aperture via the glued ring. Doing that might work fine as Bjørn says but you would be stressing the attachment with each adjustment. I know nothing about the relative value of the two types of Cassar-S lens we are discussing. If yours is an earlier model it might be more collectible. If so, you might consider selling the one you have and find one of the threaded type.
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Another possibility might be a slip on Series VI ring plus a added Series VI step up ring to ??mm standard filter.

Here is an example on eBay

Be forewarned, the step up ring may be hard to find.

 

Perhaps tight fit along with a bead of silicone sealant adhesive...... if you are brave.

I don't think I would trust a slip on much, the Baader U is rather expensive!

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If you don't want to use conventional adhesives, you could wrap some thin double-sided tape around the barrel. Then you can choose a step-up ring that will screw onto the tape. I have done this and it is a very firm connection, but simple to remove if you decide to sell the lens.

 

[Note: be sure to wind the tape on clockwise. That way when you screw the step-ring on - clockwise, of course - the tape won't bunch up.]

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I'm planning on using electrical tape and my Bay 1 adapter for the moment. If I come across a black plastic tube of the appropriate ID, I might devise something a bit less amateurish. Film canisters, alas, are a wee bit too small. As I have a trip coming up in a few days, I do not know when I will do this yet. It is not very hot around here this time of year. (generally 20-50F.)
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Perhaps is it possible to mount a front part (optical elements removed and eventually modified) of a different lens with filter thread which is bigger in diameter over the lens.

 

Using two rubber gaskets (automotive) inside the gap between the barrels could avoid light coming in through the gap. There are a lot of different diameters and some suppliers deliver custom made rings.

 

Drilling three holes through the outer barrel and cutting threads in offers the use of three screws to fix the two parts to another without damaging the inner lens. Of course the screws will leave some traces.

 

Edit:

 

I'm talking about a solution similar to that on the picture below. I use it to fix a M42 ring with built in filter to my telescope:

 

http://up.picr.de/20787186vx.jpg

 

 

What is the outer diameter of the lens front?

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Well, I went and tried the electrical-tape method as described before. This proved quite challenging. The tape must be cut into narrow strips and the flange of the adapter is only about 0.5mm long, which provides little purchase. Nevertheless, I eventually produced a mount which was secure enough to bear the weight of the filter:

 

post-66-0-96344700-1422332235.jpg

 

The taped mount was not, however, sturdy enough to withstand the torque of attempting to change the aperture setting, and its general fragility and difficulty of setup make this scheme impractical, in my view. I did manage to get off a few trial shots, including this landscape:

 

Sony A900, Steinheil 50mm lens, Baader U2 filter; 2 seconds@f/5.6 and ISO 100; display intent BGR; slightly boosted colors in workup.

post-66-0-72617700-1422332567.jpg

 

The lens covers the full frame with its image circle, which is nice (I was unsure if it would.) There is only very modest focus inshift visible at nominal infinity and f/2.8 (which curiously is less at the corners than the center; perhaps the focal plane is not quite flat.) At f/5.6 the sharpness is respectable and f/8 is quite sharp. Bandpass (judged by color rendition) is much better than the stock Minolta lenses and perhaps approaches that of the Fresnel test optic (if not quite that of the Makowski.) I could begin to like this little lens.

 

I think my longer-term approach to the adapter problem may take the form of cutting a disk from some semi-soft material (wood?) and drilling a hole through the center just large enough for it to be wedged over the lens barrel. A stepper ring could then be glued to the outside of the disk; with proper hole size, the adapter could have enough torque for aperture change while still being easily detachable.

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What happens when you lift the shadows a bit? Does this Cassar S show any vignetting? Not that that would be unexpected, of course.

 

I don't have a Steinheil in my small "collection" of UV-capable lenses.

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There is a problem in that my monitor is displaying images paler than those of many others; my posted images end up looking a bit dark on other screens. I'm working on that. On my screen, the bare branches at right are clearly differentiated from the darker coniferous foliage.

 

I see no vignetting with this lens, just some slight cosine falloff such as any 50mm lens must have; also, there is little sign of a UV hotspot and not much veiling. I have not had time to check it on the IR side; and it will be a few weeks before I can do anything further.

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What gamma setting is applied? If you process with a gamma different from the usual 2.2 setting, images appearing perfect on your monitor(s) might be rendered very dark (or very bright) as seen by others.
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  • 2 months later...

THE SOLUTION

 

1) With a dial saw, cut a disk out of a thickish board.

 

2) In the center, drill a 1 3/8" hole with a flat bit.

 

3) With black duct tape, pack out the interior of the drilled hole to enable the hole's interior to grip the outside of the lens barrel firmly..

 

4) With the same tape, affix a step-down ring with 55mm interior thread to the outer face of the torus.

 

Two views of the adapter are shown here:

 

post-66-0-10364700-1428979568.jpgpost-66-0-77792700-1428979592.jpg

 

and here it is mounted on the lens and bearing a filter:

 

post-66-0-76732100-1428979624.jpg

 

When the rear is pressed onto the end of the lens, the adapter holds any filter quite securely without worry of its falling off. Holding the focus barrel on the lens and turning the ring adjusts aperture. The adapter also doubles as an impromptu lens hood.

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