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UltravioletPhotography

Lens Clamp Filter Holder Experiment


Andrea B.

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I found a lens clamp filter holder kit at a video gear site Vid-Atlantic and tried it on the Rodenstock 50mm f/3.5 Omegaron, an enlarger lens which has no front filter threads.

 

The lens clamp filter holder is 60mm wide and is clamped onto the lens with three screws. Vid-Atlantic also sells a 72mm wide version.

 

There are two male-threaded base rings in the kit with 52mm and 58mm sizes. So to fit a male-threaded front lens filter, a gender-changer is required. Additional step rings might be required to move from 52/58mm to the filter thread size.

 

Because the screws could dig into the metal body of the lens, I decided to put three patches of Velcro on the lens to protect it. I used the fuzzy piece from a pair of Velcro dots, not the loopy piece.

 

The Good: The lens stack consisting of helicoid, lens, lens clamp, step rings and filter worked very well photographically for making the African violet UV photos shown here: LINK. The lens clamp and ring combo covered the Omegaron aperture window which would help prevent light leaks. The aperture window might also need to be taped over in some shooting scenarios.

 

The So-So: It was a bit difficult to center the Omegaron in the clamp fitting, but I did get better with practice. I was also unsure of how much I could tighten the screws for fear of exerting too much pressure on the lens body.

 

The Bad: The lens clamp and ring combo covered the Omegaron aperture ring so the filter would have to be removed in order to use stop-down focusing.

 

 

Lens Stack:

Helicoid, Omegaron lens inside the lens clamp filter holder, base ring, gender-changer, step-ring1, step-ring2 and Baader-U filter.

DSC_0054pn201.jpg

 

 

Deconstructing the Stack:

Helicoid, Omegaron lens inside the lens clamp filter holder with base ring & step-rings, Baader-U filter with 52-48mm step-ring.

DSC_0015pn201.jpg

 

 

Deconstructing the Stack:

Back - Helicoid, Omegaron lens, Baader-U filter with 52-48mm step-down ring.

Front - Gender-changer, lens clamp filter holder with base ring, 58-52mm step-up ring.

The gender-changer here is actually a 62-58mm step-down ring which is wide enough to accomodate the 58mm threads of both the base ring and the step-up ring.

DSC_0017pn201.jpg

 

 

Front View:

The Omegaron inside the lens clamp filter holder with Baader-U removed.

DSC_0043pn201.jpg

 

 

Side View of Lens:

The Omegaron has an aperture window that might leak light. The external portion shown here was covered by the lens clamp and ring combo. The internal portion on the base of the lens is easily covered with tape.

(The lens is resting on the lens clamp filter holder.)

DSC_0033pn201.jpg

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In my humble opinion, Andrea, you should learn to operate a Dremel device. Put a suitable step ring flush to the front of that lens and drill 3 holes for fixing screws. Forget that clumsy holder.
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:P

Bjørn, you are exactly right !! I think my hesitation at this point comes from not wanting to permanently alter any lens because it might affect resale value. However, I grant you the side of the argument that says a lens like the Omegaron, which is easily available, is hardly valuable enough to worry about permanent alternation affecting resale value. In fact a filter mounting might increase its resale value to those photographers who like using such darkroom lenses outside the darkroom.

 

Mike has lots of tooly stuff so I wouldn't even have to buy anything new.

 

The side benefit of the lens clamp filter holder is that is provides some coverage of the external aperture window.

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I assumed your Omegaron was a surrogate for the UV-Rodagon in this assembly. One would certainly not wish to scar one of those! However, one would not shy away from drilling the front of the helicoid.

 

Perhaps a filter mount such as seen attached onto point and shoot cams would solve all problems.

 

Here is the idea:

 

1. Take a 42x1mm (male) to 52mm (female) step up ring and screw it into the helicoid to hold it exactly centered..

2. Drill 3 holes through the step ring into the helicoid for screws to hold it on.

3. Remove the step ring and take a Dremel wheel and cut off the 42mm male thread from the threaded side so as not to mar the front side.

4. Take a Dremel cutting bit and enlarge the hole so that the diameter is slightly >42mm.

5. Reattach the modified step ring to the helicoid with screws.

6. Screw in your lens.

7. Screw a 52mm K5 ring into the female 52mm thread of the modified step ring. If the K5 does not extend beyond the end of the lens add a K4.

8. Attach filters to female 52mm K ring thread.

 

You would still have to remove the filter to adjust the aperture. May be a job for one of those quick change magnetic filter rings or a K3/K2 quick change junction like Bjørn has described. The K rings are probably wide enough you could reach in and turn the aperture adjustment since it is on the front of the lens.

 

Light leaking through the external aperture window will still likely be a problem but it could be easily blocked by stuffing a small block of gray foam padding or some felt in between the lens and K-ring.

 

The entire lens would be enclosed and unscathed, UV Rodagon good to go. What do you think? :P

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Let's see if I have this: 42-52 modded step-up attached to helicoid + K5 + K4(if needed) + filter. Lens sits inside the K5+K4 and screws into the helicoid (and not into the modded step-up ring).

 

Yes, it would work. And it is nicer to drill into an Ebay helicoid than it would be into a lens.

 

But --- I'm not sure I really want to enclose the lens and have the problem of having to unscrew the filter to change the aperture setting? Stop-down focusing is quite handy for accurate focusing when using Live View. Well, for me anyway. "-) So there are pros & cons on this method also.

 

I think you could use a larger step-up ring also. For example I have some old 48-52 rings. Then you wouldn't have to fool around with modding the ring interior ?

 

But everyone stay tuned. Next up is my simple Velcro solution for the UV-Rodagon in order to be able to shoot it at infinity. I will try to get that posted this evening.

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But --- I'm not sure I really want to enclose the lens and have the problem of having to unscrew the filter to change the aperture setting? Stop-down focusing is quite handy for accurate focusing when using Live View. Well, for me anyway. "-) So there are pros & cons on this method also.

 

Yep, that would be the main drawback.

 

I think you could use a larger step-up ring also. For example I have some old 48-52 rings. Then you wouldn't have to fool around with modding the ring interior?

 

Not sure I follow you there, how would you attach your 48-52 ring to the helicoid? You would still need to screw it to the helicoid and there is not much of a ledge there on a 48-52. You might could use a 46-52 if you can find one but either way you still have to grind off the threads so it sits flat against the front of the helicoid.

 

But everyone stay tuned. Next up is my simple Velcro solution for the UV-Rodagon in order to be able to shoot it at infinity. I will try to get that posted this evening.

 

Sounds interesting, I will try and post another attachment idea also.

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But if you are going to attach the 42-52 to the helicoid with screws and thus have to enlarge the inner 42 diameter, then why not attach 48-52 to the helicoid with screws and skip the enlarging part??
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But if you are going to attach the 42-52 to the helicoid with screws and thus have to enlarge the inner 42 diameter, then why not attach 48-52 to the helicoid with screws and skip the enlarging part??

 

You can screw the 42-55 into the helicoid to hold it in place while you drill. Also 42mm diameter of male thread to grind off is less than 48mm.

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