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UltravioletPhotography

UV-Rodagon Velcro-ed to Helicoid


Andrea B.

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I have long wanted to use the Rodenstock 60/4.5 UV-Rodagon at infinity focus on my broadband Nikon D600. Enrico Savazzi found that this enlarger lens would sit nicely inside a wide-diameter 16-30mm helicoid against an internal baffle to which a 39mm threaded ring had been glued. In that recessed position the UV-Rodagon could be focused at infinity when the helicoid was mounted on the D610. I ordered up an Ebay wide-diameter helicoid from Hong Kong. John Dowdy kindly sent me a nice 39mm ring to use.

 

But before I went ahead with gluing the ring onto the baffle, I decided to try an idea I had for using adhesive backed Velcro® to fix the lens in the recessed position inside the wide-diameter helicoid. The fuzzy side was wrapped around the lens and the looped side was placed inside the helicoid against the baffle. When the UV-Rodagon is Velcro-mounted, its knurled aperture ring extends beyond the helicoid for easy aperture changes. The aperture window is obscured, but I know this lens and can set the aperture 'by feel'.

 

The Velcro-mounted lens feels solidly stuck inside the helicoid and so far cannot be shaken loose. Whether it will prove to be a useful long-term solution remains to be seen. It certainly is easy to accomplish. Do be sure to buy a strong Velcro® if you want to try this.

 

 

UV-Rodagon Velco-mounted inside the wide-diameter helicoid with 35.5 - 52mm step-up ring.

DSC_0056pn04.jpg

 

 

Thin strip of fuzzy-sided Velcro® is wrapped around lens body.

DSC_0060pnpn.jpg

 

 

Strip of loop-sided Velcro® is placed inside the helicoid against the internal baffle.

DSC_0062pn.jpg

 

 

A scrap of Velcro® was used to cover the internal light guides to help prevent light leakage.

DSC_0058pn.jpg

 

 

I made a UV test photo of a Gerbera using the Velcro-mounted UV-Rodagon. The lens is quite sharp and provides good detail. A long exposure was taken in order to light-paint over the large flower with the UV torch.

Nikon D600 + Rodenstock 60/5.6 UV-Rodagon + Baader-U UV-Pass Filter + Nichia 365nm UV-Led

f/11 for 4" @ ISO-400. Converted in Photo Ninja to B&W.

gerberaSpUVBaad365UVLed_20150207wf_pnCrop01.jpg

 

 

I did not quite succeed in preventing light leakage. You just couldn't see it in the preceding cropped version of the photo. I do not yet know whether the light leak is occuring through the aperture window or the helicoid or around the mount adapter. It disappears at some extension lengths.

 

UPDATE 13 Feb 2015: The light leak was from an uncovered aperture window on the UV-Rodagon. It is not enough just to cover the light guides on the base of the lens. Nor is it enough just to recess such a lens into a helicoid or tube.

 

Unedited, uncropped version of preceding photo showing light contamination.

gerberaSpUVBaad365UVLed_20150207wf_2950401.jpg

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The FFD for Nikon is 46.50mm and for the UV-Rodagon 56.60mm, so the lens base needs to be 10.10mm from the plane of focus. I haven't actually measured this heli when using it at infinity except to observe that the helicoid is not fully retracted. I do have to rotate it a tad to focus beyond 30 feet.

 

I fixed one light leak. And now I seem to have another. Strange. I'll try to get a foto posted to show the new one.

The UV-Rodagon works with no light leaks on a "normal" M42 heli with the aperture window and light guides blocked.

Maybe there is something wrong with this wide heli??

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The FFD for Nikon is 46.50mm and for the UV-Rodagon 56.60mm, so the lens base needs to be 10.10mm from the plane of focus. I haven't actually measured this heli when using it at infinity except to observe that the helicoid is not fully retracted. I do have to rotate it a tad to focus beyond 30 feet.

 

I was just wondering how much optical depth you had to spare between the lens and the inner baffle of the helicoid. I cannot find where Enrico's wide helicoid with the glued in 39mm ring is posted. Would you please post a link to our prior discussion of his setup?

 

I fixed one light leak. And now I seem to have another. Strange. I'll try to get a foto posted to show the new one.

The UV-Rodagon works with no light leaks on a "normal" M42 heli with the aperture window and light guides blocked.

Maybe there is something wrong with this wide heli??

 

I seem to recall the wide end of the helicoid is 52mm, is that correct? If so and you have a 52mm screw in lens cap you could pull the lens and screw on that light tight cover and put to rest the question of the helicoid itself leaking.

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I know the light leak is not from the UV-Rodagon. Here is a photo made with that lens on another helicoid.

 

helianthusSpUVBaadSB14_20150213wf_29618pnPf301.jpg

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John, everything below the fuzzy-velcro band on the lens sits below the helicoid baffle.

 

Here is the post where Enrico first shows us the helicoid adaptations for the UV-Rodagon.

LINK: http://www.ultravioletphotography.com/content/index.php/topic/1028-uv-capable-lenses-seen-on-ebay-sept-2014/page__view__findpost__p__4507

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Alex, so far I've seen no UV activity or reflections with the Velcro. But you can be sure I'm going to try further tests. "-)
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The loop-side of Velcro® fluoresces a tiny bit green. But the loops are covered by the fuzzy-side Velcro® so I really don't think that could cause a big wash of contamination across the foto.

 

The helicoid does not leak. I capped it and shined lights onto it all around.

 

So it's still a mystery !!!

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Well, thank you, I guess !!?? :lol:

 

The light leak has something to do with the flash.

 

Here is a foto made with the 365nm Nichia UV-LED torch. I used a little light painting technique over the sunflower face to ensure it was evenly lit. But there seems to be no evidence of light contamination.

Nikon D600-broadband + Rodenstock 60/5.6 UV-Rodagon + 365nm UV-LED Torch + Baader-U UV-Pass Filter

I have cleaned up the background dust bunnies in this photo.

f/8 for 3" @ ISO-400

600_5251pn.jpg

 

 

Now here is the same scene illuminated with SB-14-mod flash. And there's the cyan-ish light contamination again. This is driving me crazy!! Because of the light contamination, this photo was impossible to properly white balance in the editor.

Nikon D600-broadband + Rodenstock 60/5.6 UV-Rodagon + SB14-Mod UV-Flash + Baader-U UV-Pass Filter

I have not cleaned up all the background dust bunnies in this photo because I got bored with the effort.

One flash.

Look at the background shadow to see the washed out area. Shouldn't happen in a shadow.

f/8 for 3" @ ISO-400

600_5253pn.jpg

 

 

Nikon D600-broadband + Rodenstock 60/5.6 UV-Rodagon + SB14-Mod UV-Flash + Baader-U UV-Pass Filter

Two flashes.

f/8 for 15" @ ISO-400

600_5257pn.jpg

 

 

Same flower using SB-14 flash again, but without the white background panel. You can more easily see the smear of cyanish light around the flower.

Nikon D600-broadband + Rodenstock 60/5.6 UV-Rodagon + SB14-Mod UV-Flash + Baader-U UV-Pass Filter

f/8 for 2" @ ISO-400

600_5265pn.jpg

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Next experiment. Try a velcro-ed UV-Planar in place of the UV-Rodagon to test once again whether it is the helicoid/velcro combo causing the problem.

And try to figure out why the problem happens with flash and not with torch.

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You are systematically reducing the potential sources of the light leak.

 

A couple of thoughts.

 

1. Most of the LED spectral output is in the Baader-U passband. Possible result of this could be that any of this narrow band UV leaking around your velcro mount would not overwhelm the filtered narrow band UV coming through the filtered lens. Conversely, there is likely a good deal more bandwidth from the UV-Flash even if it has a UG type filter. Perhaps more importantly a lot more of it is going to be scattered about the scene to be reflected at many angles more likely to align with gaps in the velcro junction.

 

2. You tested the helicoid with a metal screw in lens cap and reported no leaks. Now put the opaque cap on the lens, via step ring if needed, and see if the leak is still there.

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