Rodenstock Omegar 75mm f/4.5 for UV

[Andrea B.]

Rodenstock Omegar 75mm f/4.5 for UV

 

This 3-element 'economy' enlarging lens was made by Rodenstock for an Omega enlarger.

It has a 35.5mm thread mount. When used with an adapter and an appropriately sized helicoid,

it easily reached infinity focus on both a Pentax K5 and a Nikon D600 during my tests.

I estimate its flange focal distance to be between 60-65mm.

 

NOTE: This lens has no front threading for filters, so some kind of filter adapter will be needed

which would fit over the zebra edge but not permit visible light contamionation.

For the indoor close-up test shots posted below I simply held the filters in place.

 

Inexpensive enlarger lenses abound on Ebay and on darkroom equipment websites. Look for the 3 element or Tessar style for some chance of UV-capability if buying an unknown, untested EL. And remember that adapters and helicoids will be an additional expense if you don't already have a few of these items.

 

Rodenstock Omegar 75mm f/4.5 enlarging lens bought for $20 on Ebay. This EL does not have windows on the mount end for illumination of the aperture setting in the darkroom like many more expensive ELs. That's a good thing when you want to use the EL on a DSLR.

 

Aluminum M35.5 to M42 adapter from Portugal via Ebay for about $21. The black paint won't last long - some has already gotten scraped off. There are shallow gouges on the flat part of the adapter, but it does not seem to be causing any problem. The threading is excellent.

 

The Omegar was manufactured in Germany. The locking ring is needed for enlarger work, but has been removed for use with DSLR adapters.

 

Two M42-to-M42 aluminum helicoids from Hong Kong via Ebay for about $30 each. They are nicely made and turn smoothly. The top one is 12-17mm and the bottom 17-31mm. Prices for these items seem to vary widely, so just look for the lowest price from a well-ranked seller.

 

Here's the Omegar 75/4.5 kitted up with its adapter and helicoid. (My face is red because this is OOF!!)

 

My broadband Pentax K5 was given an authentic Pentax K-to-M42 mount adapter to ensure a robust build and a good fit. At least half of my UV-capable lenses are M42, so the adapted K5 will see a lot of use.

So far, so good - I really like the K5.

 

Ready to shoot UV for only $70 - assuming you already have the broadband cam. And - if you don't mind handholding filters in place. :D

 

 

Although I just displayed the Omegar/Pentax kit, the UV photos I'm going to show you were made instead with my broadband D600 on which the Omegar works equally well. I couldn't get the tripod adapter plate off of the D600 to put it onto the K5, so I didn't shoot with it this time. Needless to say, I have already hit B&H for a second tripod adapter plate which will be permanently placed on the K5.

 

Armeria maritima 'Rubifolia' in Visible Flash Light

f/8 for 1/10" @ ISO 400

This flower is commonly known as Thrift. One flower is only about 10mm wide, so these photos have been greatly cropped.

 

View 1: Armeria maritima 'Rubifolia' in 365nm Nichia UV-LED Light with Baader-U UV-Pass Filter

f/8 for 1/4" @ ISO 400

The Thrift flower is mostly UV-bright with some extra-shiny areas due to surface conical cells.

The central area is slightly darker (better seen in the next version).

The UV-LED light produces a more monochrome look, so the false colour tends to be subdued.

 

View 2: Armeria maritima 'Rubifolia' in 365nm Nichia UV-LED Light with Baader-U UV-Pass Filter

f/8 for 1/15" @ ISO 400

The central, slightly darker area is better seen in this closer version made with a bit less illumination.

The UV-dark midline on the petal is also more evident here.

[Alex H]

Andrea, small correction of this your statement: "Look for the 3 element, Tessar style..."

 

Tessar lenses are four elements in three groups, not 3 elements. Enlarger lenses with three elements will most commonly be Triplets.

 

Also, Omegar, Omegaron, etc, are names used by an American importer, who supplied Omega enlargers, and can be found on lenses made by Rodenstock in Germany, and a number of different manufacturers from Japan.

In Europe, lower cost Rodenstock enlarger lenses will be designated "Trinar" for triplets and "Ysaron" for tessars.

[Alex H]

Here is a test someone did with Rodenstock Trinar 75mm F/4.5 on the other forum: http://forum.mflenses.com/found-a-new-cheap-lens-for-reflected-uv-photography-t56085.html

[nfoto]

JML (Japanese company if I recall correctly) also had a dirt-cheap 50 mm f/3.5 enlarger lens with 39 mm Leica thread. 'Dirt cheap' here means they sold for $10 or even less. Again relying on memory, it was a triplet. Its UV performance is very good to excellent although sharpness might not make it to UV-Nikkor/Coastal 60 levels. At the price nobody should complain, though.

 

As the focal length is a tad short on the DSLRs, it's hard to push it towards infinity and from what I saw it delivers on my Panasonics, not really worth the efforts. Let it work in the

 

To use this lens on cameras without internal UV bandpass filters, I seated one of my samples into a dedicated custom-made extension tube (BR-3 actually so female 52 mm filter threads were available). The female "F" mount on the BR-3 was replaced by a male one so as to further cut down on the adapters required. I also cut a slit along the side of the tube to access the aperture ring with a long extension screw fixed to the ring itself). Works like a charm. Another copy of the JML was fitted with a 39-42mm step ring and put onto one of my M42-F focusing helicoids for use on cameras with internal filtering.

 

I'll post a picture of this contraption later when I return from the current trip.

[Alex H]

Yes, I remember some long discussions about the JML 50/3.5 lens on the Nikongear.com. It seems to me as it was sold under a countless variety of brand names, with slightly different outer cosmetics. But I have never used the exact JML version, or any other ones, so I have no direct experience with it. On the other hand, I have tested few of the cheap enlarger lenses of the longer focal length, 75mm and 150mm. Both of them appear to be triplets to me. I had to disassemble and clean both so I hope I would have noticed if one of the optical elements was a doublet. Both these lenses transmitted deep into UV, producing nice images with the 325BP10 filter, thus reaching below 330 nm.

 

The 75mm F/3.5 lens I tested is called Spiratone, and is similar to one of the versions of Spiratone flat field macro lens (tested before by Rob Kerr from Nikongear). It is rather sharp when stopped down to F/8 but not any better than my other lenses in the same range (El.-Nikkor 80mm F/5.6 for example), so I do not have it any more.

 

 

The 150mm F/4.5 lens I tested was branded as Saunders, but the same lens I have seen under other names, including some versions of Spiratone Macrotel. When I got it, I compared it directly to the Fax-Nikkor 160mm F/5.6 I had, and the Saunders transmitted more UV with the 325BP10 filter than the Fax-Nikkor. Unfortunately, Saunders was never really sharp lens when shot in UV. Also, it does not have a front filter thread.

 

 

As a conclusion, even though both lenses transmit sufficient amount of UV, down to around 330-335 nm (approximately!), I would not recommend the 150mm version for serious UV documentary photography. The 75mm version may be satisfactory to some.

[Andrea B.]

I had meant to write "3 element or Tessar". Thanks for catching that. :D

 

This little Omegar I bought on a whim really surprised me. It is plenty sharp even at infinity focus. It shouldn't be too difficult to figure out a "push on" filter holder.

 

I also have a Rodenstock 50/3.5 Omegaron which looks good. I can't quite nail down its FFD - seems to be between 40-45mm.

 

I'm not sure why the JML 50mm f/3.5 M39 EL is not on our Sticky Lens list, but I will make a note to add it when I do the next batch of updates.

Also the Rodenstock Trinar 75mm F/4.5 EL from Alex's link.

 

I've been enjoying myself recently searching out fittings and helicoids to bring my various assortment of UV lenses to infinity focus on the D600, K5 or GH1. Currently I have an M52-M42 helicoid on order from Hong Kong so that I can try Enrico Savazzi's idea of gluing an M39 ring on the inner lip of this helicoid and fitting the M39 UV-Rodagon down inside it in order to be able to attain this lens's 56.6mm FFD which is a mere 10.1mm over Nikon's FFD and 11.14mm over Pentax. The shortest helicoid I could find so far is 12mm. (And, of course, you need some play in helicoids for focusing.) Here is the link to Savazzi's UV-Rodagon idea - scroll down: http://www.savazzi.net/photography/focusing_helicoid.htm

Of course, the GH1 is the backup to any failures in reaching ∞ on the D600 or K5. :D

[colinbm]

Thanks Andrea for introducing me to these heliciods :D

The link was broken ?

This is the one I got.

http://www.savazzi.net/photography/focusing_helicoid.htm

Cheers

Col

[Alex H]

Also the Rodenstock Trinar 75mm F/4.5 EL from Alex's link.

 

I am almost sure Omegar is a US distribution name for Trinar, but right now I can not find the reference to it. I will check later on. The test in the link I provided does not give all important for UV shooters information, so I would not rely on it without proper re-testing.

[nfoto]

Aha. I have the recommended Pentax focusing helicoid in my cache of potentially useful stuff :D

[Andrea B.]

Col - thanks for the broken link notice. Don't know what happened. But I fixed it. :D

 

Helicoids and adapters abound on Ebay and Amazon, so with a little searching we should be able to get most of our UV-capable finds kitted up to work on our various converted cams. Infinity focus is not mandatory, of course, but it is nice. I do get tired of shooting close-up flowers sometimes.

[igoriginal]

Fantastic find, Andrea!

 

And thanks for referencing some of the additional specimens, guys!

 

Yes, I imagine that there are many enlargers out there, that would exhibit a useful level of UV transmission, given that their designs were not tantamount to actually blocking UV radiation from sunlight to begin with (since they were used in dark-room environments) ... hence, the lack of strong UV-suppressive multi-coatings, otherwise introduced into the majority of "outdoor" dedicated optics, post-1960's.

 

(And, unless I am mistaken, some types of specialized imaging transference / copying back from the film era did indeed require some UV transmittance capability for optimization. No?)

 

On a related topic, I have also recently been experimenting with projection lenses, for UV-transmittance capabilities. My results have been mixed, thus far (some have satisfactory transmission, but otherwise poor resolving ability / definition / sharpness). There are a few exceptions, however. And, I have also been able to "sharpen" them up a bit, by disassembling the projection pieces, and inserting my own home-made "aperture" inserts (either using washers of varying sized and hole slots, painted black to eliminate internal reflections), or even rudimentary, quick assessments using cardboard with varying diameters of cut holes in the center.

 

The one problem with many projection lenses is that they typically flare very badly, when pressed to do photography / image capturing (instead of projecting light from the inside-out). I believe this has to do with the fact that they were designed to push light from the rear to the front (projecting images), rather than a "taking" lens (designed to pass light from the front to the rear). But, again, I am not an optics expert, so this is an assumption.

 

Alex, any thoughts on this?

 

Anyway, glad to be back on UVP, and hopefully going to catch up with everyone's posts ... since I have been away for over a week.

 

Thanks!

[JCDowdy]

Andrea,

 

Here is an approach you might consider for mounting your 35.5mm thread mount enlarger lens with an internal mounted filter held near the sensor.

(eBay item numbers provided for reference only)

 

1) Pentax K 52mm reversing ring, eBay item number: 291104374468

 

2) 42mmX1mm to 52mm Step Ring for M42, eBay item number: 400458800434 (female 52mm, male M42 thread)

 

3) Short M42 to M42 Mount Focusing Helicoid (reversed and mounted onto the male M42 thread)

 

4) Pentax m42 to 35.5mm filters step down reverse mounted lens adapter eBay item number: 371015641670 (female M42 to female 35.5mm)

 

I do not have items (1) or (4) but the space between the 52mm-µ4/3 reversing ring I have and item (2), 42-52 step ring, is ~3mm X ~48.5mm, ample room for an internal unmounted 52mm filter or similar trapped filter disc. Also a regular 52mm filter will screw in between my (1) and (2) but I don't know if that provides sufficient strength when weight is added outboard from there.

 

-JD

[Alex H]

On a related topic, I have also recently been experimenting with projection lenses, for UV-transmittance capabilities. My results have been mixed, thus far (some have satisfactory transmission, but otherwise poor resolving ability / definition / sharpness). There are a few exceptions, however. And, I have also been able to "sharpen" them up a bit, by disassembling the projection pieces, and inserting my own home-made "aperture" inserts (either using washers of varying sized and hole slots, painted black to eliminate internal reflections), or even rudimentary, quick assessments using cardboard with varying diameters of cut holes in the center.

 

The one problem with many projection lenses is that they typically flare very badly, when pressed to do photography / image capturing (instead of projecting light from the inside-out). I believe this has to do with the fact that they were designed to push light from the rear to the front (projecting images), rather than a "taking" lens (designed to pass light from the front to the rear). But, again, I am not an optics expert, so this is an assumption.

 

Alex, any thoughts on this?

 

There are many different projection lenses, with different complexity in their design: triplets, Petzval-derived, Double Gauss-derived and more. Properly made projector lenses should have well-baffled internal surfaces to avoid any internal reflections as it does not matter where the light comes from - the light scattering will occur in any case. Try to use deep lens hoods with them.

 

As far as their usability for UV - I have experience with two lenses, but now I will only speak about one, just because I have no example pictures to show from the other one. I tested the Pentacon 100mm F/2.8 projection lens, which is identical to Meyer Diaplan 100mm F/2.8 projection lens, and is thought to be similar optically to the notorious Meyer Trioplan 100mm F/2.8 lens. It is a simple Triplet. It does not have the aperture or focusing. It does transmit some UV but not nearly close to Noflexar or Kyoei - my copy did not transmit anything with 325BP10 filter. It is not sharp wide open and is not useable for documentary UV-photography. Here is one example that was worth saving: Winter Aconite again.

 

http://www.holovachov.com/img/s8/v78/p1478626410.jpg

[Alex H]

Yes, I imagine that there are many enlargers out there, that would exhibit a useful level of UV transmission, given that their designs were not tantamount to actually blocking UV radiation from sunlight to begin with (since they were used in dark-room environments) ... hence, the lack of strong UV-suppressive multi-coatings, otherwise introduced into the majority of "outdoor" dedicated optics, post-1960's.

 

Here is an exact explanation on why enlarger lenses are transmitting UV-light, taken from one of the brochures on El-Nikkor lenses. Copyright: Nippon Kogaku K.K.

 

[colinbm]

Thanks Alex

[Andrea B.]

JD - Yes, a rear mounted filter is probably the best way to go.

And thank you for the detailed "specs" on that.

Very useful for those of us who might never have put together a rear filter setup.

 

I'll assess how many lenses I have that could make use of that and perhaps give it a try.

I only hesitate because it might require unmounting a Baader-U (or other such) and Baader-UVIR cut and dedicating them permanently to the effort.

 

Alex - Thanks for the copy from the EL-Nikkor brochure. I had run across mention of UV capablilty of EL lenses and paper sensitivity on one of the forums somewhere (maybe Manual Lens Forum?) but had never seen the actual source. Always good to know.

[JCDowdy]

You are welcome Andrea.

 

That is not the way I am running rear mount filters because on micro4/3 I have yards more register depth to play in. With only 19.25mm flange focal depth versus your Pentax K' 45.46mm one doesn't need to resort to an ultra thin reverse macro adapter to reach infinity. They are handy for other projects though ;-)

 

What is the outside diameter of that locking ring?

[Andrea B.]

Yessir - one of the benefits of m4/3 and Sony Nex is that shorter FFD which permits extrension of so many good UV-capable lenses to infinity focus. :D

 

The outside diameter of the Omegar locking ring is 39mm.

[JCDowdy]

The outside diameter of the Omegar locking ring is 39mm.

 

If the locking ring is not to thick, at OD=39mm perhaps it could be trapped between the male M42 of the reversed helicoid and a female M42 to M39 step down ring (see eBay item#280663510595)

 

Here is a bit of my lunacy - the fiber optic adapter is trapped under the 39mmx1-42mmx1 ring.