Discussion on cameras and lenses for UV

[Alex H]

What I mean by obtaining "patent rights", is not in the optical formula itself, but the actual design authentication (mimicry) of the original Petzval lens BODY / CASE appearance, as well as the extrusion points and decorational / ornamental shaping of the metal.

 

There are no "patent rights" for the design of the lens body in this particular case. Only of the optical construction. And please do not get me started on the ergonomics of that Lomography lens...

 

Speculation is good, no problem with that. I understand your excitement. We all have been there. We all found some lenses that are good for UV. "Speculations" are, well, speculations. But you will not get published just based on your speculations. You get published based on your facts and result. Please read all those hundreds of posts over at invisible section of Nikongear.com to avoid "reinventing the wheel".

 

But, to be honest, I am sort of tired by the fact that people on many internet forums are posting things without checking facts first.

 

The Sony NEX / mirrorless systems also have a relative short flange / register, although a bit larger than the Micro-4/3 system.

 

Sony NEX flange distance is 18 mm

Panasonic/Olympus MFT flange distance is 19.25 mm

[igoriginal]

Speculation is good, no problem with that. I understand your excitement. We all have been there. We all found some lenses that are good for UV. "Speculations" are, well, speculations. But you will not get published just based on your speculations. You get published based on your facts and result. Please read all those hundreds of posts over at invisible section of Nikongear.com to avoid "reinventing the wheel".

 

 

I never expected to get anything published, without further testing. As a scientist and researcher, myself, I would not expect anything of the sort. I, in fact, would DENY anything published from any of my assumptions, until I have tested things first, replicated those tests, and then have others duplicate and confirm the same results, first. This is the cornerstone to the 'Scientific Method', and I am quite familiar with the process ... because it is required from my already prior lab experience.

 

And as far as I know, no one else has ever considered the Wollensak Velostigmat 1" 25mm F/1.5 for its UV transmission before. So, I wouldn't be "reinventing" someone else's wheel. Believe me, I searched and searched, endlessly, to see if someone else found what I discovered with this lens. And my search turned up nothing. So, I would be the first, it seems, with discovering this lens's UV capabilities.

 

My "results", so far, are based on photo testing of this lens. And, as you can see by the photos that I have already posted, its UV transmission is confirmed.

 

What I do, however, need to follow up with, is buy that spectrometer that I have been saving up for, so that I can then confirm the precise uv-transmission bandwidth and transmission intensity-curvature of this lens. That is my next step. So, yes, it's a work in progress.

 

(But, if someone else goes ahead of me, and has a spectrometer to test the same lens, then I would be extremely happy to learn any additional information that they may divulge.)

 

But, to be honest, I am sort of tired by the fact that people on many internet forums are posting things without checking facts first.

 

I understand your frustration. I get wary of endless statements without fact-checking, myself. Which is why I follow up my initial "hunches" with further testing, rather than go on and on indefinitely.

[igoriginal]

Sony NEX flange distance is 18 mm

Panasonic/Olympus MFT flange distance is 19.25 mm

 

Ahhh. So, I had them reversed. Thank you for clearing that up! I knew they were close.

[nfoto]

There are a lot of parameters to consider for a lens if it is going to be a useful tool, whether it is pressed into service for UV or something entirely different. Some of the areas to consider are how easy you can attach filters to it, options for mounts or mount modification, the focusing capability, the size of the projected image size, optical aberrations and their dependence on aperture and focused distance, propensity for flare and ghosting, and of course its spectral transmission curve. However, if a lens transmits UV freely, that alone will not suffice as the better criterion is how sharp the images are. Many lenses do not draw a really sharp image in UV so using them is moot: why bother about getting a lot of UV through the lens when the image itself will be a smeared mess? Maybe this is borderline OK for non-scientific imagery, but quality UV work depends on lenses that can perform.

 

There are UV-capable lenses out there, no doubt about that. Highly probable that unknown gems are in existence as well. But locating them is best compared with finding a needle in a haystack. I won't hold against any enthusiast keen on trying every possible candidate, but for me time is better spent with the certified UV lenses I already own and use on a regular basis.

 

If a putative candidate is found, at the very least do a cursory test of it to evaluate its general usefulness. That should include ascertaining performance at the wider apertures, plus of course its behaviour when stopped well down.

[JCDowdy]

(nfoto on 18Feb14 asked: "My GH-2 has 3 slots for custom w/b - has Panasonic decreased the number over time?")

 

My DMC-G3 and DMC-G5 both only have only two savable custom WB settings, not counting adjustable color temp setting.

However, WB does not seem to be a saved parameter under the three custom mode sets of dial setting C2.

Also, the C1 dial position on G3 & G5 has no similar custom sets I have yet found.

Perhaps I simply have not discovered them.

[nfoto]

Strange these models should behave so differently from my GH-2 cameras. The GH-2 definitively can store three w/b settings (plus other relevant options). Plus you have whatever balance the camera is set to if none of the C1-C3 slots is selected. I use this feature a lot.

[JCDowdy]

Well, perhaps I have not discovered how yet. Must now consult manual........

[igoriginal]

There are a lot of parameters to consider for a lens if it is going to be a useful tool, whether it is pressed into service for UV or something entirely different. Some of the areas to consider are how easy you can attach filters to it, options for mounts or mount modification, the focusing capability, the size of the projected image size, optical aberrations and their dependence on aperture and focused distance, propensity for flare and ghosting, and of course its spectral transmission curve.

 

Indeed. Which is something that I've already been working on, and testing is in progress. Including a "knowledge base" on the lens which I have forwarded to a few other interested individuals that I am in constant contact with, which are also going to test the lens for me and confirm what I have already attained ("peer review"). I have already shot at various aperture ranges, distances, and lighting conditions ... therefore, the detailed information which you speak of has already been going through a compilation period for the past 9 months, long before I went to public about it (just last week).

 

Not only that, but I have also been in email contact with Miss Andrea G. Blum on the lens, involving its attributes, so that she has enough detail on it for her upcoming "UV Lens Sticky" update.

 

However, if you desire some of the same information that I have been divulging to her, and a few others, here is a simplified summary / review:

 

Wollensak Velostigmat 1" (25mm) F/1.5 Cine / C-mount lens

(Note: The two-tone earlier variant, with the dark-copper front hood-like barrel, and the chrome body; Not the all-chrome later variant, which may not exhibit the same useful UV transmission.)

 

 

1. It has a 25mm front filter mount (and an adapter "step-up" ring from

25mm to 52mm, or 25mm to 48mm, can easily be found and purchased, in order to accommodate

standard-sized 48mm or 52mm threaded filters).

 

2. This lens appears to have NO visible coatings at all (bare glass). All elements appear to be air-spaced, with NO evident cementing. However, more testing is underway.

 

3. The lens can be easily taken apart without tools (twisted open completely), and each element can be hand-removed and cleaned by hand, then reinserted by hand. A completely tool-less procedure, and with minimal effort / time invested. (I've been able to clean it, within 5 to 10 minutes!)

 

4. Because of the front element being so deeply recessed inside of a deep hood-like front barrel, flare is very well controlled, and the lens is surprisingly contrasty for a crude and uncoated air-spaced design. It's quite possible that this glass was baked from very superior processes of "seeding" and "doping" certain proportions of other minerals mixed into the SiO2 (silicon dioxode) base. In other words, a more lab-controlled production of finely-procured silicate esters, which are known to produce a finer "micro-contrast" (and higher "resolving" power). Hence, "premium glass" with a higher refraction index. But that is a hunch, for now. More testing required.

 

5. It can be easily adapted to micro-four-thirds camera systems, via an

easy-to-find Micro-4/3 to C-mount adapter.

 

6. Its rear-element image circle is large enough to fully cover the

sensors of micro-four-thirds format cameras (Panasonic G and Olympus E

series of mirrorless / interchangeable lens systems), and any other

cameras with sensors that are smaller than the micro-four-thirds

standard. Some "porthole" effect will likely occur, with Sony Nex systems, given the larger APS-C sensor format. Although this porthole effect will become increasingly restrictive, with increasingly larger flange / register distances, from thereon.

 

7. Even when using macro extension rings between the rear lens mount and the camera body, there is no evident sign (in real-world test) of severe image drop-off, or darkened corners. In fact, I have mounted this lens on as many as 4 macro rings stacked together (5mm thick each), for a total macro stack spacing of 20mm ... and STILL, the image circle of this lens covers the entire Micro-4/3 sensor!

 

8. It will properly focus to infinity, when adapted to a

micro-four-thirds system, without any need for image-degrading

corrective glass involved.

 

9. It will likely never be susceptible to fungus (tendril growth), since there are no evident coatings on any of the element surfaces! (Coatings are "fungus food." Take the coatings away, and it has nothing to feed on). Concurrently, this is precisely why I have yet to find any specimen with "ruined glass." Thus, this lens will TRULY endure the test of time, indefinitely, so long as it's not abused.

 

10. Having a maximum aperture opening of F/1.5, this lens is easy to focus in even the most demanding low-light conditions! This makes it that much more of an asset, when trying to initially focus with a very dark UV-only stack. This is probably the "brightest" (fastest) lens I have ever used, for useful UV-only photography.

 

11. Focus shift seems to be moderate to minimal, when the aperture is pulled down to F/8 and smaller. Focus shift is significantly more apparent, when aperture is wide open at F/1.5. But, this is to be expected, as I cannot imagine a lens that is so well-corrected, that there would be absolutely 0% focus-shift at such a wide-open F/1.5 aperture and so thin of a depth-of-field. That would be asking too much. Especially from such a simple, retro design. More testing will be required (via proper instrumentation), to more precisely ascertain focus-shift % at all settings.

 

12. Sufficiently "proper UV coloration" can even be attained, hand-held (no tripod or long-exposure required), at an exposure of 1/10 sec, and ISO 800, when shot at wide-open F/1.5 aperture (on clear sunny day / direct sunlight, and temperate latitudes), when utilizing a Baader-U (or sufficiently dark enough UV stack). This is a good sign of the lens's potentially deep UV transmission. However, as stated earlier, a spectrometer test will be required to confirm precise transmission capabilities. Note, though, that UV-color saturation does fall off, if photographed at such a wide aperture. But this can be bumped up, in post-photo editing.

 

However, if a lens transmits UV freely, that alone will not suffice as the better criterion is how sharp the images are. Many lenses do not draw a really sharp image in UV so using them is moot: why bother about getting a lot of UV through the lens when the image itself will be a smeared mess? Maybe this is borderline OK for non-scientific imagery, but quality UV work depends on lenses that can perform.

 

It's darn sharp, actually. TACK SHARP at F/8 and F/11. I've spent 9 months shooting with this lens, and it's sharp aplenty. Photo results are very comparable to some other, more DEDICATED uv-lens ... at least at print sizes below 20 x 30. I have full-sized photos, upon request, if someone is interested in "pixel peeping." They won't be disappointed. However, as stated above, I am already in communication with a few other individuals who are going to run this lens through its courses, so that we can compare notes.

 

In short, Fiece Bear, everything you have stated is something I am already in the middle of doing. :D

 

(But I do realize that I am still very inexperienced in this game, and hence will need help from others, as well as ongoing peer review. Thank you all!)

[nfoto]

Good to see you took my comments this seriously - even before they were written :D

 

My post, however, was on a general level not directed towards any one or anything particular.

 

Currently I'm experimenting with tandem lenses for UV. Because the overall focal length of the tandem system is reduced compared to the pair of lenses involved, the "loss of light" can be assuaged to a surprising extent.

[igoriginal]

Good to see you took my comments this seriously - even before they were written :D

 

I want to be serious about this, because I greatly respect what you and other experienced individuals like yourself have done in this specialized field. It is because of people like you (pioneers), that I have the honor and privilege of UV photography. So, I am grateful beyond measure.

 

I, therefore, aspire to follow in your footsteps, and I hope that my level of presentation can eventually match your own, so that I can aspire to the same level of competence. In short, I want to do honor to this field. It is something that I have wholeheartedly embraced.

 

My post, however, was on a general level not directed towards any one or anything particular.

 

I suppose I pay very close attention to everything you say, to the point that I believe it should not be taken lightly ... and that when it applies to everyone, it should also apply to me, too.

 

Like I said, I hold you and your colleagues in high esteem. It is precisely why I opted to join this family, the moment I found this website. I realize that I still have much to learn, so this is why I am here. And, over time ... as I also gain experience ... I hope that I can eventually be of value to others.

[igoriginal]

Currently I'm experimenting with tandem lenses for UV. Because the overall focal length of the tandem system is reduced compared to the pair of lenses involved, the "loss of light" can be assuaged to a surprising extent.

 

What exactly do you mean by "tandem lenses?" Are you talking about lenses specifically designed for biological / laboratory tissue imaging / sampling, for the detection of various epidemiology?

[nfoto]

By definition, two separate lenses joined to make a common optical system.

[Andrea B.]

binoculars ?? :D

[colinbm]

stereo, 3D ?? :D

[nfoto]

No. More like a relay system.

[igoriginal]

By definition, two separate lenses joined to make a common optical system.

 

Ahhh, ok. I get you.

 

I have done "lens coupling" before, particularly for macro-photography.

 

So, are you saying that you are experimenting with joining together individual element pieces (cannibalized or scavenged from disassembled optical tubes)? Or "coupling" entire lenses together?

 

I've also messed around before with ripping apart lenses, and stacking / rearranging various element pieces together. In fact, I have a whole box of loose element pieces sitting around, from past experimentation.

 

(I, myself, am interested in experimenting will creating a "minimalist" optical formula from individual bare glass pieces, to see just how much UV I can pass through it.)

 

Another curiosity of mine, is to see how various mirror-based (reflective) optical systems would fare, with UV photography, versus the typical refractive system.

[igoriginal]

More examples of the Wollensak Velostigmat 1" 25mm F/1.5 Cine lens, in VIS and UV comparisons.

 

(It should be noted that these images are somewhat cropped versions of the originals, and hence the feeling of "sharpness" is somewhat degraded through magnification. Also, there was no post-photo "sharpening" involved with these images. They are, therefore, "out of camera" for the most part, with the exception of some saturation increase applied.)

[igoriginal]

My DMC-G3 and DMC-G5 ...

 

Hey, JC. Seeing as we use the same systems for our UV work, and that we are also in the same "deep south" region of the USA ... we need to hang out, sometimes, and maybe even plan some sort of field trip.

 

I have actually been trying to put together a "camera club", locally. So that a team of shooters can take day trips, and compare notes.

 

Just some thoughts.

[Alaun]

Bjørn, the tandem lenses, is that something similar to what they do with these 4 little lenses?

 

http://www.eso.org/public/teles-instr/vlt/

 

Werner

[igoriginal]

Good afternoon, Folks! (well, it is afternoon in my time-zone, anyway. :D)

 

I finally got around to disassembling the Wollensak (again), and this time giving it a more thorough test / inspection (rather than a spot check).

 

My inspection confirmed that there is no cementing. As it turns out, this does in fact look like a miniature double-doublet optical formula.

 

I wasn't able to separate the rear doublet away from its enclosure module (without risking damage to the old screw heads), but I was however able to separate the two elements in the doublet up front. The bi-convex and bi-concave elements were "nestled" together, with absolutely no adhesive, whatsoever. They just "spoon together", and are held in place snugly against each other, when the front enclosure module is screwed in tightly. The same can be assumed of the opposing bi-convex / bi-concave doublet in the rear of the optical design.

 

That's about it.

 

Here is my rough illustration of what I was able to ascertain of the optical design (although this is a rough sketch, as I am not a "master optician.")

[nfoto]

Bjørn, the tandem lenses, is that something similar to what they do with these 4 little lenses?

 

http://www.eso.org/p...eles-instr/vlt/

 

Werner

 

*Slightly* smaller optics are involved :D

[JCDowdy]

Iggy,

When I finally finish building my lens UV transmittance apparatus perhaps we can properly scan that little c-mount lens of yours.

- JD

[igoriginal]

Iggy,

When I finally finish building my lens UV transmittance apparatus perhaps we can properly scan that little c-mount lens of yours.

 

That sounds good!

 

Are you talking about having access to an actual high-resolution spectrometer ... or simply creating a home-made array (strip) of narrow band-pass filters (ex: 325BP10, 340BP10, 360BP10, etc.), to test UV transmission within a general resolution of 10nm wide? (Per Steve Smeed's "Sparticle Bandpass" test).

 

If so, I recently acquired those very same narrow-bandpass glasses, so I can start devising my own tests.

 

Either way, it will be nice to compare notes!

 

(Although I would love-love-love to put my lens through an actual spectrometer test, for the ultimate transmission-curve measurements!)

[Andrea B.]

Be sure to verify those narrow bandpass filters do not pass any IR !!

 

From which company did you purchase them?

[igoriginal]

Be sure to verify those narrow bandpass filters do not pass any IR !!

 

From which company did you purchase them?

 

These are industrial-grade narrow band-pass filters. Rated at > OD4 suppression of all other bandwidths, up to 2000nm.

 

Seller is a trusted merchant: omegabob2, on Ebay.

 

Been buying filters from him, for years.

 

(Same seller which I believe that Steve Smeed gets his filters from, for his Sparticle test).

 

I don't mess around. :-)