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UltravioletPhotography

SOM Berthiot Cinor 17/1.5 C-mount lens


rfcurry

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I thought it would be fun to try an early, fast, cine lens made in Paris in 1950 or 1951, in ultraviolet wavelengths. I used a C-mount adapter on my full-spectrum Lumix and shot the following images. The only lighting is sunlight through a window. All shots will have vignetting because the rear element on the SOM is smaller than the sensor of the Lumix. The images were reduced to 1000px width.

 

Lumix GF-1, ISO 100, f16, 1/25s, distance 12"

http://uvrdefensetech.com/images/Visgc1000px396.jpg

 

 

The same in UV. Again, the light source was the sun through doubled-pane windows.

Lumix GF-1, PrecisionU, ISO 100, f11, 6.0s, distance 12"

 

http://uvrdefensetech.com/images/UVgc1000px399.jpg

 

The lens wide-open, f1.5, excels for distant - 10' plus - objects. The vignetting adds some glamour, IMO.

I think I will play with this some more. :D

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different in-camera white balance settings?

They do look a tad bright.

Light leak thru the viewfinder?

Maybe you forgot to put the filter on?

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I do not see how WB can change colors that much, or how leak through the viewfinder can do it too. Correction: the camera is a mirror-less Panasonic, it does not have optical viewfinder.

 

More like IR or visible leaking through the filter.

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I just looked through my daffodill shots. Cannot find any bright ones in UV. They are not UV-black, but are dark-er than this. I agree that this is not from a WB setting. This looks very much like what one gets with an unfiltered shot on a broadband cam. When you take the photo into an editor and white balance it, it comes out as an almost Visible photograph.

 

Reed, what is going on here?

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I do not recall seeing much on Precision U shots, how different will UV false color rendition be from familiar Baader U?
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I'll tell you what I did. I didn't use in-camera white balance because when I set the custom WB against TPFE, it was too yellow. So I used the 3000K setting and didn't perform a WB at all.

 

Just a minute ago I took some more shots. It is raining and little UV, so I added my UVP100 lamp indirectly.

I performed a custom WB against PTFE. However, this time the lens is wide open and the ISO went from 100 to 400.

 

Lumix GF-1, PrecisionU, UVP100 lamp, f1.5, ISO 400, 2.5s -- no post processing except reduce 4000 width to 1000px.

http://uvrdefensetech.com/images/UV1000px422.jpg

 

So, those are my store-bought daffs.

P.S. - I found it hard to handhold my lamp and reach the shutter button, my remote has a dead battery. So the lighting is not very even.

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Alex,

Forgive my overexposure.

I just set the aperture at 16, the time at 25s, and covered the lens hood with my hand. The result was a bright blue - kingfisher blue - over the bottom 2/3 of the image. Answer, a light leak because of the adapter on the lens. The lens takes a 23mm filter ring. I didn't have one, so I used a Series III to Series IV adapter, then a 33->37, a 37->52, and the PrecisionU. The problem was the Series III connection to 23mm. The leak was more apparent when I used the 6.0s exposure on ISO 100. It didn't show as badly on the 2.5s on ISO 400, but was still there.

 

Oh well, I must make a 23mm to 52mm adapter.

Thanks for catching that.

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OK, looks much better now. Thanks for the reshoot, Reed.

I was a bit worried there for a second. :D

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JC Dowdy writes: I do not recall seeing much on Precision U shots, how different will UV false color rendition be from familiar Baader U?

 

It can be slightly different because the two filters have slightly different ranges and transmission peak.

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First of all, I don't believe it would be possible to get "proper UV colors" through the in-camera 'CWB' (custom white balance) mode, using PTFE, when utilizing sunlight through modern double-pane windows ... because modern double-paned windows suppress UV almost to a nominal level. This is also why a person can typically sit in front of a closed window, all day long, and never get a sunburn.

 

So, for starters, the modern double-pane window already cancels out a lot of the broader UV-A spectral bandwidth needed for a properly white-balanced exposure (or, it probably clips off the UV-A bandwidth on the lower end, leaving about roughly 20 to 30nm of remaining UV-A brandwidth to play with. Probably no lower of a transmission than about 380, or 370, at most. But, this is an estimated guess on my part, as I have never measured this to precision. And, depending on manufacturer, these numbers are somewhat variable, rather than exact.)

 

Secondly, the only reliable way to get "proper UV colors", in-camera, using a mirrorless camera like the Panasonic / Olympus M-4/3 systems (with full-time live view and an electronic viewfinder) ... is through the CWB (custom white balance) "shoot to set" function, and then save that CWB in the associated memory space / slot amid all the other default white-balance modes.

 

And yes, objects (including flowers) will indeed go through different "color" schemes, as one cycles through all of the non-CWB (default) white balance modes in the white-balance options. However, most of them will be predominantly "monotone" images, aside from what is set in the "shoot to set" CWB mode, after setting it to PTFE.

 

Just be aware, trying to set CWB through modern double-pane windows, with respect to UV photography *proper color* schemes when utilizing PTFE, is an exercise in futility ... if not a process of utter frustration. Well, it has been proven to be so, with all of my own experiences, anyway.

 

(Sure, you're still getting some nominal and barely sufficient levels of UV through the window to see "UV patterns" in flowers ... but you'll probably never obtain reliable 'UV color' schemes with PTFE, via the CWB function. Unless you have no double-pane windows between the light source and the subject)

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Many windows on the East coast are not particularly modern. I can shoot UV in my dining room via Southern window light. Windows are probably 60 years old. The 'storm windows' over them about 30 years old. They will all need replacement soon because the putty is all falling off, and the window sills and sashes are all dried out.
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Yes. From what I understand, it is specifically the double-pane (and specially treated) designs of more "modern" windows that bends light in such a way, in which the higher-energies of the lower end of UV-A (along with the whole of UV-B ) will not pass through. It may explain why you can still get somewhat of a "sun tan" in front of such a window, but you will likely never get burned (unless maybe you're an albino :D ).

 

(Most rapid "tanning" often involves the release of melanin within the skin, from melanocytes, in response to less damaging, longer-waved UV-A radiation just right below the violet-end boundary ... whereas "burning" usually is the result of more prolonged exposure from the deeper, shorter energies ... including a bottom portion of the UV-A, and of course, the UV-B range. Although it is true that both, UV-A and UV-B can induce "tanning", just through different biological mechanisms.)

 

And, as far as I can tell (from the descriptions and associated photos offered here), the reason that Mr. Reed has a problem with setting the "proper" (neutral-grey) WB scheme of a UV-A exposure, via PTFE, is precisely because a good portion of the remaining (lower half) of the broader UV-A bandwidth has been largely suppressed by his double-pane window.

 

Now, single-pane, untreated, simple windows ... such as those found on storm doors, shed doors, etc. (and yes, some of the remaining windows of colonial-era homes - Haha! - joking) ... will probably pass enough UV-A to obtain a sufficiently white-balanced image to render the 'UV standard' look that we all have come to live by and strive for.

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Mr. Igor,

 

I fear you are wrong. I have modern multipane windows separated by internal faux-mullions and a gas such as argon.

Here is a quick shot of some camouflage (Australian as denoted by the bunnies) in visible light. All photos below were taken with a Meyer-Optik Gorlitz Primagon 4.5/35 lens on a Lumix GF-1.

1/125s ISO 400 f16

http://uvroptics.com/images/Vis1000px441.jpg

 

The same with a PrecisionU - all that follow are with the PrecisionU - and custom white balance in-camera set to PTFE.

1.6s ISO 400 f5.6

http://uvroptics.com/images/UV1000px442.jpg

 

Now outdoors in full sunlight on brick steps

10/13s ISO 400 f8

http://uvroptics.com/images/UV1000px445.jpg

 

Finally, some grass and a deer-chewed shrub with that same custom WB, in the UV.

2.5s ISO 400 f8.0

http://uvroptics.com/images/UV1000px447.jpg

 

As you can see, the custom WB, when set in the UV, gives the same result whether indoors, through a window, or outdoors. Personally, it is just too close to a visible light palette for my palate.

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The spectral cut off of older single pane residential window glass is comparable to Schott WG-320 to WG-335 depending on thickness. Thicker tempered commercial windows are more like WG-335-WG-345. Window glass should begin to clip the short wavelength side of the various usable UV-photography filters to some degree. However, given what is reported about the transmittance of UV-A capable normal lenses convoluted with sensor response at these wavelengths the effect may not be profound. One should still be able to see ~360nm UV-yellow OK and likely only some loss of ~340nm UV-green. Without a quartz fluorite lens you are already attenuating shorter wavelengths than that to a degree with your glass lens.
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Reed, what interesting camouflage - some portion of the patterns 'disappear' in UV. Thanks for posting these.

I think you could make a nice post of this camouflage in the UV Forensics section sometime when you have a moment.

And tell us a little more about it?

 

John, I'm not sure why 360nm equates to something called UV-yellow and 340/UV-green. :D

But your main point about the WG glass is that we can indeed shoot UV well enough through windows.

I've been doing it for years. Never knew I couldn't.

 

I'm sure there are some types of window glass which do more blocking of UV.

I've seen advertisements which make such a claim.

 

Of course most of what I've been shooting in UV is flowers, so I suppose I'm just hoping to catch the stuff between 360-400nm.

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John, I'm not sure why 360nm equates to something called UV-yellow and 340/UV-green. :D

 

Andrea,

 

Sorry, I am probably not using correct nomenclature.

I was trying to refer to the false "UV-colors" that record as yellow and green in a properly UV white balanced Baader-U filtered image.

The following links were the basis for my calling ~360nm UV-yellow and ~340nm UV-Green.

 

http://forum.mflense...ion-t51237.html

 

http://photographyof...lower-leaf.html

 

I seem to recall you discussing naming of false UV-colors elsewhere, are there standardized or preferred names I should be familiar with?

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Window panes do absorb some UV and alter the spectral distribution of what UV goes through. The effect is readily seen with triple-glazed windows like those used in Nordic countries. Thus, I prefer shooting UV subjects in the great outdoors, or when indoors, using a setup with big studio strobes having uncoated Xenon flash tubes. However, if your interests tend towards depicting floral structures and you don't mind long exposure times, you can get nice UV flower shots even indoors.
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I seem to recall you discussing naming of false UV-colors elsewhere, are there standardized or preferred names I should be familiar with?

 

No UV false colour names that I know about. Maybe you are thinking about names of bee colours? For example, when the bee's UV and green receptors are both stimulated, the colour response has been labeled "UV-green".

 

OLD: It is not yet clear that one can or should associate a particular false colour with a particular UV wavelength. Too much is dependent on Bayer array, UV-Pass filter, lens, sensor and editor/converter being used. They are false colours, after all. :D

 

NEW: It is not yet clear that one can or should associate a particular false colour with a particular UV wavelength without taking into account the variables of Bayer array, UV-Pass filter, lens, sensor and editor/converter being used as well as whether edits are done on the luminance layer, chrominance layer or both. All these things can affect the false colour seen in a UV photo.

 

We have found some uniformity of UV false colour made with the Baader-U in the white balancing step across various sensors and across various editors. But one of my converters (Capture NX2) gives more green than does another (Photo Ninja). There are other anomalies. So nothing is certain on the false colour thing, in my opinion. We use false colours partly because they make the UV photography pretty. We use them here on UVP to present a standardized 'look' in our UV floral signatures.

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Andrea,

I understand your point, and certainly accede to your experience.

I had assumed within those instrumental and methodological constraints the UVP standardized approach gave better indication of spectral content.

- JD

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You should definitely make your own investigations into the topic, John. It is a very interesting topic.

 

BTW, I have modified my statement above. I put a line through the old statement. It looked too much like I was totally against the association of UV wavelength with UV false colour. I remain open to the possibility. I do not have the tools to pursue this technically, so I hope to see some other folks make some measurements and investigate it further to clear up the ambiguities.

 

*****

 

We have veered too far off topic! :D

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