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UltravioletPhotography

Things You Should Know: Test Yourself with These Questions


Andrea B.

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This is all Just for Fun!

 

Except for the first question. You should absolutely know the answer to that one. :lol:

Some questions are real; some aren't.

Some might not have an answer at all.

.

  1. What is the approximate UV/Visible/IR composition of sunlight at sea level on the equator at high-noon during summer?
     
     
  2. Same question - but at sea level somewhere in Norway at 16:00 in the dead of winter?
     
     
  3. Where does that strange magenta color come from anyway?
     
     
  4. Which has the longer exposure time, all other factors being equal, a UV photo or an IR photo?
     
     
  5. Which is the best reflected UV-photography forum in the world?
     
     
  6. What is Ultraviolet light?
     
     
  7. Is it permissible to photograph some other subject in UV than a flower?
     
     
  8. Who made the first reflected UV photograph?
     
     
  9. Is owning 6 converted digital cameras considered excessive? What about 10?
     
     
  10. For US members only: what is a UV torch?
    For everyone else: what is a UV flashlight?
     
     
  11. For UK members only: what is UV false colour?
    For everyone else: what is UV false color?
     
     
  12. Does an on-board flash output any IR?
     
     
  13. When was UltravioletPhotography.com founded?
     
     
  14. And why doesn't UltravioletPhotography.com have a logo?
     
     
  15. How many UV-capable lenses constitutes a handful? A boatload? A sign of true madness?
     
     
  16. What might you be missing if your UV lens does not reach 300nm?
     
     
  17. What factors affect how much UV there is in sunlight? List at least 5.
     
     
  18. What can happen if you try to convert your camera yourself?
     
     
  19. What brand of UV-pass filter glass has the prefix 'UG'?
  20. What factors affect the false colour you see in your UV images?
    Hey, is this a trick question?

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If you are reading this, then I hope you have tried to answer the questions already! You wouldn't skip trying to answer the questions would you? Hmm......

 

Here are some answers. They may not be The Answer? :D

 

1. Say that sunlight consists of about 3%/43%/54% UV/Vis/IR and then go be happy. We note in passing that Wikipedia is just a wee bit too generous with their estimates of the amount of UV in sunlight at 10%. I wonder where we could find that location? It would greatly decrease most of my exposure times.

 

2. 0%/5%/0%. Man, does it ever get dark early there in winter! Just kidding about the values, but maybe Bjørn can tell us.

 

3. Magenta is an additive mix of red and blue light. Magenta is the color resulting from stimulating the human eye with approximately the same amounts of red and blue light, thus simultaneously triggering both the red and blue receptors in the eye/brain. There is no single wavelength associated with magenta. Magenta is one of the many non-spectral colors about which I have been thinking recently for no particularly good reason. But it is kind of fascinating.

 

4. Usually UV shots have longer exposure times than any companion IR shots made during the same shoot. But have you ever used that RG 1000 in a 3mm thickness? Takes a while.

 

5. Who's the best UV website?? Why it's us right here at UVP !!

 

6. Ultraviolet light is the electro-magnetic energy between 100-400 nm, give or take a few nanometers on those endpoints.

 

7. NO. You may NOT photograph anything in UV except for a flower. We decree it to be so! I've told everyone this before but nobody ever listens.....sigh......

Should I add a [humor][/humor] alert?

 

8. Don't know. I've seen mention of early UV film photographs in science paper references.

 

9. Six converted cameras is just about right. Ten may be getting to be excessive. Out of the six, only three are typically in current use. The others just have not been sold yet because who would want an old converted D200 which lacks Live View and only has 10 MP?

 

10. UV torch = UV flashlight = a UV-Led illumination device. And, do please wear your UV-blocking Goggles when using these torches.

See how smoothly I worked in that public service safety annoucement?!

 

11. UV false colour = UV false color. Color in reflected UV photography is a by-product of a camera's Bayer filter together with any color effects from the lens or filter in use. UV wavelengths or UV light mixes, being outside the human visible range, cannot be associated with any human colors because the UV does not stimulate our visual receptors. For most of us anyway.

 

12. Yes, on-board flashes output some IR.

 

13. UVP was started 22 March 2013. We have just turned 5 years old.

 

14. I guess that UVP does not have a Logo because neither Bjørn nor Andrea have ever thought about designing one. Hmmm......should we use purple in it?

 

15. Three (3) UV-capable lenses constitutes a handful for the typical hand. Once you get past that you are headed towards having a boatload full of UV lenses. But who counts?? UV photography is all true madness I tell you!!

 

16. Nobody knows what's down there at 300 nm. My guess is -- not much that you have not already seen at 365 nm. So don't let this "reach" thing prevent you from thinking that you are somehow not making interesting, beautiful UV photographs, OK?

Yeah, yeah, I know, I know. Somebody knows what's down there at 300 nm. But it's not us here. Go dig it out of a research paper. :)

 

17. What factors affect the amount of UV in sunlight? Apparently everything affects how much UV there is in sunlight. Which is Not.Very.Much. But let's be rational and list location, altitude, atmospheric conditions, time-of-day and time-of-year for five good factors and let it go at that.

 

18. If you convert your own camera, you can potentially fry a circuit board or fry yourself. So please be very careful.

 

19. UG for Schott. And U- for Hoya.

 

20. What factors affect the false colour in UV images? Again, apparently everything you touch between subject and final image can affect the false colour finally seen in a displayed UV image. This is why it is rather remarkable that we see a fairly similar UV false color palette across the various Bayer-filtered gear platforms.

But let me list a few actual answers.

  • Converter - not all apps convert your raw image the same way when applying autoscaling, gamma tone mapping or camera color profiles.
  • Demosaicing algorithm - For a given Bayer-filter there is more than one way to demosaic it to produce the color pixels.
  • White balance - an art, not a science. Even when using the best UV-reflective white standards, you can get some variation in WB results. Inherent in the white balance factor is the kind of illumination used to produce the photograph. Each kind of lighting has its own temperature.
  • Lens and Filter - hardware can add its own colour shifts.
  • Color Spaces and Gamut - a very complex subject. Intent alone would take up a few pages to explain its effect on final color.
  • Viewing conditions - often ignored when discussing color results informally but extremely important and necessary when accurately representing and reproducing colors.

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So tell me what do you think we should know about our favorite activity - UV photography? Let's hear your questions!!

 

And I prolly got something somewhere wrong or typo-ed. You know I'll always fix it, so let me know.

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2: Oslo or Svalbard? (In the latter case we may be talking about the average of all starlight--how does its profile compare to the output of a single G-class star?)

 

4: The answer depends on sensing medium and light source (some sensing media are almost blind to IR.)

 

8: I think that that Robert Wood may have made some of the first UV photos, if not the absolute first.

 

10: An oxyacetylene cutting torch puts out loads of UV--so I guess you could call it a UV torch!

 

14: No, you should use ultrapurple in it. Only reflects below 400 nm. As to how to get monitors to do this, well.....

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10: An oxyacetylene cutting torch puts out loads of UV--so I guess you could call it a UV torch!

 

 

10: I would guess that the output spectrum depend on what material is cut. If that is correct we might find a an optimal one for UV-photography.

 

The arc from stick welding is also a strong UV-source. The problem would be the power supply when using it in the field. A local generator might be better than long cables. :)

 

In both cases UV-blocking Goggles will not be enough to protect you! Also, do not forget to bring suitable firefighting equipment.

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#14=http://ultravioletphotography.com/content/uploads/monthly_04_2018/post-24-0-60682800-1524837004.jpg, as appears on browser tab and bookmark?

Maybe. That was a quick hacky to make sure something showed. I could work on it.

 

In the latter case we may be talking about the average of all starlight--how does its profile compare to the output of a single G-class star?

Good one!!

 

14: No, you should use ultrapurple in it. Only reflects below 400 nm.

A logo only UVP members could see would be kinda cool. A secret blacklight signal. Although we'd have to be careful not to scare people as we wave our UV-Led torches and flashlights around looking for it.

 

A local generator might be better than long cables.

We have a generator on wheels. I'm having hilarious visions of dragging it onto the local park to power my welding torch for illuminating the little fleurs I want to photograph in UV. Many melted filters ensue.

As it is, I already need a Pack Llama to carry the huge pile of UV photography gear. (I would consider a Pack Donkey but they always want to eat the flowers.)

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Bill De Jager

Fun quiz, Andrea!

 

4. Usually UV shots have longer exposure times than any companion IR shots made during the same shoot. But have you ever used that RG 1000 in a 3mm thickness? Takes a while.

 

My first answer was the UV photo.

 

But then I began to think about it. You said "all other factors being equal". If we take the word "all" literally.... so if the light source provides equal amounts of light (for the UV and IR sensitivity ranges), the subject is equally reflective in both, the filter in from of the lens provides equal transmittance, the lens provides the same transmittance, the sensor is one that is equally sensitive in both bands (including transmittance from any filters over the pixels), etc., etc., etc., then the exposure should be the same! But gather that's not what you meant. :P

 

6. Ultraviolet light is the electro-magnetic energy between 100-400 nm, give or take a few nanometers on those endpoints.

 

I usually see 10-100 nm being included as the "extreme UV" range. This is an important waveband for imaging the sun's surface from space. https://cseligman.co.../sun/sundex.htm

 

We have a generator on wheels. I'm having hilarious visions of dragging it onto the local park to power my welding torch for illuminating the little fleurs I want to photograph in UV. Many melted filters ensue.

 

'Melted' fleurs, too, even if just from the UV.

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I thought there was a logo, it was just in bee vision.

I use to use 320nm all the time to image aggregates. There is a lot of dust at 320nm. Below you get interesting illumination of proteins and double conjugated carbon bonds. The emmission of tryptophan is about 350nm. But you also get other NADPH and mitochondrial proteins if your looking at cells. The auto fluorescence is quite fun.

Uv light varies, so on a high uv index day it may actually be 10%. But you would need to be in a clean air town. I think the air polution in Mexico city woild get you before the uv. Also higher up may help with less atmospheric filtering. So Colorado, may work. But I don't know.

 

 

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I thought there was a logo, it was just in bee vision.

 

Love it!

If we ever do design a logo, I'll be sure to include versions as seen in IR, Bee Vision, UV+Blue+Green, B410, UVI-VisFluor, UVI-IrFluor and other nifty filtration.


 

You said "all other factors being equal". If we take the word "all" literally.... so if the light source provides equal amounts of light (for the UV and IR sensitivity ranges), the subject is equally reflective in both, the filter in from of the lens provides equal transmittance, the lens provides the same transmittance, the sensor is one that is equally sensitive in both bands (including transmittance from any filters over the pixels), etc., etc., etc., then the exposure should be the same! But gather that's not what you meant.

 

oh la!

 

So anyway.....

I got to wondering if your scenario is feasible? We certainly can have subjects which are equally reflective across UV/Vis/IR -- the Labsphere standards, for example. And we could probably select UV and IR bandwidths where our converted cameras, appropriate filters and a lens like the CO60 are equally responsive. So it is the illumination which is the really big factor, isn't it?

 

Well no surprise I suppose to anyone who has been fooling around with this stuff for a while.

 

Outdoors in strong summer sunlight even with a boost from my SB-14 flash mod, the UV exposures are always longer than the corresponding Vis or IR photos made with no supplemental artifical light boost. Indoors in a studio setting I suppose it is possible that with multiple UV lamps and UV flashes, we might be able to get equally matching amounts of UV/Vis/IR light.

 

So, Bill, go for it!!! :D :D :D

 

added: Bjørn's Broncolor might qualify for producing equal amounts of light in the hypothetical scenario above. I recall hearing thunder every time he fired that thing. It puts out a LOT of uv.

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