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UltravioletPhotography

Monochrome DSLR imaging UVA-VIS-NIR


Herra Kuulapaa

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Herra Kuulapaa

In addition to my introduction behind the link below I'm writing more about experience with monochrome modified cameras.

http://www.ultraviol...1805#entry11805

 

I started experimenting with camera monochrome modifications a few years ago mainly by astrophotography purposes to improve the response of deep red H-alpha emissions. Process is to delicatly remove RGB bayer matrix to make every pixel on sensor equally sensitive to all color light. In short it has worked very well on Nikon/Canon /Sony cameras.

 

Here is a one sample of mono modified sensor response. I didn't have a proper wide spectrum light when I tested this so UVA range may be reduced to what it is in real life.

http://www.kuulapaa.com/Spectra/D5100_resp.jpg

 

I will post some UV samples soon.

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Herra Kuulapaa

Some IR comparison from last summer:

http://www.kuulapaa.com/IR/IR_2.jpg

 

Missed the IR focus in hurry I didn't notice until afterwards:

http://www.kuulapaa.com/IR/IR_A.jpg

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Herra Kuulapaa

Very impressive images Oleksandr !!

 

I'm a beginner and learning new things on UV practically every time I click my camera. Slowly getting along :)

Unfortunately it's still so early spring that we have no natural flowers in Finland. But something still:

 

http://www.kuulapaa.com/UV/Kukat_VIS.jpg

 

http://www.kuulapaa.com/UV/Kukat_NIR950.jpg

 

http://www.kuulapaa.com/UV/Kukat_UVA.jpg

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Even though is is still cold in Stockholm too, winter aconite (Eranthis hyemalis) has been flowering for past two weeks, and it is a good subject for UV photography.

 

I do not know if I had ever posted this shot on UVP, can not find it in searches:

 

http://www.holovachov.com/img/s/v-2/p1495191300.jpg

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Herra Kuulapaa

Simply beautiful image with snow and everything!

 

Here's a combination of UVA and VIS images above.

http://www.kuulapaa.com/UV/Kukat_VISUV.jpg

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Herra Kuulapaa

I'm a tester type, imaging tester :)

 

http://www.kuulapaa.com/UV/Hedelmat_VIS.jpg

 

http://www.kuulapaa.com/UV/Hedelmat_UV.jpg

 

http://www.kuulapaa.com/UV/Hedelmat_VISUV.jpg

Lesson learned, it may not be the best idea to take images hand held. Alignment was a slightly difficult task... :)

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Herra - a couple of questions.

What UV-pass filter are you using?

And I'm curious how are you making the composite VIS + UVA? Is this the UV as a luminosity layer over the Visible frame? I've made some composities like that in the past and enjoyed the result.

 

Nice to see the tulips and fruit in UV. I remember that I made some UV tulip photographs some years back and never posted them. I should try to find them!

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Andy Perrin

An interesting thing about the banana is that it absorbs visible blue/violet light very strongly, yet when you "cross over" into the UVA, you see quite a bit of reflection. I know that absorption in one band isn't any guarantee of absorption above or below, but the switch seems to be dramatic in this case. I want to get some bandpass filters for blue and just above and see what is going on there now.

 

[Edit to add a bunch of research on what's going on here.]

It seems that carotenoids are what makes bananas yellow, and I found a full breakdown of the composition of the pigments in the book "Biochemistry of Fruit Ripening" edited by G.B. Seymour, J.E. Taylor, Gregory A. The table from that book (p. 91) shows it to be:

post-94-0-59284000-1458539347.jpg

 

The dominant chemical appears to be lutein, which has an absorption spectrum that I snagged from this paper:

post-94-0-45749900-1458539570.jpg

 

Ditto beta-carotene (ref: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC438021) :

post-94-0-25938100-1458540181.jpg

 

You can see the sharp drop in absorption when you hit the UVA!

 

---

Separately, this article suggests something else interesting might happen with bananas under UVIVF:

http://www.rsc.org/c...er/23100802.asp

Paper link: http://www.ncbi.nlm....les/PMC2912500/

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Herra Kuulapaa

Impressive info on the pigments Andy!!

 

Herra - a couple of questions.

What UV-pass filter are you using?

And I'm curious how are you making the composite VIS + UVA? Is this the UV as a luminosity layer over the Visible frame? I've made some composities like that in the past and enjoyed the result.

 

Nice to see the tulips and fruit in UV. I remember that I made some UV tulip photographs some years back and never posted them. I should try to find them!

 

I'm using a simple Schott UG1 filter with scavenged IR filtering. There is a clear IR leak though and I can see it so I'm in process to improve the IR filtering. Also the flash I used was not perfectly filtered so the imaging may be slightly leaky.

 

About the composite, I'm coming from astrophotography scene and I'm familiar with tools used there. It's common to shoot colors separately and then add a luminance data on RGB. Just like you said :) Despite of the aligment process the tulip image suffers from channel aligment errors so the channel mixing image doesn't look that good (and I may have mixed the channels wrong anyway):

 

http://www.kuulapaa.com/UV/Kukat_Bee.jpg

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We have lots of info about filtration and filter stacks.

 

Run this search tag to find a list of filter topics: Filters

 

Our member Cadmium has a lot of knowledge about UV filter stacks. Here is one such post:

http://www.ultraviol...dpost__p__11695

 

Also see the Filter Sticky for other suggestions about UV-pass filtration such as the BaaderU, PrecisionU or AndreaU.

Sticky :: UV/Vis/IR Filters

 

Here is a specific UG-1 chart from Cadmium showing effects of different IR-blockers in suppressing the IR leak:

http://www.ultraviol...ndpost__p__7838

 

*****

 

I had thought that the UV tulips in post #8 did not look quite dark enough. But that is understandable with the UG1 if that filter is not properly IR-blocked. Indoors the IR leakage would be somewhat less of a problem if there was little ambient window light or incandescent light. That's why your fruit photo looks better.

 

As you have noted, there can be shifts between the UV and the Visible frames depending on several factors. The lens used, slippage of the tripod setting, wind motions, flower droop, and so forth. I'm sure you are already aware of these factors! :)

 

Do you plan to do some UV astrophotography? I'm so fascinated by astrophotography. It's quite amazing what can be captured. Your work (as shown on your website) is beautiful and very interesting.

 

******

 

We have other Banana topics !!!

Andy, that is great banana pigment info. Remind me to ask you whenever I want any research done. :lol:

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Herra Kuulapaa

Thank you Andrea :)

 

I'll look into the links you provided. Such an interesting information!

 

I have some plans using UV sensitivity on sun with Calcium band 393nm in addition to regular H-alpha 656nm. Most likely the low quantum efficiency at UV range reduces the usefulness of UV in astrophotography, but the nearest star is on my list at least :)

 

Here are couple of more off topic astrophotos. https://www.flickr.com/photos/herrakuulapaa/ There are also some high speed ballistics images, but they're are not too offensive - I hope.

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Herra Kuulapaa

Testing continues - now with better alignment

 

http://www.kuulapaa.com/UV/Hedelmat_II_VIS.jpg

 

http://www.kuulapaa.com/UV/Hedelmat_II_UVA.jpg

 

http://www.kuulapaa.com/UV/Hedelmat_II_VISUV.jpg.

 

I need to focus next time in prevention of the highlight shine.

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Looking good, Herra.

Here is one of my efforts with fruit: Satsuma Tangerine

Fruits can make beautiful photographic subjects.

 

Typically we post photographs on UVP with some info about the equipment used. This is, of course, not a requirement, but it is useful to others. And helps us all to give better suggestions, when asked or as needed.

If you are so inclined, please let us know camera + lens + filter + lighting.

 

The highlight shine is natural feature of these fruits and flowers in either visible or UV light. So I'm not sure you really need to deal with it?? What was your thinking there when you made that statement about preventing it? The highlights could be pulled back in an editor perhaps.

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Herra Kuulapaa

Thank you Andrea,

 

All of the images above have been taken with a combination of monochrome Nikon D600 (so called astromono) and a regular Nikon D800. So far I've used 50/1.8G lens, bu the latest flower test below was shot with 50/1.8D in both cameras. That helped me do the camera switching. Filter I've been using is the Schott UG1 and a surplus IR filter, but the IR leakage is clear so I need to update it. Latest images were taken with Yongnuo Flash. Settings were ISO400, 1/60s flash sync with f/3.2. You're right about the highlights, they're part of the deal. I'm a big fan of your macro shots!

 

I visited a flower shop today and took briefly couple of pictures. This tread is quickly becoming an image show, but I think it's a nice method to illustrate things.

 

http://www.kuulapaa.com/UV/Kukat_1_VIS.jpg

 

http://www.kuulapaa.com/UV/Kukat_1_UV.jpg

There is an interesting petal in one of the daisies.

 

http://www.kuulapaa.com/UV/Kukat_1_VISUV.jpg

 

http://www.kuulapaa.com/UV/Kukat_1_Mixed.jpg

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Given that you are stacking an image from the D600-mono with an image from the D800, I am totally impressed with how well the two are matching up. When using the same camera for both visual and UV images with only a filter change between shots, I do not always manage to get matching frames.

 

I wonder how the D600 UV exposure settings will change from f/3.2 for 1/60" @ ISO-400 when you use a stronger UV-pass filter?

 

Another interesting point is that you are not using a particularly UV-capable lens. I have an old manual 50/1.8 AIS. I don't think I've ever tried it for UV work.

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Herra Kuulapaa

Given that you are stacking an image from the D600-mono with an image from the D800, I am totally impressed with how well the two are matching up. When using the same camera for both visual and UV images with only a filter change between shots, I do not always manage to get matching frames.

 

I wonder how the D600 UV exposure settings will change from f/3.2 for 1/60" @ ISO-400 when you use a stronger UV-pass filter?

 

Another interesting point is that you are not using a particularly UV-capable lens. I have an old manual 50/1.8 AIS. I don't think I've ever tried it for UV work.

 

It is very difficult and I need to compromise with croma. I'm in process to test a human subject with same processing method (UV luminance), fingers crossed..

I believe I'd end up using a quite bit longer exposure time if used a narrower filter. In fact it would be very interesting exercise to see if I would be able to retain the 1/60 sec exposure with higher ISO. But first I need to get rid of the IR leak. It would be also very interesting to test a proper UV lens instead of 50mm/1.8 D/G models.

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I'm thinking that the lens testing is slightly less important than the filter testing. That is, before you go much further with your explorations, make sure that you are shooting a "proper UV" without excess visual or infrared light contamination. Generally speaking, we want NO infrared contamination. And in the visible band, only a small amount of violet or violet-blue is acceptable. With a monochrome UV camera it seems likely that it is more difficult to determine whether you have violet or violet-blue visible light being recorded? (Also this is hard to know with a colour UV camera.) But IR contamination will be readily apparent when you photograph a known, very dark UV-absorbent subject and see that it appears less dark in your photos.

 

Did I mention using a Sunflower as a test subject? The common Sunflower in UV has a dark UV-absorbent ray band surrounding the central disk. The rays are otherwise UV-bright. Here in the US we can find Sunflowers at the florist or the grocery store sold as cut flowers. I don't know if these are available in Finland.

 

BTW, I liked your channel stack above. It looks like maybe you put the UV into the red channel?

 

In photoshop, mismatched edges can be sometimes be cleaned up a bit when frames don't match. (Although I'm sure you already know this!)

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Herra Kuulapaa

Yes, flowers looked much better with UV in red channel than in blue/green swab :)

 

I think I have identified couple of issues, both related to lens/filter stack I'm using. Like you actually already mentioned. In the Mono D5100 thread I wrote that I cannot see as large improvement as I expected when moving from full spectrum to mono sensor. Main issue is the UV absorption of the lens and IR leakage of IR block. Well, it's a budget setup so far, but I need to address the IR filter issue.

 

I can also reduce the post process boosting of dark areas to keep UV base level, well, at the base, but the lens transmittance issue is much harder and costly to fix. Also before taking care of that it makes little sense changing filtering from UG1 to U340 etc due to the limited response under the 350nm :(

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No, don't change to U-340 because any added IR-blocker (which passes Visible + UV light) will move that 340nm transmission peak to the right back towards the 360nm peak. We do not currently know of any IR-blockers which don't do this.

 

You can find UV-capable, inexpensive, old manual 35/3.5 lenses on Ebay with a little searching and a little patience. Look for a 35/3.5 with a T2 mount so that it can be adapted to provide infinity focus on a converted Nikon body. Other possible lenses are listed in the Lens Sticky. Some are still very inexpensive.

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Herra Kuulapaa

Thanks again for the advise Andrea :)

 

I received some VIS filtering today for my flash and now it's much more user friendly. Well, actually it's user friendly, but not subject friendly due to an almost invisible flash. It works fine though.

I had oldish grapes and decided to take a couple of test pictures.

 

Nikon D800+D600m combination with 50/1.8G and SB-700/YN560-III flashes, UV was taken f/5, 1/40s sync with ISO400, full power.

http://www.kuulapaa.com/UV/VR_RGB.jpg

 

http://www.kuulapaa.com/UV/VR_UV.jpg

 

http://www.kuulapaa.com/UV/VR_VISUV.jpg

Oh Boy they look delicious!!

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