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UltravioletPhotography

Real-Time Near-UV Viewing with B/W CCD Cameras


prutchi

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Real-time viewing of scenes in the near-UV has applications in creative UV photography, astronomy, and forensics . There are a number of CCD video cameras optimized for ultraviolet imaging that use sensors that are specifically designed for this application. Many of these are based on Sony’s ICX-407BLA CCD chip, which is a Lumogen-coated sensor usable down to 200 nm. Unfortunately, these cameras are not inexpensive (over $3,000).

 

However, Sony makes one analog black-and-white machine-vision camera that is UV-sensitive which is sufficiently affordable that it has attracted some attention for use in creative, astronomical, and forensic near-ultraviolet photography. The XC-EU50 camera has a peak sensitivity around 369 nm, and sensitivity down to 300 nm. The camera produces analog video with 768 (H) x 494 (V) effective pixels, so at 0.38 megapixels, it is nowhere near DSLR resolution, but this is not bad at all given its sensitivity in the ultraviolet. The camera retails for around $700, but surplus XC-EU50 cameras often show up on eBay® for a fraction of that price. However, the XC-EU50 is not as special as its specifications would make you believe, and DIY alternatives can be made at very low cost.

 

The following Technical Note discusses my experience with the XC-EU50: UVIRimaging_dot_com TN 2016-2 - Near-UV BW CCD Video Cameras

 

Cheers,

 

David

www.UVIRimaging.com

post-62-0-20397600-1468609447.jpg

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Andy Perrin
That's what I was going to ask. For video, the requirements for noise and so forth are much more lenient (the eye and brain are kind to moving images), so any of our cameras ought to take decent video in UV.
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Andy Perrin
Sensitivity... Please take a look at the attached graph. You can see at much lower illumination levels and with smaller apertures than with a DSLR.

Yeah, but it's rather expensive if you already have a converted camera! It might be interesting for lower-UVA/upper-UVB imaging, though, which is something I'll certainly keep in mind. (Edit/Addition: And I noticed at the bottom you say it can be matched with a cheap Videology board, which is interesting.)

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I drew it based on my comparison of normalized sensitivity curves (Sony's published data vs. my measurements of a DSLR sensor's sensitivity).

 

I did this some time ago, and meant to include it as part of my new book on near-UV photography, but ended up having to cut more than half of the material due to editorial constraints. I'm releasing the material that I cut out as posts and/or technical notes. I'll try to find the source Excel spreadsheets to share with the group.

 

Cheers,

 

David

www.UVIRimaging.com

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Yeah, but it's rather expensive if you already have a converted camera! It might be interesting for lower-UVA/upper-UVB imaging, though, which is something I'll certainly keep in mind. (Edit/Addition: And I noticed at the bottom you say it can be matched with a cheap Videology board, which is interesting.)

 

Yup! $4.95 camera from www.skycraftsurplus.com/ccdvideocamera-board.aspx with a C-mount Edmund Scientific UV lens and Baader-U or UG-1/BG-39 performed as well as XC-EU50. I used the Edmund lens for the comparison just to eliminate any attenuation by the lens, however, a cheap CCTV lens works just fine.

 

Cheers,

 

David

www.UVIRimaging.com

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Andy Perrin
Did you test it in the shortwave UV (shortERwave...) region at all (I mean 300-325nm)? You would need a different filter combo, though, but you could get one from Omega on ebay. I don't think there's much point in making a new setup for the close-to-400nm region because our usual cameras do fine there, especially for moving images, as I said above. But I'm quite curious about UVB imaging.
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.... For video, the requirements for noise and so forth are much more lenient (the eye and brain are kind to moving images), so any of our cameras ought to take decent video in UV.

 

They do, but if one wants anything else than b/w UV video, the better option is using a camera capable of setting a decent UV false-colour balance in-camera. To this end I'm using the Panasonic GH-2. Certainly not the world's greatest achievements in terms of camera technology, build, and robustness, but otherwise works well enough.

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Yup! $4.95 camera from www.skycraftsurplus.com/ccdvideocamera-board.aspx with a C-mount Edmund Scientific UV lens and Baader-U or UG-1/BG-39 performed as well as XC-EU50. I used the Edmund lens for the comparison just to eliminate any attenuation by the lens, however, a cheap CCTV lens works just fine.

 

Cheers,

 

David

www.UVIRimaging.com

 

Great, 5 dollar camera. So if I buy it, I can take pictures with it right away, without spending time and money on anything else, right?

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Andy Perrin

They do, but if one wants anything else than b/w UV video, the better option is using a camera capable of setting a decent UV false-colour balance in-camera. To this end I'm using the Panasonic GH-2. Certainly not the world's greatest achievements in terms of camera technology, build, and robustness, but otherwise works well enough.

I think all of our cameras do that? Why would one choose a camera for UV work that can't set a UV false-color WB in the camera in the first place? It was one of the things I looked for, anyway, based on comments in this forum.

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Sensitivity... Please take a look at the attached graph. You can see at much lower illumination levels and with smaller apertures than with a DSLR.

 

Cheers,

 

David

www.UVIRimaging.com

 

Does that graph represent a stock DSLR or a converted DSLR? It would seem to me that a converted DSLR is sensitive to lower UV than what that graph shows.

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Did you test it in the shortwave UV (shortERwave...) region at all (I mean 300-325nm)? You would need a different filter combo, though, but you could get one from Omega on ebay. I don't think there's much point in making a new setup for the close-to-400nm region because our usual cameras do fine there, especially for moving images, as I said above. But I'm quite curious about UVB imaging.

 

I didn't, but that would be an interesting test. I do have narrowband filters available for that range. I'll try it out when I get some time to do it and report back.

 

Cheers,

 

David

www.UVIRimaging.com

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Does that graph represent a stock DSLR or a converted DSLR? It would seem to me that a converted DSLR is sensitive to lower UV than what that graph shows.

 

Converted Canon T1i. IR/antialias filter replaced by high-quality UV-to-IR window. Sensor chip window, microlens array, and Bayer color filters left untouched.

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Most of the DSLRs we use now are indeed more sensitive in the lower UV region than that Canon T1i.

There is more than one UVP member routinely shooting at a 340nm peak with their current converted DSLR or Mirrorless body and an Omega (or other) filter.

 

******

 

When we were shooting in the desert, I watched Bjørn use his Lumix GH3 video as a UV viewer. Worked good. But of course there are situations where it would not work as well as it did there.

 

*****

 

Why would one choose a camera for UV work that can't set a UV false-color WB in the camera in the first place?

 

(1) Image quality

(2) Capability of using UV-dedicated lenses

(3) Image quality

(4) Image quaility

This is why I use Nikon DSLRs. Good IQ (wide dynamic range, good high ISO, low noise) and ability to use the F-mount UV-Nikkor and Coastal 60. Nikon DSLRs don't set in-camera UV false-colour WB, but it doesn't matter. It is simply a one click fix in the converter/editor.

 

There is nothing sacred about false-colour WB in UV. White balance is a concept from the Visible world. We usually only set false-colour WB in UV to produce a uniform look in documentary photos. In other UV photo work, anything goes. That's my rant and I'm stickin' to it!! :lol: B)

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I think all of our cameras do that? Why would one choose a camera for UV work that can't set a UV false-color WB in the camera in the first place? It was one of the things I looked for, anyway, based on comments in this forum.

 

No Nikon can do that, just to name one example.

 

However, as UV video tends not to be the first priority for regular UV photography in my case, most of my UV still images have been captured (in RAW format) by "incapable" systems, then correctly w/b balanced later in the processing work flow. This has the added advantage of giving total user control of the end result.

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Hi!

 

I think that the point of my original post was missed, or maybe misunderstood. I feel that the question “why do it any other way when my DSLR does what I want to do just fine?” is too narrow minded. I look at it as asking “why would I want to learn about any other tools when I have a great hammer?”

 

This might be true, if all you do is “hammer nails”, but there is more to UV photography than false-color renditions of nectar guides.

 

UV-capable video cameras are indeed the right choice for many other UV viewing and imaging applications (e.g. machine vision, industrial inspection, forensic evidence sleuthing, solar astronomy, etc.) where a DSLR would be a very poor choice.

 

My experiments with the XC-EU50 and suitable substitutes (at $4.95 !!) relate to this broader range of applications.

 

Cheers,

 

David

www.UVIRimaging.com

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Andy Perrin

No Nikon can do that, just to name one example.

 

However, as UV video tends not to be the first priority for regular UV photography in my case, most of my UV still images have been captured (in RAW format) by "incapable" systems, then correctly w/b balanced later in the processing work flow. This has the added advantage of giving total user control of the end result.

Interesting — I didn't know that! I suppose as long as you can see some kind of image on the camera then live view works for focusing.

 

David- For me the issue is simply money. To make use of that extra sensitivity at short wavelengths, I would need a quartz lens. Putting a several hundred dollar lens on a $5 low resolution camera doesn't make a lot of sense to me. And if I'm just interested in the near-400nm region, I have something already paid-for that works. While I can certainly imagine how this info might be useful to SOMEone, it's just not for me. That doesn't mean I don't think it was a good post! Maybe someday I'll have a use for it.

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David, yes you are right!! Forgive us! We were all a bit too single-minded there for a minute. I think that because there is less experience with the kind of set up you have shown, we focused (oh la) on thinking about it for our typical photo uses rather than envisioning the gear used in experiments we have never tried.

 

And of course we veered off topic, a common occurence. :D

 

Added Later: I really do find it extremely interesting to read about such gear.

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Thanks Andrea and Andy!

 

I do realize that my interests are a bit outside the mainstream, but hopefully the results will help someone.

 

Cheers,

 

David

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