• Ultraviolet Photography
  •  

Jonathan made the MaxMax newsletter

UV Camera
6 replies to this topic

#1 Andy Perrin

    Member

  • Members+G
  • 4,408 posts
  • Location: United States

Posted 27 February 2021 - 16:52

Quote


One of our customers is Dr. Jonathan Crowther ( https://jmcscientificconsulting.com/ ) from the UK who has been working with UV light for close to two decades. Part of his Bio:



I graduated from Durham University with a BSc in Chemistry in 1994, and went on to do a PhD in Surface Modification and Analysis which I completed in 1997, and loved the research so much that I stayed on for an extra 3 years as a Post Doctoral research assistant. During this time I developed a strong Analytical chemistry background with a wide variety of surface analytical techniques (XPS, Auger, ToF SIMS, Raman, ATR-IR, SEM and TEM, AFM) for materials analysis, along with cold plasma treatment of materials for the manufacture of metal surfaces and ultra low energy materials.


It is the cross discipline background I have from working at the boundaries between chemistry, physics and engineering, which I have now applied to my assessment of skin. I apply a strongly analytical approach to my work, and am known for being open and impartial and working with the highest integrity. I’m also a scientist through and through, and am driven to understand how the world works. As such if you have an interesting problem where you think I may be able to help get in touch.


Specialties: Skin assessment methods, Confocal Raman spectroscopy, clinical testing of skin care and hair removal products, imaging, photography and microscopy (visible, IR, UV and fluorescence), in vivo and in vitro method development, cosmetic claim support, clinical study design and execution, scientific communication to a wide ranging audience, publication writing.



Dr. Crowther bought a Nikon D850 camera from us converted to monochrome and fitted with a fused silica coverglass. This is a rather rare beast of a camera which is only available from us. He also owns some UV capable lens like the Nikon 105mm UV lens and an ultra rare (about 40 made) Asahi Ultra Achromatic Takumar UV 85mm lens.


Dr. Crowther wrote on his blog about his capturing images in the UVC region (100-280nm). With his permissoin, we repost his blog post.


You can jump directly to his post by clicking here


You can go to his home page by clicking here.



UVC photography at 254nm – into the darkness….


With some experiments, the end result is fairly easy to predict. Others, not a chance. With this piece of work I had no real idea what to expect, or even whether I’d be able to see anything at all. Essentially, it was this – can I image at 254nm using the equipment that I already have?


To start with some background. I have an interest in UV photography because of my work on sunscreens, and as part of my research in the area, I’m always looking to push the limits of what can be photographed with the kit that I have. My monochrome converted Nikon d850 camera has a really nice sensor for UV, visible and IR imaging, and I was able to measure the spectral response of it down to 280nm which is the limit of my measurement capability. At 280nm there was still a little bit of sensitivity there, but it had dropped to almost nothing and I’d assumed (always dangerous) that below 280nm it would be essentially zero. When it comes to UV imaging, very often specific wavelengths are discussed, as they correspond to lines in the mercury emission spectrum. 365nm and 313nm are quite strong emission lines, and they lay within the UVA and UVB regions respectively. However drop below 280nm and you get in to the murky world of UVC. While there is UVC in light coming from the Sun, it does not reach ground level as the atmosphere blocks it. However there are artificial sources of UVC. Welders are often exposed to it due to ionisation of the air and metal, where it can result in bad burns to skin and damage to the eyes, and in our new Covid related world UVC sterilisation of surfaces is becoming more and more widespread. This got me wondering whether I could break through into the UVC region and capture photos at 254nm which is another one of the strong mercury emission lines.


This would be no simple task. Even if the camera was sensitive enough to capture an image there, the sensitivity it has would be extremely low, meaning that the presence of any other wavelengths would completely swamp the signal from 254nm. Therefore really good filtration would be needed. For the filter I used a 254nm bandpass filter I got from a Sirchie forensics camera a while back. While it has relatively low transmission at 254nm, it has good out of band blocking, and it meant I didn’t need to spend a fortune on a new filter. Any glass in the lens would absorb the UVC, so I chose the 105mm Rayfact UV lens for this experiment – it has quartz and calcium fluoride lens elements instead of glass and is good for using down to around 220nm. Camera was my monochrome converted Nikon d850 from MaxMax. When I had this made I requested a fused silica sensor window, in case I ever wanted to go below 280nm. Light source was an interesting one. In the end I got a pair of 8W 254nm UVC fluorescent tubes from ‘a well known internet auction site’. These are normally used for sterilisation of water, but they fit my UVP UV lamp so I thought I’d try them out. Subject wise, a small vase with a couple of feathers and a Spectralon 20% diffuse reflectance standard was chosen.


For imaging, everything was done in a dark room, and the subjects were placed in a box painted with Semple Black 3.0 paint which has low reflectance and low fluorescence, to cut down on stray light. I wore UV protective glasses (in fact that point deserves capitals – I WORE UV PROTECTIVE GLASSES – please do not play around with UVC lights without wearing these). In addition to imaging the subject using the 254nm filter, I also took another image with a Schott WG305 long pass filter in front of the 254nm filter, to check for stray light getting through.


Right, that is far too much waffle. Was it possible to capture a UVC image with this setup? Well, yes it was, and this is what it looks like.




#2 colinbm

    Member

  • Members+G
  • 2,741 posts
  • Location: Australia

Posted 28 February 2021 - 02:39

That is an interesting article by Jonathan, & thank you to Andy for posting it.

#3 dabateman

    Da Bateman

  • Members+G
  • 2,999 posts
  • Location: Maryland

Posted 28 February 2021 - 08:34

Yeah I got that news letter and thought it was funny.

Good for Jonathan to get some PR. He does do good work.
I think Dan is a good guy. but some Only speak in the writing is a little off.

Edited: reread the blurb and Dan is correct. The Monochrome converted D850 with fused silica glass is only available from him. So I edited this. The language is well used in the writing to be correct.

Other available cameras or other suppliers of fused silica cameras aren't mentioned but are available.

It took a couple months to convince him to get a monochrome pi HQ camera. But being able to do UVC video I think will be fun in the future. Just extremely dangerous with kids running around.

Edited by dabateman, 01 March 2021 - 05:30.


#4 colinbm

    Member

  • Members+G
  • 2,741 posts
  • Location: Australia

Posted 28 February 2021 - 10:20

Just saw this good video on UVC safety at home...
https://www.youtube....nnel=CureUV.com

#5 dabateman

    Da Bateman

  • Members+G
  • 2,999 posts
  • Location: Maryland

Posted 28 February 2021 - 12:43

Colin cover up indeed.
But placing your food in a ziploc bag and shinning a UVC lamp on it will not sterilize your food. That bothered me. I am also not at all surprised that the dark coat with 65% polyester leaked UV. You should always wear 100% cotton. Polyester is transparent to uv. Thus why its good material for Lee filters. If you look closely at the spectra provided, you can see uv and IR bumps with most of the color filters.

#6 JMC

    Member

  • Members+G
  • 1,363 posts
  • Location: London, UK

Posted 28 February 2021 - 15:19

Ooooh, my ears were burning. Dan asked me if he could share a page from my blog in his news letter so I said yes. A bit of free advertising is always nice.
Jonathan M. Crowther

http://jmcscientificconsulting.com

#7 Andrea B.

    Desert Dancer

  • Owner-Administrator
  • 9,110 posts
  • Location: UVP Western Division, Santa Fe, New Mexico

Posted 01 March 2021 - 18:28

It was nice to read about you, Jonathan. :cool:
Andrea G. Blum
Often found hanging out with flowers & bees.