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UltravioletPhotography

Hello from Canada


LC2

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Hello! Glad to be here :)

 

I work as a forensic image analyst for a police service in Ontario, Canada. Part of my duties includes researching and teaching forensic photographic techniques. A couple years ago, I was tasked with procuring a camera system capable of photographing both the UV and IR spectrums. I put together a good camera kit for our forensic unit: a Nikon D7100 converted to full spectrum, Jenoptik UV-VIS-IR 60mm APO macro lens, Baader U-Filter and a couple IR pass filters. However I've been having trouble with the UV spectrum (specifically, light sources and and ideal (forensic) subject matter for reflected UV). I am hoping you guys will be able to help me, as you all seem incredibly knowledgeable!

 

I have been doing some testing, and I would like to get your thoughts... apologies in advance if I should be posting my question in a different thread... I am very new to forums.

 

What's puzzling me is the different results I am getting with a LED light source (PowerTac NH375, rated at 365nm) versus a regular (UV filter not removed) speedlight (Nikon SB-910). My test subject was a piece of paper that I had written on with a variety of pen ink brands/types/colours. With the speedlight as my light source, some of the inks disappear. But with the LED torch, the inks did not change... I would expect the LED torch to produce better results than the speedlight (and when I say better, I just mean I would like to see visible changes amongst the different inks, like I did with the speedlight, but even more pronounced).

 

I plan to try out our Polilight 400 (forensic light source, 400 watt metal halide lamp - the UV output is 350nm, 80nm bandwidth), but I haven't had a chance yet...

 

 

Thank you in advance!

Lieah.

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Hi! Nice to meet you! It sounds like you have a fantastic setup. I wish I had the money for a Jenoptik.

 

Based on what people have done in the past, it's probably best to make a separate thread for that specific question. We have a "forensic" subforum here where you could put it. I don't know the answer to your question exactly because it hinges on the emission spectrum of that speedlight and also the absorption spectrum of the inks, but we probably have other members who could help with that. My specialty around here is computational processing of images, so if you have questions in that area, I might be of more use there. You can see some of my investigations here and here and here.

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Thanks for your reply Andy! I will be sure to post my question in the forensic subforum, that totally makes sense.

 

I just checked out the links for your processing endeavours, and all I can say is WOW! I haven't even thought that far ahead yet, about the processing possibilities... I plan to (hopefully, depending on funding) learn MATLAB, as I see it as the next step in my career. I just work in Photoshop right now, but I'm starting to feel a bit limited, as I start to expand my horizons in imaging. I've been working in forensics for about 12 years now, so I think it's time to up my game :D So it'd be great if I could ask you about that, once I know enough to ask questions :P

 

And yes I agree, our gear is great... we had a big budget that year ;)

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Before MATLAB, a good background in linear algebra (and preferably calculus) is really needed to get the most out of it. I tutor that sort of thing online, if you need a brush-up. If you are starting fresh you should take a course or two at a masters level. If you want to discuss this, PM me using the board's system. We should not talk about it further here.
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Welcome to the UVP community. We would love getting more contributions in the field of forensic photography, for sure.

 

Indeed there are a lot of members with vast knowledge here and taken together such resources make UVP the place to ask about anything UV (and photography).

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Welcome to the UVP community. We would love getting more contributions in the field of forensic photography, for sure.

 

Indeed there are a lot of members with vast knowledge here and taken together such resources make UVP the place to ask about anything UV (and photography).

 

Thanks so much Birna :)

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Hello and welcome to UVP. I hope we can help answer some of your questions and that you find good info here.

 

I've responded to your question over on the topic you started. :)

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