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UltravioletPhotography

Hello from Dubai


Chris Rooney

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Hi all, thank you for accepting my application mods..

I am a camera and lens engineer in a Dubai rental house, we have been asked to provide equipment on a skincare commercial to show sun damage, I'm sure you all know the type, enhanced blemishes etc.. We hope to use a Red Weapon Helium with a modified OLPF ( full spectrum), and UG11 and hot mirror filters. I have found a manufacturer in China who will make the UG11 in cinema sized 4 x 5.6" and should start experimenting when they arrive. As for lighting I was going to try the sun as it is not in short supply here smile.png . Really excited as it is something I haven't been asked in 30 years working this industry, any advice is much appreciated and welcome, I have done some research on this forum, very informative, thank you.

 

Chris R

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Welcome. Blimey that's a hell of a camera. I work in the skin measurement area, on the measurement and imaging of skin, so would be interested to see how your work goes. What lens are you planning on using - not sure whether you are aware, but most modern lenses aren't great for UV as the coatings and adhesives block most of it.
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Firstly, welcome to UVP !

 

Secondly, at the suggested price for that camera system, adding a UV-nikkor/Rayfact/Coastal lens would almost not be noticed ....

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We hope to use a Red Weapon Helium with a modified OLPF ( full spectrum), and UG11 and hot mirror filters. I have found a manufacturer in China who will make the UG11 in cinema sized 4 x 5.6" and should start experimenting when they arrive.

 

Chris R

 

Hi Chris and welcome to our little world!

 

The UG11 alone cannot be used for UV-photography as it transmit some IR-light too.

I hope that the UG11 will be the real Schott material and not some "equivalent" copy made in China.

They often are less well defined and less efficient in transmission and attenuation of different parts of the spectrum.

 

Please observe that the UG11 has transmission in the IR range too.

Also, the camera sensor has a much higher sensitivity for IR than for UV.

With the UG11 only your film will be almost all IR.

 

To solve this you need to stack the UG11 with a second filter that surpress the IR-part of the spectrum.

A sheet of Schott S8612, 2mm thick is rather optimal.

Other filter materials as Schott BG40 2mm or thicker might be OK too.

 

If the Chinese filters fail to work properly for you, a member here "Cadmium", Steve Smeed is running a company specialising in optical filters, UVIROptics.

He is often open to custom jobs for filters if he has the raw material in reach.

You could try to PM him and see if he can help.

I have bought most of my filters for UV-photography from him and never been disappointed with them.

 

Good luck with your project.

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Welcome to UVP, Chris. Your project sounds interesting. And is quite topical these days. We have other members here who have worked in photobiological areas as researchers, dermatologists or photographers. Although I am not at all knowledgeable about the specifics of video cameras, I think that you would still have the same basic requirements as we do for our DSLRs and mirrorless cameras.

  • A video camera, like any still camera, must have a sensor receptive to UV with no internal UV or IR blocking filtration. We have that filtration easily removed from our still cameras, but I'm not knowledgeable about how such UV/IR-blocking filtration is used in video cameras.

  • The video lens must transmit UV in at least the 360-400 nm range, although for that I would ask any of our photobiology members to weigh in on whether 370-400 nm would be sufficient. If you haven't already, please do check out our portraits section to see what to expect for how people look in UV. UV People

  • The filter system must block all contaminating IR and visible rays. If your Red is fitted with an internal UG11 (...this was not clear to me from your post...), then you will also require some type of blue-green glass on the lens to block the IR. Ulf has covered this well in the preceding post. One of our filter glass experts here here on the forum, member Cadmium, could recommend optimal thicknesses for stacking UG11 with an S8612 blocker. I'm not sure if he can cut large filters like you require, but he could let you know. Granted you have more than enough sunlight in Dubai for good UV photography, but you will need to carefully consider the thickness of the filtration system to ensure it does not cut down your incoming light any more than necessary.

  • How do you focus? Now, that's a thing I don't know about the Red! Is there a viewfinder, a Live View or what? Will the Red's filtration be internal or external on the lens? The point being that you will need to be able to "see through" your filtration system in order to focus. OR, you will need to focus without the filter, add the filter and make some focus tweak for the shorter UV wavelengths. With some of our mirrorless still cameras we can often see through the dark UV filtration using either its Live View of its EVF. It is often more difficult to see through the filtration with the mirrored cameras, so additional UV light is required for focusing. Or one has to go to the old tried-and-true method of focus, add filter, adjust focus.

  • I am required to provide the following standard warning. :excl: If you should be using any artificial UV illumination in addition to your sunlight (such as mentioned in the precding point about focusing), then everyone's eyes must be protected because UV-lamps or UV-flashes or UV-LEDs are much more concentrated over a short period of time than sunlight and can cause eye damage. UVEX UV-block goggles are easily obtained. B) B) B)

  • Unfortunately, several of us here have experienced some difficulties with Chinese UV-pass filter glass which leaks visible light and which does not transmit UV at the higher rate of either authentic Hoya or Schott glass. Another possible place to source your filter needs would be to directly talk to Schott in Germany.

I hope this high level overview helps! Kindly forgive me if I have talked about things you already know. :D There is lots more information available about general UV matters in References, Lists & Stickies.

 


added later....

Those Reds are awesome things!!! I'm going to go look up the specs on the one you mentioned.

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https://en.wikipedia.org/wiki/List_of_large_sensor_interchangeable-lens_video_cameras

 

Wikipedia comes through!

The Red Weapon Helium, which can shoot 8K!!!, has an incredible 15.2 stops of dynamic range at native ISO!!! That is good news for UV shooting which often has black/white extremes. It can shoot raw, which is good news for the white-balancing effort.

 

It has internal low pass and IR-blocking filtration which is interchangeable (in some way) with a low-light filter. That is great news because it sounds to me like the internal filtration system might be easily adapted to use UV-pass filtration!?

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Thank you all for your knowledgeable feedback, Yes I will have to filter all visible and IR wavelengths, using Infra red neutral density filters which cut the available light by controlled stops but will just use the lowest one, they have a very good IR cut built in, or add a hot mirror filter which cuts all IR too. The lenses I will just have to experiment with but we do have some old style Zeiss which I hope were before UV coating. There is live picture for focusing by eye and recording in raw for better post production grading. It is so finger in the air as to what I'll get but hope it's usable by the client. I will keep you guys posted as to my progress and may bug you for info too :)

Chris

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I am not aware of any infra red neutral density filters that has a high transmission in the UV range.

The camera sensor sensitivity is very low in the UV range and as much UV-light as possible is vital to make things work well.

Hot mirror filters are very likely to give the same problem.

 

Filters or filter stacks for UV photography need to have an attenuation ratio of minimum 1:1000 between the IR- and UV-spectras, to avoid IR-contamination.

A Schott UG11 with normal glass thickness for photography (2mm) has a UV/IR ratio of ca 1:10.

That is almost seven stops over the limit and will flood the image entirely with IR!!

 

Regarding good lenses for UV-photography, it is not only the UV-coating that is limiting, but also the buildup, glass types and thickness of the glass.

Lens elements in specialised UV-lenses are made of fluorite quartz and fused silica.

The forum has a list of conventional camera lenses that has been found to work for UV:

http://www.ultraviol...capable-lenses/

 

If you can adapt and use a normal camera lens to the video camera it will be possible to use a small specialised UV-pass filter on a lens suitable for UV.

Baader U, is working well and is quite common among us UV-nerds. You will need a step ring to the filters 48mm thread.

https://www.baader-p...-and-uv---350nm).html

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