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UltravioletPhotography

Sigma Cameras for UV, more trials.


colinbm

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Hi Guys

I have been trying to remove the sensor's cover glass (not the hot mirror) off a spare Sigma DP2 sensor. I can tell you they are stuck fast with the best, hardest, heat resistant (epoxy?) glue imaginable. Paint stripper just bounces off! I still have to find a solvent to soften this bond ??

Anyway I have settled with mechanical removal with a small diamond cut-off wheel on a Demel type tool. I cut around the inside of the glue line & got the glass cover off in two pieces, big enough to test on a USB Spectrometer to confirm that the 365nm mercury emission spike is cut to 40% & nothing else below 365nm. This is what I expected with this sensor & I am waiting to replace the cover with some quartz tomorrow. This will offer the best help with this fixed lens, compact camera to 'see' a little better in UV.

 

I did have time to do some more tests with a Sigma SD15 full spectrum camera, an older 58mm M42 mount lens with a Amici Prism Spectroscope. I combined the picture with a graph from the USB Spectroscope. The light source was a 4 watt germicidal lamp (wear UV eye protection).

 

post-31-0-33964200-1385383613.jpg

 

Cheers

Col

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Well Colin, you are wrecking the expensive DP2 just for some UV ??? Ouch !!! Whew !!!

 

***

 

What is the 58mm M42 lens used on the SD15? Thx.

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Hi again Andrea

The 58mm M42 lens is a Helios-44M-4 2/58.

I would like to know the better, near UVA options too please.

I can not afford to get quartz lenses & I don't feel that Sigma's Foveon sensor will be able to do UV much below say 350nm anyway, as the first photodiode is 0.2 um below the silicon surface & that seems ideal for about 410nm.

But I would like to get the best I can at near UVA as is possible, above say 350nm.

I haven't been able to find a domestic continuous (black body) light source in UVA, most are glass that block most UV. The best UVA lamps I have found so far are are the HID mercury gas discharge lamps, but they only give the mercury emission peaks, at 365nm & 405nm that are of use to me at the moment. This is why I am trying to get the best out of my Sigma Foveon systems at 365nm & just below. Bee vision of nature & flowers has to use the available UVA light from the Sun which is minimal at best.

Cheers

Col

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Glad to hear you have a spare sensor, Col. :D I was a little worried there for a second.

 

I don't have any Helios in my kit - yet. :D Got plenty of other non-dedicated, UV-capable lenses however. See our UV Lens Sticky for a list of such.

 

For floral UV work, you won't really need to go below 350nm for a nice capture of a UV signature. Which is not to say that some differences between captures above and below 350nm don't exist. They might. But you might be interested in other UV work now or eventually besides floral ??

 

It is having a proper filter which holds me back from shooting much below 350nm. I just haven't yet invested the money in procuring a good filter with a peak below 365nm. I have a very small diameter filter peaking at 325 (I think - it's not at hand to check), but it is pretty bad and hard to use. Well someday......

 

I use UV Flash, so am not knowledgeable about UV lamp and strobes. Bjørn has some Broncolor strobes for UV work. Don't know what their emission range is however. If he reads this, maybe he will comment here.

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Colin,

 

As a photobiologist and expert in UV radiation safety, I must warn you that the germicidal lamp poses considerable UV hazard. Even at only 9W, UV protective eye wear is insufficient when using this type of lamp. Unless you have the source completely shielded and remotely switched please cease using it.

 

Assuming you have a PL9 bi-pin base fixture a much safer alternative would be 9W long wavelength UV-A lamp such as used in a bug zapper.

 

Take care,

John

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Thanks John for the timely reminder.

To all people interested in UV photography, EVEN the small amounts of UV rays that nature gives us via the Sun through our atmosphere is very dangerous & hazardous to our eyesight & health. Artificial UV is even more extremely dangerous.

Cheers

Col

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Bill De Jager

Colin, it's not whether the UV is artificial, so much as what mixture and intensity of wavelengths it started out as and what gets filtered out along the way before it gets to your skin and eyes. The UV-C coming from a germicidal lamp or an arc welder contains much more potent UV wavelengths than, say, sunlight at the Earth's surface or a typical 365nm torch. Sunlight at the Earth's surface has the health advantage of having been powered down to a major degree by the atmosphere in general and the ozone layer in particular before it hits you; the UV-C is gone and the UV-B is greatly reduced. What's left can still hurt you, but not to any significant degree in a matter of mere seconds.

 

John, thanks for the warning. I was tempted years ago to get one of those lamps, but I could not see how to operate it safely so I never did get one. I'm glad I didn't.

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Thanks Bill for you added advice too.

I originally got the 4 watt germicidal lamp for photographing short wave UV fluorescence of minerals, I still haven't done that.

I now have a 400 watt long wave UV lamp 365nm to help with flower & outdoor UV shots with my Sigma cameras.

I will post some results soon.

Cheers

Col

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