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UltravioletPhotography

280bp10 attempt


dabateman

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To continue to test out the extreme edges of my new full spectrum converted EM1. I purchased a 280bp10 filter. The filter I thought I was getting was OD5 blocked. However that was not the case. You can see green through the filter and it leaks a little IR. So I stacked it with my 330WB80 improved filter, which may go down as far as 280nm.

 

This is an 30 minute exposure using two compact fluorescent black lights on the left and right of the died flowers about 6 inches away and my 125W mercury vapor lamp to the right at about 18 inches. I used the Pentax UAT lens set to f5.6 with an ISO of 1600, which is the max when using live bulb on the EM1.

post-188-0-36517800-1537511471.jpg

 

You can actually see something. There are leaves to the left which are reflecting some light. However this may be IR, I will never know.

 

The problem is not only is this a crazy set up, but after looking at the mercury lines from:

http://zeiss-campus....mercuryarc.html

 

post-188-0-00138000-1537511606.jpg

 

Where I am trying to image is exactly in a valley for the Mercury spectrum.

 

Here is the same dried flower scene taken using the 330WB80 improved filter, 1 second, F5.6, ISO 200

post-188-0-93490900-1537511707.jpg

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What lens?

If you want strong UVB, there might be better bulbs for that.

I have seen a three bulb box, containing separate types of fluorescent tubes I think, three switches, UVA/B/and C.

If you want UVB, then you will of course need a lens that transmits UVB well, like a UV-Nikkor, otherwise your pretty much wasting your time, seems like.

Not to mention the camera sensor capabilities.

I am not expert about all that, but obviously the lens will be your #1 bottleneck.

 

A 30 'minute' (cough cough) exposure would pretty much null and void even the strongest of out of band OD blocking. Keeping that in mind,

I barely see the leaves, actually only after I lightened the picture in Photoshop... so who knows what you are seeing,

but if the lens isn't transmitting 320-nm UV, then...

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Sorry Cadmium,

I must not have been clear. I do get stuck on acronyms. The Pentax UAT, is the rare 85mm f4.5 Ultra-Achromatic-Takumar, in M42 mount that is corrected from 200nm to 1100nm.

It is an amazing lens that almost cost me my marriage. I am not joking. But I am the only one whom can take care of our seriously ill younger child.

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I wonder if using 280nm LED lighting might be better from the standpoint of being sure you are seeing 280nm. Narrowband LEDs should not produce much out of band, I would think. And would also get a lot less hot!
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I didn't even know about 280nm LEDs. I will have to look into them.

 

I think my post is more about error than success. I was glad to see anything. The filter is junk and I am hoping still to trade in for one that was as advertised. But being an ebay listing is always risky.

 

With my filter stack I am probably letting in at most 5%. Then on top of that the light source is in a valley with little output. The lens is good, but the sensitivity of the camera is an unknown.

So I am happy to get something.

If I ever see the sun again, I will have to test this outside.

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That cost range would be prohibited.

However on Alibaba, I did see some for under $10. This one is interesting:

https://m.alibaba.com/product/60746107594/China-manufacturers-265nm-280nm-310nm-311nm.html?s=p&spm=a2706.amp_showroom#show_specifications

But minimum order is 20 units at about $9 per unit, makes it around $200, before even figuuring out the proper power per specified wavelength. But you can tune from 255nm to 310nm, makes it interesting.

 

Actually just found this one as a "free" sample for $6. This may actually be possible to build something.

https://m.alibaba.com/product/60724368235/Cheap-Free-Sample-10mW-14mW-275nm.html?s=p&spm=a2706.7843667.1998817009.29.240d35feRw3jCg

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Yes, your lens is definitely good. I didn't know you had that lens.

If I had that lens, I would probably be doing the same kind of tests you are doing. :-)

Interesting test.

Still, 30 minutes... and the sensor limits, etc..

Like with OD, I can photograph some pretty strange things sometimes that 'should' be blocked... UV 365 LED through an IR filters and things like that, given enough exposure...

What I would want to see with a lens like that is something showing up at a more reasonable exposure time.

Why do you say "The filter is junk", you mean the 280BP10, right? Oh, you mean because of the green you can see. OK.

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Thanks Cadmium,

I haven't seen that specific brand before. But I have used something similar in my old grad days.

 

The germicidal 254nm low pressure mercury lamps have really come down in price now. I just got a bulb hopefully which will work in standard E26 socket for $25. These will not have the 280nm lines, but I want to test out a possible good 254nm forensics filter I just got really cheap. Its not marked, but I am hoping its similar to the 254bp40 I have seen before.

 

These experiments by T.J. Nelson, have me hopeful I will see at 254nm as the limit for our sensors.

http://www.randombio.com/uv2.html

 

Andrea, and others. Yes wear protective googles, cover up your skin and if possible set up timed delayed exposures with a trip switch outside the room when conducting these types of images and tests.

I am hoping the E26/E27 socket bulbs will work. I see a newer type G23 socket, but I will have to build a new protective assembly to support that.

 

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Those pages by Nelson are unreliable on this subject, in my opinion. There is no UVC getting through the atmosphere. We have endlessly discussed that fact in another thread awhile back. It seems from Jonathan’s work that there should not be any UVC sensitivity although he did not actually test that far out so it is not definitive. But regardless, I would not trust Nelson’s page! Birna weighed against that page too one time.

 

ETA: Here is where we discussed whether any UVC made it to ground level (NOPE):

http://www.ultraviol...dpost__p__21879

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Ah ok, 250nm at the surface of the earth for outdoor photography. No, sorry, I'd like to see some pretty definitive proof for that. Anything below 280nm would be a stretch. And as for camera sensitivity, by the time you get to 300nm it's almost gone. Another 50nm lower, come on........

 

With the combination of sensitivity and, there not being anything there at that wavelength, it's going to be the effects of artefacts, such as insufficient blocking of other wavelengths. OD4, and the rest please....

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If you actually want to see UVC, I think using a properly designed UVC-fluorescent screen (like for the SWIR) or even better, putting something fluorescent directly on the sensor would be the way to go. You would still need artificial illumination.
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Yep I know.

However, if cheap, I like to test these things out myself. I got an amazing deal on a forensics 254nm filter. I will have to test it first to see if it leaks or was missed labeled, however at $12, not a big loss if a waste of glass. These things normal sell for $1000s, so may have been a waste of money. I hope it wasn't stolen.

 

Also the bulb I got, people say its great if you get a working copy. Apparently a lot are shipped dead or the filament easily breaks. I loved the one review where a lady litterly blinded herself as was not knowing what she was doing and didn't think it was that powerful.

So will have a chance to test the lowest limit of the EM1.

Taking an image of the sun at ISO 1600 and 2 seconds will be fun.

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I loved the one review where a lady litterly blinded herself as was not knowing what she was doing and didn't think it was that powerful.

Uh, I hope you are being sarcastic.

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Andy,

Sadly no. Her review talked about having to be rushed to the ER by her husband. She was using the light on her skin. Since she wrote the review, I hope she got better. But mentioned being diagnosed with flash burns to the eyes.

Some people need flashing lights with safety warnings on things.

I used to distribute MSDS for products at one of my old jobs. Few chemists read those things. But many are over kill. I loved the joke MSDS for dihydrogen monoxide, a killer of thousands every year.

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I have a question. How can Nelson have made an outdoor photograph in the 250 nm range?

I suppose I'll have to write and ask him. Most of us are convinced that this is not possible.

 

Nelson's essay on Sock Physics is really funny.

http://www.randombio.com/socks.html

 

Andrea, I am not buying it... what he writes sounds OK, but that first pic he shows, which is only the sky really...

"Fig. 1. Shortwave UV photo of outdoor scene taken through a 253.8 nm, 10 nm bandpass interference filter in a modified Nikon D90 DSLR (1:37 PM, 24 sec, ISO 1600, homemade UV lens)."

 

...but 253BP10 at 24s and ISO 1600, na... sorry, doesn't make sense to me.

I don't know, would have to try all of that.

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It can be a very bad idea if proper precautions are not understood, as Da Bateman's harrowing tale of the lady who seriously inured herself exemplifies.

 

If I were to attempt such a hazardous endeavor the only way would be from outside a light tight enclosure as I have described before.

 

Please note that even the briefest exposure is unacceptable, light tight means ZERO personal exposure.

 

Sorry to belabor the point, but I feel obligated.

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No John and Andy,

You are completely correct. This being a publicly viewable board, whom anyone can read. It is extremely important to indicate the real dangers of uv light.

I like to joke, but people whom are not trained will get hurt. Just like starring down a laser pointer. People do odd things.

Cameras today can be full controlled remotely via wifi, outside from a room. Use that. Extension cords can be used and timers implemented. Low cost, does not mean no thought.

If any outsider plans to image in UVC, imagine you wanted to pull the pin on a hand grenade, you don't want to be in the room when you do, you want a robot or outside control and you want to be as far away as you can until its clear. Ie, you need a way to turn it off, from outside. Don't walk up and look at it to know its clear.

 

On a different note, I received the 254nm filter in the mail and know why it was $12. The dichroic coatings have been gently cleaned mostly off. It looks like a poster child for how not to clean a filter that requires care.

Oh well, I see if it produces dreamy, ghost like images.

I have a 12.5mm 260bp10, which I may still test. But will be harder as I think it might just cut off the 254nm band. It looks to actually be a good tight 260nm filter.

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The camera sensor is not going to see 254nm or 260nm UVC.

Even at 280nm, given enough exposure time any minute peak in the out of band range is going to work through normal OD suppression and take over the sensor.

The only thing I can really imagine using UVC light for is UVIVF.

As has been noted above, UVC is extremely dangerous, that is germicidal grade and that is what they use it for, to KILL stuff.

I wouldn't leave my house plant in the same room with it... or maybe even anything that was valuable, historic, keep sake... who knows...

I am pretty sure arc welders are exposed to a lot of UVC, but they wear heavy gear that covers every part of their body.

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The camera sensor is not going to see 254nm or 260nm UVC.

Yep. You may has well say you have a 260nm filter made of aluminum foil. It will work just as well (or maybe better - at least with aluminum foil you can't fool yourself with out-of-band transmissions). There's pushing the camera to the limits and then there's just fantasy.

 

It looks to actually be a good tight 260nm filter.

I also recommend the lens cap filter. :-P

 

A few years ago, David Prutchi made some noise about a building a UVC imager, and his general plans sounded difficult-but-realistic:

http://uvirimaging.c...-ruvis-imaging/

 

However, all the UVC photos on there are not by Prutchi, and when I asked him to show us HIS photos, he never replied...

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  • 3 weeks later...

Well I tried to image something in the UV-C. Now using much better filters but small 12.5mm with good blocking I was able to see if I can see anything.

 

The short answer is not much. This is an image using a 260bp10 10 second exposure of the SUN! at f8, ISO 200. Really no light is coming down, but you can see stuff in contrast.

post-188-0-78994900-1540012298.jpg

 

 

This is a different 280nm fitler, a 12.5mm 280bp10 filter. The exposure value is 4 seconds of the sun, f8, ISO 200. A bit better than the 260nm filter.

post-188-0-21616200-1540012314.jpg

 

The blue tint to the 260nm photo may indicate that I might just be seeing IR here. If I cared I may retest this with an IR filter and try blocking with U340. However I really don't expect to see much.

 

The green/yellow tint in the 280, I think is real and this maybe the limit of my camera.

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