Jump to content
UltravioletPhotography

Cheap UV focusing light


dabateman

Recommended Posts

dabateman

I purchased the below LED black light bulb while at Home depot for $15, I wasn't expecting much as in the past I have found the 75W Black light incandescent bulbs to just not even be usable as black lights.

 

post-188-0-92168300-1525586163.jpg

 

However, I was surprised that I was now able to use live view without any issues on E510 and EM1 using Baader Venus 2 filter. With the EM1 I get 2 stops better exposure using the Baader Venus 2 with this LED black light than my previous 23W compact fluorescent bulb and grow light setup. I also got a nice bulls eye dandelion image. So I tested this light with my filters and infrared SD14 camera.

 

This image is F4, ISO100 30 seconds with Baader Venus 2 filter on Sigma EX 50mm f2.8 Macro lens. The Baader venus was purchased in 2008 and the spectrum I have previously uploaded was collected in 2011. Not sure if that matter, but recently reading that there are differences in the Baader Venus 2 filters, mine is in 48mm mount and I reversed it after purchased, green side faces sensor, red side faces subject.

post-188-0-88123900-1525586366.jpg

 

This image is F4, ISO 100 30 seconds with ZWB1 2mm and BG39 2.2 mm on same lens. Purchased in 2017 from Igoriginals. I don't know the spectrum of this filter combo, but seems not too leak into visible much. based on the below image

post-188-0-37616600-1525586469.jpg

 

This image is F4, ISO 100 30 Seconds with Just ZWBI 2mm filter. Based on this image there seems to be some IR coming out of this LED bulb.

post-188-0-62131900-1525586554.jpg

 

This image is F4, ISO 100 shutter is 1/20 seconds this is just the BG39 2.2 mm filter.

post-188-0-24533900-1525586635.jpg

 

This image is F4, ISO 100 Shutter is 1/40 seconds this image is with no filters on the Sigma SD14

post-188-0-92192000-1525586686.jpg

 

I am not sure if this is using cheap 405 nm LEDs or something shorter, I am inclined to think its possibly using 385 nm LED, as I get great Baader image, but no real ZWB1 image. Next I wan to cut off the glass/Plastic dome on the bulb so see if the UV out put is better. This thing is cheaper than the Mercury bulbs I was looking at, and is cold. The base of the bulb heats up after a while, but nothing like any other bulbs. Also the light output is not a direct focus point, So I think better than a UV flash light.

Link to comment
dabateman

Below is an image with Olympus EM1 ISo 800, F5.6, 30sec using Olympus 35mm f3.5 macro with MMF3 adapter and the Venus baader 2 filter and just this light. I tried to resize the image so not so large.

post-188-0-41844500-1525589556.jpg

 

All of these images are straight out of camera, no processing. Which should be clear from how crummy they all look.

Link to comment
Andrea B.

David, nice series of tests.

 

I have a couple of comments which I will come back later to make. We're busy around here this morning, so I'll let other members have a chance.

 

But first, please reassure me that do you have UV-blocking goggles while experimenting with your various UV bulbs and lights? Everyone knows how I worry about that! :rolleyes:

Link to comment
dabateman

Andrea, Thank you for your concern. Yes I have many different pairs of lab goggles that I have kept over the years from labs.

 

Also Update. I was wrong about the IR. That seems to be UV induced IR, as when I tested an object without the possible ability to give off IR. I saw no IR with my SD14, and the SD14 is really sensitive to IR.

Also the outshell is some type of plastic and using a Dremel tool with cutting disc it cuts off rather easily, leaving no sharp edges.

 

After removing the plastic outer, YOU Really need the UV GOOGLES. This thing outputs a lot of UV. The ZWB1 BG39 stack now works great. Making me think its really a whole bunch of 365nm LEDs. Using the SD14, and the ZWB1/BG39 stack I was getting a similar image as the first UV image I posted using ISO 100, F4, 15 seconds shutter with same Sigma 50 mm EX Macro, which is ok for UV work.

Link to comment

Well, I was at Home Depot yesterday buying a replacement lawn mower wheel.

Lawn & Garden is right next to Lighting and there was the very same bulb just hanging there waiting for me to try.....

 

When held in contact with a Solarmeter it reads only 330µW/cm² (0.3mW/cm²) which is minuscule, about 7% of UV in sunlight this afternoon.

 

I checked the peak wavelength with an Ocean Optics USB2000 and found the LED emission at ~408nm.

 

Unfortunatly this is not really a UV LED and in my opinion should not be called a "black light" at all.

 

I saw a lot of bright florescence in the room, especially from printer paper, but it is unlikely UV induced but rather violet/blue induced.

 

post-24-0-63726900-1525723970.jpg

Link to comment
Andy Perrin
dabateman, given these results for the spectrum, it seems likely your photos are mostly in the 380-400nm range.
Link to comment

I pried the dome off with a heavy screwdriver.

 

It is glued on with what appears to be some kind of white silicone caulk.

 

The peak was 407.42nm so the dome is not cutting off the peak.

 

Note the plot above is a relative log y-axis scale.

Link to comment
dabateman

Interesting, I don't doubt your results. I am surprised, as I don't think that is what I am seeing for mine. However I don't have the instruments that you do to properly test mine. Mine did go from black with zwb1/bg39 with dome to excellent exposure, once removed. There may be sample variations or I may have higher, than I expected sensitivity in the 380nm to 400nm range as you suggested.

 

Is your USB2000 actually calibrated from 200nm to 900nm? What light source are you normally using? I am still thinking about building a spectrometer, but also look out for cheap uv/vis spectrophotometers.

Link to comment
dabateman

@Jcdowdy,

Just to clarify, was the above spectrum taken with the dome on?

Staring at it, it looks odd for a 405nm led. The curve seems red shifted and broad. There may be some film or layer in the dome shifting the curve and broadening it.

Can you rescan the light now that you have the dome off?

If it really is a 405nm +/- 50nm, than may still be in uv. This would explain why I see it with dome off with my Zwb1 but not when dome was on.

But never the less, it still works well as a broad focusing light when I use my Canon 199a flashes.

David

Link to comment
Andrea B.

Interesting discussion about this black light.

 

Aside from the ongoing discussion of its peak wavelength, I think that David's tests tell me that fluorescent tubes or bulb blacklights are not too useful for general illumination in UV photography. For me, the UV-LED flashlight/torches are the better tool for setting up a UV photograph which is then illuminated by a UV-flash. Now of course, YMMV, and so forth -- this is why we make such tests and post them so everyone can figure out their preferred illumination. :D

 

David, I was going to mention that the ZBW results in the 4th photo could be visible violet leakage through the ZBW or visible red chlorophyll fluorescence leakage through the ZBW. The ZBW filters are unfortunately not reliably manufactured currently and do not always block visible light as they should. Also it is quite common for all UV-pass filters to leak a bit of visible violet which is generally accepted as not harmful to UV photography if a good UV illumination has been used.

 

BTW, I've seen a number of 405 nm peak offerings by the UV-LED vendors. I was sent a little micro 405 nm UV-LED flashlight freebie for my keychain when I bought some batteries. Given that I had no idea why I would want this on my keychain (search for scorpions in the backseat of the car? perform hotel rooom forensics?), I've put the micro 405 to use in fluor experiments.


 

 

Photographs of Spectralon Rectangle under 405nm LED

D600-mod + Coastal Optics 60/4.0 + Baader UV/IR-Cut Filter

f/4 @ ISO-200

 

All renditions of the two original photos have had a white-point adjustment (right-most histogram point moved left) because my purpose was to show the recorded colors, not the recorded brightness.

 

My conclusion from looking at these photos today is that you probably would not want to use 405 nm for any kind of UV work unless you had extremely good filtration to block out the contribution from 400 nm on. (When I was shooting these, I was looking at another topic - fluorescence of a particular subject under various types of illumination.)

 

I should remark that I do not know what, if any, drift off the peak I have from this micro LED. Is it really 403 nm? or 408 nm? Don't know. "-)

 

Illumination with 405 nm micro LED filtered with StraightEdge UV-Pass filter, 30 seconds.

This photo shows UV light only because the SEU has an almost straight right-hand shoulder cutting off just before 400 nm. The micro LED can provide enough UV between 380-400 nm to be recordable. Took a while though. This high-UV was recorded mostly in the blue channel as you see from the Raw Composite. As usual, what white balance to apply here is up for debate given that it is false color. I'm showing a typical Daylight WB and a K 10000 setting because I was testing that day whether the 405 nm could induce any fluorescence in another test subject. (It can, of course, depending on the subject.) And we know from other experiments that Daylight and high-temperature white balance are often useful in UV-induced fluorescence work.

 

The UV between 380-400nm records as a kind of raw gray-blue.

violetLightTest_lensBuvirCut_violet405microLedUvStraightEdge_20161025wf_55288rawComp.jpg

violetLightTest_lensBuvirCut_violet405microLedUvStraightEdge_20161025wf_55288daylight5200.jpg

violetLightTest_lensBuvirCut_violet405microLedUvStraightEdge_20161025wf_55288k10000.jpg

 

 

Illumination with 405 nm micro LED unfiltered, 1/5 second.

So what happens when this little micro LED is used unfiltered? There is a mix of high-UV and violet light. And it seems to me that the visible violet output is quite dominating because look at how short the exposure time was! This supports what John showed above with the LED bulb - more visible than UV. Again there is no good answer to what WB is correct for this mixed light.

(Wish I had made a third photograph with a 400 nm longpass to capture only the violet light, but I was just not thinking about that when I made these.)

 

The UV/violet mix records as a bluer blue than the raw color above.

violetLightTest_lensBuvirCut_violet405microLedNoFilter_20161025wf_55279rawComp.jpg

violetLightTest_lensBuvirCut_violet405microLedNoFilter_20161025wf_55279daylight520001.jpg

violetLightTest_lensBuvirCut_violet405microLedNoFilter_20161025wf_55279k10000.jpg

Link to comment
dabateman

Andrea,

Yes we all have our own setups. The compact fluorescent bulb in contrast to the is "Black light" was horrible. However for me, this LED is cool (Temp wise), allows for full live view, easy to adjust and place where I want. A flash light will have the benefit of being able to use outside and is more portable. So that will make sense too. However the cost of flash lights has shot up. I am keeping an eye on the conroy S2 365nm, but no longer cheap. I also have a feeling that my black light is not a 405nm but lower. As with the dome on I could not see the ZWB1, but with dome off I can.The unit is 13 LEDs soldered to the metal base and says needs 9.6 V. So I may take one apart and see if I can drive it with batteries, to make a flashlight. I do have a "UV flash light" I bought back in 2007, when I started to get into UV photography. I will have to compare it with that. I have know idea what its spectrum is but it is noticeably blue/purple.

 

So ether there is large sample variation among these lights, which is possible. Just made with what every cheap LEDs were around, or the output is just good enough for me. If its the latter I am happy, if not I hope I don't see major shift with later units.

 

However, JCDowdy I still would like to see the spectrum now that you have the dome off, Please.

 

David

Link to comment
Andrea B.

ZWB1 2mm and BG39 2.2 mm on same lens. Purchased in 2017 from Igoriginals. I don't know the spectrum of this filter combo

 

David, I don't know if it will help or not, but we do have one measurement here by member JMC for ZBW1 (2mm) and BG 39 (2.5mm) separately: http://www.ultravioletphotography.com/content/index.php/topic/1313-filter-transmission-charts/page__view__findpost__p__17214

Now your BG 39 is a bit thinner, but from JMC's chart you can reasonably infer that your combination probably has about a 45-50 % transmission peak at some point past 350 nm, probably around 360-370 nm? That's ok, about what a KolariU gets.

 

An Optima ZBW1 in 1mm can leak up to 1% visible light. See http://www.ultravioletphotography.com/content/index.php/topic/1313-filter-transmission-charts/page__view__findpost__p__17212. But by 2mm I would hope that visible is under control. "-)

Link to comment

David,

I only used my toy USB2000 to do a quick and dirty check on the wavelength peak. When I have time I will run a proper scan with the OL-756.

 

However the cost of flash lights has shot up. I am keeping an eye on the conroy S2 365nm, but no longer cheap.

 

Not sure why you are saying that.

The manufacturer of the 365nm Convoy S2+ sells direct on Aliexpress.com and the price as of this posting is $25.67 with free shipping. You could buy a dozen of them for what the MTE costs. I recommend adding their 20.5mm ZWB2 filter which is sized to fit the S2+.

Link to comment
Andrea B.
The ZBW-2 is not a good choice unless it is thick enough!! Our chart for the 1mm ZBW-2 shows 8% visible leakage. That is kinda really bad.
Link to comment

Kinda really bad as a taking filter on a lens under broadband illumination, certianly.

 

Not as good as a Baader-U or U340/S8612 stack, no question.

 

But at ~$3 for 2 of the 20.5mm made to fit the Convoy its a steal.

 

The Convoy S2+ 365nm LED has scant emission in the secondary passband of ZWB-2.

The peak seems nicely centered on the peak LED emission if the published spectra are to be believed.

 

post-24-0-78855400-1525822605.jpg

Link to comment
Andrea B.

Kinda really bad as a taking filter on a lens under broadband illumination, certianly.

oh la! And I've written so many times about how fluor filtration is """properly""" done that I finally quit mentioning it. Besides which I don't do it myself.

 

But at ~$3 for 2 of the 20.5mm made to fit the Convoy its a steal.

well I have to wonder sometimes in which direction these steals are going.....but nevermind. :lol: :lol: :lol:

 

if the published spectra are to be believed.....

weeellllllll.........that's kinda the problem. Some makers of ZBW might have better quality control than others. My ZBW is leaky stuff and I won't use it. But I'm sure there's some good versions out there. But even good filter glass has its little leakages. So how can I stand up for the good stuff when even the good stuff takes some care to use properly? Tis a puzzlement......

 

JD, I'm teasing on ya. And I'll quit now. I should simply stick to botanical pursuits. :rolleyes: It's safe there.

 

Apologies to non-US readers, this post of mine is overly US-slangy.

Link to comment

A piece of cardboard works, if you use a long enough exposure time. ;-) Maybe if the cardboard is really thin.

Problem is, those graphs you post just above are erroneous. They are an artists conception of a perfect world, but compare ZWB1 with UG11, same thickness, and it is very inefficient.

I have tried ZWB1, compared it to U-340 and UG11, and there is a lot of difference in exposure time.

I don't trust those graphs, they sure don't represent the experience I have with ZWB1.

Also, I differ, UG11/U-340 + S8612 is not my favorite stack, U-360 + S86112 is.

As far as a Convoy filter, cheap is cheap. The real thing will cost 10 times as much.

 

It will also depend on the LED, torch, light you are using, because some will have more of less blue/visual content to filter out or not, and some will even have their peak above 400nm...

But let's say, given a scenario using an LED or some other light with a broad UV peak leaking into the blue visual range, we want to concern ourselves with two things,

the cutoff point of the filter at or below 400nm (how much blue/visual it cuts or transmits), and the peak 365nm amplitude.

On the other hand, if we have a LED that has very little blue/visual content, then putting a filter on the front of it, no mater how well ti suppresses the blue/visual range will not really be doing as much.

Link to comment
Andy Perrin
Here is a question: why not use one of those Omega dichroic band pass filters matched to the LED? They seem to have pretty good blocking in my experience so far.
Link to comment

Price, size, thickness... not sure you could find one that fits inside the Convoy, or the MTE. Also, some of those have low transmission peak and might attenuate the brightness,

but mostly the size might be hard to match up.

Link to comment
dabateman

Thank you JCDowdy for a direct link. After a recent online shopping experience, I have gone back to only trusted sites I have experience with or have been directly told are real.

The price has been going up on Amazon and with ebay sellers. Though the ebay sellers throw in the odd type batteries, the light requires.

 

I know it was debated here in the past, but do think the conroy needs filtration?

Link to comment
Andrea B.

All.UV-LED.Flashlights.Need.Filtration. --- because they all leak some visible light. With good bin Nichia chips it's mostly on the violet end and not too much. With other chips, it is worse. All 3 of my Nichia-chipped torches from different manufacturers have visible leak.

 

Here is a link to a page which has a demonstration of how much light gets through a Convoy filtered with the bad ZBW2 glass. Scroll down to the header "Why Do UV Flashlights Need Filters". While the residual leakage thru the ZBW2 filter may be OK for the fluorescent rock guys, it should not be considered OK for us visible-fluorescent photography guys. https://www.naturesr...Lights-in-Years

There is a reason why that dangrabbity ZBW2 stuff is so cheap.

Link to comment

Cool link!

Of course one can use a Baader U on a torch also, would work great.

That is one advantage that the MTE's have, the front threads are 37mm (as I recall), so you can attach any filter to the front using whatever step up ring.

I prefer U-340 2mm, half the price of UG11, and works well for a torch @2mm. It is more efficient filter glass than ZWB.

Link to comment

More fun with this black LED, most likely a 405nm.

After reading some of the filtration thoughts. I remembered that the top dome is plastic. I also purchased 2 more of these lights.

So if you are careful and cut 9 to 10mm from the metal base, you not only get good clearance from the LED, but if you sand down so flat. You can now screw in a 58mm step ring adapter. I have my Baader venus 2 in a 58mm step down to 48mm adapter. This will fit nicely in front of the bulb. Then I used thick black 3M electrical tape that is insensitive to temperature. To not only secure it, but also block the 9mm of plastic from emitting blue light.

So I have a baader filtered black light. I am testing if using this I can get uvivf or uviirf. I had too much natural light in the room, so will need to test at night.

But the bad news the second cut bulb has about 1/3 to 1/2 less uv then my first bulb. Using my igoriginal 35mm f3.5 (I am going to call it that now instead of kuri clone. It looks like he not only cleaned it and adjusted it, but may have removed the lens coatings as well.)

But my first bulb was getting me iso 400, f8, 30sec, today with Baader venus 2 filter and this lens. My second bulb was for similar exposure, iso 400, f8, 40 or 50sec. So there is sample variation.

So I did end up ordering two Convoy S2 365nm flashlights, was able to grab a flash sale at $22 each. So in a month or so after they arrive I will look at them and filters for them.

Funny the order did trigger a visa alert. Apparently shops located in Great Britain aren't trusted, by my Visa company.

Link to comment

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
×
×
  • Create New...