Dabbling with fluorescence on a budget

[ChrisR]

Enrico, if you find the current batch isn't right, I imagine there are several forum members who will be very cross!

[enricosavazzi]

Enrico, if you find the current batch isn't right, I imagine there are several forum members who will be very cross!

That will happen either way. If these torches turn out to be the real deal, people who spent multi-hundred dollar prices on MTE torches will be very cross.

Edit: I had some strange SQL error messages while doing this post, then found multiple copies of this post in the thread. I think I was able to delete all duplicates.

[zzffnn]

I bought this 420nm filter from eBay just now, for $16 shipped:
http://www.ebay.com/itm/262634372466?_t ... EBIDX%3AIT

It appears to be highly similar to, if not the same as, the Thorlabs FGL420 filter that Charles uses. I don't know if Thorlabs charges shipping. So buying from eBay will save $9 + Thorlabs shipping fees.

Just in case this info can help someone:
The eBay 420 filter fits right into Nikon Labophot 2's neck dovetail, without any problem (although its dimension suggest it may be too slightly too thick and/or too wide).

[johan]

According to Gearbest, it uses the Nichia NCSU276A 365 chip - which is the chip the expensive torches of a couple of years ago used - should be all good

Enrico, if you find the current batch isn't right, I imagine there are several forum members who will be very cross!

That will happen either way. If these torches turn out to be the real deal, people who spent multi-hundred dollar prices on MTE torches will be very cross.

Edit: I had some strange SQL error messages while doing this post, then found multiple copies of this post in the thread. I think I was able to delete all duplicates.

[ChrisR]

Hmm. Possibilities remain. I'll be measuring the current..
I have access to a spectrometer but I doubt it goes to UV.

[johan]

Those filters look great. It's so annoying though that they cost 1.5 times their price each to come to Europe

I bought this 420nm filter from eBay just now, for $16 shipped:
http://www.ebay.com/itm/262634372466?_t ... EBIDX%3AIT

It appears to be highly similar to, if not the same as, the Thorlabs FGL420 filter that Charles uses. I don't know if Thorlabs charges shipping. So buying from eBay will save $9 + Thorlabs shipping fees.

Just in case this info can help someone:
The eBay 420 filter fits right into Nikon Labophot 2's neck dovetail, without any problem (although its dimension suggest it may be too slightly too thick and/or too wide).

[Charles Krebs]

I bought this 420nm filter from eBay just now, for $16 shipped:
http://www.ebay.com/itm/262634372466?_t ... EBIDX%3AIT

It appears to be highly similar to, if not the same as, the Thorlabs FGL420 filter that Charles uses. I don't know if Thorlabs charges shipping. So buying from eBay will save $9 + Thorlabs shipping fees.

Here's the graph of the filter Fan is referring to (from sellers listing):


The Nichia LED appears to be very low in emitting visible light but there is a bit of "violet" there. The area of the graph I have marked off might be a bit of an issue. At 400nm the filter passes 20% of the light. (Although at 400nm the Nichia graph appears to be at, or very close to "0".)

The Thorlabs graph is not as detailed but they provided extremely detailed numerical data. Below is a clip where you can see that at 400nm the Thorlabs FGL420 transmits only 0.017243%

445 84.087764
440 83.107053
435 81.587439
430 78.594536
425 70.883558
420 51.058068
415 18.48491
410 2.000411
405 0.0883
400 0.017243
395 0.01441
390 0.01008
385 0.014444
380 0.01638
375 0.013527
370 0.009633

Will it make a visual difference?... I don't know

[ChrisR]

I assume Paul Bertner has been using the same LED for some time, without a filter on his camera, or in the torch/flashlight.
His images don't show excess purple.
The ZBW2 high/short pass filters a few of us recently bought, to go on the source, should help.

[Charles Krebs]

I assume Paul Bertner has been using the same LED for some time, without a filter on his camera, or in the torch/flashlight.
His images don't show excess purple.
The ZBW2 high/short pass filters a few of us recently bought, to go on the source, should help.

As I mentioned the Nichia LED appears to be about the best readily available 365nm UV LEDs when it comes to not producing visible light. But I would not consider a microscope (or any other viewing arrangement) that did not include a "barrier filter" of some type. If not for visual picture reasons then to avoid staring through eyepieces that might otherwise be transmitting reflected UV.

[Lou Jost]

Paul has an inspiring write-up on UV photography on his blog:

https://pbertner.wordpress.com/reflecte ... otography/

The new Olympus cameras have an interesting feature that may be useful for the kind of UV light-painting photography he describes. These cameras can show a long-exposure photograph in Live View as it is being made, giving feedback on the light-painting.

[zzffnn]

Charles and everyone,

I apologize for overlooking Thorlabs' "Raw data" for the FGL420 filter - somehow I did not see that button (and data) when I was on their page. Indeed, the two filters are very different at 400 nm, with the Thorlabs been much better.

For me, it probably won't make much difference, as I have a black light filter coming, which supposedly should only pass UV.

[enricosavazzi]

Hmm. Possibilities remain. I'll be measuring the current..
I have access to a spectrometer but I doubt it goes to UV.

I am actually waiting for a new spectrometer (eBay item 131712440527) that, according to the manufacturer, has a range between 200 and 1200 nm. Just a USB spectrometer, not really a research lab instrument, but it should do for this kind of comparisons. I apparently lost the software for my old spectrometer, which I did not use for a couple of years, so I am currently "blind" in this respect.

Still waiting for the new torches, but what I can see from illustrations is that the chip packages at least are not the same. My MTE 301 has a ceramic LED package with a flat glass window, while these cheap torches seem to use a LED chip embedded in a plastic convex lens.

Edit - Time ago, I replaced the transparent window of my MTE 301 torch with a U-340 filter, to remove VIS radiation. With this filter, there is no visible emission.

[johan]

The Nichia LED appears to be very low in emitting visible light but there is a bit of "violet" there. <snip>Will it make a visual difference?... I don't know

A good cheap way to test is the spoon test. Shoot a metal spoon in the dark, as metal doesn't fluoresce whatever you see in the pic is leakage. I've personally always found the CREE XP-G2 (R5) UV LED is a tiny tiny bit cleaner in this respect than the Nichia NCSU033B LED (unfiltered comparisons) but Nichia pumps out much more and is a slightly lower 365 so filtering that with Badder-U was ultimately the cleanest combination.

[Beatsy]

My two torches just turned up and they look pretty good to me, although I have nothing to compare them against. Both have the same output with a little vis at the blue/violet end. Having said that, it's tough to tell as most white surfaces fluoresce to some degree but PVC seems pretty neutral and there wasn't much vis to see on that.

My eye protectors haven't arrived yet so I limited myself to a few quick flashes at plants and such. Lichen glows bright red in full daylight, moss less so, and various houseplants showed general red glows and a few bright blue patterns (and dust).

Attached picture is two quick shots with a 50mm lens composited together (one under UV). It's a pretty close crop too. I used the camera's electronic viewfinder for the UV shot so no risk to my eyes. The fluorescence is very vivid so I think these torches will do the job just fine. I have a couple of 365nm bandpass filters on the way which should take care of the relatively small amount of vis emitted.

Great find - well pleased. I suspect we'll see quite a glut of fluorescence images once all the orders land

[Lou Jost]

Wow, I can't wait for mine to arrive!!!!