lens transparency test with 365nm light

[photoni]

the Alonefire 10w 365nm flashlight has arrived (with black filter ... maybe ZWB-2 1mm)
playing with the light and the yellow glasses supplied, I saw strange "colored opacities / glazes" in the lenses I use
This is a photo with iPhone.
What can they mean?

the Nikkor-H 50 looks like milk
Nikkor-H 24 is a little orange
Pentax 85 SMC is milky orange
the only one with little opacity is the Darlot petzval 275mm ~ 1880

also Industar 300mm 4.5 ... terrible milk
Sironar 360mm 6.8 ... orange

 

Thanks. Toni

 

 

[colinbm]

Fluorescent glass or glue.

 

[photoni]

46 minutes ago, colinbm said:

Fluorescent glass or glue.

 

I also think so, the Pentax with SMC is strong orange ...
but because Nikkor-H has a different color, it's milky white, I don't think it has an anti-reflective treatment. maybe the glue between two lenses?
.
however, the projection of the LEDs onto the wall through the lens looks clear

[Nate]

I was wondering this too. When I shined my 365nm on my lenses the industar 50-2 had more green haze on the rear element compared to my Canon 50mm 1.8. So I have been using the Canon lens as it lets way more light in and has auto. 

[Andy Perrin]

We've discussed lens fluorescence before, but I don't think it's a very good test. At best, if a lens does NOT fluoresce, it is worthy of more testing. The converse is not true. We have many "good for UV" lenses like the EL-Nikkor that also show significant fluorescence. So fluorescence does not DISqualify a lens.

 

Here I have done the famous EL-Nikkor 80mm/5.6 metal, a fantastic UV performer that also glows in UV. 

https://www.ultravioletphotography.com/content/index.php?/topic/4264-lens-fluorescence-and-my-dinner/

 

Cadmium even showed that the fabulous Kuri fluoresces.

https://www.ultravioletphotography.com/content/index.php?/topic/2289-lens-glass-fluorescence/

 

[diant]

1 hour ago, Andy Perrin said:

We've discussed lens fluorescence before, but I don't think it's a very good test. At best, if a lens does NOT fluoresce, it is worthy of more testing. The converse is not true.

I think so too. Presence in glass a traces of some luminescent ions (Cu, Sb, As, Ag, V, Cr, Mn, Ni, Co, Cd etc.) may induce luminescence, but it is not obligatory that such ions should have a strong UVA absorption band. And even if they have it, their share may be so little that it can't induce serious UVA blockage.

And we should not forget that even simple Pb in old flint glasses often provides it with beautiful blue/bluish/whitish luminescence and simultaneously such flints show remarkably good UVA performance.

I add only one thought. If lens has strong UVA-induced luminescence, it may be preferred to place filters rather between lens and camera than before lens (to improve contrast).

[photoni]

2 hours ago, Andy Perrin said:

 

Here I have done the famous EL-Nikkor 80mm/5.6 metal, a fantastic UV performer that also glows in UV. 

https://www.ultravioletphotography.com/content/index.php?/topic/4264-lens-fluorescence-and-my-dinner/

HaHa

the strange thing is that the Nikkor-H 50 f2 is milky white

but the photo I put in another post, (with Alonefire 10w 365nm flashlight) is very very sharp

[Nate]

Good info, I shined my uv light all around my astro lens ( Rokinon 135 F/2) and didn't see any glow, then put my uv filter on it, and on camera, and couldn't get anything in live view using the torch as a flashlight. Got lots more reading to do on here.

[dabateman]

Ha,

Would be funny if the best lenses that don't glow block all the UV light in the first coating on the first element. 

 

I have to look at my quartz lenses.  My fused silica elements shouldn't glow by design. 

[diant]

2 hours ago, Nate said:

Rokinon 135 F/2

Modern 11-element design with modern flint-glasses - no chance for UVA, I think.