Saying Hi! from Estonia

[Foxfire]

Hello!

 

I've been exploring the site since before COVID-19, but it took years for me to figure out the username i like, so thanks for accepting my request to finally join here. 

Shortly, my interest into the topic began probably by seeing some images of flowers photographed in reflected UV. What was fascinating was the difference in the appearance of floral patterns compared to how they look like in visible light. The general idea of how things appear outside the visible spectrum has made me to experiment also with infrared photography, and thermography. Also i like to go out and search for fluorescent things with the UV flashlight.

 

My background is biology related (natural sciences), but occasionally i also do light related things in theaters, concerts and outdoor festivals. Maybe the alternate light photography is somehow a link between these. 

 

I find the UVP forum a great source and much helpful for getting started and learning about ultraviolet photography. Here are valuable information about the transmission spectra of lenses, gear, filters etc. Thank you all for sharing and doing it! Hopefully i manage to add something interesting too.  

 

As of my first image here, i will add a composite picture of a type of pumpkin (variety of Cucurbita). It's an approximate sum of what i've done so far. In this composite, if you want you can try to guess the part of the spectrum for each pumpkin or how the image was acquired. The description matrix is below.

 

 

Correspondingly: 
UV (Baader U), visible, IR 665, IR 720, 
IR 850, IR 950, IR 950 (no WB), thermal, 
UViF, UViIRF (665), UViIRF (720), IR720+850+950 RGB stack

 

All images, except thermal, photographed with unmodified Nikon D5500 and AF-P DX Nikkor 18-55 mm f/3.5-5.6G VR kit lens. Thermal image with InfiRay DV DL13 thermal camera.

Exposure times vary around 10-30 seconds, ISO 100 or higher

 

Thanks again for accepting my request to join

new user Foxfire 

[colinbm]

Welcome FoxFire
Nice variety of filter usages.
I am not going to guess & I don't know the light sources.
The ones with the best surface details are UV or visible light while the smother surfaces are IR as it penetrates deeper.

[Foxfire]

Hi! Thanks, yes that's true, IR looks smoother.

In the last row, the middle two images exhibit what i belive is UV induced IR chlorophyll fluorescence (on the ribs of pumpkin).
I'm surprised about how relatively monochromatic the infrared images are (with 850 and 950 filters). Wonder if it's because of the sensor, filter or plants in general aren't very chromatic in infrared..? 

 

Lightsource are UV flashlight (for UV, UViF, UViIRF) and incandescent bulb (for IR).

[colinbm]

Thanks FoxFire
What is the UVflashlight you are using please ?

[Foxfire]

uvBeast, it has a 365nm filter. I can feel it gives off a lot of thermal radiaton. If i remember correctly i used to shine it throught Baader U filter for UViIRF, attempting to avoid IR contamination. 

[colinbm]

That is a good UV light & filter, but it is desirable to cut the UV at the camera too, with a Zeiss T* UV cut filter.

[Foxfire]

Thanks, i keep in mind the suggestion. For UViF have tried to use somekind of Hoya UV filter, for IR i've never thought to use it. While doing UViF, haven't noticed difference in the result, so for my purposes i've mostly skipped the UV filter. Is here a topic discussing the use of UV filters while doing UVifluorescence?

[ulf]

I think that what you feel as thermal radiation instead is the result of your tissues/skin that absorbs the 365nm light-energy and convert it to heat.

That heated area too will be visible with a thermal camera the operates at much longer wavelengths than our cameras can see.

 

The law of conservation of energy states that energy can neither be created nor destroyed - only converted from one form of energy to another.

[ulf]

2 minutes ago, Foxfire said:

Thanks, i keep in mind the suggestion. For UViF have tried to use somekind of Hoya UV filter, for IR i've never thought to use it. While doing UViF, haven't noticed difference in the result, so for my purposes i've mostly skipped the UV filter. Is here a topic discussing the use of UV filters while doing UVifluorescence?

Many common "UV-filters" do not block UV much or at all.

A proper Zeiss T* UV cut filter do.

 

[Foxfire]

Interestingly, it appears to be really so that the 365nm light-energy from UV flashlight is convert to heat when matherials absorb the UV. Did a quick experiment, as it can be seen, in the thermal image (above) taken immediatly after turning on the flashlight does not show any heat coming off of it. Only after burning the lamp for some time (below) the heat signature appears.

 

 

This is actually expected and no brainer because glass (in this case the filter glass of the flashlight) is one of the best for blocking thermal radiation.

[ulf]

Yes this is exactly as expected.

Heating the glass is faster than the heating of the heatsink fins and body of the torch.

 

I have been tinkering with higher power 365nm light sources (90W and 150W input power LED arrays, -> ca 30-50W optical power)

As a ZWB2, 2mm or similar absorbs maybe 30-35% of the radiated power from the LEDs the front filters can become rather hot and should preferably be actively cooled.

 

Those projects are now on hold as I do not think I will need them and it is too much work and costs to finish them.

[Foxfire]

Yes, but i'm not sure about near-infrared, maybe i'll check it with IR filters. The filter in front of the flashlight is maybe a Schott UG2A glass, or similar. 
Also found a topic about UV-cut filters. Thanks, it's already inspirational.

[ulf]

2 hours ago, Foxfire said:

The filter in front of the flashlight is maybe a Schott UG2A glass, or similar. 

A front filter on a UV-torch is there to cut the remaining light into VIS.

A UG2A cut too little at 400nm for that purpose.

Also for a torch it is essential to keep the production costs down.

My best guess is that the filter is a Chinese ZWB2, 2mm and not any expensive Schott filter glass.

 

The UG2A is unfortunately not in production anymore by Schott.

It might be produced on request if you order a huge industrial quantity

[Foxfire]

It may be ZWB2, seems most probable. Schott UG2A was more of a quick and random guess. There was an issue that putting an UV filter in front of UV LEDs in flashlight was covered by some patent. I'm not aware if it's still unlaful to do it yourself but the fluorescent minerals community was not very pleased by it. Seems too simple thing to hold a patent for. Hope it's not anymore, at least in my country.

[Andrea B.]

Excellent composite. I hope you enjoy the forum!

[Foxfire]

Thanks, i will!

[Fandyus]

Welcome. Hope you enjoy your time here.

[Nate]

Welcome Foxfire! Excellent images. That's one thing I haven't done, look at my V3 Beast in thermal. I know it gets pretty warm.

[Doug A]

Super images. It is very interesting to see so many variations. Welcome to the forum.

Thanks for sharing,

Doug A

[Foxfire]

Thank you all for the welcomes! @ Nate it appears to be safe to look straight at it.

[ulf]

25 minutes ago, Foxfire said:

Thank you all for the welcomes! @ Nate it appears to be safe to look straight at it.

Do not look straight into the beam with unprotected eyes!!!

There are several other damages that can occur to the eye from light in different wavelengths, beside the damage to the retina caused by thermal radiation! 

Some are long term effects and accumulative.

Here the danger comes from a rather high optical power of UV-light.

That torch is very bright, but in a range you cannot see.

 

A torch in the same power range, but with white light is something you wold shy directly.

Here you are not protected by that reaction as the light isn't visible. 

You do not want to hav the same power that caused your skin to feel warm to do bad things to your much more delicate eyes.

 

[Foxfire]

@ulf By saying it appears to be safe to look straight at it i meant that it appears to be safe for the thermal camera - it's a delicate instrument!

[Nate]

I figured it would be ok to look at it through a thermal, Germaniun glass blocks all light but infrared. 

I think a lot of things we see in thermals get hotter than the glass on the torch.