UV photography box. Of interest for discussion of sources.

[ChrisR]

https://www.instructables.com/Build-a-S ... raphy-Box/

N.B. there's a Download option.

[enricosavazzi]

https://www.instructables.com/Build-a-S ... raphy-Box/

N.B. there's a Download option.

Strictly speaking, this in not UV photography. It is photography of UV-excited fluorescence in the visible range. Different UV wavelengths stimulate the emission of different VIS wavelengths in different minerals.

UV photography directly records reflected (or sometimes transmitted/emitted) UV radiation without wavelength shifts, just like IR photography records IR radiation and VIS photography records VIS radiation.

[bobfriedman]

UV photography example.. pseudo-color using WB



example without pseudo color.. since UV has no color.

[bobfriedman]

UV-induced fluorescence in the visible spectrum

[Beatsy]

Thanks for the link Chris.

All very interesting with an added bonus for me. The beams on my Convoy torches are somewhat too narrow for UV imaging on my microscope - a new thing I'm exploring. I discovered the problem after recently getting my Sony A7riv back after full spectrum conversion. The Alonefire H42UV torch they recommended in the paper is ideal for the task - nice wide beam and 3 LEDs instead of the single source in the Convoys. One is on it's way to me now...

Edit: reviews say there's a lot of visible light emitted too, but I expected that because the Convoys did the same and I fitted 365nm bandpass filters to them. UV pass filters are readily available and much cheaper, especially in large diameters as required for the Alonefires. I don't need bandpass for this application.

Cheers

[Lou Jost]

Beatsy, sounds like a nice solution. However there's a red flag: it reduces power after 3 minutes to save battery. It's not clear if this can be turned off...

[Beatsy]

Thanks Lou, I didn't know that.

However, from the published power ratings, compared to the Convoy torch, I expect to run it at the lowest power setting anyway. So that's only an issue if the "reduced power" you speak of is lower than the lowest power setting.

If it all works OK, I hope to hack and bodge it to run off a power supply eventually. It looks a bit too juice-hungry for practical use on battery power really.

I've also discovered that it comes with a UV pass filter too, but that is moot. I discovered a UV pass (visible block) filter in one of the cubes fitted to the BX61 and that appears to fully block wavelengths over 400nm or so (tested with a 405nm bandpass filter and with unfiltered bright halogen light). So I'll use that too.

Fingers crossed.

[Lou Jost]

Sounds good Beatsy. I see it can be USB-charged. maybe during use....that would be great!

Have you thought about making a cheap spectrometer to guide your filter choice? A few days ago I stuck a cheap diffraction grating spectroscope (bought on eBay for about $20-30) on a camera lens (as if it were an infinity-corrected objective) and I can now see my filter transmission spectra in seconds. I just hold the filter in front of the spectrometer and snap a photo.

Here is an example. This is the spectrum seen by an A7R with its sensor filters stripped off, and with no filter in front of the spectrometer. The dark lines are the Fraunhofer lines in terrestrial sunlight so it can be calibrated with great accuracy. This one goes from 360nm to about 860nm. So you could see exactly how good your UV filter is, using the same technique; just put your filter in front of the spectrometer.

[Beatsy]

Wow! That's really, really cool Lou.

While I don't really think I "need" one, per-se, I sure do "want" one now I've seen what it does!

I'll see if we have anything similar available this side of the pond.

Thanks again.

[Lou Jost]

It's endlessly amusing, I am sure you will enjoy exploring with it.

[Beatsy]

Just an update to say I received the spectroscope. I paid a bit more (~£50) but the only available alternatives were toy-cheap and plastic (~£8), so I skipped those.
This one is well made in aluminium with a very clear and contrasty view. I was surprised to see the Fraunhofer lines so clearly by eye! I thought I'd need it on camera to see those (not tried on camera yet).
It already induced a "wow" from seeing the stark difference between a normal green filter and a bandpass, interference version. The interference filter passes a much narrower band than I thought too.
A fun little toy, um, I mean tool, for which I have a few immediate practical uses too. Thanks again for the suggestion.

[Lou Jost]

Glad you liked it. I think every photographer "needs" one.

Actually it really is useful. It is great for checking the quality of LED lighting. for example.

And there is something cool about directly observing those Fraunhofer lines that connect cosmology and quantum mechanics.