SIGMA 70mm F2.8 DG MACRO, Art Lens

[colinbm]

I was pleased with the Canon MP E 65mm super macro, but I was looking for a bit more DOF with these rocks, so I don't need to stack the images.
Out came the SIGMA 70mm F2.8 DG MACRO, Art Lens wow what a pleaser this is to use for up to 1:1 macro.
A little more DOF, the colours are a bit truer.
Different rock & different lens, same lights.
I need to find a way to reduce the lint, especially with 365nm light, an air blaster didn't help much ?
 

Visible light...

 

UVA 365nm light induced visible fluorescence....

 

UVC 255nm light induced visible fluorescence....

[Ming]

Exquisite!  Thanks for sharing.

 

[Adrian]

What is the mineral please?

Also, what are you using for your UVC source?

Thanks

[colinbm]

The mineral sample is from Puttapa Zinc Mine, South Australia, & contains willemite, calcite & smithsonite, plus others.
The UVC here is a 255nm LED light.

[Nate]

Another great show of Fluorescence, I too struggle with lint, and was thinking using the brush on a vacuum. I may try out different methods as I seem to have an endless supply of floaties too.

[Andy Perrin]

I think I'm alone in actually liking the darn lint, haha.  I think it's pretty!

[colinbm]

I think / hope, some of it is mineral, but certainly the stringy bits are lint.

 

[ulf]

1 hour ago, Andy Perrin said:

I think I'm alone in actually liking the darn lint, haha.  I think it's pretty!

Me too, at least on minerals if the lint do not get too dominant in the picture.

 

An idea for cleaning the minerals could be to run them in an ultrasonic cleaner.

If water is used, I would use warm water to make the stones dry off faster and the water should have low calcium content to not leave residues when evaporating.

I have no idea if this will work, but it might be wort to try.

 

@colinbm It would be valuable to know more details about both the LEDs, like input power and distance to the stone and about the exposure, like exposure time and aperture setting.

Is the SW fluorescence bright enough to be seen in a not completely dark room?

[colinbm]

Thanks Ulf
I will try the ultrasonic cleaner, when I get one.
For this shot I used a 9 LED light of 0.9w 255nm LEDs & a 30sec exposure time with f22.
I have some stronger 25w 255nm LEDs as well.
The minerals do glow faintly in daylight with the 255nm light held close like 10mm away.

 

[lukaszgryglicki]

25w 255nm LEDs as well

Just to confirm - 25W power consumption, not LED's output radiant power, right?

If so then what is their efficiency of converting input power (25W) into UV-C light (radiant power)?

[colinbm]

Yes 25w consumption, I do not know the radiant power.

[Stefano]

Assuming 1% efficiency (typical for these LEDs) that's 0.25 W of output power.

[colinbm]

I don't really care, it is on band & I can photograph with it.

[lukaszgryglicki]

OK, thanks, just FYI 40W mercury bulb (low pressure) will give about 30% of power in radiant output and probably about 70+% of this will be 254nm... so about 8W at least.

[Stefano]

Yes, LEDs are much less efficient (although I still like them).

[Andy Perrin]

Intensity (how much power per square meter per steradian, where steradians are a measure of how wide/narrow the beam is) can be high with LEDs even if efficiency is low. If the beam is very narrow, even a little power goes a long way. So it depends what you are photographing and how big it is. If you want to illuminate a tiny spot, an LED might still be a reasonable choice, especially with a suitable lens. 

[colinbm]

Thanks Andy
Yes that is what I need to learn about..." a suitable lens ".