Finally fotografed the four 340s

[Andrea B.]

I promised to do this (more than once!!) and finally got it done.

However, I need to redo it in the sunlight (if it ever returns) because I'm not sure the UV-LED was proper illumination for the experiment.

 

Equipment: Nikon D610-broadband + Coastal Optics 60/4.0 + BaaderU + UV-LED

 

^{ADDED: The background is a Spectralon slab. The dry air and static electricity in my house is so bad right now that I totally could not keep the dust off anything. Thus the photos look rather disgusting! I'll try again later.}

 

The colours I got were yellow-gray and greenish-yellow-gray. I have trouble with desaturated yellows like this. They look greenish to me. But the RGB says not.

 

Hoya U-340, 4.0mm thick

 

Hoya U-340, 1.0mm thick

This one is slightly more green than the others, but not enough to call it green-green. It is yellow-green or greenish-yellow-gray.

 

Edmund Optics 340/10.

This filter has mirrored coatings. You could call this one a bit more green than the others also.

This poor filter got attacked by dust the second I took it out of its box. The air is soooo dry.

 

Omega Bob's 340/15.

This is a reject with scratches, so I got it for cheaps. It is also somewhat shiny.

[Cadmium]

Yeah cool, but do it outdoors in natural light, with the sky as the background, even overcast is better for UV-A than an LED. UV LED's are monochromatic, narrow band.

Shooting all of those against the sky (either blue or overcast) instead of whatever that background is (PTFE, or paper?) will show a lot more of everything better.

What is the band width of the top two filters?

Just a joke, but did either of the last two filters (the bottom two filters) above have any encounters with slugs? ;-)

 

Added: I felt later here that I should perhaps explain the slug joke to those many people who might not have any understanding about it.

Once upon a time, there was a famous slug that visited one of Andrea's Baader U's that had been left outside in her flower garden by accident.

At least that is how I remember the story. There was a discussion, on the old nikongear (now fotozones) forum pertaining to this dirty Baader U that had been slimed by the unnamed slug.

How to clean that filter, and so on... and these last two filters above reminded me of that endearing story.

[Andrea B.]

oh la!!! I had totally forgotten about that!!!! :D

 

I for sure have had some adventures with my BaaderUs. At least twice a BaaderU has fallen off the lens into the dirt of a garden. (I subsequently quit using that filter holder.) The tripod tipped over one time putting a lens-with-BaaderU face down in the dirt. I stepped on a BaaderU in the Anza-Borrego desert and saw the filter rendered into a handful of very sharp, but artistic, shards. The D300 + lens + BaaderU rolled out of the car in the Sonoran desert near the Mexican border dumping everything face down in the sand & dust. One BaaderU got totally soaked shooting a rare Ranunculus in a graveyard in Norway. Fortunately, rain doesn't seem to bother them.

 

 

Back to the 340s. Yes, as mentioned, I will definitely repeat the shoot outdoors in sunlight. We just got blasted with a Nor'easter full of snow, sleet, rain and assorted other miseries, so sunlight has been a bit scarce. There is some today but don't know how long it might last.

 

At least 4 (four) times, if not more, I have read about 340 filters being green and totally misinterpreted it as being about the resulting photo made with the 340s rather than the correct interpretation -- green in a UV photo of the filters. Well, Andrea, srsly, girl, get your head on straight! At least three (3) times I have promised to photograph my 340s so that I can see the green for myself. B) Getting there, getting there. B)

 

The background is a slab of Spectralon.

I don't advise buying slabs of Spectralon. They are very, very easy to scratch or discolor.

 

The static electricity is so bad in the dry house that dust simply leaps onto charged items. I gave up trying to keep the stuff dust free while shooting last night. Then Kitty Moka walked by and I had to clone kitty hair off the Spectralon slab. Sigh.

 

Bandwidth? - whatever it is for Hoya U-340 of the given thicknesses.

[Cadmium]

Oh, sorry, my mistake, you said what it was. Hoya U-340.

If the background needs to be illuminated through the filter, then it will be much dimmer than a background that is illuminated directly.

You don't need sun, you just need any old sky, clouds work fine. I don't generally point the filters at thee sun anyway, away from the sun, just at sky is better I think, makes them all miore even, if you are doing more than one PB like I do.

If you get those two lower filters cleaned up, they may work about the same against the sky as the 340BP10 filter I have in my Sparticle.

You don't need to test the U-340's, they are not a narrow bandpass, they pass mixed colors.

[Andrea B.]

Just threw the Hoyas into the test for comparison.

 

Really there's no UV in the sky right now.

[Cadmium]

OK. Here are my tests.

My 330AF20 is the closest big filter I have to my Sparticle 340BP10, so I put that up there with it, as well as a U-340 4mm filter.

Remember that shooting at a filter and shooting through a filter will not give the same results, so I have included an example of shooting through the 330AF20, optimally white balanced.

The Sparticle test, with the two larger filters is white balanced the same as I do with all Sparticle shots made through a UV-only filter (on the lens), a Baader U in this shot.

Also remember that any lens has it's own transmission profile, working like another filter stacked with the UV-only filter, the lens transmission can limit the transmission of the filter,

so your filter transmission will only go as low in nm as your the filter on your lens. So in this situation the lens and the U-340 4mm thick filter have about a 350nm (or slightly higher) peak transmission.

 

330AF20