Three UV filters compared

[Cadmium]

Comparing:

1) U-340 8mm

2) PriaLuceLab Optolong Venus U

https://www.primaluc...ltraviolet.html

3) La La U

 

Individual white balance made from Spectralon for each filter using Photo Ninja.

D7000 UVIR, UV-Nikkor 105mm.

ISO 200, f/8, Aperture Priority, Matrix

 

U-340 8mm, exposure 1 sec.

 

PriaLuceLab Optolong Venus U, exposure 1/2 sec.

 

La La U, exposure time 1/2 sec.

 

La La U, exposure time 1/2 sec.

[Andy Perrin]

Interesting and yes, now we get a much better feel for what is going on here with the 8mm. I wonder what the deal is with PriaLuceLab filter and the grass?

[Cadmium]

Comparing the PrimaLuceLab U above with Enrico's examples, they look similar, blue foliage, and some other areas more yellow/brown/green:

http://www.savazzi.n...alucelab_u.html

 

If we look at Ulf's scan of the PriaLuceLab U we see some 400nm-450nm leak and 700nm leak that are about 0.5%, between OD2 and OD3, which will become part of the recorded mix in normal UV shots.

1% transmission = OD2

0.1% transmission = OD3

https://www.ultravio...dpost__p__31987

 

I am not sure how much of that visible violet/blue range is responsible for the blue grass and foliage with the PriaLuceLab, but that would be my guess, and it is doing the same thing as Enrico's shots.

Similarly, I don't know how much of the PriaLuceLab 700nm range is responsible for the yellow coloration. I have not done a leak test with the PriaLuceLab yet.

One can expect that the visible violet/blue leak and the 700nm IR leak are influencing the overall colors of the PriaLuceLab U.

Normally with a 700nm leak, we would expect the foliage to look slightly brown or warm instead of gray or black, but instead we are seeing blue foliage. Unusual.

[Stefano]

What I like of this U-340 8 mm filter is that it passes also the entire UVB range. Probably it doesn't influence the image a lot, since the sensitivity of normal cameras to UVB is really low, but it's a nice feature. All filters that contain S8612 block below 300-320 nm.

[Andy Perrin]

There is almost no UVB in sunshine. Between that and the gain issue you cannot see any difference from UVB even with a quartz lens. It’s the same issue you are having with the 365nm light but even more so for UVB.

[Cadmium]

Stefano, you can do practically the same thing with only 4mm as long as you use light that contains more UVB and limited visual and IR.

For example, like Jonathan did here:

https://www.ultravio...__fromsearch__1

 

I think the 8mm version is working quite well. I have never tried using anything as thick as 8mm before, but I didn't expect it to look this sharp,

and the exposure of 2X the other two I compared to in this set doesn't seem bad at all for a filter that blocks above 380nm.

I honestly didn't think it would work this well.

Granted, I have not tried this with an 'accidental' UV lens, such as a Kuribayashi/Kyoei 35mm or a El-Nikkor 80mm, say...

The colors and exposure time might be a little different when testing on a non-UV-Nikkor.

I am sure I will try using the U-340 8mm with the Kuri at some point to get a feel for how different it might be when limited to 320/330nm.

 

I like the color palette. There are a few very interesting differences between the U-340 8mm and the usual Baader/La La U look.

Two things that stand out for me in the U-340 8mm shot above are the windows and drapes in the upper story of the house on the hill (upper right).

I am not sure what color to call that, purple, lilac, magenta? Whatever that color is, it has a little more red in it than the usual lavender does that I am use to in UV shots.

Also the browner color of the truck cab compared to the other two filters. There are some other differences in the usual lavender/blue areas (or not).

 

Forget about sunshine... every time I see the sun shining out my window, I grabbed the stuff and headed out there, just to find a cloud moving in,

but there was a little sun in the above shots, just not strong.

It is suppose to freeze here in the next few, and the dandelions were all droopy and folded up from the rain, soaking wet.

I was afraid they would be destroyed by the freeze, so I dug one up and put it in a pot, and it is now basking under a grow light in my laundry room.

I have no idea how it will do, but if it perks up I may be able to shoot a few shots of it with the above filters.

[dabateman]

That awesome Cadmium.

You will slowly turn into a basement UV photographer, like me.

Get your ExoTerra UVb bulb ready and really have some fun.

[Cadmium]

Planning on trying the ExoTerra sometime. I have the ExoTerra Reptile UVB 200 26W, has 30% relative spectral power UVB peak at about 315/320nm.

However, Jonathan's illumination has less visual and IR than the ExoTerro does. His is also filtered.

Like I said, 4mm might work even better for that if the light is reduced to UV.

The 8mm is really more for outdoor full spectrum light, because it suppresses OOB transmission down to OD5.

[dabateman]

Yes I have the same ExoTerra light. It has an odd 708nm spike that can cause interesting IR issues, or a splash of blue into an image.

The G8T5e bulbs, Jonathan and I have, have very little IR. But some interestingly dangerous 280nm light. It spikes at 302nm and 313nm, for the mercury lines.

With the ExoTerra light I have IR leakage with my 303bp10 filter stacked with a 2mm U340 filter. But the G8T5e light can be used with that filter combination without IR leakage. Comes down to that 708nm spike.

 

My 303bp10 filter starts to IR leak hard at 750nm. The tale from that 708nm spike I think is the problem there.

[Cadmium]

Of course, with the U-340 8mm thickness the 708nm spike would not be an issue.

[Cadmium]

I forgot to mention this 5 year old topic that Alex did, testing the PrimaLuceLab Venus U filter.

I have not shot any flowers with this filter so far, but the examples Alex shows make a lot more sense to me now, given the blue grass and foliage (usually black or gray in UV) in my example above.

https://www.ultravio...__hl__primaluce

[ulf]

I place the the PrimaLuceLab Venus U filter in the artistic UV-pass filter category.

In a way it is interesting and intriguing as the blue colour is not from any intentional blue leakage.

When stacked with a B-410, 2mm the blue colours change a bit, as the massive IR-leakage is decreased and changed.

[dabateman]

What thickness of U340 would replicate the PrimaLuce effect?

I am guessing 3mm based on the size of the 700nm peak. Its basically a 0.4% peak, in what looks to be Ug11 glass.