"UV" with a weak IR-cut glass

[ins13]

I can't understand whether there is a importance - both scientific, cognitive, and artistic - of photography with a tandem of UV-transmitting glass and weak IR-cut glass? I mean ZWB2+СЗС23 or ZWB1+СЗС23, in my case. too much extraneous parts of the spectrum. But I like this effect.

 

 

ZWB2+СЗС23

Olympus em5FS, Sigma 30mm F2.8 DN, f2,8, 1/5 s, iso 800

 

"The Meshchersk Chainsaw Massacre"

Olympus em5FS, Sigma 30mm F2.8 DN, f2,8, 1/8 s, iso 800

 

ZWB1+СЗС23

Olympus em5FS, Ennalyt 35 3,5, f3,5, 1/13 s, iso 1600

 

 

Olympus em5FS, Sigma 30mm F2.8 DN, f2,8, 1/15 s, iso 1600

[Andy Perrin]

I agree, and we cannot get reds without channel flipping in pure UV photography, so allowing a bit of IR through seems like a good idea on artistic grounds. Many of us here come from a science background where any IR is “contamination” and I think we have a hard time flipping perspectives.

[nfoto]

Also there are practical considerations. A lot of lenses don't manage too well in terms of aberrations when they are to cover a very wide spectral region. Plus there often are significant focus shifts. Thus many reasons to use narrower parts of the spectrum to keep such issues at bay.

 

That being said, I for one find these UV+?? pictures interesting from a pictorial point of view. And they are quite moody as well.

[Cadmium]

Your photos are quite nice!

 

Yes, stacking that filter with some U filter, in this case a UG1 type Chinese filter will give you a good amount of 700nm range IR leak.

I am guessing 2mm for both filters?

Always a good idea, when mentioning filters/stacks to include the thickness of the filters. Thickness make more difference in a stack than it does for a single filter.

 

In a word, BG38, but a real nightmare to overlay.

Turns out, these Russian filter graphs are not linear, they are compressed, sideways, every 100nm is more compressed than the 100nm before it.

So it makes it pretty laborious to do an overlay with a linear graph.

See the numbers at the top of this overlay, see how they get closer together? I had to stretch each consecutive 100nm of the Russian filter graph to fit the linear Schott graph.

 

See how the Russian filter graphs have nm lines closer and closer together as the nm goes up? Then it starts over with that progression at 700nm.

Why the closer and closer progression?

This makes comparison problematic.

 

Furthermore, I think the Russian filter graph is probably what the Schott calculator calls a 'Normalized' graph, because so many of the Russian filter plots reach 100%.

That is not normal, and probably not real.

I will show you a comparison of Schott BG glass at the bottom, in both Linear and Normalized graph modes.

Also, keep in mind, the Russian graph is 3mm glass, and who knows how that exactly compares with the 2mm Schott version, I don't know.

Here is a linear Schott BG38, BG40, and BG39 overlaid with the Russian filter graph re-stretched to line up with the linear graph.

 

 

Linear vs Normalized graph example:

[ulf]

Also there are practical considerations. A lot of lenses don't manage too well in terms of aberrations when they are to cover a very wide spectral region. Plus there often are significant focus shifts.

The aberrations might sometimes add some to the artistic qualities of an image too.

 

I had similar problems in the IR-end when playing with my green Pixonyx filter.

http://www.ultraviol...dpost__p__17010

As the transmission of that filter is dominated by the longer wavelengths, I saw much chromatic aberration in some of the images, when they competed with the VIS content in the image.

 

That being said, I for one find these UV+?? pictures interesting from a pictorial point of view. And they are quite moody as well.

I also like the pictures and the idea of not-pure UV images for creative purposes.

 

Maybe there could even be a separate tag for this types of images, just as the recently discussed for EIR-simulations.

The tag might be UV+??.

[ins13]

Thank you very much for all the comments!!! :)

 

Andy Perrin, yes, it is for artistic purpose only. and nothing more!

 

Birna, thank you very much! :) The focus shift is present, yes. Sometimes the focus shift turns out to be so significant that already begins to carry with it an artistic touch. I can't show the attached photo because I unfortunately have already spent all my 30 MB

 

Cadmium, I will try to always write about the thickness of the filters and not to be mistaken anymore :)

Those were ZWB2 2mm, ZWB1 2mm, СЗС23 3mm

Yes, the graphs of the russian glass is very bad in terms of comparison. But these graphs are exactly the same years as the glass - these our squares 80x80mm and 40x40mm. it's authentic :D

 

UlfW, thanks a lot!

[ins13]

The focus shift was with Sigma 30mm and ZWB1 2mm + СЗС23 3mm

f2.8, 1/30 s, iso 800

I like this effect

 

 

I have filter ZWB1 thickness of 5 mm. It transmits such a combination of UV and red+IR that the focus shift arises even stronger

f2.8, 1/4 s, iso 1600

 

 

[ins13]

Winter

 

Olympus em5FS, Industar-50 lens, ZWB1 2 mm + СЗС23 3mm

 

f3,5, 1/20 s, iso 800

This arbour is white in the visible

 

1/80 s, iso 800

 

the silver and the white cars

1/10 s, iso 800

 

 

The bunch ZWB2 2mm + СЗС21 3 mm gives other colors

1/25 s, iso 1600

 

 

The color difference is very noticeable in the sun and in the shade. IR more in the sun, UV more in the shade. This is due to their differences in scattering and reflection

[nfoto]

Some of the images with ZWB1 (5mm) show indications of non-planar filters as well. Sharpness undulates across the frame.

[ins13]

nonsmooth glass? No, it's a giant shift focus

[Andy Perrin]

Yeah, the reflected spectrum changes from pixel to pixel, so the focus does also. I have seen this variable blurring effect when taking full spectrum pics at night, where some parts of the image are strongly iR and others strongly visible.

[ins13]

Yes, and here this effect is even stronger, UV - IR. And it's very funny to see in the viewfinder alternately two sharpnesses on everything - for IR and for UV :)