Kolari Vision UV redness

[Stefano]

Does a lens make so much difference? Assuming a 1 stop difference between a good and a bad lens (in UV), it would be like changing the IR OD blocking by 0.3 OD. It is borderline. It is like seeing a leak with a OD 4 filter and not being able to see it with a OD 4.3 filter. If it happens (it can), the difference should be minor. Unless your lens is worse than one stop loss...

[Cadmium]

Andy B, You need to white balance those, would help, however I think everyone above is correct.

Think of the lens as the first and most important filter. It includes or excludes UV.

So given a lens with poor UV transmission (minimally deep transmission below 400nm) the result is a little like stacking a UV-pass filter with a ~380nm longpass filter, which mostly suppresses the UV and passes the IR.

Exactly like UlfW said above, "A lens with lesser UV-transmission alters the UV/IR-ratio making IR more dominant."

Excellent observation. I have never really thought about such an extreme scenario before.

 

If you shot the test I mentioned already, you would see the IR separated from any UV.

Instead of stacking with S8612, stack the second shot with a red filter, use the same exposure time, and you will see the IR ghost alone.

[Andrea B.]

But why does my Novoflex photo not show IR contamination if the KUV leaks IR?

 

And why are the leaves under the flower dark in both the Nikkor and Novoflex photos if the KUV leaks IR?

 

I actually did stack the KUV with a 695 nm longpass, used the same exposure time and got no IR ghost on the UV-Nikkor.

 

Tomorrow I’ll try that on the Nikkor 35/1.4 if I can figure out how to re-block my D610 light leak. (I don’t want to use duct/duck tape over the upper LCD because it became a sticky mess in the hot sun.)

[Alaun]

 

 

And why are the leaves under the flower dark in both the Nikkor and Novoflex photos if the KUV leaks

 

Perhaps because the scattering of light for UV and IR is different? Using a polfilter might indicates something like that (the IR contamination is larger on the reflected leaves, the shadows stay similar while rotating the pol filter)

[Cadmium]

1) But why does my Novoflex photo not show IR contamination if the KUV leaks IR?

 

2) And why are the leaves under the flower dark in both the Nikkor and Novoflex photos if the KUV leaks IR?

 

3) I actually did stack the KUV with a 695 nm longpass, used the same exposure time and got no IR ghost on the UV-Nikkor.

 

4) Tomorrow I’ll try that on the Nikkor 35/1.4 if I can figure out how to re-block my D610 light leak. (I don’t want to use duct/duck tape over the upper LCD because it became a sticky mess in the hot sun.)

 

You got me thinking again now. :-) Hmm...

 

1) I thought because you had shown that the KV (not to be confused with Schott KV filters, such as KV418) doesn't leak, but instead the Nikkor 35mmr lens is like stacking the KV with a longpass filter.

You should try the same test using a Baader U on the Nikkor lens to compare maybe.

 

2) You mean those leaves on the ground pebbles?

Just an observation on my screen, but not only does that flower in the center of the photo look warmer in the Nikkor lens shot, but the entire area around the flower looks warmer, even the rock,

and there is no reason the rock would look warmer, so perhaps there is also some hot spot involved with that lens, I don't know, but there is something 'funny' about the center of that shot that isn't just about the flower.

Aside from that observation, the rest of the foliage in the surrounding shot looks about the same as the Novoflex shot, except the lavender color is not as strong, and the black leaves might not seem quite as black, but perhaps I am imagining the black difference, definitely a difference in the lavender (or call that color what you may).

 

3) Good. I would think the 695nm would be enough.

 

4) Gaffer's tape, great stuff, sometimes requires two layers, but doesn't leave sticky stuff, comes off easy, but stays on. Way better than any other tape I have found. Get some black stuff, B&H and Film Tools have it is various widths and colors. Here is the 1" I have:

https://www.filmtool...tape-black.html

[Andrea B.]

Cadmium, thanks for the link!

---

 

 

With reference to point (2) above: You have indeed described what I think to be a "hot spot" with the Nikkor 35/1.4 + KolariU. In this case it is more like a "hot central area".

 

What I think we are seeing, however, is a "UV hot central area". I see no evidence of IR contamination. All the leaves in the photo are UV-dark. If IR were leaking, those leaves would show some evidence of that. Here are two black and white versions of the preceding photos to support my hypothesis.

 

And, please note that I have used the word hypothesis as I'm always willing to be proved incorrect in any UV discussions.

 

Look at the moth to the left. Look at the foliage above and below the flower.

 

---

 

 

From above: FWIW, I think my results will show that the KolariU has about 1 level more OD than the BaaderU.

I'm going to change my mind about this statement. I think that my results show that the KolariU and BaaderU have about the same OD for blocking IR. It is difficult to judge OD "by eye".

 

 

---

 

I will work on this some more today after I return from some errands.

[ulf]

This thread has drifted.

Originally it was about Nemo Andrea's problems with this type of filter.

At first he got a really faulty leaking filter that was replaced.

The second filter he got might also be leaking, but to a lesser degree.

 

Now the discussion is about Andrea G. Blum's filter and strange imaging results and wether that filter leaks or not and what caused an anomaly with one lens.

I think the anomaly is due to some leakage or reflection, but not necessarily by the filter.

 

It seams like Kolari do not check the performance of their filters or incoming filter-materials good enough to catch these flaws.

 

Andrea's earlier tests indicate that Kolari's filter has a better OD than Baader U, but The OD of different Baader Us differ over the years.

Nemo Andrea's filter might well be completely different from Andrea's filter.

 

It seams like this all ends in a total confusion, name-wise as well as filter-wise.

 

Panta Rehi!

[Andrea B.]

Ulf, to clarify -- I put an EDIT statement by my original comment in Post #50 about the KolariU/BaaderU OD strength. After looking at more photos I think that perhaps the KolariU and BaaderU have approximately the same OD. I also mentioned my rethinking in Post #56.

 

Of course, one cannot truly judge OD simply by eyeballing a few photos. But there is a similarity in IR "leakage" between the KolariU and the BaaderU. And I can only get that to appear if I "force" the either the BaaderU + RG695 stack or the KolariU + RG695 stack with long exposures.

 

---

 

It is entirely possible that the formulation of the KolariU has also changed. But there has been no announcement of a New & Improved UV-Pass KolariU as would be typical, so we don't really know.

 

I know that KolariU tests their filters sometimes because one of our members tested the KolariU. Nobody tests every filter. Only a few samples would be tested from a batch newly arrived from manufacturer (we don't know who makes these filters for Kolari) to customer (Kolari). Obviously if you test a KolariU on a dedicated UV-lens it looks just fine.

EDIT: That was a stupid thing for me to say!! I can only assert that *my* KolariU exhibits no problems on a dedicated UV-lens.

 

---

 

Ideally we would try to test Andy Broomé's KolariU on a UV-Nikkor. If it looked good there, then the kit lens failures could be revisited to determine whether there is some kind of UV hotspot or other problem.

 

Even more ideally, the actual transmittance of Andy's KolariU could be measured.

 

---

 

As for Nemo Andrea's slightly reddish flowers, I truly think that is simply a WB problem. His other photos did not show that. But I (or someone else) would need to look at the raw file to be completely sure.

 

It is so very very easy to shift the WB in a UV photo especially when cameras sometimes do not accurately measure WB in-camera. Alternately noise reduction or JPG processing in the camera can possibly alter the color profiling. If the files were converted, then there is another possibility of color shift because some converters do not accurately read the camera's WB setting (often due to a manufacturer's in providing compelete EXIF data.) So there are many places where false colour can go wrong.

[Cadmium]

Someone send one to Ulf, he might scan it for you.

[eye4invisible]

Sorry for the late response on this.

 

I have the EL-Nikkor 80mm ƒ/5.6 that I could test with. Owning a UV-Nikkor is just a pipe dream for me, unfortunately :)

 

That said, I would expect similar results to using the Kuri clone. Next opportunity I get, I will shoot with a stacked KV UV and red filter, just to see what I get. The weekend weather forecast is looking favourable!