Video samples using Universe Kogaku lenses

[Stefano]

This YouTube channel (https://www.youtube.com/@invisiblerays) has some videos on UV/IR photography. The latest videos uploaded show footage taken with Universe Kogaku lenses. These lenses have been already discussed on UVP, for example here: https://www.ultravioletphotography.com/content/index.php?/topic/4784-uv8040bk2-does-it-make-sense

 

These lenses are not chromatically corrected, as they only use one type of glass (fused silica), thus they need to be refocused when changing wavelength. From the videos below, image quality looks to be pretty good, and there's not much chromatic aberration visible (I can't see any of it).

 

They offer lenses from 6 mm to 105 mm, but only lenses from 35 mm cover an APS-C sensor (actually not, as the diameter of the image circle is 22 mm, which is the side, and not the diagonal, of a Canon APS-C sensor, but maybe they cover a few extra millimeters).

 

Two videos:

https://youtu.be/6Rok76Quulk

https://youtu.be/NvtFJsU8bTM

[lukaszgryglicki]

Yes I was considering one of such lenses in the past, but finally decided to go with UV-Nikkor.

 

[Stefano]

They could still be useful if you want a UVB-capable lens with a shorter focal length. They also have slightly larger apertures than a UV-Nikkor. I don’t know how much they cost though, I bet they aren’t cheap.

[lukaszgryglicki]

Actually good idea with my UV-B 3-filter stack. I will reconsider.

They cost around $1400-$1800 if I remember correctly.

 

Maybe I should revisit this one: https://www.universeoptics.com/wp-content/uploads/UV6035B-2.pdf

 

 

[Stefano]

The shortest lens they offer that covers a full-frame sensor is this one: https://www.universeoptics.com/product/uv5035bk-ultraviolet-quartz-lens-assemblies/

 

It has a focal length of 50 mm, half that of the UV-Nikkor.

[lukaszgryglicki]

Well and it might be usable with my almost monochrome filter stack, and then I wonder what is its image circle?

 

[Stefano]

They say 18 mm and max 43.266 (mm). I don’t know why they specify two sizes. Anyway, the diagonal of a full-frame sensor (36*24 mm) is 43.27 mm.

https://www.universeoptics.com/wp-content/uploads/UV5035BK-1.pdf

[lukaszgryglicki]

They specify at T-mount (43.266) and C-mount. But I wonder if the image circle is just like this 43.266 or is this just the value for FF copied from elsewhere - they are too close, usually lenses have a bit larger image circles but this one is really hard to get from any manufacturer.

 

[ulf]

The drawings for both UV5035BK and UV6035BK are full of strange contradictions, if not interpreted in a certain way.

The 18 mm and max 43.266 (mm) is identical for both lens versions.

Then there is some dimensional numbers that are impossible for the two lenses:

There is a diameter dimension of the rear cylindric part said to be Ø46.0 just to the left of that is an indication of a T-Mount Thread M42.0 P=0.75

 

It could be that that rear part with Ø46.0 just is an adapter structure to a C-mount.

If that is what they mean, things can be interpreted like this:

Image circle including the C-mount adapter = 18mm

Image circle when not obstructed with the C-mount adapter 43.266, (usable on a full frame sensor)

[lukaszgryglicki]

Yes this is the case, I've cleared those questions when considering this lens maybe an year ago. I had many conversations with them regarding many various things, finally I decided not to buy this lens due to very very focus changes when changing wavelengths which almost limited those lenses to monochrome or maybe call it very narrow wave lengths ranges, otherwise chromatic abberrations kill any quality.

 

[ulf]

6 hours ago, lukaszgryglicki said:

Yes this is the case, I've cleared those questions when considering this lens maybe an year ago. I had many conversations with them regarding many various things, finally I decided not to buy this lens due to very very focus changes when changing wavelengths which almost limited those lenses to monochrome or maybe call it very narrow wave lengths ranges, otherwise chromatic abberrations kill any quality.

 

That makes sense.

These lenses seams to be intended to be used with very narrow band filters.

As two of your filters are dichroic, it might be a good idea to consider the lens FOV angles when deciding type and FL.

I have no idea about how sensitive the filters are for off axis beams, but the blocking will suffer. 

[lukaszgryglicki]

This 308nm looks OK with 105 mm, I don't see issues even in image corner on 44x33 sensor. But this can become a problem with 50mm, but from the other side, image circle will certainly be smaller than 55mm (I'm so much suprised that UV-Nikkor actually covers 44x33 (55mm circle) at inbfinity, I'm seeing vingetting at close distances, but then, at close distance you usually have a lot of out of focus area -target is usually in the center, so I would say that UV-Nikkor is 98% compatible with GFX sensor size).

 

BTW: UV5035BK lens is $1,700.00.

 

[ulf]

7 minutes ago, lukaszgryglicki said:

This 308nm looks OK with 105 mm, I don't see issues even in image corner on 44x33 sensor. But this can become a problem with 50mm, but from the other side, image circle will certainly be smaller than 55mm

 

(I'm so much surprised that UV-Nikkor actually covers 44x33 (55mm circle) at inbfinity, I'm seeing vingetting at close distances, but then, at close distance you usually have a lot of out of focus area -target is usually in the center, so I would say that UV-Nikkor is 98% compatible with GFX sensor size).

 

That is exactly what I meant.

 

I think that some old medium length 100mm and 135mm tele lenses from Olympus work well on a GFX sensor too (for VIS and NIR).

They are supposed to have very little IR-hotspot problems and are quite sharp. https://www.edwardnoble.com/hotspots

 

[lukaszgryglicki]

OK I've ordered UV5035BK, once I have it - it will become clear very quick.

 

[dabateman]

3 hours ago, lukaszgryglicki said:

This 308nm looks OK with 105 mm, I don't see issues even in image corner on 44x33 sensor. But this can become a problem with 50mm, but from the other side, image circle will certainly be smaller than 55mm (I'm so much suprised that UV-Nikkor actually covers 44x33 (55mm circle) at inbfinity, I'm seeing vingetting at close distances, but then, at close distance you usually have a lot of out of focus area -target is usually in the center, so I would say that UV-Nikkor is 98% compatible with GFX sensor size).

 

BTW: UV5035BK lens is $1,700.00.

 

I remember reading once that the design of the Nikon 105mm f2.8 AF-D macro was similar to the Nikon 105mm UV lens. In that just like the Sigma 105mm macro and the Nikon 105mm f2.8 AF-D macro you need to add a 18mm tube to get 1:1 without vignetteing on the gfx sensor. 

Maybe you should try that. 

Its interesting that these 1:1 macro lens need a 18mm tube to be used for 1:1 on the Gfx, but it does work.  It might also work for the UV-Nikkor as well.

[lukaszgryglicki]

Interesting but with UV-Nikkor I'm getting no vignetting at infinity but the closer I focus the more vignetting I'm getting.

I also have AF Micro Nikkor 105/2.8 - but I think I didn't try it yet on GFX.

 

[dabateman]

58 minutes ago, lukaszgryglicki said:

Interesting but with UV-Nikkor I'm getting no vignetting at infinity but the closer I focus the more vignetting I'm getting.

I also have AF Micro Nikkor 105/2.8 - but I think I didn't try it yet on GFX.

 

Yes that is how the 105mm f2.8 AF-D macro seems to act. Vignetting only when reaching macro, but good beyond.  So an 18mm tube is needed to avoid the vignetting at macro focus distance. The inner tube of the lens must be causing the vignetteing as the lens elements move away for macro. Adding a Fujifilm or Viltrox 18mm tube, which is wider, avoids that vignetteing. 

[lukaszgryglicki]

Will try AF Micron Nikkor 105/2.8 with GFX and report.

In the meantime I've purchased UV5035BK so will report that one too - I should have it in 10 days max.