Universe Kogaku UV5035BK lens (50/3.5)

[lukaszgryglicki]

UPDATE: link to review: https://teststats.cncf.io/backups/UV5035BK/

 

Hi, just received the lens.

I don't have much time today, but I just wanted to show some first images.

When used without any filter it covers Fuji GFX !! WoooooooooW - I love it.

When I add 55->52 step down ring - it still covers GFX frame.

And now when I add basically ANY filter or hood - it starts vignetting - but then, depending on stack thickness I just need a bit of cropping.

 

Lens is said to be non-corrected for different wavelengths, and at f=3.5 it is really dreamy and chromatic aberrations are visible (in non-converted body) - on mono body it looks just dreamy or a bit soft wide-open - but not that bad. Stopping down helps a lot.

 

Now some photos with:

- My UV-B 3-filters stack: step-down 55->52, Hoya U-340, 2 x IV308nm + hood.

- UVB-Plus from uvroptics

- SEU from uvboptics.

- without any filters.

 

 

I forgot to change setting to save raws, so those are just downsized full JPGs SooC.

WIll contribue this review in next days, with very careful ISO 1000 tripod RAW files - those are from tripod (but I forgot raw) for UV-B 3-filter statck, others are all hand-held.

 

The lens look very promising for me as a general all-purpose UV-lens :-D 

 

[colinbm]

Looking Good Lukas

[Stefano]

Some test suggestions:

- sharpness at various apertures (using a filter of your choice, or several different filters);

- photos taken with a normal color camera and photos taken with a UV/IR bandpass filter, like Hoya U-340 alone, to see how much focus shift and chromatic aberration this lens has;

- tests to see how much internal reflections and general image quality this lens has in IR since it is optimized for UV.

 

As for vignetting, try to reverse mount your filters to mount them closer to the front element.

[lukaszgryglicki]

Not sure how can I reverse mount them - they are all standar 52mm filters and that big stack is 3 filters that are all combined maybe 15mm thick?

For mount I use:

- Lens has T-mount

- I add either T-mount -> GFX or T-mount -> Nikon-F + Nikon-F->GFX - both methods work.

 

I will do the tests requested/suggested - thsi was just a first glance, I only had 1 hour before soccer training.

 

I love that this lens really covers GFX sensor (55mm diagonal) when no filters are use. It really does - if I stop to f=16, then I see no hard vignettign and no corner darkening.

 

I wonder why Kogaku guys said that this lens is unusable in visible light due to chromiatic aberrations - it does have chromatic aberrations, even if stopped down to f=8 - but not that extremely severe to say that it is ususable.

Wide open is maybe a bit softer than Nikkor 55/1.2 AiS wide open too.

At f=11 or f=16 it is very sharp.

 

Will provide detailed images and full scale test maybe over the weekend.

 

 

[lukaszgryglicki]

Added a review - available here: https://teststats.cncf.io/backups/UV5035BK/

Universe Kogaku Optics UV5035BK lens tests 50mm f/3.5

Each image name is like "camera-type" "filter" "aperture".
- "camera type" can be either "stock" (Normal Fuji 50R) or "bb" (Fuji 50R broad band converted, monochrome, quartz sensor cover glass).
- "filter type" can be "no-filter", "uvir-cut" (Kolari UV/IR cut/hot mirror), "ir" (760nm IR filter), "uv" UVROptics Straight EdgeU (SEU Mk2).
- "aperture" can be "f3.5", "f4", "f5.6", "f8", "f11", "f16".

[Stefano]

Thanks. Chromatic aberration is noticeable, although not too bad. I wouldn't attempt to build a corrected lens myself, as calcium fluoride is delicate and probably it wouldn't be worth it.

[lukaszgryglicki]

It is very noticable wide open and still visible at f=8, but as you said - not that bad, and you can focus on narrow bandpass to have it mostly gone - my main target is deeper UV-A and UV-B.

[photoni]

 

photos 1-2-4 with a little photoshop

 

 

can you specify better the filters you used?
Thank you

Toni

[lukaszgryglicki]

- UV-B stack (3 filters): 2 x Invisible Vision 308nm + 1 x Hoya U-340 4mm thick. Transmission data for this stack is here: https://docs.google.com/spreadsheets/d/1zMXCT4vtTR6PGf-yzFgUJgUop3gfkpaRAZ50IqN2lsQ/edit#gid=416424503, https://docs.google.com/spreadsheets/d/1zMXCT4vtTR6PGf-yzFgUJgUop3gfkpaRAZ50IqN2lsQ/edit#gid=1329577068

- UVROptics StraightEdgeU mk 2.

- No-filter at all.

 

If I remember correctly. My UV-B stack can only be used with this lens and UV-Nikkor - others give 0 transmission and PURE noise at ISO 12800 and 30s exposure.

 

 

[dabateman]

Interesting,  now you have 50mm and 105mm options. 

Do you have Gf-mount to M52 adapter, then add your filters, then M52 to T-mount adapter.  That shouldn't have vignetting and the lens shouldn't be too heavy to offer stress to the filters.

It wouldn't be quick to change filter stacks, but might be fun as a walk around setup if you only wanted UVB or UVA.

[lukaszgryglicki]

Ok so you suggest adapter: GFX->M52 then filters and then M52->T-mount? OK but how about the exact FFD needed? My current adapter has a fixed length (it's just T-mount->GFX), - I would prefer to put my 3-filters stack there, so that would make: 2xIV308+4mm-Hoya-U-340 - I think that this stack is about 14-15mm thick.

So I need rather think adapters: GFX->M52 and M52->T-mount, otherwise I won't get infinity focus, right? And I definitely NEED Inf focus.

 

EDIT: actually I cant - this 2xIV308 does not have a thread at end - it was not possible to do this with rings I have... possibly this can be done somehow by dismounting those 2 IV308 filters again (which si a bit dangerous - those glasses dismounted are so fragile imho and IV308 is so crazy expensive alone), but I think that I would prefer front mount instead, will think about this.

 

 

[dabateman]

Was just a thought to avoid vignetteing.  But it is a pain to change filters that way.

You would still have infinity focusing, you're forgetting that when you add glass behind a lens, it pushes the focusing further away. So the lens needs to be further from the sensor with the more glass you add.

[lukaszgryglicki]

I'm not forgetting this, I just didn't know, I've never put a filter behind the lens actually. Good to know, thanks.

 

[ulf]

That phenomenon is directly related to the optical path length due to different refractive index in the filter material compared to air or vacuum.

https://en.wikipedia.org/wiki/Refractive_index

There is a short section about optical path length.

As a very rough estimate the refractive index of the filter materials is in the region of 1.5-1.7. (varying also with the wavelength)

The gained apparent distance for the lens  by placing the filter at the rear end will be (n-1) x glass thickness.

If the filter is 2mm thick and n = 1.5 the change will be 1mm. 

1mm is a small change in focus adjustment for a tele lens, but big for a wide angle lens.

[lukaszgryglicki]

Right, good to know.... my "UV-B" stack is about 14-15mm thick.

[dabateman]

54 minutes ago, lukaszgryglicki said:

Right, good to know.... my "UV-B" stack is about 14-15mm thick.

Yes but you have 55mm for back focus distance for a T-mount lens.  

So 55mm-26.7mm (Gfx mont) gives you 28.3mm to work with. 

 

the Gfx to 52mm Adapters add about 1-2mm. Then the M52 to T-mount adapters I have are at most 5mm. So still 20 ish mm to work with, and added space with glass. So should be easy to add up to 4 filters with 5mm rings. 

Repacking your 308nm filters into a longer tube, might not be worth the damage risk though.