Testing UVRoptics "UVBplus - 331BP75" filter in Warsaw

[lukaszgryglicki]

https://www.uvroptics.com/index.php?UVBplus

Gear:

- Fuji 50R full spectrum, mono by maxmax.com.

- UV-Nikkor.

- "UVBplus - 331BP75" filter.

- Additional BG39 2.3mm for extra IR-blocking (just in case).

- Apertures usually 16, 22.

- Tripod.

- Time usually from 3-4s to 50s.

 

Weather:

- Full sunlight around 11 AM, no clouds at all.

- Very weak wind.

 

Files resized to 35% of their X & Y dimensions and quality of JPG set to 70%.

According to filter specs and extra IR block, I'm assuming this is mainly 330-360nm light - but of course, I cannot prove it this is pure guesswork.

 

[KhanhDam]

thanks for this. there filters are reasonably priced comparatively at least.

[Andy Perrin]

The longwave end of things always dominates so we’re probably seeing mostly the 360nm’s. To really tell we would need to do the two filter spectrums times the camera sensitivity and the illumination spectrum.

[lukaszgryglicki]

Can be 360nm, sure.

 

[Stefano]

What happened with the first photo? It looks like a double exposure.

 

I noticed you like stopping down. Do you do that to increase the depth of field? At least diffraction shouldn't affect images in UV at least up to f/11 or f/16. Maybe f/22 will look slightly softer.

 

Nice images anyway.

[lukaszgryglicki]

On 1st photo I walked away, I was thinking the exposure will be 10s, but it was actually about 30s.

I'm stopping down for sharpness, I see diffraction is lowering quality only at f=22, did a few exact same shots of far away railway electricity, and I saw that f=22 was the sharpest, actually couldn't tell the difference between f=16, but f=32 was softer, so no shots are using f=32 - most are 22 or 16.

 

BTW: even with full sunlight araound noon - all looks like total overcast and a bit of fog.

 

 

[Stefano]

Your lens should be sharp already wide open. The fact you mentioned far away objects makes me think you are not reaching infinity focus for some reason.

 

Do you need to stop down that much also at other wavelengths?

 

Edit: is it possible that you are actually focusing beyond infinity?

[lukaszgryglicki]

My lens is UV-Nikkor, it will be sharp (and is) even at f=4.5 but then overall shapness will be worse at the edges and for anything that is closer - I just want to maximize this.

Yes I can focus beyon infinity with UV-Nikkor no matter if at f=4.5 or f=32 - can also do this with visible and infrared light.

I just prefer stopping down, and you can ask others here, UV-Nikkor is not perfect, it will be slightly less sharp and a bit less contrast/dreamy on f=4.5/5.6 than on f=8 or 11. This is the case with almost all lenses, maybe, again, maybe only some top newest ones are very very sharp wide open, but also only happens for leenses that are quite slow (Uv-Nikkor is very slow - it is only f=4.5).

 

[cazza132]

Nice work! You have some good gear for the job - pointing very high upwind in UV. It would be very interesting to see a colourized image using the UVBplus - 331BP75 vs Dichroic 376BP41 (or Kolari UV, BaaderU) bicolour or tricolour.

They have some interesting filters at a good price. Might have to buy a few myself. The CuRB ir blocker and UVBplus - 331BP75 do look interesting.

[lukaszgryglicki]

I have CuRB, I can use it with 331BP75. I think I even did that, The effects will be similar because the BG39 2.3mm that I used here also blocks IR well.

 

[cazza132]

I really have to sort out the humidity issue living in a sub tropical region on the east coast of Australia. My camera gear is exposed to 70-80% humidity 24hrs. The ZWB3 rocks up corroded already from AliExpress, the ZWB1 slowly corrodes and the ZWB2 is ok. Other filters corrode - esp hot mirror types also (Kolari Hot Mirror V2 clip in and Astronomik OWB (ordinary white balance) clip in). I have the B+W 403 (UG1) that is still perfect after 15 years. The CuRB looks pretty good for storage in high humidity environments given the encasement with fused silica. How does the 331BP75 look like with regard to susceptibility to humidity?

Hey, I would love to see the 331BP75 used vs a UVA style filter for bi-colour or even tri-colour with a third filter. You definitely have the gear to do that!

[lukaszgryglicki]

I see no corrosion on 331BP75, I also see no corrosion on CuRB (which is just a glass with a liquid solution of CuSO4 inside).