Double Invisible Vision 308nm stack results (this is pure UV-B IMHO).

[lukaszgryglicki]

Yes, it IS underexposed a lot.

But this is already ISO 3200 and 30 s exposure at f=8.

If I bump ISO to 6400 (max native of D600) or Hi1 or Hi2 - nothing will change - RAW will be the same and JPG will be more exposed but with a lot more noise - RAW data doesn't change with ISO - it is used to create JPG IMHO. Sensor sensitivity cannot be higher.

 

So to get something correctly exposed I should use about 3 minutes of exposure with f=8. This would give 32x times as much for ISO 100 which gives 1,5 hours.

 

So let's compare it with mono Fuji.

Normalized to ISO 100 this gives:

- Fuji ISO 100 f=8 needed 50s and was exposed OK or even slightly overexposed.

- Nikon D600 fs Bayer would probably need at least 1 to 1,5 hours at the same ISO and aperture.

 

This means that the difference between mono and Bayer is around (30-60s) vs. (1h-1.4h) --> 64 to 180 times which is 6 to 7.5 stops. 

 

D600 and Fuji 50R use different sensors but I think most of this difference comes from Bayer filter. Not also sure what is used in D600 as full-spectrum glass - this is not quartz so it may be also blocking some UV - obviusly when I was converting that Nikon I wasn't thinking about deep UV, the best it could be using is 280+ nm glass (that was a standard one with maxmax when I was requesting mono conversion - but I requested special quartz one 180+ nm instead).

 

 

[JMC]

I saw a 5.3 stop difference between a mono converted Canon EOS 5DSR and a multispectral converted EOS 5DSR at 313nm when I was looking at this - https://www.mdpi.com/2313-433X/8/3/54

 

So you're 6-7 stops is about what I would expect between 'with' and 'without' Bayer filter at around 310nm, especially when comparing 2 different cameras. The WG280 MaxMax uses for their normal conversions wont be having any major effect for blocking UVB through the IV308 filters.

 

 

[lukaszgryglicki]

Today we have very good sunlight, I'm going to try one more stack type:

+ Double Invisible vision 308nm + Hoya U-340 (4mm thick) - with that stack blocking will be at least OD8 in < 270 nm and > 358nm (and this is OD8 from the peak which is 18% at 306 nm).

See this chart: https://docs.google.com/spreadsheets/d/1zMXCT4vtTR6PGf-yzFgUJgUop3gfkpaRAZ50IqN2lsQ/edit#gid=1329577068

Transmission ranges:

- > 10%: 304-316 nm.

- >1 %: 300-322 nm.

- > 0.1%: 396 - 324 nm.

 

Blocking (I'm not listing in short waves, because sunlight has no output there anyway, and it only matters at longer wavelengths, also I'm listing blocking relative to peak so OD2 is 20%/100: 0.2% 0.002):

- OD3 from 328nm.

- OD4 from 330nm.

- OD5 from 332nm.

- OD6 from 336nm.

- OD7 from 346nm.

- OD 8 from 358nm.

 

Then there is at least OD 8.899 in everything after 358nm (max leak everywhere above 358nm is OD 8.9 relative to peak data or OD 9.63 relative to 100%). That stack will be UV-B only IMHO and effectively will report 300-320 nm almost exclusively IMHO.

 

[lukaszgryglicki]

I just got 2 good shots, it's too windy for a tripod and it also looks like I have some light leak/internal reflections when using those 3 filters stack - I was only able to figure this out afterward.

 

Typical exposures: 1 or 2 minutes, f=11, ISO=100. Full sunlight,  around noon, 14th of May so the sun is quite high.

Barely able to use Lv/EVF to do focus in magnified mode with fully opened UV-Nikkor to f=4.5. Other lenses are pitch black.

This is going to be my final UV-B stack, I only hope I can do something with this light leak/reflection which lowers contrast and creates ghosts in some images - now that I know this, I will maybe add one longer hood.

2 images and 100% crops:

 

 

[Andy Perrin]

I guess try to have the light coming from behind the camera (and as you say, a good hood). With so many filters and other interfaces, some reflections are probably unavoidable. This gear is being pushed to its most extreme, one can’t ask too much. But now you should probably go find some more interesting photographic subjects. I don’t think much further improvement to the equipment is possible. 

[lukaszgryglicki]

Yeah, that one is the final stack, 3 filters, or any combination of those two.

I didn't go any shooting because it is too windy, so the tripod still gives blurry images, and each one needs 2 minutes, only 25% or less were OK.

I need a sunny and calm day. I did some IR shooting instead, but didn't processed photos yet :p