Voïgtlander Nokton 25mm f0.95

[colinbm]

A friend has suggested that the Voïgtlander Nokton 25mm f0.95 in m4/3 mount is a good UV lens ?
 

[ulf]

23 minutes ago, colinbm said:

A friend has suggested that the Voïgtlander Nokton 25mm f0.95 in m4/3 mount is a good UV lens ?

I think that would be highly unlikely.

Look at the lens element diagram here:

https://photorumors.com/2014/02/12/cosina-announced-voigtlander-nokton-25mm-f0-95-type-ii-lens/

• modern lens design
• high speed - optically optimised for VIS
• likely designed with modern optical glass types that often have poor UV reach.
• total optical path long through much glass material 
• many lens elements and AR-coated surfaces

My guess is that if at all, this lens has a quite marginal UVreach.

[colinbm]

Thanks Ulf
This is my thoughts too ?

[Stefano]

From this video, at 2:42: "My favourite lens by far is this Voigtländer, it is a very fast piece of glass, it's f/.95, and, when I tested it with the UV filter, I found that I could actually see through this one very well, even in the ultraviolet; so this was the main lens that I used for shooting in the ultraviolet."

 

We already discussed this video here.

 

Yes, modern lenses, especially ultra-fast lenses with a lot of glass, are unlikely to be good for UV. And yes, you can compensate poor UV transmission with speed; but the only way to be sure of how good/bad this lens is, is to actually test it. We cannot be 100% sure until then.

 

The usefulness of a lens depends on what kind of photography you are interested into. If you want deep reach, and thus rich false-colors, then you may prefer an enlarger lens or an old lens with good reach (EL-Nikkor, Soligor, etc.); if you want to go even deeper and want to try UVB or UVC photography, then you need a specialized lens, or to build one yourself.

 

If however all you want is speed and the upper 360-400 nm range for nectar guides and sunscreen, even a modern lens can be fine. I know that my Canon 40 mm pancake doesn't transmit below ~350 nm, but it's still a useful lens for UV.

[colinbm]

Thanks Stefano, perhaps this is what he meant ?

But he did say it was good for UV SW ??

[Stefano]

Shortwave UV?

[colinbm]

Yes.
And he does know his UV SW from UV LW.

[Stefano]

I would be very surprised if it reaches below 350 nm, so I am very skeptical.

 

Is there a way for you to test this lens?

[colinbm]

Yes I could test it, I have a quartz grating.

No I don't have one & it is for m4/3 mount.

If it was a good lens I could think about it, But convert it to L-Mount & have an extra  0.75mm flange distance to cope with & loose infinity ?

[dabateman]

@colinbm,

These were my points the last time we talked about this 

https://www.ultravioletphotography.com/content/index.php?/topic/5382-best-worst-cameras-for-conversion-updates-welcomed/&do=findComment&comment=58635

 

[colinbm]

Thanks Dave
I did a search, but I didn't see this.
I will pass this on to him.

[Lou Jost]

Don't forget that a f/1.0 lens with 12% transmission passes more UV  light than an f/2 lens with 40% transmission. Transmission percentages are not enough, by themselves, to make judgements. Lens speed can make up for lower transmission percentage.

[ulf]

6 hours ago, Lou Jost said:

Don't forget that a f/1.0 lens with 12% transmission passes more UV  light than an f/2 lens with 40% transmission. Transmission percentages are not enough, by themselves, to make judgements. Lens speed can make up for lower transmission percentage.

But low transmission percentages almost always is a sign of a steep cutoff in the upper UV-A range. An increased lens speed do not compensate for the lost information due to that cutoff in spectra just below the upper UV-A range.

 

Also the final result is a combination of filter- and Lens-transmission. Normally UV-pass filters have a cutoff close to the upper UV-A near 400nm, that decrease the gain from a fast lens.

[Lou Jost]

Yes, but cut

4 hours ago, ulf said:

But low transmission percentages almost always is a sign of a steep cutoff in the upper UV-A range. An increased lens speed do not compensate for the lost information due to that cutoff in spectra just below the upper UV-A range.

 

Also the final result is a combination of filter- and Lens-transmission. Normally UV-pass filters have a cutoff close to the upper UV-A near 400nm, that decrease the gain from a fast lens.

Yes, these two numbers (transmission and wavelength cut-off) are correlated if the cutoff falls in the wavelength range that was used in measuring the transmission. My statement applies when transmission was measured specifically at the wavelength of interest to the photographer.

[ulf]

I understood that but wanted to clarify further implications as your statement could have been interpreted as a faster lens will compensate for all lost performance.

I think we fully agree on this.

[Lou Jost]

6 minutes ago, ulf said:

I understood that but wanted to clarify further implications as your statement could have been interpreted as a faster lens will compensate for all lost performance.

I think we fully agree on this.

Yes, I agree with that completely.

[Dmitry]

I tested similar lens

 

[DKoch]

On 2/25/2024 at 8:27 PM, Lou Jost said:

Don't forget that a f/1.0 lens with 12% transmission passes more UV  light than an f/2 lens with 40% transmission. Transmission percentages are not enough, by themselves, to make judgements. Lens speed can make up for lower transmission percentage.

I'm in the preliminary testing phases using very high performance high speed cinema lenses and I'm seeing this. I was comparing an Industar 50.. f3.5 lens that was recommended for UV work to a Zeiss Master Prime 50mm T1.3 ( f 1.2?)...I thought that nothing would get through the modern super high performance lens but this does not seem the case at all.I'm only interested in 350-400 nm range basically... this was just a quick first look though....

[colinbm]

Thank you
The Canon EF 40mm f/2.8 STM pancake lens has about that reach too.

[Andrea B.]

Time to remind folks of Birna's Maxim:  You can force UV through almost any lens in the right conditions.

 

So, you need to think about what you are trying to demonstrate with a "reflected UV photograph". Do you want a broadband capture using a UV-Nikkor + BaaderU, or not? Do you want a narrowband capture using a narrow UV-bandpass filter, or not? Is a capture in the very-near UV/violet region 380-400 nm acceptable, or not? 

 

I kinda, sorta get a bit miffed by some of the UV photography on YouTube. Like, c'mon, at least rent a real UV lens to make your vids. Excuse me for being slightly snarky today. Bad weather, aching wrist. 

 

 

[Lou Jost]

10 hours ago, DKoch said:

I'm in the preliminary testing phases using very high performance high speed cinema lenses and I'm seeing this. I was comparing an Industar 50.. f3.5 lens that was recommended for UV work to a Zeiss Master Prime 50mm T1.3 ( f 1.2?)...I thought that nothing would get through the modern super high performance lens but this does not seem the case at all.I'm only interested in 350-400 nm range basically... this was just a quick first look though....

I'm glad to see this example. It is not the percent transmission that matters but rather the actual amount of light that comes through, and this depends strongly on the aperture as well as the transmission.

[Andy Perrin]

12 hours ago, DKoch said:

I'm in the preliminary testing phases using very high performance high speed cinema lenses and I'm seeing this. I was comparing an Industar 50.. f3.5 lens that was recommended for UV work to a Zeiss Master Prime 50mm T1.3 ( f 1.2?)...I thought that nothing would get through the modern super high performance lens but this does not seem the case at all.I'm only interested in 350-400 nm range basically... this was just a quick first look though....

Like people were saying above, you may get a decent exposure but nearly monochromatic due to the 350-380nm part being drowned out by the 380-400nm. Then you won’t be able to make a decent white balance that shows false yellows etc. 

[Lou Jost]

That's a good point Andy.

[ulf]

I can force some UV through my Canon FDn 85/1.2 too, but the UV-reach is horrible.

The exposure-time is reasonable, but as the UV/IR ratio is worse than with a lens with better UV-reach it is very easy to get IR-leakage.