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UltravioletPhotography

TEST: EL-Nikkor 50mm f/2.8N vs EL-Nikkor 80mm f/5.6


Hornblende

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Hornblende

Intro:

 

I recently acquired a EL-Nikkor 50mm f/2.8N (plastic version) and I wanted to test its UV capabilities.

An f/2.8 apperture is interesting because it means the best image quality is reached around f/5.6, in comparison to the EL-Nikkor 80mm in which good image quality correspond to f/16 or f/22. It was because a glass element was mounted in the wrong side, the lens is totaly useable at f/5.6.

My thought was: even if the EL-Nikkor 50mm f/2.8N transmit less UV light than the 80mm, more light will reach the sensor using the 50mm at f/5.6 in comparison to using the 80mm at f/16 or f/22.

According to Dr. Enrico Savazzi, the EL-Nikkor 50mm f/2.8 (metal version) reaches 50% trans at ~365nm. In principle, the plastic version should perform a little bit worse. However, it seems good enough to record UV signature of flowers.

Last thing, the EL-Nikkor 50mm f/2.8N is a great macro lense given its very short FFD, and it takes good quality pictures! Plus, there is almost no flares/glares. It is a great advantage in comparison to the EL-Nikkor 80mm, which is almost unusable in macro using extension rings.

 

 

Methodology:

 

A Baader-U filter is placed in front of a "lens-cap pinhole" mounted on my Canon 6D full spectrum.

A piece of white PTFE is placed behind the lens in order to evaluate the transmission.

White balance is done on the PTFE piece.

 

Results:

 

Canon 6D - Pinhole - ISO 1600 - 4" exposure

post-136-0-73395600-1495894828.jpg

Right: 50mm, Left: 80mm

 

As expected, the EL-Nikkor 50mm f/2.8N transmits less UV light than the EL-Nikkor 80mm, but it is not as dramatic as I thought it would be! Remember my previous test of the Carl Zeiss Jena Tessar 50mm, this lens WAS unusable in UV.

In my opinion, the EL-Nikkor 50mm f/2.8N is still "usable", taking into account its good image quality at f/5.6 and its great macro capabilities.

 

I wanted to show a flower picture using the lens but there is too much wind for the moment, maybe later :(

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Thanks for this addition to UV lens testing.

 

That's a good point about the sharpness and macro qualities of the EL-50/2.8N even though it might have a llower range or lower rate of UV transmission.

 

It has reminded me to round up some of my lenses and try the UV Pinhole Test again. I did enjoy my previous test and found it useful.

 

Try a lens shade for your EL-80 and keep the illumination well behind it. That might help with flares? Also, sometimes extension tubes can be leaky. Cover them with a dark, dense cloth if that is the case.

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Hornblende, Is there a reason you would prefer the newer plastic El-Nikkor 50mm f/2.8 more than the older metal El-Nikkor 50mm f/2.8?

I have all three here that I have tested, and the older metal version definitely transmits UV deeper, closer to that of the El-Nikkor 80mm f/5.6 (80mm chrome mount version is best).

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Hornblende

I bought the plastic version from a store at low price, and I wanted to see how it performed in order to expand the UV capable lens database.

In the future I might get the metal version.

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The point you make about the importance of the widest usable diaphragm aperture of a lens for UV imaging is a very important one. The other question I have realised is that using the StrightEdgeU filter vs. the Baader U filter makes, as one could expect from first principles, a huge difference when assessing the suitability of objectives and even cameras for UV imaging.
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Andy Perrin
Cadmium, have you done a shot of the Sparticle using a pinhole anywhere? I always wonder what it would look like with no lens!
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Andy Perrin
I don't know, Hornblende did it at the top of this thread, ask him! I would think you could just stick the Teflon behind the Sparticle and snap a photo through a pinhole, as with the lens test.
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Sparticle pinhole lens test.

Not a very sharp looking pinhole lens shot. Just aluminum foil and a needle, stacked with Baader U.

High ISO to compensate for the small size of the pinhole, thus the noise.

post-87-0-11245400-1496114734.jpg

 

What I was meaning to ask, Andy, was how to make a pinhole.

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Andy Perrin

OH! I did not understand, needless to say. Well, that is pretty much what I had in mind, though, although it could use a longer exposure I think. Sharpness doesn't matter very much for that application anyway.

 

I think we can conclude that either the sensor does not respond to 325nm, or that the light source does not contain any. Therefore the lack of 325 in the other tests doesn't mean anything.

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The Baader U has a limit also.

I think you will see a little more 325nm in the tests I did with the Kuri 35mm vs Focotar-2 50mm, than with the El-Nikkor 80mm which doesn't transmit UV quite as deeply.

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I think there may be just as much 325nm in the pinhole test as there is in the Kuri 35mm and Focotar-2 50mm tests, but the pinhole is just a lot more fuzzy and harder to see.
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Andy Perrin
Only if by that you mean "none." I think you had it right above, the filter just cuts it all, essentially. (Slight exaggeration, but there isn't enough to do anything very interesting with, anyhow.)
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Andy. Look at some of my other tests, you will see a bit more color from the 325nm bandpass filter.

So what I am saying is that the El-Nikkor 80mm shows slightly less 325nm, and the pinhole is just fuzzy, because it should look the same or better than that Kuri 35mm and Focotar.

OK?

OK.

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Andy Perrin

You were perfectly clear the first time. There is a tiny bit at 325, and it's practically speaking pretty useless regardless of lens because it's too dim compared to all the other wavelengths to affect the results. At least with that filter.

Get it?

Got it.

Good.

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Not useless at all, Andy, quite useful, to me anyway. :-)

If you use a filter that transmits lower than the Baader U, and some people do sometimes, then with certain lenses you would see deeper than 325nm even, if there were lower bandpass filters present.

I would have a few lower range bandpass filters included if there was more room, but practically speaking, the ones I have included are the range I test for.

The 325nm filter is quite useful to me, like with the Kuri 35 and Focotar-2, those lenses show some color from that filter, where as other lenses will not.

Because I have the 325BP10 I am able to see that some lenses work better than others.

So I don't understand why you say it is not useful. :-)

Here is an example of using another filter that transmits lower, and how the 325nm filter works with that.

post-87-0-10772900-1496190033.jpg

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The primary problem might be finding enough UV illumination around the 330 range? UV gets pretty scarce pretty fast in sunlight once you get past 340. At the moment I don't recall the charts for Xenon flashes, etc. and what they produce in that range.

 

I've never gotten a thing with my 293 filter.

 

Here is a Pinhole Body Cap. Or you could make your own body cap pinhole. (I don't know anything about the linked website. Just wanted to show a pinhole body cap.)

https://www.pinholeresource.com/index.php/all-products/pinhole-digital-no-dust-body-caps

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Andy Perrin
Because I have the 325BP10 I am able to see that some lenses work better than others.

So I don't understand why you say it is not useful. :-)

I feel like you're not understanding what I was talking about at all? What I was saying is that there are zero lenses where 325nm LIGHT is of any use in taking actual photographs using the Baader filter, or anything more restrictive than the Baader either. I was not knocking the usefulness of having a 325 bandpass in the Sparticle, which is a totally separate issue and just not what I was referring to.

 

The original request for the pinhole photo of the Sparticle was because I wanted to know if the lenses were blocking the 325nm light, so the test was to remove the lens altogether and test that. It became clear that the lenses were not the main culprit, it was the Baader itself not letting the light through. The other lenses, Kuri 35mm et al., make the 325nm Sparticle filter only slightly brighter, not enough to affect a photo taken with the Baader.

 

Your last post shows a photo taken with a different filter than the Baader, and of course that one shows interesting things! I was not disputing that.

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OK, that's cleared up!! :D :D :D The BaaderU won't work well, if at all, around 325 nm.

But again, illumination might be part of the problem??

 

You know, I have this little BaaderU 1.25" filter from somewhere which has on its label: 300-400 nm.

What the heck is this little thing? My big 2" BaaderU labels read, variously, as:

  • CWL 350nm #2458291 [This one has a thinner mounting ring than the other two.]
  • HWB 325-369nm #2458291
  • 60nm HBW 320-380nm #2458291

What the heck is going on with these BUs ??? I've lost track of when I bought them so have no idea which is oldest/newest.

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The 1.25" is likely the gen.1 Baader U with inadequate IR suppression. Could function on say a D70 unmodified, but a disaster on any "full spectrum" camera.
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I have some Sparticle shots from outdoors that show 325nm a bit stronger, so there might perhaps be more 325nm from natural light than from the 199A.

The flash is much more convenient and makes for more uniform comparisons.

The Baader I have is labeled: Baader-U 2" (HWB=325-369nm) optically polished #2458291

HBW means the bandwidth at half of the peak amplitude.

https://chem.librete...=352&height=302

So if the labeling is accurate, and it means what I think it should mean, then it should transmit lower than 325nm, but the lower slope may be fairly sharp,

and Baader U's vary from year to year, because I have seen more than several years tested since the 1.25" gen, and they all have slightly different slopes.

 

Perhaps I will try to do a test comparing outdoor light and flash sometime. But flash is nice. :-)

I forget the lighting that Enrico used for his.

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enricosavazzi

(...)

I forget the lighting that Enrico used for his.

Almost always, Bowens studio flash units with non-coated Bowens tubes, with any filters. Except landscape subjects, of course.

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