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It's not just about the lens transmittance

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#1 Andrea B.

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Posted 15 August 2019 - 18:50

There is naturally a strong emphasis by posters here on "how far" a particular UV-capable lens reaches into the UV. But a good UV-capable lens needs more than just reach.

Do you know how to test a UV-capable lens for chromatic aberrations, spherical aberrations, focus shift, flare? Do you have any charts which can test for resolution and acutance? Do you know how to look for diffraction effects? Can tests for these lens problems show differences in UV not apparent in Visible light, or v.v.?
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#2 SteveE

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Posted 16 August 2019 - 00:28

I am no expert on lens testing, not even close, but I have been looking for test charts online. Here is what I have found so far. All these have links to printable PDF or SVG files. For precise reproducible resolving power numbers you would probably want a commercial chart printed to exact dimensions, but these might be useful for relative comparisons.

USAF 1951 Resolving Power Test Chart:
SVG version in the images section and PDF version in the external links section
https://en.wikipedia...tion_test_chart

Tech note on this chart
https://www.phys.uconn.edu/~eyler/phys4150/R/efg's%20Tech%20Note_%20Resolution%20Test%20Charts.pdf

Links to Siemens Star Focus Chart and one resembling an old TV test pattern are in the "What You Will Need" section of this page
Note: has 4 ads and asks you to accept that they use cookies
https://photographyl...utofocus-issues

ISO 12233 Test Chart
https://www.graphics.../res-chart.html

Koren 2003 new lens test chart
VERY detailed analysis of his charts
Has several ads but does not ask about cookies
If you publish results using these charts, you must credit him, include a link to his page, and notify him by e-mail.
http://www.normankor...rials/MTF5.html

Edited by SteveE, 16 August 2019 - 18:12.

- Steve

#3 Mark Jones

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Posted 16 August 2019 - 00:53

I'm happy to just find a lens that transmits UV, lol. But now that you bring it up what are the sharpest UV lenses that money can buy? Obviously the quarts ones that cost thousands are at the top, but how about the ones that are using cheaper standard glass.
Peace, Mark Jones, Charlotte, NC, UV amateur photographer.

#4 Andy Perrin

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Posted 16 August 2019 - 01:32

Mark, quartz does not imply sharp. You can get a cheap quartz singlet lens and they are terrible from a chromatic aberration standpoint. The nice quartz lenses also have fluorite in them to correct the lens.

That EL-Nikkor 80mm/5.6 (metal version) is pretty sharp. Also the Noflexar 35/3.5 is also, and that lens has a neat built-in extender that lets you take macro pics.

Edited by Andy Perrin, 16 August 2019 - 04:05.


#5 UlfW

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Posted 16 August 2019 - 04:19

I have looked into different test patterns and prefer the one from Norman Koren in SteveE's post above. I think that is best for normal lens testing distances.
Siemens stars are also very useful.
Making such tests is yet another of my stalled projects, I hope to eventually restart.

One problem when you want to test lenses in closeup distances down to 1:1 is to print a test pattern patches small enough and still with high resolution.
One way might be an old-fashioned B&W darkroom process with quality equipment and suitable material, but I do not know anyone doing such processing anymore.
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#6 Andy Perrin

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Posted 16 August 2019 - 04:33

Ulf, laser printers reach pretty high resolution these days, easily in the micron range (1200 dpi is 21 microns between dots).

#7 UlfW

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Posted 16 August 2019 - 06:39

Andy, that is correct, but Norman Koren's test patterns are partly grayscale and then the raster of a laser printer won't work.
Ulf Wilhelmson
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#8 JMC

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Posted 16 August 2019 - 09:13

You're right Andrea, it certainly isn't just about lens transmittance. Personally, I went after that as I was asked a while ago how camera sensitivity, filter and lens transmission and light source spectra would all work together to help define the range of UV being imaged for a given subject. For me, the lens transmission work has been there in the back of my mind for a while and I've spent a significant chunk of time and money on getting an answer to it. Having developed methods for measuring camera sensitivity and now the lens transmission, the flash spectra and filter transmission were relatively simple to crack.

As for the other measures, I know of them, but I am certainly no expert on them. Put it this way, I'd be more than happy if others want to take the challenge of digging into them more :)

#9 dabateman

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Posted 16 August 2019 - 10:30

Andrea, we know these aspects to be important. But:
  • Focus shift is mostly solved by using live view iff you have enough transmission through the lens.
  • Aberrations can be solved in software. Unless really bad, then either it's a quality of the photo/subject or you shift to monochrome, where we are almost imaging. 330nm to 390nm is a fairly tight spectral window.'
  • Now resolution is the big one and probably next most important. I like flower hairs on a dry dandelion. But that's not a standard others can use.
So, how I see it:
  • Do you see any UV through your lens and what are the exposure settings?
    This hits intensity or transmission. At 365/370nm I think is ideal for most.
  • What is the range of that lens, can you see to 380nm, or 313nm or 200nm?
    This hits at your how far comment.
  • Now that you have filtered 20000000 lenses down to 5.
    How sharp are they, which has the best pop or resolution?
    This is really two separate things as some will have excellent macro (10/20 line pair resolution) and others excellent micro contrast (50 and more line pairs).
    For example, my UAT seems to do well paired with a Em1 at 16Mpixels and a BaaderU filter in order to have the best image pop. The crispness is great. But this depends also on the filter. My UG1 filter isn't as sharp, nor are some of my bandpass filters. My 330WB80 improved filter is close but not as good as the BaaderU. So it can get convoluted when you look for sharpness. Camera, filter and lighting will have a major affect.
  • Flare, we can never have too much flare right? Oh wait we are still talking about lenses. Add a hood and hide your self.


#10 dabateman

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Posted 16 August 2019 - 11:09

After my rant next big question:
What about the lenses for the other half of our community?
Looking at a flat mat test chart verses fluorescent lights are totally different things. Do any of us know the best lenses for UV induced fluorescence? Best for Induced IR?
Looking at light is different than a flat object and control of that point light will be important. But here I would expect more lens options.

#11 Andrea B.

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Posted 16 August 2019 - 15:30

  • Lens optics is a fascinating subject. I'm thinking we could all learn at least a little bit about how factors other than transmittance affect our UV-capable lenses.
  • Expert testing of lenses relies on very specialized gear and specialized software. I (ymmv) have *no* particular desire to dig that deep! But, when a new lens arrives (and by "new", I mean new-to-me and not necessarily newly-manufactured), I think it would be a good idea to check out the performance and general characteristics of the lens with some simple tests.
  • Roger Cicala over on LensRentals.com is a master of MTF charts.
    Me? I don't even know how to interpret them. :lol:
    Roger has pioneered some new charts using his MTF bench. And then there is Olaf, the name of the Optikos machine which LensRentals uses to test for abberations and adjustments. Roger's blog is full of other interesting info. Here is an entry about cleaning lenses: linkie. OK, I'm digressing a bit. I started reading those blog entries and found it difficult to pull away.
.

David......what rant? I didn't see any rant. :lol: :lol: :lol: And, "the other half of our community"? I didn't realize we had "halves". But nevermind.... :cool: :rolleyes: :wink:

If there is some area which has not been covered with a Sticky, then any member is free to begin gathering information and writing up a Sticky worthy topic. For example, see Andy's recent SWIR sticky, a most excellent effort. In the same vein, I've always encouraged anyone to create an ongoing experiment and will provide space if it proves worthy. For example, see Dmitry's interesting work at estimating UV reach of a lens using a jeweler's loupe. And see Jonathan's and Ulf's on-going lens transmittance work. (We should probably provide a new section for this??)

This forum depends on group participation. There's no way I can do everything. So if there is an area which could use some definition and write-up, then go for it! (I can help with formatting and editing when.I.have.time. La!)


Ulf, thank you for the list of charts! I have printed some charts in the past, but I've been thinking about buying one printed on something more substantial than paper.
Andrea G. Blum
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#12 Andrea B.

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Posted 16 August 2019 - 15:49

But now that you bring it up what are the sharpest UV lenses that money can buy?

The consensus of opinion is that the Coastal Optics 60/4.0 and the Nikon UV-Nikkor 105/4.5 (or its sister the Rayfact UV-Nikkor 105/4.5) are the "sharpest" in UV of the UV-dedicated lenses.

I really truly do NOT wish to open the Worm Can with that statement.
I'm reporting here, not taking a side, OK???

And that is a generic usage of the word "sharp". If you were to go full geek in lens analysis, then you would not use the word "sharp". You would discuss features like lens resolution, detail, acutance and micro-contrast.
If anybody mentions "circle of confusion", I will run screaming out into the 90% humidity and start sweating buckets while waving canned worms around.
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#13 dabateman

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Posted 16 August 2019 - 19:39

Andrea,
Since you opened up that can of worms and you and Jonathan are the only people on the planet whom can do this test.
Can either of you image a flower with small details, like little hairs and large detail, like a sun flower, with the Coastal optics 60mm, the Nikkor 105mm and the UAT.
That would draw the line in the sand. My gut says if the hotspot of the Coastal optics 60mm can be avoided it will be first, followed second by the UAT and the Nikon 105mm will be last.
If the hotspot can't be avoided I think the UAT is the sharpest. But I don't have or ever can afford the other 2.
The UAT is sharper than the Resolve 60mm macro.

#14 Mark Jones

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Posted 16 August 2019 - 20:51

Yes, everyone knows the 60 and 105mm quartz that cost thousands are the best, but what about lenses us mere mortals can afford? 80mm nikkor seems to get good comments.
Peace, Mark Jones, Charlotte, NC, UV amateur photographer.

#15 nfoto

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Posted 16 August 2019 - 21:02

I don't have the UAT but several copies of the other lenses mentioned :) The UV-Nikkor stands up to time by being a super sharp lens -- for UV. It seemingly cannot do visible equally well, however. In the latter case the CO 60 is excellent

#16 Andrea B.

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Posted 16 August 2019 - 23:18

I will try to run a test with UAT, UV-Nikkor and CO 60. But how does one best shoot the flower (or whatever) for a comparison given the difference in focal lengths? At the same distance? Or should I fill the frame equally in each photo at different distances? What is the fair way to do this?

IIRC, in UV the CO 60 and UV-Nikkor are about the same "sharpness".
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#17 dabateman

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Posted 17 August 2019 - 05:29

View PostAndrea B., on 16 August 2019 - 23:18, said:

I will try to run a test with UAT, UV-Nikkor and CO 60. But how does one best shoot the flower (or whatever) for a comparison given the difference in focal lengths? At the same distance? Or should I fill the frame equally in each photo at different distances? What is the fair way to do this?

IIRC, in UV the CO 60 and UV-Nikkor are about the same "sharpness".

I don't know. I look forward to other answers. As you can see from my Resolve vs UAT thread. I slapped on a 17-31mm helicoid to the UAT to get it to equal the Resolve on the Stock DF. But is that fair?

I just wanted to know if the Df was full spectrum can I still use my lenses and filters without vignetting. The 25mm were limited and the depth of field and WB was a pain so not going down that road.


#18 dabateman

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Posted 17 August 2019 - 15:40

View PostMark Jones, on 16 August 2019 - 20:51, said:

Yes, everyone knows the 60 and 105mm quartz that cost thousands are the best, but what about lenses us mere mortals can afford? 80mm nikkor seems to get good comments.

Mark my sharpness UVa lens is the Sigma 30mm f2.8 art lens with the smooth focus ring. Its only available in E-mount and M43rds. After that it gets muddy.
With Nikkor 80mm EL, Olympus 43rds 35mm f3.5, igoriginal 35mm f3.5, Olympus 30mm f3.5 macro, maybe in that order. Maybe not.

#19 Andrea B.

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Posted 20 August 2019 - 15:55

IIRC, in UV the CO 60 and UV-Nikkor are about the same "sharpness".

I wanted to add that I wasn't neglecting the UAT in that statement. It is rather that I don't know where the UAT stands in the sharpness ranking in UV. :rolleyes:

I get hung up on what is actually being measure when "sharpness" is mentioned and my Geek Brain has kicked in. Edge acutance can be improved in the converter, but detail resolution cannot. So my criteria would be first to look for detail resolution and then worry about edge accutance when judging a lens for reflected UV use.

As a partial response to Mark J. -- Enlarger lenses like any other lenses vary in quality. But generally speaking the few I've used for UV are "sharp" enough.
Andrea G. Blum
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#20 dabateman

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Posted 21 August 2019 - 00:59

View Postdabateman, on 17 August 2019 - 15:40, said:



Mark my sharpness UVa lens is the Sigma 30mm f2.8 art lens with the smooth focus ring. Its only available in E-mount and M43rds. After that it gets muddy.
With Nikkor 80mm EL, Olympus 43rds 35mm f3.5, igoriginal 35mm f3.5, Olympus 30mm f3.5 macro, maybe in that order. Maybe not.

I should clarify, I ment muddy in my brain. None are clear second place winners. They are all good, but Sigma 30mm f2.8 lens is the sharpest of this set.