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[INDEX] Lens Spectra with Jeweler's Spectroscope by Dmitry


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Editor's Note: To avoid persistent HTML formatting problems in the first post of this topic, at Dmitry's suggestion, I have transferred his topic here to my name so that I can help with the editing. This forum software does not seem to permit a member to have full HTML privileges.


 

Similar Experiment by Colinbm:

 

http://www.ultraviol...__fromsearch__1

 

http://www.ultraviol...ch__1#entry1640

 

http://www.ultraviol...ch__1#entry1826

 


 

Lens Spectra with Jeweler's Spectroscope

by Dmitry K.

 

Goal: To test and compare lenses for UV-capability using photographs of the solar spectrum made through a jeweler's grated prism spectroscope. Filters are used to reveal the UV and IR areas of the spectrum while hiding the Visible portion. The Fraunhofer lines can be seen for estimation of wavelengths.

 

This topic will contain an index and short summary for each tested lens. Comments and discussion about the methodology is welcome here. Comments about specific lenses should be made in the link lens topic.

 

Spectroscope: Jeweler's grated prism spectroscope from China (about $30).

Example LINK.

Spectroscope and camera assembly

scopeOnCam.jpg

 

Filters

Filter Thickness Equivalence
ZWB1 2 mm U-340, UG11
ZWB2 2 mm U-360, UG1
ZWB3 2 mm U-330, UG5
QB21 2 mm BG38

 

Camera: Olympus E-PM1 full spectrum conversion.

I converted the E-PM1 myself. The internal blocking filter was not replaced with clear glass. The sensor assembly was adjusted using thin shims between the case and assembly. The original internal blocking filter is about 2.6mm thick (dimensions: 2.6 x 17.3 x 22.3 mm). The shims are 0.6 mm on average. So without replacement glass I needed to move the sensor plane about 0.7 mm (or 0.9 mm ?). Therefore I omitted the reinstallation of the shims which leaves a 0.1 mm distance increase in the flange focal distance. For native AF lenses this is acceptable. For adapted lenses I use a shortened adapter to reach infinity focus.

 

Lens List

For all lenses spectral tests were made in sunlight. For some lenses an additional spectral test was made using a mercury (Hg) arc lamp. The approximate reach was estimated using the results found here. Any lens reaching below 370 nm is given a 'yes'. A lens reaching 370-375 nm is labeled as 'ok'. If the lens cannot reach below 380 nm, then it is given a 'NO'.

 

 

Brand Type & Solar Link Hg Lamp Link Focal Length Speed Mount AF/Man OK for UV? Focus Shift Reach Est
Helios 44M-4 58 mm f/2.0 M42 man Yes   360-370nm
Industar 50-2 50 mm f/3.5 M39 M42 man Yes   360-370nm
Industar 26m 50 mm f/2.8 M39 man Yes   350-360nm
Industar 61LD 53 mm f/2.8 M39 M42 man Yes   365-375nm
Jupiter-3
Юпитер-3
3 50 mm f/1.5 M39 man Yes   355-360nm
Lomo T-43 40 mm f/4.0 custom man Yes   330-360nm
Meike aka Kaxinda Neewer 28 mm f/2.8 MFT APS-C man Yes yes 360-370nm
MIR
МИР
1B 37 mm f/2.8 M42 man ok   370-375nm
Olympus M. Zuiko Digital 12 mm f/2.0 MFT AF ok   375-385nm
Olympus M. Zuiko Pro 12-40 mm f/2.8 MFT AF NO   385-390nm
Olympus M. Zuiko EZ 12-50 mm f/3.5-6.3 MFT AF ok   375-385nm
Olympus M. Zuiko EZ 14-42 mm f/3.5-5.6 MFT AF ok   365-375nm
Olympus M. Zuiko II R 14-42 mm f/3.5-5.6 MFT AF ok   370-375nm
Olympus M. Zuiko Digital 17 mm f/1.8 MFT AF ok yes 370-375nm
Olympus M.Zuiko Digital 25 mm f/1.8 MFT AF ok yes 370-375nm
Olympus M.Zuiko Digital 45 mm f/1.8 MFT AF ok   370-375nm
Olympus M.Zuiko Digital Macro 60 mm f/2.8 MFT AF NO   385-390nm
Panasonic Lumix G Vario 12-32 mm f/3.5-5.6 MFT AF NO   390-395nm
Panasonic Lumix G 14 mm f/2.5 MFT AF Yes yes 360-370nm
Panasonic Lumix G Vario 14-42 mm f/3.5-5.6 MFT AF ok   375-385 nm
Petzval link 85 mm f/2.2 Canon
Nikon
etc
man Yes   355-360 nm
Sigma EX DN 30 mm f/2.8 MFT APS-C AF Yes   360-370 nm
SLR Magic Hyperprime Cine 25 mm T0.95 MFT man ok   375-385 nm

 

Link to comment

Spectrum does contain UV part of second-order spectrum on right side overlapping IR part.

 

Wavelengths are guessed, based on this topic spectrum labels.

 

 

Brand Type & Solar Link   FL       Speed     Mount     AF/Man OK UV? FShift Reach Est
Helios    44M-4           58 mm    f/2.0     M42       man    Yes           360-370nm
Industar  50-2            50 mm    f/3.5     M39 M42   man    Yes           360-370nm
Industar  61LD            53 mm    f/2.8     M39 M42   man    Yes           365-375nm
Lomo      T-43            40 mm    f/4.0     custom    man    Yes           330-360nm
Meike/Kaxinda/Neewer      28 mm    f/2.8     MFT APS-C man    Yes    yes    360-370nm
MIR/МИР   1B              37 mm    f/2.8     M42       man    ok            370-375nm
Olympus   M.Zuiko Digital 12 mm    f/2.0     MFT       AF     ok            375-385nm
Olympus   M.Zuiko Pro     12-40 mm f/2.8     MFT       AF     NO            385-390nm
Olympus   M.Zuiko EZ      12-50 mm f/3.5-6.3 MFT       AF     ok            375-385nm
Olympus   M.Zuiko EZ      14-42 mm f/3.5-5.6 MFT       AF     ok            370-375nm
Olympus   M.Zuiko II R    14-42 mm f/3.5-5.6 MFT       AF     ok            370-375nm
Olympus   M.Zuiko Digital 17 mm    f/1.8     MFT       AF     ok     yes    370-375nm
Olympus   M.Zuiko Digital 25 mm    f/1.8     MFT       AF     ok     yes    370-375nm
Olympus   M.Zuiko Digital 45 mm    f/1.8     MFT       AF     ok            370-375nm
Olympus   M.Zuiko Macro   60 mm    f/2.8     MFT       AF     NO            385-390nm
Panasonic Lumix G Vario   12-32 mm f/3.5-5.6 MFT       AF     NO            390-395nm
Panasonic Lumix G         14 mm    f/2.5     MFT       AF     Yes    yes    360-370nm
Panasonic Lumix G Vario   14-42 mm f/3.5-5.6 MFT       AF     ok     yes    375-385nm
SLR Magic Hyperprime Cine 25 mm    T0.95     MFT       man    ok            375-385nm
Sigma     EX DN           30 mm    f/2.8     MFT APS-C AF     Yes           360-370nm

 

Pending updates to table

Link to comment
I think you are using a prism spectroscope which is why your images look different than I am used to. This may be fine for uv detection, as they tend to spread to shorter wavelengths and compress the larger ones.
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I seen scheme of this spectroscope. It does have both prism and grating. Prism is to line up things to compact cylinder.

 

Single prism never give second-order spectrum.

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Dmitry - Thank you for all this work and the index !!

I am eager to get one of the jeweler's spectro loupes and try this myself. :)

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Trying my best :) Cloudy week, had few minutes to catch sun before sunset.

If someone want to use 12-40pro for UV and have large filter, its possible to use on not modified Olympus body without loss of UV range.

I think its 380+ nm

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  • 2 weeks later...

Hi Dmitry K

 

" Spectroscope used

Jewelry spectroscope from China (about $30). "

 

Where can we see what this is please ?

 

Cheers

Col

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Thanks Dmitry K

Yes it is a diffraction grating spectroscope.

The wavelength scale across the image is quite linear.

Cheers

Col

Link to comment
Yes, it is. You may notice magnified second order spectrum on right side on some of images. Its not possible on prism only spectroscope.
Link to comment

Yes that is the problem with the diffraction grating, the second order overlapping the first :-(

I have found that the Amici Prism spectroscopes are very suited for UV research, as the UV scale is expanded compared to the IR scale.

post-31-0-26159200-1527982316.gif

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  • 2 weeks later...
  • 2 weeks later...

Got Kaxinda/Meike/Neewer 28mm f2.8 myself and did quick test

 

manual focus

reach est 360-370nm

Mounts - MFT, APS-C sized others (Sony E, Nikon 1,Canon EOS M,Fujifilm X)

focus shift - yes

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  • 2 weeks later...
Dmitry, it would be interesting to see UV scenes made with each lens when you get the time to set up some kind of comparative test. For example, how would a photo made with the Meike 28mm lens compare to the same subject shot using a 28mm setting on the Lumix 14-42mm lens which is less UV-capable?
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Andrea, its interesting task, but I need idea about scene, filters and lenses :) I can't take everything with me, can you please list most interesting lenses?

Oh, waiting for portable UV-tube lamp to arrive for more testing and as light source for scenes at home.

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Dmitry, sorry about the bad link !! I did a copy/paste but forgot it included an old link. Your updates are scheduled for this evening.
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  • 2 weeks later...
  • 2 months later...

Hi Dimitry, Andy, Michael, Andrea, et al.,

 

A couple of weeks ago I did some measurements of my objectives using an Ocean Optics Maya 2000Pro spectrometer and the Godox AD200 flash with the bare lamp recommended by Enrico as light source. I had not seen this thread until today. I estimated wavelengths at -3 EV compared to the average of the central part of the visible band (430-660 nm). Some of the objectives are the same as measured by Dimitry and with data in the table at the top of this thread computed with Andy's MATLAB script. My measurements are: M.Zuiko 12-50 mm, 376 nm; M.Zuiko 25 mm, 372 nm, M.Zuiko 45 mm, 371 nm, M.Zuiko 60 mm Macro, 388 nm. So, agreement is almost perfect! I guess we can conclude that both approaches are reliable, with this not-planned but useful cross-validation. :) :)

 

As an aside, the Sigma 30 mm f:2.8 DN A 013 in MFT mount reaches 356 nm at -3 EV and 369 nm at -1 EV, so this explains why it works nicely in UV.

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Pedro, thanks for this very interesting confirmation. It's great to hear that Dmitry's jeweler's spectroscope method provides an excellent estimate for UV lens transmission.

 


At Dmitry's suggestion I have transferred this topic to my name in order to avoid the HTML formatting problems we have periodically experienced. I'll add a note to the first post to clarify this.

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