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UltravioletPhotography

Solar spectrum lens test - Lomo T-43 40mm f4


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Gear used:

Olympus e-pm1 body full spectrum converted myself.

Lomo T-43 triplet lens.

 

Its shortest wavelengths I can see as for today (17 May 2018)

 

Note - far IR part is out of field of view.

 

Unfiltered full spectrum

post-192-0-19824100-1526577969.jpg

 

ZWB1

post-192-0-29569300-1526577984.jpg

 

ZWB1+QB21

post-192-0-13788800-1526577989.jpg

 

ZWB2

post-192-0-24322300-1526577994.jpg

 

ZWB2+QB21

post-192-0-27657100-1526577999.jpg

 

ZWB3

post-192-0-00758400-1526578005.jpg

 

ZWB3+QB21

post-192-0-37792900-1526578009.jpg

 

All photos processed from RAW without any color correction.

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I commented the other Spectrum topic and requested thicknesses of the filters used, please. That is very important in analyzing these kinds of photos.

 

I'm so fascinated by these spectra.

 

Another question: When you say "processed from Raw without any color correction" what exactly do you mean? Thanks.

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2mm thickness.

 

Processed using XnView, its know nothing about applying profiles or corrections to Olympus ORF files (file extension for its RAW format).

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XnView uses dcraw for raw file conversion and will have a specific recipe of settings to tell dcraw. So there will be changes being made to the files. I think only Raw digger actually looks at unprocessed raw data.

If you want to compare open an orf in ufraw, infran viewer and xnview. All use dcraw and all are free and the output raw will look slightly different.

 

But more importantly how are you setting up your test?

What grading are you using? How many lines per mm?

What is your light source? If the sun what time of day or where is the sun position?

 

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Handmade adapter and jewelry spectroscope from China (about $30). Have no idea about number of lines. I point it to light white clouds around sun or to silver reflector if no clouds.

Direct sunlight is very narrow and does not lit full range.

Time of day 2-4pm local time.

 

Photo of setup.

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Thank you Dmity.

I am in process of setting up something similar. I have 1000 line/mm film that I purchased, which the spectrum of which was posted here. The advantage of using sun light is its free. But depending on time of day and your location, the available wavelengths will change. So not consistent, I am hoping to build something with consistent and reproducible measurements.

What I do find interesting is the sharp color seperation you see. Not really a full spectrum, but some filtering is going on there. I am not sure how that is occuring.

Keep up your tests, they are interesting. But don't forget to include all the details. Iso, shutter speed, aperture, lens, camera, light source, filters, filter thickness, subject, and processing for each post, as I and other may just stumble into a single post by using searches. I was not following your history.

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NOTE: right part of zwb+qb21 photo display misaligned lines and different color hue, compared to others. My guess its UV part of second-order spectrum.
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  • 3 weeks later...
  • 2 months later...

If I denoise and follow your guesses, this is what I get. By the way, as an experiment I also tried labeling only the 358 and 373, and the program then guessed 338 for the 336 line, so I think you are correct. By the way, all numbers left of the 336 line should be ignored -- when fitting curves, extrapolation is usually not very accurate, but interpolation between known points is good.

post-94-0-17162500-1534009966.jpg

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  • 7 months later...

I would guess, if just to try setting the white balance in this photo ZWB1+QB21, from this test,

would be visible such gradient of transmission for the ZWB1+QB21 stack, for this T-43 test lens.

post-242-0-86329400-1554542700.jpg

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One more with direct sunlight using zwb2 4mm filter.

iso 200 1/2s shutter.

 

One dust piece somewhere on 350nm, another somewhere at 360nm

 

This one from in camera WB set on fullspectrum on white sheet target and 2.0 gamma applied

post-192-0-14819900-1555336427.jpg

 

This one from ORF file converted without any changes using xnview

post-192-0-18220900-1555336432.jpg

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