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Minolta W.Rokkor-QE 1:4 35mm - Discovery of yet ANOTHER good UV performer.

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#1 igoriginal

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Posted 27 October 2014 - 01:07

Minolta W.Rokkor-QE 1:4 35mm - Discovery of yet ANOTHER good UV performer

Well, folks, I've finally gotten around to returning to testing yet some more copies of my growing collection of "suspected" UV-potentials, based on optical designs.

In this particular case, I've been holding on to two good copies of the late 50's / early 60's-era Minolta W.Rokkor-QE 1:4 35mm (non-auto, "preset" aperture design) for quite some time, now, but have thus far not gotten around to testing my hunches that it would turn out to be a good UV performer. Until now.

Alas, my hunch in this case turned out be true, and joyfully rewarded (which is not something that I could say for all of my hunches. :()

Although I have yet to do a "Sparticle Band-Pass Test" to confirm actual transmission depth ... what I can say with sound certainty for the time being is that this baby is a true gem, and performs just about as good (if not better) than the Kyoei / Kuribayashi 35mm F/3.5 optical design (and many of its cloned / re-badged / re-seller offerings). I do not make this claim with any light-mindedness.

My claim, to be clear, is based on actual field tests (photo results). In other words, real-world results. However, I do understand that more extensive testing (including spectrometer testing) would validate things down to greater precision. Thus, take my find with a measured grain of salt, for the time being. ;)

Below, I have supplied some of my earliest results.

But, before we get to the comparison shots, first some basic facts about the lens:

- Mount: Minolta SR (MD / MC); Early "preset" design, no auto-aperture lever.
- Front filter threading: 55mm
- Focuses down to: 15 inches (pretty good for a lens this old, I think!)
- Focus-shift is very minimal (at F/11 or smaller aperture, just about non-existent).
- There are apparently two design variants that were made (although, from what I have read thus far, they are mostly cosmetic changes, and the optical formula itself has remained unchanged. I do, however, need to investigate this further, before making any potentially uninformed statements about this, because even a slight variation in the coatings could have notable changes in the UV-transmission.). For the time being, though, let it be known that my test involves the FIRST of the two variants of this lens. (Both of my copies are identical, and of variant #1 design, by the way).

And now, for the UV / VIS photo comparisons:

Panasonic Lumic G5 (full-spectrum-converted); Filter: S8612 2mm-thick; ISO 800, F/11, 1/1600 sec.
Specimen: Chrysanthemum x hortorum ("Citronella" / "Winter Aster")
Attached Image: 2014-10-26-1100514-edit-0005-c-8bit-1000x750.jpg

Panasonic Lumic G5 (full-spectrum-converted); Filter stack: ZWB1 1.6mm-thick & S8612 2mm-thick; ISO 800, F/11, 1 sec.
Specimen: Chrysanthemum x hortorum ("Citronella" / "Winter Aster")
Attached Image: 2014-10-26-1100512-edit-0005-c-8bit-1000x750.jpg

Panasonic Lumic G5 (full-spectrum-converted); Filter: S8612 2mm-thick; ISO 160, F/8, 1/400 sec.
Target: Cadillac 2006 CTS (UV & VIS analysis of various surface reflectance / absorptive properties of the vehicle)
Attached Image: 2014-10-26-1100496-edit-0003-c-8bit-1000x760.jpg

Panasonic Lumic G5 (full-spectrum-converted); Filter stack: ZWB1 1.6mm-thick & S8612 2mm-thick; ISO 160, F/8, 2 sec.
Target: Cadillac 2006 CTS (UV & VIS analysis of various surface reflectance / absorptive properties of the vehicle)
Attached Image: 2014-10-26-1100494-edit-0003-c-8bit-1000x760.jpg


Sample photos of the actual lens discovered, and used, for the comparison photos:

Attached Image: Minolta W.Rokkor-QE 35mm F4 - 0001.jpg

Attached Image: Minolta W.Rokkor-QE 35mm F4 - 0002.jpg

Attached Image: Minolta W.Rokkor-QE 35mm F4 - 0003.jpg
Igor Butorsky

#2 colinbm

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Posted 27 October 2014 - 02:41

Good find Iggy
I have been looking closer at the older lenses that I have, to check their suitability to passing UV.
One thing that I have noticed, is when I shine a 365nm capable UV lamp into the front of a lens & viewing from the same side, some of these lenses look like Pea Soup :D
Is this a reliable, & quick, indication of them not being suitable for UV.
These 'Pea Soupers' take OK visible light photos.
Col

#3 igoriginal

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Posted 27 October 2014 - 03:11

Hey, there, Col! How have you been?

That's interesting.

I'm not really all that certain what those observed properties could indicate. However, perhaps you are partially eliciting the excitation of intra-element cement / balsam / glue / adhesive that is probably also UV transmission-distruptive in optical properties? Just a thought.

(It is understood that one of the factors which cause the more modern lenses to be UV-poor, is due to the UV-interruptive properties of the element-gluing / cementing adhesive being used in their design.)

Edited by igoriginal, 27 October 2014 - 03:16.

Igor Butorsky

#4 colinbm

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Posted 27 October 2014 - 03:15

It's a rage in a cage Iggy
Are you able to try this on some of your best & worse, to see if it holds true for you too please ?
Col

#5 igoriginal

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Posted 27 October 2014 - 03:18

Well, now that you brought this to my attention, I most certainly will give this a try. Absolutely. Thanks for this!

(And if there is some truth to this, then perhaps certain ranges of UV-A wavelength bands excite this adhesive more than other UV-A wavelength bands.)

Edited by igoriginal, 27 October 2014 - 03:19.

Igor Butorsky

#6 igoriginal

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Posted 27 October 2014 - 04:08

By the way, here I have found a database / infobase on the differences between variant #1 and variant #2.

Looks like (according to this), that the optical formula (5 elements / 4 groups) and coatings (orange-blue complimentary) remain the same, across both design variants.

One key change, that I notice, is a reduction in filter threading size (from 55mm to 52mm), and also the silver / chrome-colored front barrel edge replaced with black-painted front barrel.

But, you know, no matter how much we read on the net ... no one can know for certain of any transmission differences, until ACTUAL and PHYSICAL test comparisons are made between the two.

(For one thing, I don't recall my own copies' coatings to seem orange-blue at all, but rather golden-dominated. And this leads me to believe that maybe there were even several changes made in coatings batches, even WITHIN a single variant series. Who knows for certain. I will go back, tomorrow, and check both of my copies again on their coatings appearances.)

http://minolta-datab...4/R_35_4_en.htm

Edited by igoriginal, 27 October 2014 - 04:33.

Igor Butorsky

#7 Alex H

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Posted 27 October 2014 - 07:38

View Postcolinbm, on 27 October 2014 - 02:41, said:

Good find Iggy
I have been looking closer at the older lenses that I have, to check their suitability to passing UV.
One thing that I have noticed, is when I shine a 365nm capable UV lamp into the front of a lens & viewing from the same side, some of these lenses look like Pea Soup :D
Is this a reliable, & quick, indication of them not being suitable for UV.
These 'Pea Soupers' take OK visible light photos.
Col

What do you mean "pea soup". Canada Balsam that was used to cement lens elements in good old times fluoresces under UV.

Edited by Alex H, 27 October 2014 - 07:38.


#8 colinbm

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Posted 27 October 2014 - 07:48

Thanks Alex
What I mean is fogged-up, can't see through it, looks like 'pea soup', even though they are clear in visible light.
Col

#9 nfoto

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Posted 27 October 2014 - 08:28

This is my first quick-and-dirty test for UV capability. If the appearance is like dense grey fog (usually on an inside element and not the front one), experience tells me it's usually not worth the effort to try the lens in UV.

#10 colinbm

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Posted 27 October 2014 - 08:51

That seems to be my experience, so it is good to confirm.
I haven't tried any yet, but does the fogging affect the image when you are doing UV induced Visible Fluoresence ?
Col

#11 nfoto

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Posted 27 October 2014 - 09:07

Nope, only "pure UV". UVIFL is in the visible range.

I'd like to add that one can get these 'foggy' lenses to give [very] sharp UV images, but they never go deep into UV and exposure times are significantly longer. The Nikkor 85 mm f/1.4 AIS is a good example. It delivers exceptionally sharp UV images, even set wide open, but the low sensitivity for UV means it always will be bound to a tripod.

#12 colinbm

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Posted 27 October 2014 - 09:27

Thanks Bjorn
Col

#13 enricosavazzi

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Posted 27 October 2014 - 11:34

I have not tried yet UV photography with one of these fluorescing lenses. However, in principle, to avoid image fogging and loss of contrast by the VIS fluorescence one should mount the UV pass filter at the rear of the lens. This is one of the very few cases in which substantial image differences should be expected when using front-mounted vs. rear-mounted UV pass filters.
-- Enrico Savazzi

#14 colinbm

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Posted 27 October 2014 - 11:44

Thanks very much Enrico for this tip.
When Reed makes his filters they should be able to do this easily, & particularly with the EL lenses on M42 extension tubes & the like.
Col