diant Posted October 20, 2021 Share Posted October 20, 2021 Yesterday I carried out a simple UVA test of my 15 lenses and found out an expected leader. The test was consist in illuminating of PTFE plate by the head of Nemo torch ("would be 15W", but not really of course) and imaging it by the testing lenses through the stack of ZWB1 2mm and QB39 2mm. Nemo torch's head was dismounted from torch and powered by Lab Power with 1,50A CC limitation (around 5,5W). The head switched on only for a short periods to avoid light power drift with its heating. Main light output of such high-powered 365nm leds lies in 365-370nm band. All lenses were been mounted on mono ASI183mm camera and all images were been made with gain=200, offset=0 and exposure time 10ms in SharpCap software. After that I opened a RAW images (FITs in reality) in FitsWork and determined a mean value in square region well inside of the PTFE plate. Distance to PTFE plate was around 5m. All images had 16-bit depth so a mean value could vary from 0 (black UVA lens) to 65536 (great UVA lens). All my enterprise was conducted in view of idea to compare some of my lenses in near UVA region (360-400nm) with my Super Takumar 3,5/35mm (SN 3759215) - very good performer in this region. Some note. Because 360-400nm is the most near UVA region - where balsam does not display its blinding influence and where the most old flint glasses have rather good transparency - I suspected that a good transparency in this region should be a function rather (1) a number of air-glass surfaced and (2) a coating of these surfaced. I tested only short focal distance lenses (<55mm) so I adopted that they have not a thick flint glasses inside at all. As I preferred to avoid MC lenses in my test, I speak in point (2) mainly about single-coating or (more frequent) double-coating (TiO2/SiO2 or ZrO2/SiO2 etc) used in 50-70s years. As such double-coating has more frequent purple or bluish tint and had a huge raising of % reflection in Violet and the more so in near UVA - I expected that a winner should be find among simple lens (3-4 elements) without such purple or bluish coating lens, but with yellow tint coating. Or it should have a single-coating, hard seen ever by eye. And now my result. The main "control" lens - Super Takumar 3,5/35mm - showed at f3,5 mean value 33500. A purple coating of half surfaces spoils it a little in UVA... Two samples of Industar-69 2,8/28mm showed at f/4 23400 and 25400 but at f/2.8 they showed 37500 and 42000 - not so bad... But a purple coating. Two samples of T-43 triplet 4/40mm showed at f/4 24500 and 25600 - I expected more... But again a purple coating. Mikar S 4,5/55mm showed at f/4,5 only 16000 - not good for a triplet... purple coating of all surfaces... Macro-Revuenon 3,5/28mm showed at f/3,5 15800 - bad. Revuenon 3,5/35mm showed at f/3,5 24400 - I expected more... Auto Revuenon 1,7/55mm showed at f/3,5 19700 - unexpected high result, in view of its complicated 6/5 design (at f/1.7 it showed more than 65536 value and went off-scale!) Zenitar 1,9/50mm showed at f/1,9 only 13900 - worst of all. Old EL-Nikkor 2,8/50mm showed at f/4 23200 - strange to say, but I expected much more for a lens with all around yellow-tint coating... EL-Nikkor 4/40mm showed at f/4 26200 - not so bad for a modern lens with a modern coating... Old MC Nikkors (35 and 50mm) show such bad result that I won't to say about it. And finally the winner - Soligor enlarging lens 3,5/50mm, triplet, all six surfaces are yellow-tinted. This lens was designed for a working with a photopapers (sensible to UV-Violet region mainly) and was coated in absolutely right manner for a such purpose. Its two-layers coating (I suspect two-layers, but how knows...) has its hotspot wave-length somewhere around 400-450nm - that is very very good for UVA working. At f/3.5 this Soligor showed 49400 ! And I suspect it has T365 more than 70% (may be around 75%), being "another Focotar". If its cut-off point prove to be in 310-320nm region - it will show itself as another best UVA-performer. But I have not such spectrophotometer that would allow me to determine its curve up to UVB. PS. I've received this lens in rather poor condition from ebay, but - alas! - there were no any fungus on its lens. I disassembled it "to the screw" and cleaned all its surfaces to a present good appearance. All unpressed (unmounted) edges of lenses were also blackened by me. I bought it after reading this thread of course ;) - thank you, bvf! It is probably twin-brother for Soligor enlarging lens 3,5/35mm, referred by bvf there. Link to comment
Guest Posted October 20, 2021 Share Posted October 20, 2021 Not the winner? Auto Revuenon 1,7/55mm showed at f/3,5 19700 - unexpected high result, in view of its complicated 6/5 design (at f/1.7 it showed more than 65536 value and went off-scale!) Soligor is a good deal on eBay. Looks a lot like the Vivitar. Can you test for yellow colored LoCa in the background blur at say 1:1 or 2:1? Link to comment
diant Posted October 20, 2021 Author Share Posted October 20, 2021 1 hour ago, Blazer0ne said: Not the winner? Auto Revuenon 1,7/55mm showed at f/3,5 19700 - unexpected high result, in view of its complicated 6/5 design (at f/1.7 it showed more than 65536 value and went off-scale!) Yes, you are right - it is a winner, if we close our eyes on f/1,7. It is an easy thing to be near-UVA winner at f/1,7 - but Soligor displays almost the same near-UVA light-gathering at f/3,5. In other words Auto Revuenon has proportional low UVA-transparency as compare with its Vis-transparency. But Soligor has almost the same transparency in 360-400 nm as in 400-700nm. BTW, such unexpected good UVA-transparency of Auto Revuenon 1,7/55 (with its 6/5 design) is partially explained by the fact that more than half of its surfaces have yellow-tinted coating. 1 hour ago, Blazer0ne said: Can you test for yellow colored LoCa in the background blur at say 1:1 or 2:1? I don't understand what does it means? Link to comment
Guest Posted October 20, 2021 Share Posted October 20, 2021 Longitudinal chromatic aberrations. Sometimes the specular highlights in the blurred background have a yellow fringe under reflected UV. I was wondering how much or little this lens might show in addition to its good UV transmission. This is where it becomes an aesthetic value. Link to comment
diant Posted October 20, 2021 Author Share Posted October 20, 2021 Blazer0ne, I am not understand you fully, but may be you want me this: Small letters here have height around 0.6mm (this is a small instruction). Pixel size 2,4 microns. Crop in 100% scale. First image - in Visible, second - under Convoy torch illumination (Nichia led 365nm with ZWB2 filters). All scene: Link to comment
Andy Perrin Posted October 20, 2021 Share Posted October 20, 2021 Was the second image white balanced with PTFE? It’s hard to see chromatic aberration if there is a cast to the image. Link to comment
diant Posted October 20, 2021 Author Share Posted October 20, 2021 13 minutes ago, Andy Perrin said: Was the second image white balanced with PTFE? Excuse me, no. Only by paper itself. Link to comment
Andy Perrin Posted October 20, 2021 Share Posted October 20, 2021 Ah. The paper is usually not white in UV. Link to comment
diant Posted October 20, 2021 Author Share Posted October 20, 2021 Ok, I'll repeat it on Friday with PTFE in the field. Link to comment
Guest Posted October 21, 2021 Share Posted October 21, 2021 4 hours ago, diant said: Blazer0ne, I am not understand you fully, but may be you want me this: Small letters here have height around 0.6mm (this is a small instruction). Pixel size 2,4 microns. Crop in 100% scale. First image - in Visible, second - under Convoy torch illumination (Nichia led 365nm with ZWB2 filters). Ok, did you use the mono ASI183mm camera or something with bayer? I think you would need bayer or RGB filters combined, because the visual effect is bound by colors or in this case false colors. Take a look at the second photo in this post. Top left corner of image. Do you see the yellow in the background blur? https://www.ultravioletphotography.com/content/index.php?/topic/4015-myosotis-sp-forget-me-not-stacking-a-tiny-flower/ Link to comment
diant Posted October 21, 2021 Author Share Posted October 21, 2021 7 hours ago, Blazer0ne said: Ok, did you use the mono ASI183mm camera or something with bayer? I think you would need bayer or RGB filters combined, because the visual effect is bound by colors or in this case false colors No, it was not 183, but ASI533MC - bayer camera without any filters on sensor and with AR coated window with transmission around 100% at 400nm and 30% at 350nm (smooth slope). 7 hours ago, Blazer0ne said: Take a look at the second photo in this post. Top left corner of image. Do you see the yellow in the background blur? Are you mean the upper left corner of the second image? Is it these yellow patches in bokeh region: Link to comment
Guest Posted October 21, 2021 Share Posted October 21, 2021 >Are you mean the upper left corner of the second image? >Is it these yellow patches in bokeh region: Yes. I think a test on dark background might appear easier. I do see some artifacts with your black text on white paper. I would like to find a bargain macro lens for UV that does not have this behavior. Right now I have to stack to remove the color. Link to comment
diant Posted October 21, 2021 Author Share Posted October 21, 2021 56 minutes ago, Blazer0ne said: I think a test on dark background might appear easier. I do see some artifacts with your black text on white paper. Ok, I understand. Tomorrow I'll try something in this manner, but unfortunately my ASI533MC is almost blind below 350nm, and I haven't any continuous UVA light source. And the weather now (for using sunlight) is cloudy. But Convoy S2+ (or any other UV365 torch) has a too narrow band to observe LoCA. 56 minutes ago, Blazer0ne said: I would like to find a bargain macro lens for UV that does not have this behavior. Right now I have to stack to remove the color. As I could observe to the present - triplets have moderate LoCA in near UVA. And a complex-design lenses (like for example Nikkors) have a lot of LoCA in UVA. As I understand, never usual lenses, were it modern or old, wouldn't have a low LoCA level in UVA for a simple reason: they weren't been designed for that region. CA was minimized in them only for Visual region and so should have a steep raising in UVA and near-IR. I guess only that some loophole may be found in a land of enlarging lenses. No all of course - for their manufacturers not often recalculated fully its design and manufacturing technique for near-UVA/Violet working (to conform exact to a sensitivity of old photopapers). But if we have an enlarging lens with such happy properties (and a yellow-tinted coating may be one of the sign) - we may have a little hope that it will display a little level of LoCA in near UVA. IMHO. Link to comment
diant Posted October 23, 2021 Author Share Posted October 23, 2021 Blazer0ne, I've tried to image Geranium in two modes: 1). In the light of usual visible white led (now here is evening) 2). In the light of Nemo torch head (365nm led 3W and ZWB2) But it is seems to me that such imaging could not display all LoCA of Soligor 3,5/35mm enlarging lens for two reason at least: (1) very narrow UV 365nm led band and (2) very poor camera sensitivity below 350nm. I've done both image with ASI533mc color camera and Soligor 3,5/35mm enlarging lens at f/3.5 - in first case (visual) with UV/IR cut filter (400-700nm pass) - without any filters in second image (UV 365nm) Black cardboard in the background proved to be a gray one in UV. White square in the upper right angle - PTFE for white balance. Both images - 50% of original. The scale - around 1:4. I have a one idea as to how I can verify this Soligor on far UVA transparency (320-350nm). Sometime late I'll try to realize it. Link to comment
diant Posted October 23, 2021 Author Share Posted October 23, 2021 And now: alkali intrusive Pegmatite from Khibini Mountains (Russia). Soligor 3,5/35mm enlarging lens at f/5.6 and ASI533mc 1). In visible light 2). In Nemo torch light (UV 365nm) Link to comment
diant Posted October 23, 2021 Author Share Posted October 23, 2021 And here is Corundum in the same condition as previous (Pegmatite). But here 100% crop of original. Link to comment
Guest Posted October 23, 2021 Share Posted October 23, 2021 Something about fluorescence must be wired into our brains. I find it so fascinating. Link to comment
diant Posted October 26, 2021 Author Share Posted October 26, 2021 Some UVA-test of this lens (Soligor) in sunlight. All was done through a two windowpane. Idiotic step - by I have no time to move to and positioning my spectrograph at my balcony as the sun was near a neighbouring house and could went beyond its wall at every minute. Link to comment
Guest Posted October 26, 2021 Share Posted October 26, 2021 Diant, we all have difficult days. The good news is that you can try again another day. Oddly enough, I bet many people actually shoot through widows. So, this information is actually useful in a weird human behavior type of way. Next time available you can compare outside Moscow sun and determine what is the loss from your house windows. Cheers! Link to comment
diant Posted October 26, 2021 Author Share Posted October 26, 2021 Blazer0ne, I've compared yet and some minutes late you see the result. Only instead Sun I've used Exoterra UVB lamp. If I did not go mad, this Soligor sees 290nm... no, no 320-330nm only. And film grate of course should not allow it to see 290 :) Here you can evaluate LoCA. It is present of course, even at f/8. Link to comment
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now