Andy Perrin Posted May 13, 2020 Share Posted May 13, 2020 Irises seem to have a lot of iridescence going on, both in UV and visible? Link to comment
Cadmium Posted May 13, 2020 Share Posted May 13, 2020 The dandelion pic that Andi Broomé shows is definitely not iridescence, and not white balance either.https://www.ultravio...dpost__p__35603 Link to comment
nfoto Posted May 13, 2020 Share Posted May 13, 2020 They, in fact looked like what I got with the very first version of the Baader U. Which subsequently was shown to be quite "leaky" outside the UV passband. Link to comment
nfoto Posted May 13, 2020 Share Posted May 13, 2020 Here is an example. Not Dandelion, but Coltsfoot Tussilago farfara, which has a very well know, and stable, UV appearance. Baader U, 1st generation Baader U, 2nd generation Both with D200 full-spectrum, Noflexar 35mm f/3.5. Link to comment
colinbm Posted May 13, 2020 Share Posted May 13, 2020 Does the Schott S8612 block the IR leak in the Kolari Vision UV filter ? Link to comment
nfoto Posted May 13, 2020 Share Posted May 13, 2020 No idea. I haven't got the Kolari filter. Perhaps Nemo can do the test? However, there are several unknowns in the equation. Firstly, the Kolari filter itself. Secondly, the lens used, and thirdly, the camera. No real degrees of freedom are left. Link to comment
dabateman Posted May 13, 2020 Share Posted May 13, 2020 Birna very pretty BaaderU version 1 image. Almost makes me want one.You have a Valentine's day poppy looking flower there. Link to comment
Andrea B. Posted May 13, 2020 Share Posted May 13, 2020 I have the Kolari KUV and several S8612s. But --- my KUV does not leak IR so there's no point to testing it (again). I think that perhaps Nemo or Andy B. should contact Kolari and try to determine whether he got one from a bad batch. This can happen. Link to comment
Andrea B. Posted May 13, 2020 Share Posted May 13, 2020 Ulf: Are there any examples of flowers showing real Iridescence with a distinct colour the way some butterflies do?Birna: Not like a butterfly. More like a minutely varied mosaic of colour. Andrea B: Concur. This is my observation. You get either a mosaic of colour or you get flashing which varies by angle of illumination. David: Andrea, You learned about the Sigma here and were surprised then: https://www.ultravio...dpost__p__20606 This makes me laugh!! Two years ago!! It seems I no longer can remember where everything is on the pages of UVP. Not surprising, I think, given that we have had an explosion of technical topics over the last couple of years. But David, how did *you* remember this?? :lol: I have almost pushed the button on buying a 35/1.4 Sigma Art more than once because I really could use a good auto 35/1.4. I have Nikon's newest 24 and 28 (for visible work), but thought that the Sigma 35 might be the better buy than the Nikon 35. So I'm going to go do it NOW !!!!! Link to comment
Cadmium Posted May 14, 2020 Share Posted May 14, 2020 Birna, I am flabbergasted! My goodness, both of those photos are beautiful!...but didn't the 1st generation Baader U have quite a little bit more of a 700nm range leak than does the 2nd generation? I have the 2nd generation graph here, but I can't access Shane's filter graph page,where he shows the difference in graph form. His sight seems to be down right now...Shane, where are you? Your page is down again... Anyway, what I see in Andy's dandelion photo is a leak, and I don't know if part of that has to do with a camera sensitivity difference, there is an essential difference between Andi's photo and Birna's 1st generation Baader U shot.Best to do the leak test that I described. You can do it with just some simple red filter, R25, etc.. Shane's Baader U spectrometer graphs, 1st and 2nd generation comparison (link not working at this moment) :http://www.beyondvis...BV3-filter.html Link to comment
Cadmium Posted May 14, 2020 Share Posted May 14, 2020 David posted Shane's Baader U graph (1st and 2nd generation compared) here:https://www.ultravio...dpost__p__33009 The 1st generation Baader U has several 700nm and above IR peaks between OD3 and OD2, anything above OD 3 will definitely show up as a leak. PS: I keep forgetting to mention: I like that cat! Link to comment
eye4invisible Posted May 14, 2020 Share Posted May 14, 2020 I have the Kolari KUV and several S8612s. But --- my KUV does not leak IR so there's no point to testing it (again). I think that perhaps Nemo or Andy B. should contact Kolari and try to determine whether he got one from a bad batch. This can happen.What's odd is that it didn't use to exhibit this behaviour on my D3200, about a year ago when I last used it. I need to dig out my old D3200 and re-test it on both that and my A7, with and without a stack of S8612. Waiting on a suitably sunny day before the dandelions turn into puffballs. Link to comment
Andrea B. Posted May 14, 2020 Share Posted May 14, 2020 Yes, Andy B., that is for sure a bit strange. You might also want to test the cameras for light leaks. They can occur around LCDs, loose mounts, slightly warped adapters and through open port doors and open viewfinders. Most light leaks cause a localized "contamination" in the photo like a streak, blob or band. Your photo does not look like that. But I haven't seen all light leaks, so who knows? I got surprised by a light leak on the upper LCD of my D610 conversion. It does not always cause problems because it depends on angle of illumination, but I can't trust that so I taped it up. Testing by capping the lens and making long exposures is probably something we should all do as "routine maintenance" for our cameras. (She said. But does she remember herself to do this? Nope! ) Link to comment
Cadmium Posted May 15, 2020 Share Posted May 15, 2020 Andy B (starting to get mixed up now, Andrea B and Andy B), stack that filter with a red filter, 25A or something, and see if there is an image using the same settings as an optimized shot using the UV filter alone.Like Jonathan did here:https://www.ultravioletphotography.com/content/index.php/topic/3903-idas-125-uv-pass-filter/page__view__findpost__p__35729That will rule out a leak, or not. I don't think is is a light leak, but I do think different camera sensors can have differing sensitivities. If you no longer have both cameras, then doing a direct comparison between them is off the table,but if you do still have both cameras, then try a direct comparison for that also. Link to comment
Cadmium Posted May 16, 2020 Share Posted May 16, 2020 Birna, Were all of the 1st generation Baader U filter 1.25" size? Link to comment
nfoto Posted May 16, 2020 Share Posted May 16, 2020 Not sure as it's been so long since I last used one of them. However, I think there might have been 2" as well. Link to comment
eye4invisible Posted May 17, 2020 Share Posted May 17, 2020 Andy B (starting to get mixed up now, Andrea B and Andy B), stack that filter with a red filter, 25A or something, and see if there is an image using the same settings as an optimized shot using the UV filter alone.I had some limited time to run another test today. Basically comparing a bare KV 365nm and one stacked with an S8612, on both the Sony 28-70mm kit lens vs my M42 mount Kuri 35mm ƒ/3.5 clone. I had a couple of theories:* Either my filter has degraded over time and is now leaking IR, compared to my old Nikon D3200 photos (I'm now shooting with a Sony A7) and/or* My Sony kit lens is so poor in UV transmission (vs the Nikkor 18-55mm kit lens) that it's exacerbating the IR leak of the Kolari. Unfortunately, these tests were done on the spur of the moment (got some sunny breaks) so I didn't have time to charge up my old Nikon batteries to do a comparison between cameras. These are all screen-grabs from the video I took (I usually make a check-list but since I didn't have much time today, I narrated the video to keep track of each filter/stack). Also, for the purpose of these tests, I am not focusing on white balance, shutter speed or anything other than how dark the centres are vs lens and vs stacks. First up, the KV365nm on the Kuri, sans S8612: Now the KV365nm on the Kuri, with a stacked S8612 2mm: Barely a difference in darkness. Hmmm. Now the KV365nm on the kit lens, no S8612: And the KV365nm on the kit lens, with a stacked S8612 2mm: Dark centres are back with the S8612. So it's definitely leaking IR. I can only surmise that a UV-friendly lens, like my Kuri, is transmitting enough UV to not be affected too much by the small amount of IR leakage, since there's an ever-so-slight difference between a stacked and unstacked KV365nm on that lens (possibly even due to the sun going in and out of the clouds today). Was expecting way darker centres with the Kuri + S8612 stack. I therefore suspect that doing a comparison between cameras and their respective kit lenses would be moot anyway. Link to comment
Andrea B. Posted May 20, 2020 Share Posted May 20, 2020 I'm going to try to illustrate the problem which might (or might not?) be the the problem you (Andy B.) are seeing. My point is that sometimes it is the lens which is causing the problem. Even though my washed out UV photo (to be shown below) looks like it is a bit IR leaky, I assure you there are no IR leaks happening with the gear being used. I made visible and UV photos with the following two lenses:Novoflex 35/3.5, a UV-capable lens with small focus shift between visible and UV.Nikkor 35/1.4 F manual focus lens. This isn't exactly a kit lens, but it does have UV problems like those seen with some kit lenses when used for UV.First the visible reference photos. The flower is a yellow Columbine. Both fotos were converted identically in Photo Ninja: WB/Color profile applied, B/W points adjusted and detail enhancement added. After saving and resizing, some sharpening was added in Capture NX2.BTW, the vignetting error in the Novoflex photo is my error. I do not have the filters properly mounted for that particular lens. Now the UV photos. Again both photos were converted identically in Photo Ninja and sharpened in Capture NX. White balance was made on a section of the flagstone (to the left) which I know to be UV neutral. Note the discoloration (as if you could miss it!) in the photo made with the Nikkor 35/1.4. I couldn't tell you whether that is a hot spot or whether it is due to coatings or some other cause. Also note that the Columbine is not as UV dark as it should be when properly UV photographed. Here are some crops of the two preceding UV photos. (I was going to add something else but changed my mind.) Columbines, for the record, have some specular reflections in UV like many other flowers.(Edit: removed reference to monocot/eudicot etc. Not relevant.) Link to comment
Andrea B. Posted May 20, 2020 Share Posted May 20, 2020 Sooooo, Andy B., I don't think you can say with any certainty that your KolariU is leaking IR. But if you do think so, then I would recommend sending it in to Kolari Vision. If you did happen to get one from a bad batch, then I'm sure they will replace it. I wonder if the Nikkor 35/1.4 is showing some "UV veiling" because not all UV rays are properly focused? I said above maybe it is a kind of hot spot. But I don't really know what is causing the problem. Link to comment
dabateman Posted May 20, 2020 Share Posted May 20, 2020 Doesn't that prove that it does leak IR?As in IR and UV are getting through the filter. But then the lens acts as a UV filter only allowing the IR signal to dominate the image. Which is also exasperated by the IR hot spot.Best test would need a 2mm U360 stack with 2mm S8612, to show black or similar as that stack has the least IR leakage I know of that is practical to use. Link to comment
ulf Posted May 21, 2020 Share Posted May 21, 2020 I agree with David's conclusions here.A lens with lesser UV-transmission alters the UV/IR-ratio making IR more dominant.The same effect is true if comparing cameras with more or less UV-sensitivity. Link to comment
nfoto Posted May 21, 2020 Share Posted May 21, 2020 As almost any lens, the 35/1.4 does pass *some* UV. However the optics don't appreciate this spectral range much and an unsharp central "ghost" image is overlaid the frame if one closes the aperture just a few stops. Thus it can be said the lens acts as a (weak) UV filter on its own thus making IR more visible. Set wide open, more impressionistic UV images result, but they hardly constitute a valid test of any filter. A proper spectral scan of the filter seems in order. Oh, I see the essential same answers have been posted by David and Ulf, while I procrastinated making morning coffee .... Link to comment
Andrea B. Posted May 21, 2020 Share Posted May 21, 2020 Could be. But if the KolariU is leaking IR,then why doesn't the Novoflex photo show any IR contamination??? I'll stack my KolariU with some IR pass filters and see what happens. I've posted (elsewhere) some 13" long KolariU exposures which show no hint of IR contamination. Link to comment
nfoto Posted May 21, 2020 Share Posted May 21, 2020 Because the Noflexar transmits UV much better? Link to comment
Andrea B. Posted May 21, 2020 Share Posted May 21, 2020 But.....there is so much more IR in sunlight than UV. We have always said that a even small amount of IR leak can be damaging to a UV photo. It's kinda funny that this is the first time ever that I have heard anyone make the argument that a lens which is good at passing UV can prevent IR contamination. This is not what I've seen when using "bad" UV-pass filters or dual bandpass UV+IR filters with dedicated UV lenses. So you need to give me a little time on this one. Also I was wondering if anyone noticed in the photos I posted above, that the UV-dark leaves under the flower on the gravel have the same darkness in both photos (but slightly different false colours). If there is IR leakage in the KolariU, then it seems to be centered. That would be way weird, wouldn't it?? Anyway, what I just did was to run some exposures using the BaaderU and KolariU. First I stacked them with the Baader Green Bandpass. I was just curious whether there might be any kind of visible Green leak. Then I stacked them with the Schott RG695 to look for those Red/IR bumps. Finally I stacked them with the Schott RG780 to look for IR leak. It will take me a moment to get these labeled and posted. I could not wear my contact lens today, so focus may be goofy. Sorry 'bout that!Then there were gusts up to 20 mph. Geez, it is windy here. EDIT:Well, I had a test snafu and the test photos cannot be posted. The blocking tape on the upper LCD of my D610 seems to have loosened (heat?) and some of the series was ruined by camera light leak. I will reshoot the tests tomorrow. FWIW, I think my results will show that the KolariU has about 1 level more OD than the BaaderU.EDIT: I'm going to change my mind about this statement. I think that my results show that the KolariU and BaaderU have about the same OD for blocking IR. It is difficult to judge OD "by eye". Link to comment
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