Andrea B. Posted September 16, 2016 Share Posted September 16, 2016 NOTE 10 Aug 2021 This filter test refers to an AndreaU Mk II, but that is not the same as AndreaU Mk II which is currently being sold by UVR Optics. 16 Sep 2016 I just got the Andrea 'U' MK II from UVR Optics to use in a new series of filter tests. I'll be using the following filters, in alphabetical order: AndreaU MK II [This model no longer sold by UVR Optics.] BaaderU [Baader Planetarium] StraightEdgeU [This model no longer sold by UVR Optics.] U-360 (2.0mm) + S8612 (2.0mm) [UvirOptics (Ebay: uviroptics)] It is my choice to use a 2.0 mm IR-blocker. With a thinner 1.5 mm S8612, you will still have excellent IR blocking with higher UV transmission. Note: In the recent series filter tests here in UV/IR Techniques & Tests, I was using the "old" AndreaU. Here are 4 photos to give you a peek at how things look. I have converted the files in Raw Digger to preserve the raw colour palette without any additional white balance step. The files were then polished up in Photo Ninja where some highlight and shadow control were applied amongst other minor edits. All UV-pass colours are false, of course, but I think that the raw UV false colours are quite interesting and rather pretty. I'll post some click-white balanced versions later. Both the AndreaU-2 and the StraightEdgeU raw false colours feature more blues and purples. The BaaderU and the U-360 show more oranges. Of these 4 filters, the BaaderU has the deepest transmission peak, while the StraightEdgeU has the least deep transmission peak. But you must please note that all 4 filters have successfully (and beautifully) captured the UV-signatures of these flowers. I think the AU-2 gains its raw blue/purple tones by way of a minor violet transmission just imediately past 400nm. The SEU picks up some blue/purple because it has a transmission peak at 379nm together with a rather vertical right shoulder so is recording heavily in the 370-390 nm range. The AndreaU-2 is the fastest filter, but not by much. The U-360+S8612 stack (total 4.0 mm thickness) is the slowest filter, again not by much. All photos click up to 1200 pixels wide in an expanded browser. AndreaU MK II :: f/11 @ISO-400 for 1.5". Transmission peak of 65% at 360 nm with minor violet transmission just past 400nm. StraightEdgeU :: f/11 @ ISO-400 for 2". Transmission peak around 87-90% at 379 nm with nearly vertical right shoulder and no violet transmission. BaaderU :: f/11 @ ISO-400 for 2". Transmission peak of about 80% at 350 nm with very minor violet transmission. U-360-2 + S8613-2 :: f/11 @ ISO-400 for 3". Transmission peak of 60% at 365 nm, approximately. With a thinner 1.5 mm S8612, you will still have excellent IR blocking with higher UV transmission. Visible :: f/11 @ ISO-400 for 1/800" I did not realize while I was shooting that I had a little intruder fly into the scene . Link to comment
Andrea B. Posted September 17, 2016 Author Share Posted September 17, 2016 Here are the UV photos each with its white balance set using Labsphere Spectralon reflective standards of 99% and 75% reflectivity. The color balance was set using a Photo Ninja visible colour profile made with the XRite Color Checker Passport. All photos click up to 1200 pixels wide in an expanded browser. The keen-eyed viewer will see that there is some noise in the grassy background. This is from global application of both of the Photo Ninja sharpener and detail sliders. Usually I will stack sharpened flowers over an unsharpened background, but this takes extra time which is not available to me currently. White balances in this group were set by reference to a 99% white Spectralon disc. AndreaU MK IIThere is a bit more green in this photo than in the others. Green saturation could be increased or decreased during conversion or editing depending on your artistic choices. StraightEdgeU BaaderU U-360 (2.0 mm) + S8612 (2.0 mm) Link to comment
Andrea B. Posted September 17, 2016 Author Share Posted September 17, 2016 Now the 4 photos will be shown with a white balance adjustment applied on the same place in each photo. I have chosen the center disc of the middle sunflower for the white balance area. You can see some subtle colour shifts from the previous photo set- - most evident in the grassy background. The colour shift is stronger in the AndreaU MK II which showed some green tones above when white balanced using a white reflective standard. I suppose we could say that the prior white balance made using white standards (which retain their reflectivity in both UV and IR as well as visible light) is the "correct" white balance. But these are false colours we dealing with, and I will leave it up to you to decide what constitutes a well-defined notion of false white in UV. All photos click up to 1200 pixels wide in an expanded browser. White balances in this group were set by averaging over the sunflower disk in each raw photo. AndreaU MK II StraightEdgeU BaaderU U-360 (2.0 mm) + S8612 (2.0 mm) Link to comment
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