Andrea B. Posted September 17, 2016 Share Posted September 17, 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. Here are the usual photos of the CC Passport and Labsphere Spectralon Standards (99%, 75%, 50%) without which no series of filter tests would be complete! Filters - from "reddest" to "magenta-est": 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. BaaderU [Baader Planetarium] StraightEdgeU [This model no longer sold by UVR Optics.] AndreaU MK II [This model no longer sold by UVR Optics.] I am fascinated by the raw UV false colours produced by these filters. The AndreaU MK II and the StraightEdgeU photos both have raw false blue/magenta tones. The StraightEdgeU and S360 Stack both show a raw false red/orange tone. From left to right from "reddest" to magenta-est": U360-2+S8612-2, BaaderU, StraightEdgeU, AndreaU MK II. This 4-panel strip is 1200 pixels wide when clicked-up to full size. I sampled each photo over the top center white standard to find the hue (in degrees). In this little chart, the 2nd row shows the fully saturated version of that hue for each of the 4 filters together with some reference hues. The 1st row contains a less saturated version of the hue (as in the raw photo). During white balance of the raw photos, the raw hues are turned into yellow, blue and neutral tones - and sometimes a little dark cyan or green shows up. For this particular subject, after white balance there is not as much variation between the filters as can be seen in in the recent flower bouquet series. Remember that resizing the photos and saving them as sRGB JPGs may slightly alter the colours. The AndreaU MK II and the StraightEdgeU appear to have slightly better contrast initially. Of course, contrast improvements could be made in the BaaderU and U360 photos but that's an extra editing step. "-) From left to right from "reddest" to "magenta-est": U360-2+S8612-2, BaaderU, StraightEdgeU, AndreaU MK II. This 4-panel strip is 1200 pixels wide when clicked-up to full size. Link to comment
nfoto Posted September 17, 2016 Share Posted September 17, 2016 Interesting and valuable contribution. Thanks. A small nitpick: the filters are shown in the same sequence as declared in text if one goes right to left, not left to right. You might want to edit the text to bring it in accordance with the pictures. Link to comment
Andrea B. Posted September 17, 2016 Author Share Posted September 17, 2016 oh la!!I'll fix that now. Link to comment
Andrea B. Posted September 17, 2016 Author Share Posted September 17, 2016 You know what? It is bugging me no end that the 3rd photo strip above is not showing proper white balance. Each TIF was white balanced over the top center white standard. But it is quite apparent in the composite photo strip that there are cyan and blue casts.What the???? Link to comment
Andrea B. Posted September 18, 2016 Author Share Posted September 18, 2016 I figured it out. The BaaderU photo was overexposed so the 99% and 75% reflective standards (top middle and top right) were clipped. Sometimes "highlights" can be recovered to the proper colour but sometimes they cannot. In this case there is no way to fully recover the correct white or light grey colour in those two areas except by directly applied colour replacement in Photoshop or some other app. Mystery explained. Whenever I think I know what I'm doing, I always learn that it isn't so !!! I had thought I was properly exposing the BaaderU UV shots, but nope. I blew it, figuratively and literally. :lol: Link to comment
Andy Perrin Posted September 18, 2016 Share Posted September 18, 2016 but nope. I blew it, figuratively and literally. :lol: Heee. And you blue it, too! Link to comment
Andrea B. Posted September 19, 2016 Author Share Posted September 19, 2016 groan!! :D :P Link to comment
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