Andrea B. Posted August 24, 2017 Share Posted August 24, 2017 Experiment: Using various UV-pass filters and filter stacks, shoot a medium distance landscape type scene and compare the resulting white balanced photos. Look at the raw composites of each shot to determine where the UV light is being recorded. Scene: In Deep Cut Park the summer demonstration garden features some scarecrows, vegetables and flowers along with many bees and butterflies. One of the exhibits in the garden is an Insect Hotel designed to provide habitat for cavity dwelling bees and other critters. A Scarecrow next to the Insect Hotel made a nice subject for the shoot. I enjoyed chatting with the kids and moms who were walking through the garden looking for little hidden gnome statues under the flowers. BTW, it was breezy so you will see foliage movement throughout the series. Camera: Panasonic Lumix GH-1 -- Broadband Conversion Hands down, the easiest camera I've ever used for UV or IR work is my little old Lumix GH-1. The menus are easy. The buttons make sense. It is super-easy to measure white balance. That said, the GH-1 has its drawbacks. The dynamic range is not what I'm used to with the Nikon D610, so highlights go bad and shadows are very noisy. Good illumination and shooting practices overcome much of that though. In this early model, neither the electronic viewfinder nor the low-res LCD offer the best support for focusing a manual lens through a dark filter in spite of massive amounts of sunlight. You are quite likely to see a bit of missed focus below. :) . Lens: Kyoei W. Acall 35/3.5 I wanted to shoot a medium distance scene with various UV-pass filters and filter stacks, but over the m4/3 sensor I can't get too wide with the lenses I have. Decided to go with this Kyoei over another 28 simply because I had not used it in awhile. The Kyoei has good sharpness and transmits enough UV for to capture a nice sunny outdoor scene. And I had no hotspotting from this lens when shooting some companion IR photos. Here is a link to an earlier test in which the Kyoei 35/3.5 was used: Lens Field Test [M42-mount, Infinity, Vis/IR/UV] My sunlight for the following scene was coming from over my left shoulder. I did not use a lens hood. (Bad Andrea.) So I recorded quite a bit of chromatic aberration which you can easily see around the scarecrow's head. So much for touting good shooting practices. I'm always going to show you exactly what I've shot -- mistakes and all. :) But we must also remember that this Kyoei 35/3.5 is not at all corrected in the UV wavelengths. Filter Groups The four posts which follow contain results for these filter groupings. Manufactured UV-Pass Filters UV-Pass Filter Stacks Some Infrared Results UV + Blue and More . Photo Apps Photo Mechanic: Extract straight-out-of-camera JPGs. Raw Digger: Extract raw composites (before white balance step). Photo Ninja: Conversion, white balance refinement and minor edits. Photoshop Elements 11: A pole sticking out of the Scarecrow's head was erased in my old PSE11. . Edits Edits are always kept to a minimum for such an experiment. I'm not trying to show you a complete, finished photo. I just want to show you the "look" which can be obtained using a particular UV-pass filter. My edits usually include: Highlight recovery (almost always). White & black point adjustments (almost always, but the adjs are very small). Shadow lift (sometimes). Midtone curve lift (sometimes). Color profile for camera in use. Noise? No, I don't tackle noise adjustments for a demo like this. Resizing eliminates much of it. Sharpening/detail? Yes, even though this is a finishing step, nobody wants to see soft demo photos. . White Balance for Each Filter In this experiment I had some very interesting white balance results. For each filter I made an in-camera white balance measurement against a 5x5" Spectralon rectangle before shooting the scene. The in-camera white balance measurement I got from the GH1 was not always what I would have expected to see. Later when I was converting the raw files in Photo Ninja, I used the white balance dropper over a neutral area in the photo and obtained a completely different WB result. So I'm going to show you both versions in each filter presentation. But as a preliminary example of these two different WB results, let's look at the results from the BaaderU UV-pass filter. On the right is the scene as recorded by the GH-1 after measuring white balance against the Spectralon. On the left is the Photo Ninja conversion for which the usual white balance dropper drag was made over a UV-neutral portion of the photo. This left side has the false colors which we have come to expect in a BaaderU-filtered, white-balanced, reflected-UV photograph. The GH-1 white balanced version on the right does not. What is going on here? Why is my GH-1 not giving me the expected white balance? If I did something wrong, I sure don't know what it was. Visible Reference View So what was she trying to focus on anyway? Sigh. Well, the scarecrow's eye. Maybe that wasn't the best choice. Do you note the haloing around the Scarecrow's head and horns? Perhaps this is caused by light entering the Kyoei 35/3.5 off-axis? Perhaps it could be prevented by using a lens hood? Am I getting scatterbrained in my stout middle age to forget such things when I run out the door all excited to shoot a handful of new filters? Probably. Still, this is a servicible scene for looking at different filtration. We will make do and proceed. f/8 for 1/640" @ ISO-100 Link to comment
Andrea B. Posted August 24, 2017 Author Share Posted August 24, 2017 Manufactured UV-pass FiltersI have just gotten in some nice Uviroptics (Ebay) filters and wanted to see how they looked. I'm using the BaaderU for a reference UV photograph because we are all so familiar with it. However, I'm sure other folks might have their own idea of what is the best reference filter. We have a lot more to choose from now, don't we? Please remember when viewing these UV photographs, that the haloing around the Scarecrow's head is from the un-hooded Kyoei 35/3.5 lens.Baader Planetarium BaaderUTransmission chart link: http://www.beyondvis...BV3-filter.htmlUviroptics La La U: 363FWHM50, OD5The La La U produces nice versions of the typical UV false blues and yellows.(Although I have not pushed saturation here, that could be done to bring out more color.)Clearly, there is no evidence of IR contamination. That background foliage is dark.Uviroptics LuvU 2: 359FWHM53, OD4And the LuvU 2 also has a pretty false blue and yellow finish.(Again, yellow sat could be pushed more, if desired.)There is no IR leak here either. Uviroptics MoonU: 365FWHM55, OD4.7The finished frame has a very cool blue, doesn't it?The Moon U transmits a tiny bit of violet to give this look after the white balance step. Link to comment
Andrea B. Posted August 24, 2017 Author Share Posted August 24, 2017 UV-Pass Filter StacksA new piece of stackable filter glass just arrived from Uviroptics -- the 2mm Schott UG-1 which I had been wanting to play with for some time. It is always nice to have on hand a variety of filter glass in different thicknesses for experimentation. Roll your own!Schott UG1 (2mm) + Schott S8612 (2mm)Hoya U-360 (2mm) + Schott S8612 (2mm)Hoya U-340 (4mm, is this a 2+2 stack?)I did not stack an IR-blocker over this thick U-340. The raw composite has the typical 340 yellow-orange appearance, but I think the finished frame is showing some evidence of IR leak because it is just a little bit too colorful as compared to a typical UV photograph. Link to comment
Andrea B. Posted August 24, 2017 Author Share Posted August 24, 2017 Some Infrared ResultsIt is alway nice to see how UV scenes look in the longer wavelengths. Here are results from a small, somewhat random selection of IR-pass filters.(I had just been testing whether there were major differences between RG-645 and RG-695. No.)Schott OG-570: Orange + Red + InfraredSchott RG-645: Red + InfraredSchott RG-695: Mostly InfraredSchott RG-850: Infrared Only Link to comment
Andrea B. Posted August 24, 2017 Author Share Posted August 24, 2017 UV + Blue and MoreI decided I might as well go ahead and shoot with the following Blue and UV+Blue+Green filters and stacks since they were already on board. :)Hoya B-410This is a UV+Blue+Green+IR filter which blocks most red.Schott BG-3This is a UV+Blue+IR filter which blocks most green and red.Hoya U-330 (1.5mm) + Schott S8612 (2mm): Ultraviolet + Blue + GreenThis and the next stack are often used to model trichromatic UV/Blue/Green insect vision.Schott UG5 (1.5mm) + Schott S8612 (2mm): Ultraviolet + Blue + GreenThis and the preceding stack are often used to model trichromatic UV/Blue/Green insect vision.Uviroptics BugU3: Ultraviolet + Blue + GreenAlthough passing only UV+B+G, this filter has an interesting red component when white balanced in a certain way. Link to comment
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