Archived posting to the Leica Users Group, 2009/02/13
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Henning I follow. I was thinking about UV attenuation when I assumed the window glass would reduce IR too. Sounds like that we agree on my moon reflection. Care to comment on the elements described in my cantina shot?. I'm not convinced those are window glass reflections. Did you look at Nathan's pub shot, Alternate 9? No window involved there. I think that both of these are internal reflections related to having a filter on (not just UV/IR) I don't think that any of these are sensor bloom either. Probably I'm the only one thinking (too deeply) about these technical aspects ;-) Thanks for contributing on this and other areas when I post opinions. 2009/2/14 Henning Wulff <henningw@archiphoto.com> > Hi Geoff, > > Sorry; my comment was rather abrupt and gruff. I sent it too quickly. :-) > > With the IR thing I just meant that window glass isn't that useful in > attenuating IR to any degree; it's better at blocking UV, especially if > it's > glass that's been installed in the last 10 years. Most glass now has some > degree of UV protection. > > On a summer's day you'll see all kinds of IR induced changes to an image; > in the winter it's a lot less. > > Regarding reflections; note that in your shot of the moon the spurious > image is located symmetrically; ie, the image is on the opposite side and > the same distance from the centre. That's the usual location when the > reflection occurs off flat surfaces like a filter. It's not always the > case, > as there are possibilities for other reflections, but they are usually of a > lower order. > > If you see multiple images close to each other when shooting through glass > it's usually due to reflections off multiple layers of window glass; ie, > double glazing. The two layers of glass deform differentially as the > temperature changes; then the two layers aren't parallel anymore and will > show reflections just a little apart. If two spots are fairly close > together > and not hugely different in intensity, this is the usual cause. > > > > > At 7:52 PM +1000 2/13/09, Geoff Hopkinson wrote: > >> Henning I meant that I wouldn't expect significant IR from those subjects >> behind glass. I agree those subjects would not be big IR candidates >> anyway. >> I assumed that the window glass would attenuate IR as well. Sounds like I >> should not have linked the two ideas. I'm no scientist there certainly. >> For >> fun I must have a play and educate myself on that now. >> >> Regarding the small blue highlights, I have seen secondary mirror images >> of >> point light sources in some of my shots. For example this shot with the 75 >> Summicron and UV/IR. (4 second exposure). You should be able to make out a >> ghost image of the moon crescent as well as some stars repeated as blue >> dots. I assumed this was due to reflections back into the camera from the >> filter. I based that on an article in the Feb 2007 LFI demonstrating this >> with a night street shot of street lights and headlights. The article >> states >> that the ghost images are caused by the presence of the filter. >> http://gallery.leica-users.org/v/gh/a/ns/Sky.jpg.html >> >> In Chris's shot you can certainly see a set of reflections on the window >> glass. I love to play with reflection shots like this myself which is >> partly >> why I was staring into this enjoyable one by Chris. I believe that the two >> blue spots above the girl to the left, are a ghost of another set of >> reflections on the window glass! The blue colour is a clue to me. Note the >> yellow original sets above and to the left that are on the window glass I >> think. Never mind just some technical opinion from me that I thought might >> be of interest. As a practical matter those spots are easy to retouch of >> course. >> I put another up for discussion on this subect >> http://gallery.leica-users.org/v/gh/a/usa/f/Cantina.jpg.html >> This is a 28 uncropped, through a window at close range. Of interest maybe >> is you can see my left arm and watch over the back of the guy to the left >> and I think our table edge on the lady's back to the right. Look at the >> hat >> of the background guy to the right and the blonde hair of the lady just >> below her left ear position. You probably need to look at the larger >> version >> to see more clearly. Anyway I find these details fascinating to learn >> about. >> I'd value any comment from you, or others. >> Cheers >> Geoff >> 'Licence to Chill' >> >> >> >> 2009/2/13 Henning Wulff <henningw@archiphoto.com> >> >> A nice set, Chris but to clarify what Geoff has written: >>> >>> The window glass won't do anything for/against the IR. Your available >>> light >>> just happens to be low IR content, which is usual in winter. >>> >>> The reflection may or may not be due to the UV filter. It looks like the >>> picture is shot through glass, the most likely cause is the window glass >>> as >>> that causes way more reflections than filters, an of a somewhat >>> different >>> type. >>> >>> >>> >>> >>> Chris that is a thoughtful and well constructed group. The second ice >>> shot >>> >>>> is especially appealing. >>>> There's nothing in any of the content that might provide a reason for >>>> the >>>> UV/IR . >>>> If you'd like a technical comment on that aspect,look at the >>>> Selfridges shots. I suspect that the window glass has prevented any >>>> possible >>>> mis-rendering of the dark fabrics anyway. But your UV has given you the >>>> same >>>> minor artefacts that a UV/IR (or any filter) would have. See the small >>>> blue >>>> internal reflections (second shot) of the point light sources? >>>> >>>> 2009/2/13 Christopher Birchenhall <crbirchenhall@googlemail.com> >>>> >>>> LUGers >>>> >>>>> >>>>> I took my recently acquired M8 out with a LTM 50mm Summicron f2 >>>>> collapsible on two occasions. This lens came as part of a very >>>>> collectible IIIf R/D kit. I am not a collector so I decided to cash in >>>>> the body and case (sigh). But the lens is for me one of my best. We >>>>> get on very well. We "clicked" :-) One or two of these pics may >>>>> appeal but I can't but offer to share my delight at using the new >>>>> electronic camera with a "peach" of a classic lens (with a standard UV >>>>> filter and no 6-bit coding). >>>>> >>>>> I managed to get into the centre of Manchester (UK) with some good >>>>> winter sunlight. Some of the subject matter (graffiti/street art?) may >>>>> not appeal to all but I am ok with this stuff - a couple do involve >>>>> the "fair" sex? >>>>> >>>>> http://gallery.leica-users.org/v/crb/M8/Manchester/ >>>>> >>>>> We had a quick walk along my staple venue (Macclesfield Canal) when it >>>>> was cold and the canal was partly frozen - a barge had clearly passed >>>>> through and broken up the ice - we had a fine half pint of a winter >>>>> warmer ale half way through! >>>>> >>>>> http://gallery.leica-users.org/v/crb/M8/canal/ >>>>> >>>>> Needless to say C&C are welcome. >>>>> >>>>> Chris B >>>>> >>>> > > -- > > * Henning J. Wulff > /|\ Wulff Photography & Design > /###\ mailto:henningw@archiphoto.com > |[ ]| http://www.archiphoto.com > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information > -- Cheers Geoff 'Licence to Chill'