malcolm.mcintyre Posted March 4, 2010 Share #1 Posted March 4, 2010 Advertisement (gone after registration) Can anyone explain the central concentric ring artifact I got on all of my M8 shots of the Aurora recently? Shooting Elmarit fully open at 2.8, ISO 320, 60 seconds exposure (midnight at minus 38C !) ..and more importantly, can anyone advise a good photohop fix? thanks Link to post Share on other sites More sharing options...
Advertisement Posted March 4, 2010 Posted March 4, 2010 Hi malcolm.mcintyre, Take a look here lens artifact with 2.8 28mm. I'm sure you'll find what you were looking for!
jaapv Posted March 4, 2010 Share #2 Posted March 4, 2010 It looks very much like a reflection of the edge of a filter. Link to post Share on other sites More sharing options...
malcolm.mcintyre Posted March 4, 2010 Author Share #3 Posted March 4, 2010 Could be, I forgot to remove the IR filter, because I was having so much trouble keeping the camera from shutting down with the cold every few minutes. Any ideas for a clever fix? Link to post Share on other sites More sharing options...
malcolm.mcintyre Posted March 4, 2010 Author Share #4 Posted March 4, 2010 more obvious here Link to post Share on other sites More sharing options...
jaapv Posted March 4, 2010 Share #5 Posted March 4, 2010 Well, you could mask it and correct contrast/brightness in Photoshop. If you get the mask and feather right it should be quite effective. Link to post Share on other sites More sharing options...
SJP Posted March 4, 2010 Share #6 Posted March 4, 2010 Cool! OK,OK I know it is irritating. I think you are the first to show Fabry-Perot inteference fringes (probably) from the sensor. You get these fringes if you have two semi-transparant mirrors or flat reflective surfaces due to constructive/destructive interference of the light going straight through and the light that bounces to and fro between the reflective surfaces. It is a similar to Newton rings & fringes that are visible when two smooth surfaces touch each other. See here for the gory details Fabry–Pérot interferometer - Wikipedia, the free encyclopedia Why you see it in this picture is because northern-lights are plasma lines from ionised gas and are nearly monochromatic (well defined wavelength). In all normal photography situations the colors are broad spectral range peaks and the inteference fringes overlap and wash each other out. You should be able to reconstruct this effect with a laserpointer. EDIT: sorry, I can't help you with photoshop removal. Looks like a pretty impressive aurora display. Link to post Share on other sites More sharing options...
jaapv Posted March 4, 2010 Share #7 Posted March 4, 2010 Advertisement (gone after registration) Brilliant lateral thinking, Stephen. Now that you have penetrated the dense fog in my brain, I realize this is the way Leica tests lens surfaces. Link to post Share on other sites More sharing options...
ArtZ Posted March 4, 2010 Share #8 Posted March 4, 2010 Cool! OK,OK I know it is irritating. I think you are the first to show Fabry-Perot inteference fringes (probably) from the sensor. You get these fringes if you have two semi-transparant mirrors or flat reflective surfaces due to constructive/destructive interference of the light going straight through and the light that bounces to and fro between the reflective surfaces. It is a similar to Newton rings & fringes that are visible when two smooth surfaces touch each other. See here for the gory details Fabry–Pérot interferometer - Wikipedia, the free encyclopedia Why you see it in this picture is because northern-lights are plasma lines from ionised gas and are nearly monochromatic (well defined wavelength). In all normal photography situations the colors are broad spectral range peaks and the inteference fringes overlap and wash each other out. You should be able to reconstruct this effect with a laserpointer. EDIT: sorry, I can't help you with photoshop removal. Looks like a pretty impressive aurora display. Bien vu! Bravo! Here's a test done 5 minutes ago with a laserpointer. Fabry-Pérot interferences aclearly visible in many places of the test picture. . Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/114367-lens-artifact-with-28-28mm/?do=findComment&comment=1247309'>More sharing options...
malcolm.mcintyre Posted March 4, 2010 Author Share #9 Posted March 4, 2010 The aurora got better, but the camera got so cold that I could no longer keep it working, even putting it down my underpants! Link to post Share on other sites More sharing options...
SJP Posted March 4, 2010 Share #10 Posted March 4, 2010 Bien vu! Bravo! Here's a test done 5 minutes ago with a laserpointer. Fabry-Pérot interferences aclearly visible in many places of the test picture. . Nice:) Link to post Share on other sites More sharing options...
SJP Posted March 4, 2010 Share #11 Posted March 4, 2010 The aurora got better, but the camera got so cold that I could no longer keep it working, even putting it down my underpants! arriving at the hospital with a camera frozen to your private parts. Where was this taken anyway? Link to post Share on other sites More sharing options...
malcolm.mcintyre Posted March 4, 2010 Author Share #12 Posted March 4, 2010 Oulanka, northern Finland, week before last. BTW. the M8 seems particularly sensitive to shutting down when cold compared to the Nikon/Canon SLRs that the others had. I've had my M8 fail at just zero Celcius before. I really did have the batteries in my underpants at 37C (the camera tended to steam up), but could still only get one 60 second exposure per battery before it shut down. Anymore ideas about Photoshop removal? I bet there's a clever fix in there if you know where to find it. Link to post Share on other sites More sharing options...
SJP Posted March 4, 2010 Share #13 Posted March 4, 2010 Great! I was in Finland last year (Rovaniemi) but no joy as far as aurora boralis was concerned. They appear quite bright. EDIT: don't have any experience with Photoshop, with Paintshop-pro I would consider using a clone brush, possibly selective blurring would do the trick? EDIT2 like this: Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/114367-lens-artifact-with-28-28mm/?do=findComment&comment=1247358'>More sharing options...
wstotler Posted March 4, 2010 Share #14 Posted March 4, 2010 I think you are the first to show Fabry-Perot inteference fringes (probably) from the sensor. Congratulations! Seriously, this is EXCITING. A genuinely new "M8" issue provoked by the environment! It's been a long, long time since somebody reported a genuine issue like this that's repeatable. Love the shots. Yes, it's the clone tool and careful reconstruction for your shots. They're beautiful, BTW. Having been in the cold at Jukkasjarvi (Sweden) during late January, I understand your situation first-hand. 60 seconds is a long time in that kind of cold. And I'm jealous--the sky was overcast and the Northern Lights didn't make an appearance during our three days there. I do remember reading in another thread somebody saying that chemical hand warmer packets could be activated and then gaffer-taped to the bottom of the M8. Because the M8 is all metal it would warm up the casing and camera innards via induction. Me? I'd use two and wrap that puppy good. BTW, this seems to be an older piece of advice for arctic conditions, as well. From Kodak: "You can use several small hand warmers to supplement body heat ... Some photographers tape a hand warmer to the back of the working camera." Thinking about it, forget the camera. We could've used these for our hands and toes at Jukkasjarvi. Cheers, Will Link to post Share on other sites More sharing options...
ho_co Posted March 4, 2010 Share #15 Posted March 4, 2010 Malcolm-- Wonderful images. For me as a Texan, such cold temperatures would have precluded using a camera, let alone considering where to put the batteries "inzwischen." Stephen, Art, Will-- Agree, this is a fascinating discovery. Is there a way, do you think, that Leica might use a laser technique like this to reveal a "red-edge" problem with an M9 body before shipping (assuming that it arises from the sensor, as seems to be the current theory)? Art-- How did you make that proof-shot? Point the laser toward the lens? Paint a wall with it? How long an exposure? Etc. Link to post Share on other sites More sharing options...
ArtZ Posted March 5, 2010 Share #16 Posted March 5, 2010 Howard, Nothing especial. I set the camera on "AUTO" plus self-timer mode, pre-focused it with a Summilux 50 @ f/1.4, ISO 160 and tried to hit the center of the sensor with the laser beam. That's all. I tried three times. The first one was the best. The second one, didn't work. I could see myself and just a small red dot on the laserpointer (light beam). On the last one, Fabry-Pérot efect was less visible than in the first picture. I posted the first one. Regards Link to post Share on other sites More sharing options...
wda Posted March 5, 2010 Share #17 Posted March 5, 2010 If I am looking at the right artifact, dark area over the sea, why not simply clone it out? Link to post Share on other sites More sharing options...
malcolm.mcintyre Posted March 5, 2010 Author Share #18 Posted March 5, 2010 Our luck was amazing with perfect skies, but we only got the Lights on the first night of a week stay. Frustrating, as I had sorted the cold camera problem by day two. The locals said it was the only decent display this winter. It is actually a frozen lake in a national park, and you can just see the snow shelters (quincy) we built to sleep in, in the foreground. The inviting looking village in the distance was not accessible as the ice was too thin. The artefact is the series of concentric rings, best seen right in the centre of the second image. I imagine the best way to correct would be to clone each section of ring separately. Sorry about the skewed horizon, I was rather overcome by the display to notice at the time. But I know how to fix that. p.s. thanks for all the thoughts. I would never have considered the interference fringe theory in a million years. My physics studies were a while ago now. I wonder if they've fixed it in the M9 ;-) p.p.s.I had a carbon Gitzo tripod, which was a good thing, as the others had their hands stick to metal ones p.p.p.s. My back-up Dlux2 never missed a beat in the cold Link to post Share on other sites More sharing options...
jpattison Posted March 5, 2010 Share #19 Posted March 5, 2010 wda, look again, you'll see concentric rings in the dead centre of the image, better in the second image. John Link to post Share on other sites More sharing options...
SJP Posted March 5, 2010 Share #20 Posted March 5, 2010 Howard, Nothing especial. I set the camera on "AUTO" plus self-timer mode, pre-focused it with a Summilux 50 @ f/1.4, ISO 160 and tried to hit the center of the sensor with the laser beam. That's all. I tried three times. The first one was the best. The second one, didn't work. I could see myself and just a small red dot on the laserpointer (light beam). On the last one, Fabry-Pérot efect was less visible than in the first picture. I posted the first one. Regards I don't think it is neccesary (or indeed desirable) to aim the laser pointer at the sensor, so long as the light source is monochromatic this effect should be visible, e.g. by aiming the laser pointer at a wall Link to post Share on other sites More sharing options...
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