marchellow Posted August 30, 2007 Share #1 Posted August 30, 2007 Advertisement (gone after registration) Dear Colleagues (... M8 owners), this is my first post even if I'm reading this forum since the end of 2006 when I bought my M8. (I'm an happy M8 owner , and this forum is very interesting and useful, thanks to all of you participating). a few days ago I got some pictures with a WATE 16/18/21 @ 16. the pictures hadn't any "artistic" intention, meaning that i took them just to document the state of a ruined building for a file to be presented to the local authorities. It's the first time I had the strange effect as on picture B. while I suppose that the red exhagonal stain in picture A is due to the light refraction due to the dirt that was on the lens (It was dirt!). To give you more info, even without IR filters mounted I set the camera options concerning the lenses to WATE@16 with IR. thank you in advance for your comments. regards marcello Link to post Share on other sites More sharing options...
Advertisement Posted August 30, 2007 Posted August 30, 2007 Hi marchellow, Take a look here a strange effect. I'm sure you'll find what you were looking for!
bayerische Posted August 30, 2007 Share #2 Posted August 30, 2007 This green band happens to all M8 when a strong lightsource is right on the edge of the sensor. Link to post Share on other sites More sharing options...
carstenw Posted August 30, 2007 Share #3 Posted August 30, 2007 The red mark in the first image could be lens flare. Try holding your hand up to shade the lens when sun hits the front element directly. The hood is unfortunately a little on the small side. Link to post Share on other sites More sharing options...
marknorton Posted August 30, 2007 Share #4 Posted August 30, 2007 I agree that the first is lens flare and the hexagonal shape is probably the lens aperture. The second is seen from time to time and occurs when a bright light source is exactly at the edge of the frame. The masked guard pixels, which serve to provide a black reference for a half row of pixels are affected by the bright light - the masking is not completely light-proof. The purpose of the reference pixels is to track changes according to ageing, temperature and operating voltage and stop the camera going out of alignment with time. In this case, the black reference is no longer "black" so that when actual pixel data is referenced against it, errors occur and you see the green streak. It's green because there are more photo-sites in a row interpreted as green content than there are red or blue. It's a problem with the design and fabrication of the sensor or the sensor masking - light can leak where it should not. I've previously suggested to Leica that they could circumvent this problem by recognising the out of range condition of the reference pixels and perform a second "dark" exposure after the shutter has closed - to obtain correct values for the corrupted reference pixels, a bit like they do with noise reduction for long exposures. Sadly, because this modification is more complex to implement than a user lens selection menu, they have so far done nothing to fix it. Link to post Share on other sites More sharing options...
marchellow Posted August 30, 2007 Author Share #5 Posted August 30, 2007 Thanks for the very detailed answers. this forum is always a great learning resource... in the future I'll try to avoid having the light source just on the edge of the image even if one has to make several trials in order to be sure that this effect wont happen since the frame doesn't match exactly with the image edges best regards marcello Link to post Share on other sites More sharing options...
Speenth Posted August 30, 2007 Share #6 Posted August 30, 2007 Thanks for the very detailed answers. this forum is always a great learning resource...in the future I'll try to avoid having the light source just on the edge of the image even if one has to make several trials in order to be sure that this effect wont happen since the frame doesn't match exactly with the image edges best regards marcello Just a comment - posts like this are what this forum is all about! I learned something interesting and practical thanks to the expert and detailed explanations and thanks also to you, Marcello for highlighting this interest cause of artefacting. Link to post Share on other sites More sharing options...
marknorton Posted August 30, 2007 Share #7 Posted August 30, 2007 Advertisement (gone after registration) Worth just adding too that the problem only occurs when the bright light is at either short edge of the frame. It does not occur if it is at a long edge. Link to post Share on other sites More sharing options...
kknyc Posted October 17, 2008 Share #8 Posted October 17, 2008 Hi, I just bought a used 28mm f2 lens for my M8 and have been testing it all day. I'm experiencing a strange flare like area in the center of some images that are long exposures. It is a bit of a lighter, purple area without defined edges (almost like a smudge) but shows up mostly in darker shots or on darker areas (maybe just harder to see). Can anyone tell me if this sounds like the same problem Marcello was experiencing? I am/was afraid it was the lens I just bought. Thank you in advance, Kellie Link to post Share on other sites More sharing options...
fotografr Posted October 17, 2008 Share #9 Posted October 17, 2008 Hi, I just bought a used 28mm f2 lens for my M8 and have been testing it all day. I'm experiencing a strange flare like area in the center of some images that are long exposures. It is a bit of a lighter, purple area without defined edges (almost like a smudge) but shows up mostly in darker shots or on darker areas (maybe just harder to see). Can anyone tell me if this sounds like the same problem Marcello was experiencing? I am/was afraid it was the lens I just bought. Thank you in advance, Kellie If you post the photo in question, it will be easier for people here to analyze the problem. Link to post Share on other sites More sharing options...
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