jlw
Rangefinder camera pedant
I've been puzzling over an artifact that I've noticed in some of my R-D 1 pictures: very bright areas against a dark background sometimes seem to show a well-defined "halo" in one direction only. For example, see the area below the red line in the attached file.
Normally I'd suspect lens flare or some other optical fault, but I've been getting these artifacts with lenses that do NOT produce the same type of effect on film. Some sort of image-handling quirk within the R-D 1 might be another possibility, but that seems negated by the fact that even under the same lighting conditions, I see the effect with some lenses but not others. So if it's not the lens and it's not the camera, what is it?
My latest suspicion arose in reading an article somewhere (Pop Photo?) about the "digital optimized" lenses that manufacturers now are offering for DSLRs. The article said that one of the ways these lenses differ from film-only designs is that the manufacturers take greater care to reduce reflections that might be bounced off the digital sensor and then re-reflected by the lens' rear element.
The article didn't give a name for this phenomenon, so I've decided to dub it "sensor bounce." You can see why it might be an issue: since the surface of film has a fairly matte finish, reflections off it would be diffuse (rays going in all directions) while a sensor is fairly glossy, so reflections off it would be specular (rays that remain directional.) Apparently there are cases in which image rays can bounce off the sensor, hit the rear element, and be bounced back toward the sensor again, which (I'm theorizing) would often just lower overall contrast, but in some cases could form a fairly well-focused, slightly offset "ghost" of the original scene. Apparently, the DSLR lens manufacturers are trying to avoid this in the design of the rear elements and/or by applying special coatings.
I'm wondering if this might explain the artifacts I've been seeing occasionally in my R-D 1 pictures. They DO look rather well-defined, like reflections, and this also would explain why they tend to extend in one direction rather than being evenly distributed around the bright part (as you'd expect with ordinary flare.) I'm guessing that a lens with a relatively flat rear element would be more likely to bounce back well-focused reflections than one with a steeply curved element, and this could explain why I see the effect with some lenses but not others under the same conditions.
But for the life of me, I can't think of any way to test this hypothesis! I experimented a bit with shining a laser through a lens onto a glossy surface, but the beam was broken up enough that I couldn't tell whether it produced a "sensor bounce" reflection or not.
Any ideas? Any thoughts?
Normally I'd suspect lens flare or some other optical fault, but I've been getting these artifacts with lenses that do NOT produce the same type of effect on film. Some sort of image-handling quirk within the R-D 1 might be another possibility, but that seems negated by the fact that even under the same lighting conditions, I see the effect with some lenses but not others. So if it's not the lens and it's not the camera, what is it?
My latest suspicion arose in reading an article somewhere (Pop Photo?) about the "digital optimized" lenses that manufacturers now are offering for DSLRs. The article said that one of the ways these lenses differ from film-only designs is that the manufacturers take greater care to reduce reflections that might be bounced off the digital sensor and then re-reflected by the lens' rear element.
The article didn't give a name for this phenomenon, so I've decided to dub it "sensor bounce." You can see why it might be an issue: since the surface of film has a fairly matte finish, reflections off it would be diffuse (rays going in all directions) while a sensor is fairly glossy, so reflections off it would be specular (rays that remain directional.) Apparently there are cases in which image rays can bounce off the sensor, hit the rear element, and be bounced back toward the sensor again, which (I'm theorizing) would often just lower overall contrast, but in some cases could form a fairly well-focused, slightly offset "ghost" of the original scene. Apparently, the DSLR lens manufacturers are trying to avoid this in the design of the rear elements and/or by applying special coatings.
I'm wondering if this might explain the artifacts I've been seeing occasionally in my R-D 1 pictures. They DO look rather well-defined, like reflections, and this also would explain why they tend to extend in one direction rather than being evenly distributed around the bright part (as you'd expect with ordinary flare.) I'm guessing that a lens with a relatively flat rear element would be more likely to bounce back well-focused reflections than one with a steeply curved element, and this could explain why I see the effect with some lenses but not others under the same conditions.
But for the life of me, I can't think of any way to test this hypothesis! I experimented a bit with shining a laser through a lens onto a glossy surface, but the beam was broken up enough that I couldn't tell whether it produced a "sensor bounce" reflection or not.
Any ideas? Any thoughts?
J. Borger
Well-known
Perhaps it is the phenomenon called "sensor blooming" ... i do not know about the technical ins and outs ..... but with Canon DSLR;s it shows in transition areas between dark and light when shooting fast lenses (like the 35 1.4L or 85 1.2L) wide open.
It looks almost the same as Chromatic Abbiration but is Sensor instead of lens-related!
You might do a search on the Canon Forum at www.fredmiranda.com
Han
It looks almost the same as Chromatic Abbiration but is Sensor instead of lens-related!
You might do a search on the Canon Forum at www.fredmiranda.com
Han
ulrik
Established
Raw?
Raw?
If you shot this in RAW - how did you process the file? I´ve seen this problem with files processed with the Epson RAW plugin (as you already know), CS2 does a better job with theses edges; try the color noise reduction slider.
Sorry ... I just realized you where the one working with my RAW file reguarding the edge artifacts - Thaks again - I think it may be the same problem. Something could be wrong in the Epsons RAW plugin. Please try another RAW converter and let us know.
Raw?
If you shot this in RAW - how did you process the file? I´ve seen this problem with files processed with the Epson RAW plugin (as you already know), CS2 does a better job with theses edges; try the color noise reduction slider.
Sorry ... I just realized you where the one working with my RAW file reguarding the edge artifacts - Thaks again - I think it may be the same problem. Something could be wrong in the Epsons RAW plugin. Please try another RAW converter and let us know.
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LCT
ex-newbie
I don't know if it is related but you've got a lot of blown highlights at first glance.
Then if you shot jpeg i'd advise you to try raw and if you shot raw i'd convert the file again and use the highlight control if i were you.
FWIW
Best,
LCT
Then if you shot jpeg i'd advise you to try raw and if you shot raw i'd convert the file again and use the highlight control if i were you.
FWIW
Best,
LCT
jlw
Rangefinder camera pedant
I know this particular shot has a lot of blown highlights (@#$% back-diagonal theater lighting) but picked it because it exhibits the effect most clearly. It's present on other images in which the highlights are NOT overexposed, just not in such a visible way.
I'm pretty familiar with the effects of "blooming" from when I used to work in the video field, and that's certainly another possibility. The fact that the artifact retains a lot of the structure of the original image makes me think it's an effect of this type, rather than a conversion artifact.
As I said, the frustrating thing is that so far I haven't figured out a dependable way to reproduce the effect, which frustrates organized attempts to determine exactly what's causing it!
(I tried again using a laser, this time with a fresnel lens that expands the beam into a line rather than a dot. It showed a somewhat similar effect -- a "halo" that's equally distributed on both sides of the laser line when the laser is on-axis, and distributed more on one side as the laser is moved off-axis toward the other side. But the laser is so intense vs. an ordinary image that I couldn't be sure this was the same effect -- and even if it is, this brings me no farther toward guessing what causes it!)
I'm pretty familiar with the effects of "blooming" from when I used to work in the video field, and that's certainly another possibility. The fact that the artifact retains a lot of the structure of the original image makes me think it's an effect of this type, rather than a conversion artifact.
As I said, the frustrating thing is that so far I haven't figured out a dependable way to reproduce the effect, which frustrates organized attempts to determine exactly what's causing it!
(I tried again using a laser, this time with a fresnel lens that expands the beam into a line rather than a dot. It showed a somewhat similar effect -- a "halo" that's equally distributed on both sides of the laser line when the laser is on-axis, and distributed more on one side as the laser is moved off-axis toward the other side. But the laser is so intense vs. an ordinary image that I couldn't be sure this was the same effect -- and even if it is, this brings me no farther toward guessing what causes it!)