Purple flare: Causes and remedies (continued)

Richard said:

Richard wrote:

Richard said:

tt321 wrote:
What you just said here is well known and widely practised, and therefore uninteresting to the point of boring. What Anders et al have been doing is intelectual work backed by well planned and reasoned experiments exploring the possible reasons of an observed phenomenon previously poorly explained, and thus very interesting. Hence the popularity of these threads.

Hacked and intuitive practical techniques might well work better than what organized research could turn up in the short term, but ultimately almost all elegant and reliable solutions are the results of the latter, esp. as the human intellect further develops. In addition, to some people at least, the process of intellectual work is rewarding in itself. These threads is my exhibit A for this claim, if you need convincing.

Click to expand...

It is a forum. I am entitled to my opinion and to post it here regardless how simple the solution is. Pseudo intellectuals like yourself who cannot even spell practiced or intellectual are invited to give input too, but in my experience, rules like keep it simple stupid dominate over elegant and reliable solutions that you are suggesting coming from pseudo intellectuals that ar usually not simple, elegant or reliable. It is just a bunch of people arguing or trying to prove they have some technical prowess, when most can see they don't.

I guess after seeing this is a problem in some of the later post, the issue is with the camera and not the lens, I am just glad that I use Nikon and Canon that do not have these issues or if they do, they are so negligible, they are not worth talking about. But you can carry on with your pseudo intellectual discussions without me, good luck.

Click to expand...

Where do you think the technological advancements which have allowed Nikon and Canon to stay in business and continue to lead for decades come from? Hap-hazard intuitive ad-hoc tweaking by people who are not interested in intellectual exercises or organized research?

Where do you think the "guessed" knowledge that "the issue is with the camera and not the lens" comes from? Precisely the work by Anders et al and the discussion inspired by it that you seem to regard as "a bunch of people arguing or trying to prove they have some technical prowess, when most can see they don't" - and this "most" is from what poll you have taken? It's this bunch of people who were curious about an observed phenomenon and explored it further then exchanged their findings, ideas and opinions in the forum, which is exactly what a forum like this is for in my opinion.

Having curiosities and willing to expend some effort to satisfy them is a characteristic in humans, at least some of us.

Attacking the source of an opinion personally is usually regarded as a useless exercise in a debate. Making a point to not listen to sources one has labelled negatively restricts one from potentially valuable information.

Oh by the way, according to the Oxford English Dictionary:

practise | practice, v.

a. trans. To pursue or be engaged in (a particular occupation, profession, skill, or art).

I'm not a native speaker of English. So thanks for offering this opportunity for me to improve myself.

Richard said:

Richard wrote:

Richard said:

Anders W wrote:

The original thread on this subject

http://forums.dpreview.com/forums/thread/3391811


has now expired. Since there appears to be things left to discuss, I started this new thread as a continuation of the first.

Click to expand...

I don't have a 4/3rds, but I do get flaring on lenses when pointing them into the sun or strong light or even sometimes just outside of the frame.

Click to expand...

Tell me again about these intensively purple flares you are getting with non m43 systems. And tell me how do avoid flares to turn purple.

Because that is what this thread is about, purple flares not normal flares.

Macx said:

Macx wrote:

Has interpixel capacitance been considered?

"In [CMOS] arrays, small amounts of stray capacitance can couple pixels to neighboring pixels and influence the voltage read for that pixel. This coupling is interpixel capacitance. [...]

"Interpixel capacitance creates two effects. The first and most obvious is that cross talk is generated—a strong signal in one pixel creates a weak signal in neighboring pixels. This observed cross talk may easily be mistaken for a more common cross talk, diffusion cross talk, which occurs when photocarriers generated within one pixel diffuse to adjacent pixels. A second effect naturally exists as well. The signal appearing in those neighboring pixels is a signal that should have appeared in the central pixel had there been no interpixel capacitance. The signal in the central pixel is therefore attenuated. This attenuation may also be mistaken for attenuation resulting from diffusion. [...]

"Interpixel capacitance is expected to become more significant with modern arrays. As detector array designers continue to strive for the simultaneous qualities of high pixel density requiring small distances between pixel centers, high quantum efficiency, low diffusion cross talk, and low latent images requiring 100% fill factor—small gaps between pixel implants, and high sensitivity low capacitance multiplexer nodes, the stray capacitance to neighboring pixels will be more pronounced. Stray capacitance to a detector node is the result of the presence of conductors adjacent to the detector node. Detector nodes must be conductive to accumulate charge. Thus, the nearest conductors adjacent to the pixels in the lowest capacitance detector arrays will be the neighboring pixels." (Moore et al. 2006 http://ridl.cfd.rit.edu/products/publications/intepixel paper downloaded from SPIE.pdf )

Click to expand...

Hi Macx,

The particular kind of crosstalk we have so far been talking about (called diffusion crosstalk in the paper you refer to) can explain certain types of purple flare (as shown in the previous thread) since it is linked to the angle of incidence of the light involved. Interpixel capacitance, by contrast, does not appear to have any properties that can be specifically linked to flare/reflections. But thanks for calling our attention to its existence anyway. It's always good to have an inventory of the potential sensor flaws we might be dealing with.

Anders W said:

Anders W wrote:

Anders W said:

Macx wrote:

Has interpixel capacitance been considered?

"In [CMOS] arrays, small amounts of stray capacitance can couple pixels to neighboring pixels and influence the voltage read for that pixel. This coupling is interpixel capacitance. [...]

"Interpixel capacitance creates two effects. The first and most obvious is that cross talk is generated—a strong signal in one pixel creates a weak signal in neighboring pixels. This observed cross talk may easily be mistaken for a more common cross talk, diffusion cross talk, which occurs when photocarriers generated within one pixel diffuse to adjacent pixels. A second effect naturally exists as well. The signal appearing in those neighboring pixels is a signal that should have appeared in the central pixel had there been no interpixel capacitance. The signal in the central pixel is therefore attenuated. This attenuation may also be mistaken for attenuation resulting from diffusion. [...]

"Interpixel capacitance is expected to become more significant with modern arrays. As detector array designers continue to strive for the simultaneous qualities of high pixel density requiring small distances between pixel centers, high quantum efficiency, low diffusion cross talk, and low latent images requiring 100% fill factor—small gaps between pixel implants, and high sensitivity low capacitance multiplexer nodes, the stray capacitance to neighboring pixels will be more pronounced. Stray capacitance to a detector node is the result of the presence of conductors adjacent to the detector node. Detector nodes must be conductive to accumulate charge. Thus, the nearest conductors adjacent to the pixels in the lowest capacitance detector arrays will be the neighboring pixels." (Moore et al. 2006 http://ridl.cfd.rit.edu/products/publications/intepixel paper downloaded from SPIE.pdf )

Click to expand...

Hi Macx,

The particular kind of crosstalk we have so far been talking about (called diffusion crosstalk in the paper you refer to) can explain certain types of purple flare (as shown in the previous thread) since it is linked to the angle of incidence of the light involved. Interpixel capacitance, by contrast, does not appear to have any properties that can be specifically linked to flare/reflections. But thanks for calling our attention to its existence anyway. It's always good to have an inventory of the potential sensor flaws we might be dealing with.

Click to expand...

Well, looking at the glare in Timur's pictures, IPC looks to be a good explanation for the pattern of light smearing.

teeranui said:

teeranui wrote:

Any practical solution?

Click to expand...

In the thread to which this one is a continuation, it was shown that certain kinds of purple flare can be significantly reduced by means of a linear polarizer and by means of a strong purple filter. Regrettably, it seems as if neither solution is a cure-all for all kinds of purple flare. They are also difficult to use with some lenses, including the one most badly affected by the flare (the Panasonic 7-14 which can't take filters without a special filter holder) and like any filter they imply a loss of light.

Speaking for myself, my primary interest is to understand why certain types of flare has a tendency to go purple with the E-M5 as opposed to some other MFT cameras. If that in turn can generate ideas for practical solutions, I am happy of course. But I am not too optimistic in that regard. Understanding the circumstances under which a phenomenon appears and not may still be helpful in one way or the other, for example when evaluating the new sensors to appear in future cameras.

Macx said:

Macx wrote:

Macx said:

Anders W wrote:

Macx said:

Macx wrote:

Has interpixel capacitance been considered?

"In [CMOS] arrays, small amounts of stray capacitance can couple pixels to neighboring pixels and influence the voltage read for that pixel. This coupling is interpixel capacitance. [...]

"Interpixel capacitance creates two effects. The first and most obvious is that cross talk is generated—a strong signal in one pixel creates a weak signal in neighboring pixels. This observed cross talk may easily be mistaken for a more common cross talk, diffusion cross talk, which occurs when photocarriers generated within one pixel diffuse to adjacent pixels. A second effect naturally exists as well. The signal appearing in those neighboring pixels is a signal that should have appeared in the central pixel had there been no interpixel capacitance. The signal in the central pixel is therefore attenuated. This attenuation may also be mistaken for attenuation resulting from diffusion. [...]

"Interpixel capacitance is expected to become more significant with modern arrays. As detector array designers continue to strive for the simultaneous qualities of high pixel density requiring small distances between pixel centers, high quantum efficiency, low diffusion cross talk, and low latent images requiring 100% fill factor—small gaps between pixel implants, and high sensitivity low capacitance multiplexer nodes, the stray capacitance to neighboring pixels will be more pronounced. Stray capacitance to a detector node is the result of the presence of conductors adjacent to the detector node. Detector nodes must be conductive to accumulate charge. Thus, the nearest conductors adjacent to the pixels in the lowest capacitance detector arrays will be the neighboring pixels." (Moore et al. 2006 http://ridl.cfd.rit.edu/products/publications/intepixel paper downloaded from SPIE.pdf )

Click to expand...

Hi Macx,

The particular kind of crosstalk we have so far been talking about (called diffusion crosstalk in the paper you refer to) can explain certain types of purple flare (as shown in the previous thread) since it is linked to the angle of incidence of the light involved. Interpixel capacitance, by contrast, does not appear to have any properties that can be specifically linked to flare/reflections. But thanks for calling our attention to its existence anyway. It's always good to have an inventory of the potential sensor flaws we might be dealing with.

Click to expand...

Well, looking at the glare in Timur's pictures, IPC looks to be a good explanation for the pattern of light smearing.

Click to expand...

In specifically what way does it look like a good explanation? What hypotheses with regard to purple flare did you deduce from IPC theory and how do these hypotheses fit the data (the sample images at our disposal)?

Anders W said:

Anders W wrote:

Anders W said:

teeranui wrote:

Any practical solution?

Click to expand...

In the thread to which this one is a continuation, it was shown that certain kinds of purple flare can be significantly reduced by means of a linear polarizer and by means of a strong purple filter. Regrettably, it seems as if neither solution is a cure-all for all kinds of purple flare. They are also difficult to use with some lenses, including the one most badly affected by the flare (the Panasonic 7-14 which can't take filters without a special filter holder) and like any filter they imply a loss of light.

Speaking for myself, my primary interest is to understand why certain types of flare has a tendency to go purple with the E-M5 as opposed to some other MFT cameras. If that in turn can generate ideas for practical solutions, I am happy of course. But I am not too optimistic in that regard. Understanding the circumstances under which a phenomenon appears and not may still be helpful in one way or the other, for example when evaluating the new sensors to appear in future cameras.

Click to expand...

A polarizer film at the rear of the lens may be able to suppress both the specific purple flares and ordinary flares (might add a flare of its own?). But is not particularly practical, unless one manages to attach it with a rotating holder.

Mind skies will look odd with an UWA lens with a polarizer.

_sem_ said:

_sem_ wrote:

_sem_ said:

Anders W wrote:

_sem_ said:

teeranui wrote:

Any practical solution?

Click to expand...

In the thread to which this one is a continuation, it was shown that certain kinds of purple flare can be significantly reduced by means of a linear polarizer and by means of a strong purple filter. Regrettably, it seems as if neither solution is a cure-all for all kinds of purple flare. They are also difficult to use with some lenses, including the one most badly affected by the flare (the Panasonic 7-14 which can't take filters without a special filter holder) and like any filter they imply a loss of light.

Speaking for myself, my primary interest is to understand why certain types of flare has a tendency to go purple with the E-M5 as opposed to some other MFT cameras. If that in turn can generate ideas for practical solutions, I am happy of course. But I am not too optimistic in that regard. Understanding the circumstances under which a phenomenon appears and not may still be helpful in one way or the other, for example when evaluating the new sensors to appear in future cameras.

Click to expand...

A polarizer film at the rear of the lens may be able to suppress both the specific purple flares and ordinary flares (might add a flare of its own?). But is not particularly practical, unless one manages to attach it with a rotating holder.

Mind skies will look odd with an UWA lens with a polarizer.

Click to expand...

Yes, you are right (unfortunately) in both regards.

Anders W said:

Anders W wrote:

The original thread on this subject

http://forums.dpreview.com/forums/thread/3391811


has now expired. Since there appears to be things left to discuss, I started this new thread as a continuation of the first.

Click to expand...

Hi Anders,

Been away from the group for three days, so now trying to catch up...!

Have read through to your intelligent suggestion, about halfway down thread 1, so forgive me if this has been dealt with.

On Saturday I was out with my OM-D and longer lenses to get some bird photos. The sun went in and I came across a wide angle subject. Fortunately I'd got the Panny 7mm lens with me. The shots taken in dull conditions with bright sky, looked OK at the time. When I got home I found they were cursed with a central purple flare, where the problem was not the slanting light we'd had before.These are reduced as full size is immaterial.


Out of camera RAW to jpg in LR4:-


Unlock (out of camera)

After work to reduce distortion and lightened shadows:-


Unlock after correction and lightening shadows

I've increased the saturation here to show the problem. But I wanted to get a tone mapping effect and exported to Photoshop, where I had to use colour replacement to get rid of the purple centre, but traces remain.


Final image after heavy pp:-


Unlock after post processing

My point is that the purple problem is working from the light outside towards the dark centre - and thus less likely to be caused by the sensor's internal refraction / reflection.

Not disagreeing with your conclusions, just adding information and comment. Of course, if this has already been dealt with then please ignore!

My conclusion is to keep the 7-14mm on the G1, I think! ;-(

Mike


--
Mike Davis
Photographing the public for over 50 years
www.flickr.com/photos/watchman

Anders W said:

Anders W wrote:

Anders W said:

Macx wrote:

Anders W said:

Anders W wrote:

Anders W said:

Macx wrote:

Has interpixel capacitance been considered?

"In [CMOS] arrays, small amounts of stray capacitance can couple pixels to neighboring pixels and influence the voltage read for that pixel. This coupling is interpixel capacitance. [...]

"Interpixel capacitance creates two effects. The first and most obvious is that cross talk is generated—a strong signal in one pixel creates a weak signal in neighboring pixels. This observed cross talk may easily be mistaken for a more common cross talk, diffusion cross talk, which occurs when photocarriers generated within one pixel diffuse to adjacent pixels. A second effect naturally exists as well. The signal appearing in those neighboring pixels is a signal that should have appeared in the central pixel had there been no interpixel capacitance. The signal in the central pixel is therefore attenuated. This attenuation may also be mistaken for attenuation resulting from diffusion. [...]

"Interpixel capacitance is expected to become more significant with modern arrays. As detector array designers continue to strive for the simultaneous qualities of high pixel density requiring small distances between pixel centers, high quantum efficiency, low diffusion cross talk, and low latent images requiring 100% fill factor—small gaps between pixel implants, and high sensitivity low capacitance multiplexer nodes, the stray capacitance to neighboring pixels will be more pronounced. Stray capacitance to a detector node is the result of the presence of conductors adjacent to the detector node. Detector nodes must be conductive to accumulate charge. Thus, the nearest conductors adjacent to the pixels in the lowest capacitance detector arrays will be the neighboring pixels." (Moore et al. 2006 http://ridl.cfd.rit.edu/products/publications/intepixel paper downloaded from SPIE.pdf )

Click to expand...

Hi Macx,

The particular kind of crosstalk we have so far been talking about (called diffusion crosstalk in the paper you refer to) can explain certain types of purple flare (as shown in the previous thread) since it is linked to the angle of incidence of the light involved. Interpixel capacitance, by contrast, does not appear to have any properties that can be specifically linked to flare/reflections. But thanks for calling our attention to its existence anyway. It's always good to have an inventory of the potential sensor flaws we might be dealing with.

Click to expand...

Well, looking at the glare in Timur's pictures, IPC looks to be a good explanation for the pattern of light smearing.

Click to expand...

In specifically what way does it look like a good explanation? What hypotheses with regard to purple flare did you deduce from IPC theory and how do these hypotheses fit the data (the sample images at our disposal)?

Click to expand...

Well, simply that an extremely strong signal would lead to the cross-like "diffraction" patterns, but without it needing to be explained by a physical/optical grating effect ...but I'm no technician, I just saw that IPC was a fact, and that it could be mistaken for optical diffraction, so I thought I'd mention it.


Btw, while trying to read up a bit on CMOS design, I noticed that your diagram in the first thread from the Leica-brochure shows a front-lit design, and as far as I can tell back-lit designs pretty much eliminate this problem. The E-M5 is sometimes described as having a back-lit sensor, though notably not by Olympus, as far as I can see, and the existence of this problem may be further indication that it's a regular front-lit sensor. Maybe the next generation will be back-lit.

Macx said:

Macx wrote:

Macx said:

Anders W wrote:

Macx said:

Macx wrote:

Macx said:

Anders W wrote:

Macx said:

Macx wrote:

Has interpixel capacitance been considered?

"In [CMOS] arrays, small amounts of stray capacitance can couple pixels to neighboring pixels and influence the voltage read for that pixel. This coupling is interpixel capacitance. [...]

"Interpixel capacitance creates two effects. The first and most obvious is that cross talk is generated—a strong signal in one pixel creates a weak signal in neighboring pixels. This observed cross talk may easily be mistaken for a more common cross talk, diffusion cross talk, which occurs when photocarriers generated within one pixel diffuse to adjacent pixels. A second effect naturally exists as well. The signal appearing in those neighboring pixels is a signal that should have appeared in the central pixel had there been no interpixel capacitance. The signal in the central pixel is therefore attenuated. This attenuation may also be mistaken for attenuation resulting from diffusion. [...]

"Interpixel capacitance is expected to become more significant with modern arrays. As detector array designers continue to strive for the simultaneous qualities of high pixel density requiring small distances between pixel centers, high quantum efficiency, low diffusion cross talk, and low latent images requiring 100% fill factor—small gaps between pixel implants, and high sensitivity low capacitance multiplexer nodes, the stray capacitance to neighboring pixels will be more pronounced. Stray capacitance to a detector node is the result of the presence of conductors adjacent to the detector node. Detector nodes must be conductive to accumulate charge. Thus, the nearest conductors adjacent to the pixels in the lowest capacitance detector arrays will be the neighboring pixels." (Moore et al. 2006 http://ridl.cfd.rit.edu/products/publications/intepixel paper downloaded from SPIE.pdf )

Click to expand...

Hi Macx,

The particular kind of crosstalk we have so far been talking about (called diffusion crosstalk in the paper you refer to) can explain certain types of purple flare (as shown in the previous thread) since it is linked to the angle of incidence of the light involved. Interpixel capacitance, by contrast, does not appear to have any properties that can be specifically linked to flare/reflections. But thanks for calling our attention to its existence anyway. It's always good to have an inventory of the potential sensor flaws we might be dealing with.

Click to expand...

Well, looking at the glare in Timur's pictures, IPC looks to be a good explanation for the pattern of light smearing.

Click to expand...

In specifically what way does it look like a good explanation? What hypotheses with regard to purple flare did you deduce from IPC theory and how do these hypotheses fit the data (the sample images at our disposal)?

Click to expand...

Well, simply that an extremely strong signal would lead to the cross-like "diffraction" patterns, but without it needing to be explained by a physical/optical grating effect

Click to expand...

The crosstalk whether by IPC or diffusion, is very local (neighboring pixels). But the strong signal in Timur's image (the image of the light source itself) is lots and lots of pixels away from the cross-shaped purple flare. Cross-like diffraction is a phenomenon on a very small scale whereas the scale of the phenomenon in Timur's image is on a comparatively very large scale. That's why I see no connection between IPC and the cross-like pattern we see in Timur's images (or the similar ones I showed in the previous thread).

Macx said:

...but I'm no technician, I just saw that IPC was a fact, and that it could be mistaken for optical diffraction, so I thought I'd mention it.

Btw, while trying to read up a bit on CMOS design, I noticed that your diagram in the first thread from the Leica-brochure shows a front-lit design, and as far as I can tell back-lit designs pretty much eliminate this problem. The E-M5 is sometimes described as having a back-lit sensor, though notably not by Olympus, as far as I can see, and the existence of this problem may be further indication that it's a regular front-lit sensor. Maybe the next generation will be back-lit.

Click to expand...

No "large" sensor has a BSI design yet as far as I am aware. This technology is so far used only for "small" sensors (bridge cams, P&S, smartphones).

But what do you have in mind when you say that BSI would eliminate the problem? That the CFA could be placed closer to the photodiodes thus reducing crosstalk due to diffusion? You might well be right but is this just an idea of your own or do you have a source discussing the issue?

BTW: If you look at that Leica broschure, you will see that Leica claims to have reduced/eliminated crosstalk due to diffusion by, among other things, placing the CFA closer to the photodiodes on the sensor of the new Leica M.

Michael J Davis said:

Michael J Davis wrote:

Michael J Davis said:

Anders W wrote:

The original thread on this subject

http://forums.dpreview.com/forums/thread/3391811

has now expired. Since there appears to be things left to discuss, I started this new thread as a continuation of the first.

Click to expand...

Hi Anders,

Been away from the group for three days, so now trying to catch up...!

Have read through to your intelligent suggestion, about halfway down thread 1, so forgive me if this has been dealt with.

On Saturday I was out with my OM-D and longer lenses to get some bird photos. The sun went in and I came across a wide angle subject. Fortunately I'd got the Panny 7mm lens with me. The shots taken in dull conditions with bright sky, looked OK at the time. When I got home I found they were cursed with a central purple flare, where the problem was not the slanting light we'd had before.These are reduced as full size is immaterial.

Out of camera RAW to jpg in LR4:-


Unlock (out of camera)

After work to reduce distortion and lightened shadows:-


Unlock after correction and lightening shadows

I've increased the saturation here to show the problem. But I wanted to get a tone mapping effect and exported to Photoshop, where I had to use colour replacement to get rid of the purple centre, but traces remain.

Final image after heavy pp:-


Unlock after post processing

My point is that the purple problem is working from the light outside towards the dark centre - and thus less likely to be caused by the sensor's internal refraction / reflection.

Not disagreeing with your conclusions, just adding information and comment. Of course, if this has already been dealt with then please ignore!

My conclusion is to keep the 7-14mm on the G1, I think! ;-(

Click to expand...

Hi Michael,

Yes, I am by now quite familiar with the type of flare on the 7-14 that you illustrate here, not so much from my own experience fortunately but from a pretty large number of samples similar to yours that I have seen posted on this forum. I am not yet sure to which category this type of flare (a rather diffuse purple blob caused by fairly strong but diffuse light) belongs but I suspect that it might be in essentially the same camp as the one I describe here

http://forums.dpreview.com/forums/post/50966147

(in spite of being quite different in some regards) rather than to the camp I successfully (I hope/think) managed to explain in the previous thread.

BTW: What PP strategy did you use in this case?

P.S. One additional thing I forgot to mention: If you push very dark shadows so that their color becomes more obvious, they are likely to take on a magenta (in daylight) or blue (if the light is warm, e.g., tungsten) cast for reasons entirely unrelated to flare. Possibly, there are some signs of that in your image too (although I don't know enough to really tell).

This shift towards magenta/blue in the deep shadows occurs because the read noise is clipped at the black point. The net impact of that clipping, which becomes inreasingly noticeable as we approach the black point, is to make the weakest channels (red and blue in daylight, primarily blue in warmer light) stronger relative to other channels than they should be.

tt321 said:

tt321 wrote:

tt321 said:

Richard wrote:

tt321 said:

tt321 wrote:

What you just said here is well known and widely practised, and therefore uninteresting to the point of boring. What Anders et al have been doing is intelectual work backed by well planned and reasoned experiments exploring the possible reasons of an observed phenomenon previously poorly explained, and thus very interesting. Hence the popularity of these threads.

Hacked and intuitive practical techniques might well work better than what organized research could turn up in the short term, but ultimately almost all elegant and reliable solutions are the results of the latter, esp. as the human intellect further develops. In addition, to some people at least, the process of intellectual work is rewarding in itself. These threads is my exhibit A for this claim, if you need convincing.

Click to expand...

It is a forum. I am entitled to my opinion and to post it here regardless how simple the solution is. Pseudo intellectuals like yourself who cannot even spell practiced or intellectual are invited to give input too, but in my experience, rules like keep it simple stupid dominate over elegant and reliable solutions that you are suggesting coming from pseudo intellectuals that ar usually not simple, elegant or reliable. It is just a bunch of people arguing or trying to prove they have some technical prowess, when most can see they don't.

I guess after seeing this is a problem in some of the later post, the issue is with the camera and not the lens, I am just glad that I use Nikon and Canon that do not have these issues or if they do, they are so negligible, they are not worth talking about. But you can carry on with your pseudo intellectual discussions without me, good luck.

Click to expand...

Where do you think the technological advancements which have allowed Nikon and Canon to stay in business and continue to lead for decades come from?

Click to expand...

It came from them, not from a bunch of pseudo intellectuals on a forum.

tt321 said:

Hap-hazard intuitive ad-hoc tweaking by people who are not interested in intellectual exercises or organized research?

Click to expand...

Leave that work to the intellectuals, if they want your opinion, I am sure they will ask for it.

tt321 said:

Where do you think the "guessed" knowledge that "the issue is with the camera and not the lens" comes from?

Click to expand...

The OP asked the question for both causes and resolution. Most people don't care about the cause, they want a resolution either from the manufacturer (then let the manufacturer give them a resolution) of from someone online. Shading the lens works perfectly, it is like having an extension of the shade the lens came with, it is a cheap solution, it adds very little time to getting the shot.

tt321 said:

Precisely the work by Anders et al and the discussion inspired by it that you seem to regard as "a bunch of people arguing or trying to prove they have some technical prowess, when most can see they don't" - and this "most" is from what poll you have taken?

Click to expand...

Just and opinion and an observation. Again this is a forum, I can post my opinions and observations on it, I do not need a pole to validate me.

tt321 said:

It's this bunch of people who were curious about an observed phenomenon and explored it further then exchanged their findings, ideas and opinions in the forum, which is exactly what a forum like this is for in my opinion.

Click to expand...

You scolded me for my "well known" solution but your discussions are well know as well. Basically 3 places to reduce lens flare, design of lens/camera which you can discuss all day but manufacturers are not going to listed to you because the have professionals who make those decisions. The next is my suggestion in composition, recompose or use bigger lens shade, and in post in photoshop which has also been mentioned. But this has all been discussed and talked about before.

http://www.cambridgeincolour.com/tutorials/lens-flare.htm

tt321 said:

Having curiosities and willing to expend some effort to satisfy them is a characteristic in humans, at least some of us.

Click to expand...

Here read this http://www.cambridgeincolour.com/tutorials/lens-flare.htm

As for the cause, we know what the cause is, either a poorly designed lens or camera, at least for excessive or abnormal flare, all lenses have flare. The can reduce it in a number of ways but in design they have to balance lens defects with other considerations, size, cost, lens purpose.

tt321 said:

Attacking the source of an opinion personally is usually regarded as a useless exercise in a debate.

Click to expand...

And that is exactly what you did to me, you attacked my opinion and me personal saying it was well know and acted if I am stupid, I am not, but the discussion of lens flare is well know and the resolutions are well know. Yet you attacked me.

tt321 said:

Making a point to not listen to sources one has labelled negatively restricts one from potentially valuable information.

Click to expand...

Exactly, you should listen to my resolution about shading the lens with your hand or other means to resolve the problem, but you didn't, you dismissed it.

There is another resolution, dump this camera and get a Nikon or Canon which don't suffer this problem or is at least so slight you cannot notice it.

I offered a solution because I cared enough to answer even though I don't own the camera. If this was a problem with my camera Nikon or Canon and I found it objectionable I sell the camera and get a new one or a different brand.

tt321 said:

Oh by the way, according to the Oxford English Dictionary:

practise | practice, v.

a. trans. To pursue or be engaged in (a particular occupation, profession, skill, or art).

I'm not a native speaker of English. So thanks for offering this opportunity for me to improve myself.

Click to expand...

Thanks for attacking me and generally being a jerk, had I know you just wanted someone to talk to so you could practice your english, I would have ignored you, We don't need another english speaking troll.

Anders W said:

Anders W wrote:

But what do you have in mind when you say that BSI would eliminate the problem? That the CFA could be placed closer to the photodiodes thus reducing crosstalk due to diffusion? You might well be right but is this just an idea of your own or do you have a source discussing the issue?

Click to expand...

Simply that the main source of reflection is the wiring in front of the photo diodes on the front-lit designs

Richard said:

Richard wrote:

Richard said:

Anders W wrote:

The original thread on this subject

http://forums.dpreview.com/forums/thread/3391811

has now expired. Since there appears to be things left to discuss, I started this new thread as a continuation of the first.

Click to expand...

I don't have a 4/3rds, but I do get flaring on lenses when pointing them into the sun or strong light or even sometimes just outside of the frame. First I makes sure the lens hood is attached in your case, your hood is like the one on my Nikon 14-24 2.8 permanent. Then looking through the view finder if I see flare I will change my angle or shield the lens. If my hand appears in the picture I edit it out. It is the fastest, easiest, least expensive way of solving the problem. If there is another lens of a similar focal length that does not exhibit the problem or much less, then buy it or do your home work first, most reviews report how well the lens handles flare.

No lens is perfect, they seem to balance defects against the goal of the lens, one may have more CA, vignette, flare, barrel distortion or other types of distortion.

To me, your flare problem is the easiest to rid yourself of compared to some of the other lens issues. Shield your lens from light source with your hand or paper. If you are shooting the sun in the picture and you have issues. Look for a lens that does this well and buy it.

Good luck to you, I notice this problem on rare occasion with some lenses but I just hood with my had, even hand held. So I don't worry about it, if it is on a tripod, it is even easier.

Click to expand...

Richard,

Everything you tell me is already well known to me. What makes you think differently?

And in what way do the elementary observations you make help us understand what this thread as well as the one it is a continuation to is about: Why flare that has hitherto appeared whitish or grayish turns purple with the E-M5 and some other recent cameras?

Anders W said:

Anders W wrote:

Anders W said:

Richard wrote:

Anders W said:

Anders W wrote:

The original thread on this subject

http://forums.dpreview.com/forums/thread/3391811


has now expired. Since there appears to be things left to discuss, I started this new thread as a continuation of the first.

Click to expand...

I don't have a 4/3rds, but I do get flaring on lenses when pointing them into the sun or strong light or even sometimes just outside of the frame. First I makes sure the lens hood is attached in your case, your hood is like the one on my Nikon 14-24 2.8 permanent. Then looking through the view finder if I see flare I will change my angle or shield the lens. If my hand appears in the picture I edit it out. It is the fastest, easiest, least expensive way of solving the problem. If there is another lens of a similar focal length that does not exhibit the problem or much less, then buy it or do your home work first, most reviews report how well the lens handles flare.

No lens is perfect, they seem to balance defects against the goal of the lens, one may have more CA, vignette, flare, barrel distortion or other types of distortion.

To me, your flare problem is the easiest to rid yourself of compared to some of the other lens issues. Shield your lens from light source with your hand or paper. If you are shooting the sun in the picture and you have issues. Look for a lens that does this well and buy it.

Good luck to you, I notice this problem on rare occasion with some lenses but I just hood with my had, even hand held. So I don't worry about it, if it is on a tripod, it is even easier.

Click to expand...

Richard,

Everything you tell me is already well known to me. What makes you think differently?

Click to expand...

You asked for remedies. I gave you a simple one that works to reduce lens flare regardless of color.

Anders W said:

And in what way do the elementary observations you make help us understand what this thread as well as the one it is a continuation to is about: Why flare that has hitherto appeared whitish or grayish turns purple with the E-M5 and some other recent cameras?

Click to expand...

I was not trying to help you find the cause, it is well known, either the camera or the lens or both due to design can cause more or less lens flare and different colors. I have not seen this purple issue on other cameras from Nikon or Canon. If I did and it bothered me I would switch to another brand that did not have the issue. Another resolution to the problem. I never offered to help you figure out why, any discussion like that without the manufacturers explanation would be speculation. I am a problem solver, not a speculator. Which is why I offered the resolution and not a cause that cannot be known for all we know the manufacture designed it this way to overcome some other issue.

noirdesir said:

noirdesir wrote:

noirdesir said:

Richard wrote:

noirdesir said:

Anders W wrote:

The original thread on this subject

http://forums.dpreview.com/forums/thread/3391811


has now expired. Since there appears to be things left to discuss, I started this new thread as a continuation of the first.

Click to expand...

I don't have a 4/3rds, but I do get flaring on lenses when pointing them into the sun or strong light or even sometimes just outside of the frame.

Click to expand...

Tell me again about these intensively purple flares you are getting with non m43 systems. And tell me how do avoid flares to turn purple.

Because that is what this thread is about, purple flares not normal flares.

Click to expand...

Flare is flare you see different colors depending on the lens and apparently the camera. All I mentioned was the resolution to this. This has been well documented how it happens and how to resolve it. As for why it is purple. I decided not to speculate on that because I do not have good information like the manufacturers design intentions and reasoning as to why they used the parts and design they did. Any discussion is speculation of why they did that or even if it was intentional or not intentional. For me what is done is done. You either deal with it by reducing flare your you buy a different lens/camera combination or change brands to one that does not have the purple flare and instead has a yellow, green, white or some other color.

Anders W said:

Anders W wrote:

P.S. One additional thing I forgot to mention: If you push very dark shadows so that their color becomes more obvious, they are likely to take on a magenta (in daylight) or blue (if the light is warm, e.g., tungsten) cast for reasons entirely unrelated to flare. Possibly, there are some signs of that in your image too (although I don't know enough to really tell).

This shift towards magenta/blue in the deep shadows occurs because the read noise is clipped at the black point. The net impact of that clipping, which becomes inreasingly noticeable as we approach the black point, is to make the weakest channels (red and blue in daylight, primarily blue in warmer light) stronger relative to other channels than they should be.

Click to expand...

.. the above first..

Yes, I am aware of that - but the tone of this one appeared so close to the 'typical' OM-D colour, and could be explained by strong back light, that I assumed that was the (main) cause.

I attempted to reduce purple luminosity in LR4 (which I'm still learning) but that seemed to come to a stop. So I exported into PSE10 - which I was going to do anyway - and picked up the purple magenta tones in the shadows and replaced them with a similar dark orange tone. There are, though still some purple overtones in the darker areas, that, you can see, I left.

Having got the colours about right I used an overlay created by a tone mapping algorithm (in this case ReDynaMix) to reduce the overall contrasts.


Thanks for your reply.

Mike

Good idea, kenw!

The real trouble is that one doesn't always know one has it until ones is in the comfort of the, er, darkroom!

Mike


--

Mike Davis
Photographing the public for over 50 years
www.flickr.com/photos/watchman