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< Esato Forum Index > Manufacturer Discussion > Nokia > N8´s Major Camera Desing Flaw - Poor Flare Performance Bookmark topic



Easy, Angle of incidence = Angle of reflection.



the blue line on the left is regular light.... it would hit the silver rim and go across the lens.....
the red line is stray light (as light comes from EVERY angle)... when light reaches it destination it has limited choices.... go through the object, scatter (in many directions) or reflect off in an equal and opposite direction... glare is created when the stray light reflects off in such a way that it illuminates the surface of the glass.....

This is what makes lens hoods (and out finger) so effective in reducing glare.... if you block the light that would skim across the glass/lens from the outter edges you can reduce or totally eliminate that effect as in my very poor illustration below.



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Posted: 2010-11-12 01:22:27
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You simplified things too much!
And you missed some major points.

Anyway, going with your simplified basic explanation, here the points you missed:



In the picture above are two light sources, "a" and "b".
Source "a" emitting three rays, and "b" two rays.

The perpendicular black line is the Normal line to the ring's planar area.
Given the necessary conditions, those rays should reflect at the same angle they make with the Normal.

Orange1 and Red1 relflect away from the lens.
Orange2 and Red2 go directly into the lens and refract, probably causing not only flares but also artifacts.

Orange3 is our "special" ray. It reflects from the ring into lens.

Now, the issue here, for a source to emit such rays that reflect into the lens, two conditions should be met:
- That ray hits the outer region of the Normal. In this case, O3 hits the left side of the Normal.
- It should hit it at an angle greater than 45°.. Depends however on the position of the spot hit on the ring, and the curvature of the ring as well.. It could need up to 60° to make it through the lens for instanace..

However, to meet those two conditions, teh source must be within the view, in other words visible in the viewfinder! Which means it's already resulting in some excessive amount of light in and flares already there..

In the other case of Source "b", the source shouldn't be visible to the camera, but could still result in some flares (Etaab's photos!!)..
But not caused by ring reflection..

However, capturing photos whereas the light source isn't producing rays directly into the lens shouldn't result in any flares. This happens when one makes sure that source is well maintained by the right angle of view..
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Posted: 2010-11-12 05:32:13
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@ false_morel, You now contridict yourself.... in this post you say



but then you come back telling me I miss important points only to over explain the same exact thing I just said in an extremely convoluted way? You also show a diagram totally contradictory to your statement "but never negative angle towards the lens" .... how is toward the LENS a "negative angle" anyway? Its just a reflection from the silver ring to glass or across the glass itslef, no need to make more of it than it is..... its simply A POOR IDEA to have a silver reflective surface by the lens. Its not 100% the issue (I understand this) but is certainly don't help at all.


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Posted: 2010-11-12 06:30:45
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This seems obvious. If I had a N8 and experienced flare problems, I would try a black marker to color the silver ring
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Posted: 2010-11-12 11:44:00
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You missed the trick again..

When I said that there is no way for light to bounce at negative angle and into the lens, I was referring at teh case of Source "b" illustrated in the drawing I posted. Same as what happened in teh two photos of Etaab for instance.. The source isn't within the angle of view!

However, if you have some bright light source within the angle of view of the camera, it will result in flares anyway..
Now, you can argue that the ring may make it even worse. Ok, in this case I could agree. But there's no point here blaming the ring for flares as those would already be there!

Then, as to the simplification I hinted to.. You missed that the material the ring made of isn't a perfect reflecting one!
And you missed the curving part of it..
There are many given conditoins here if considered would lead for the most of light not ot be refeclted at teh first place!

Flares mainly occur of excessive light entering the lens directly and refracting. Light bouncing off objects, even extremely near objects, shouldn't be a problem!

That's why I said I'm not very sure in my first post. There's many diverse aspects to consider and you simplified things too much.

In conclusion, if that ring does have some negative effect, it's due to only when the camera facing a light source, which isn't that wise to do, and the effect is minimal in comparison to the rather natural flare effect taking place at that condition!

Again, notice the "if's"...
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Posted: 2010-11-12 12:31:22
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A Sharp Edge doesn´t reflect the light evenly.

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Posted: 2010-11-12 16:51:17
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Good (and also bad) to know that I am not the only one who thinks that.

People that say it´s merely a lens issue don´t seem to know the issue that well.

I´ve had a Pixon12, which has 30mm of focal lenght. I´ve never seen such a great amount of lens flare with it.

Besides that, when we talk of critical lens flare with wide angle, we usually talk about super wide lenses. For instance, 14mm lenses.

28mm is not that wide for this lens to behave that badly.

That 'ring' has a sharp edge, and this kind of edge does not reflect the light evenly.

My guess is that it has been a designer´s solution. I don´t think it has a functional hole.

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Posted: 2010-11-12 16:57:48
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Vit, could you shed some more light on your sharp edge theory?
You don't have to go all geeky like mlife and I did, illustrating everything. Just some more words would do..

But again, I may agree that the ring could worsen the flare effect only if some bright light source was within the frame of the camera! Also, at certain angles, not all the time..

Otherwise, in case of Etaab's two photos, where the sun was out of the frame, there should be no way the ring could reflect some light into the lens!
In this case, the flares there are a mere wide lens downside..


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Posted: 2010-11-12 17:30:26
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At both the bottom and the top of that surface, sharp edges may not reflect the light evenly, giving way to diffuse reflection.

If that lower part were convex and the upper part were concave, then we would guarantee that nothing would come into the lens, but due to the finishing job imprecisions that can be present, the light might not reflect evenly there, and we could not precise to where light rays are directed.

Besides that, you´ve also missed something in your analysis.

First of all, you´re assuming that the inclination angles that those reflective surfaces form with any perpendicular line to the reference plane coincide with half the viewing angle, and that is mostly not true.

Secondly, you also haven´t taken the distance between that plane and the sensor into account.

Thus a light source may well be out of the range of the lens and still have an effect at the opposite side of the frame.

Take a look at these pictures:







Those two etaab´s photos may well have been affected by this brushed metal ring.

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Posted: 2010-11-12 19:51:59
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ok Vit are you a talented painter? just paint that ring black
have you tried 30FPS video yet?

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Posted: 2010-11-12 21:24:57
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