WARNING - technical thread - how are the red dots really made?

Started Sep 7, 2012 | Discussions thread
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Roland Karlsson
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WARNING - technical thread - how are the red dots really made?
Sep 7, 2012

The DP cameras have the red grid syndrome, and so have several other cameras.

Its quite clear, to me, that the red grid is somehow caused by the pixel grid. Otherwise, it would not be a grid.

That it is some kind of reflection in the IR filter for the DP cameras is clear. The reflection there is red, and Sigma has even said so.

That the grid is ONLY created if there is a small very bright light source focussed on the sensor, e.g. the sun, we know.

But ... there are some irritating questions.

  • Why is the grid image so large?

  • Why is the grid image so sharp?

  • Why is the grid image always red, in all cameras?

  • Why do the camera manufacturers accept such a misfeature?

  • Do anyone know the exact mechanism for the red grid?

Why is the grid image so large?

This is very mysterious. The grid image is MUCH larger than the sensor grid itself. How come that a greatly enlarged image of the grid is focussed on the grid? We have just accepted this with a shrug, more or less in our earlier discussions. There was some suggestions that the micro lenses could spread the light rays. In an other forum there was a suggestion that it was diffraction in the grid. But. diffraction should result in rainbow colored stuff - if the light is not monochromatic.

Why is the grid image so sharp?

This is also a mystery. Light is hitting the sensor with a rather large aperture. Then the light that hits the grid should be spread at an angle of the aperture. This should not result in dots, if the IR filter is not very near to the sensor. But - how can the image then be enlarged?

Why is the grid image always red, in all cameras?

Why the grid is red in the DP cameras we know. But - why also in all other cameras where it exists?

Why do the camera manufacturers accept such a misfeature?

Yet a mystery. Why? Is it impossible to fix if you have a large sensor and a compact camera?

  • Do anyone know the exact mechanism for the red grid?*

This is the main question. The red grid is not magic. So - someone designing digital cameras knows the exact answer to the red grid, and can even simulate it in his programs. So - there exist an answer. It would be extremely interesting to know that answer.

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