M8 sensor

[Riley]

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On the construct of the M8 Kodak sensor.

As I recall it the reflectivity of CCD's is so high that it reflects off the surface of the offset microlens glass layer. As the layer reflects back onto the sensor then .5mm by Leica's testing was as far as they could go.

 

Their (L/AG) principle concern was uneven softness, edge definition and contrast loss. The short lens register and consequent acuteness of light by direction contributed to these decisions.

 

but does anyone recall this being said by Leica, I thought (but perhaps mistakenly) they did, but have looked extensively and cannot find it

 

Can anyone recall seeing something to the effect of the above said by Leica ?

[bradreiman]

it may have been when Leica addressed this forum upon the realization of the "IR" issues. I feel like they said it too, can't be sure tho...B

[ho_co]

Riley--

I've never heard that explanation, though it might be accurate.

 

As I understood the matter, the IR absorption glass was kept to 0.5 mm because of diffraction effects caused by the glass with regard to the angle of incidence of outer rays from wide angles.

 

I think the microlenses are attached to the sensor, directly on top of the receptors. The Kodak spec might show the thickness of that layer, but I've never heard it discussed.

 

LFI is probably the best place to find Leica's design decisions explained, though that is only a semi-official source.

 

--HC

[lars_bergquist]

Is the sensor of the DMR less reflective? It has a full IR blocking filter. This smells of rationalization.

 

The real issue as I understand was light refraction in a thicker filter, making light land on the wrong pixel. The DMR does not have that problem due to the longer back focus of the R cameras.

 

Of course the spokesman may not know the difference between reflection and refraction ...

 

The old man from the Age of the SLR

[dpattinson]

I thought the reflection issue was the answer to why they used an absorption filter over the sensor instead of a cut filter. People had argued that a 0.5mm cut filter would have eliminated the IR problem, but Leica said that the vignetting that would result from red light reflecting off the filter precluded that option. I can't recall where I read this though - so it may have been speculation

[Guest Olof]

Is the sensor of the DMR less reflective? It has a full IR blocking filter. This smells of rationalization.

 

The real issue as I understand was light refraction in a thicker filter, making light land on the wrong pixel. The DMR does not have that problem due to the longer back focus of the R cameras.

 

Of course the spokesman may not know the difference between reflection and refraction ...

 

The old man from the Age of the SLR

 

The M8 have a tinner IR Filter because the last lens of the M lenses is much closer to the sensor than in the R-System. These menas that the light rays will come in a stronger angle unto the sensor and a thicker glas on the sensor means extra refractions in the optical system, which Leica tried to avoid.