why not f/1.2 by Sony?

Started May 14, 2013 | Discussions thread
tomtom50 Veteran Member • Posts: 3,244
Sensor inability to use fast lenses

This is a real phenomena, reported by DXOmark and others. Generally the photodiodes get less than a full stop more light going from f2 to f1.4, and faster than f 1.4 makes very little difference.

This is related to the angle at which the light hits the sensor. The photon has to make it through a bit of a tunnel on the way to the photodiode and if it hits the side of the tunnel it is not counted.

Wide aperture lenses collect light from more oblique angles. That is how they gather more light and it is why they have shallower DOF.

Sensor design can accommodate this. Some sensors show less of this effect than others.

In the P&S world the literature for the Sony imx144cqj used in high-end cameras with fast lenses states the following:

"Larger pixel size combined with better light collecting characteristics have vastly increased incident light angle characteristics (see figure 1) and yielded more favorable f-number dependence over the current Type 1/2.3 back-illuminated image sensors."

This is likely an aspect of sensor design that will improve over time. In the meantime the half-stop from f1.4 to f.1.2 will give little benefit on many sensors.

As far as Nikon 1, either Nikon/Aptina designed those sensors to take oblique rays or they are counting on the marketing magic of f1.2!!! to sell product regardless of function.

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