XF56 f1.2 released and specs

Started 3 months ago | Discussions thread
Krich13
Regular MemberPosts: 357
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Re: XF56 f1.2 released and specs
In reply to malcolml1, 3 months ago

malcolml1 wrote:

Yes, I follow your argument apart from one step which actually represents my original question:

>

For semiconductor sensors what matters is the total number of photons per photosite, pretty much regardless of the site area. Make two sensors: say an APS-S and FF ones both of say 16 megapixels. Expose them using the same scene for the same duration using 56/1.2 and 85/1.8 lenses respectively. Each photosite will receive the same NUMBER of photons (the number per unit area is 2.25 times larger in the first case, but the area itself is smaller by the same factor).

I agree with the area and scaling factor part, but my original question was whether it is true that the 56/1.2 will deliver the same number of photons per unit area on the APS sensor as the 85/1.8 lens on a FF sensor.

No, it will receive 2.25 times more photons PER UNIT AREA.

To me, the only way to get the same number of photons per unit area on the FF sensor is to open up the 85 lens to f1.2........

What is so damn important about number _per_unit_area_? I really don't get it. For all image quality purposes it's an irrelevant parameter.

The next stage - how those photons are transformed into an electrical signal is not something I know much about. Maybe the FF sensor is so much more efficient than the APS one

No, it isn't any more efficient. It doesn't need to be. It's just 1.5 times bigger, which is enough to achieve over one stop signal to noise gain (or to perform on equal foot at 2.25 times lower illumination level).

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