# Is there an optical or camera engineer in the house who feels like wasting some time?

Started Dec 24, 2013 | Questions thread
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Is there an optical or camera engineer in the house who feels like wasting some time?

I wonder if there is a rule of thumb for the resolution of a sensor and lens together. The one for a lens and film together is: the sum of the reciprocals of the resolution of the lens and of the film equals the reciprocal of the resolution of the two together.
(For instance: film 100 lines per mm.
lens 100 lines per mm.
combination: 1/50 + 1/50 = 2/50 + 1/25: 25 lpm.)
DXO shows some relation.
(Example: the Oly 75 mm. f2 and Panny G1 and GH2 and Oly M5.
The cameras' respective sensor scores are 53, 60, and 71; the respect sharpness score of the 75 on those three cameras is 8, 11, and 13. But DXO isn't much help here because their evaluation of sensors doesn't include resolution)
What would be the point of knowing this? For instance, is it worth it in terms of resolution to have a great lens like the Olympus 50 f.2 macro or the M4/3 75 mm. f.2 on a camera with a relatively low resolution like a Panny G1. If you can only afford one, would you be better off with a better sensor or a better lens? (Yes, I know a lot more is involved in lens quality besides resolution. I'm just fooling around, and yes, I take lots of pictures.)
For the old formula, I think the lens resolution was measured on air, and the film specs. came from the manufacturer; I don't know how they did it, maybe microscopic examination of a contact print or projection of a target on the film.
But back to the question: Is there a theoretical limit to sensor resolution involving dimensions of the sensor and megs, and what is the relation of this to what the sensor does in a raw file?
I can see finding a practical resolution number for a sensor by projecting a target onto it with a resolution so much above that of the sensor that the inevitable failure of the sensor to record the highest resolution of the target wouldn't matter that much, although I don't know if this would work.