Reading resolution charts comparing MFT lenses to FX lenses

Started Mar 29, 2013 | Questions thread
Anders W Forum Pro • Posts: 21,468
Re: Reading resolution charts comparing MFT lenses to FX lenses

KenBalbari wrote:

First, LW/PH is "line widths per picture height".  This is a measure of the resolution of the final image.  Full frame will almost always have higher possible resolution here because it is a larger sensor.  A 24mm high sensor will typically resolve more line widths than a 13mm high sensor.

If the pixel count of the sensors is the same, and the impact of the AA filter comparable, they have the same resolution irrespective of sensor size.

If you want to compare glass only, and ignore the sensor or the final image resolution, then you can use LP/MM, which is "line pairs per millimeter".  One catch here, if you want to convert between the two, you have to realize a line pair equals two line widths.  So a lens that averages 60 lp/mm resolution would be 120 lw/mm,  and could in theory produce 1560 lw/ph on m4/3 or 2880 lw/ph on full frame.  In practice though, this is really going to depend also on the characteristics of the actual sensor, including pixel density, noise characteristics, and the effect of the anti aliasing filter.

Keep in mind, how you measure this also depends on what level of resolution you deem acceptable for an individual line pair.  This can also differ between different test sources and methods.  MTF50 is one commonly used standard which tries to define this, but something like MTF10 might be closer to measuring what most people actually think of as "sharpness".

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