Lens and Sensor Resolution

Started 7 months ago | Discussions thread
Truman Prevatt
Truman Prevatt Forum Pro • Posts: 13,656
Re: Lens and Sensor Resolution
3

TukTuk wrote:

Truman Prevatt wrote:

John Carson wrote:

There is talk that the new Fuji sensor could be around 40 megapixels. I have the 18-55 mm and the 55-200 mm zooms. Does anyone know if they can resolve 40 megapixels, or would I need new lenses with greater resolving power?

I did a quick back of the envelope calculation. Making the assumption that these lenses can fully resolve the 26 MP sensor

oh dear... they don't even 16mp sensor...

Not so.  I wrote a simple Matlab program to do the calculations.  It took into account the Kell factor of .7 for a sensor (as separation of the detectors on the diagonal are Sqrt(2) times the separation on the two linear dimensions).  It also takes into account that all color sensor arrays are subsampled so it estimates an addition factor of the Kell factor as they limit the resolution.

Rolling all that up - Fujifilm did a good job on their lenses. I'm not surprised here as Fuji has a lot of good optical engineers.   For a 16 MP CFA (XTrans or Bayer - take you pick there is little difference) the Nyquist Frequency of the sensor is 22 lp/mm.   If one looks at the FujfilmX website you will find the MTF of the original lenses coming in at 45 lp/mm.  The lenses well out resolve the 16.

Now for the 26 MP sensor with all the Kell factor and CFA factors rolled in the equivalent Nyquist frequency is 30 llmm.  Again from the Fujifilm supplied MTF data - the Fuji lens are fine at 45 lpmm. Yep, plenty of margin like I suspected.

At a 40 MP sensor the equivalent color Nyquist frequency for the CFA is 37 lpmm.  That is getting close to the MTF data on the Fuji site but still 45 lpmm lenses seem quite adequate.

In the real world you always want your film to have better resolution than your lenses.  The same is true when you replace film with a digital sensor.

My conclusions.  Unless I am doing video and am concerned about focus breathing - I'm not rushing out to drop a K on new lenses.  If I am a video buff where focus breathing is a big issue with the older Fuji lenses - then that is a different story.

The code is available upon request.

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