Reading resolution charts comparing MFT lenses to FX lenses

Started Mar 29, 2013 | Questions thread
KenBalbari Regular Member • Posts: 276
Re: Reading resolution charts comparing MFT lenses to FX lenses

Anders W wrote:

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.

Generally, in theory, if there is no limit to available light. In practice though, it seems noise really is what often ends up limiting resolution.

There are plenty of 16MP cameras for example using a 1/2.5" sensor.  Even in tests with controlled studio lighting, they tend to not resolve as well as larger sensor 16MP models. DPR hasn't reviewed that many of these, but if you look at the ones they have, you invariable see in the comments, for example for the Nikon S9300 :

  • Noisy and soft photos have noticeable detail loss, even at base ISO of 125

and for the Sony HX20V :

  • Lots of detail smudging, even at ISO 100

or the TX10 :

With the TX10, there is definitely evidence of strong noise reduction at all ISO sensitivities with images even at ISO 100 exhibiting a slightly 'plastic' look when examined closely.

Of course, the reason these cameras are smudging detail even at low ISO is because noise is a problem for them even at low ISO.  If what you want to compare is different cameras, sensors, or formats, technically it's generally noise which is the limiting factor for resolution.

This can also be seen in DxO's "perceptual megapixels" measure.  It is apparent there that sensor size usually has more impact on resolution than the actual number of megapixels, so long as you are comparing sensors of near the same generation.  On the 10MP Nikon V1, for example, the four Nikon "one" system lenses all test at from 3-6 P-MPix.  Meanwhile, even on the much older Olympus E410, E510, and E3, also at 10MP, the 14-42 kit lens delivered 5 P-MPix.  So the modern Nikon "one" is barely matching the resolution available from a 4/3 sensor from 2007. But on modern m4/3 bodies with 12MP and 16MP, some similar 14-42 kit lenses are still only delivering 5 P-MPix.  Comparing other lenses going from older Panasonic 12MP bodies to newer 16MP bodies, tested with the same lenses, there are small gains.  The same lens might go from 7 to 8, or 8 to 9 P-MPix.

There seems to me to be more gain in moving to an equally current full frame sensor, even with no increase in megapixels.  The Nikon D4 for example, also with 16MP, has numerous lenses delivering 13-14 P-MPix, when the very best lenses on the GH2 or F1X are at 9-10 P-MPix.

So it seems to me megapixels and sensor size both matter.  But for the OP's original question, are the FX lenses generally sharper.  The answer is no.   The sensor is larger.  And larger sensors are generally sharper.  It's possible for sensor design decisions to trade resolution for other advantages (dynamic range, color depth, etc.) but it would take some pretty unusual decisions (or maybe using technology that is 5-years older) to produce a full frame sensor that doesn't provide higher resolution than a 4/3 sensor.

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