Any Advantage to Full Frame?

Started Aug 26, 2014 | Questions thread
Jack Hogan Veteran Member • Posts: 6,549
Final Spatial Resolution: Facts get in the way of opinions
4

Leonard Shepherd wrote:

The suggestion 24 MP FX somehow has more resolution than 24 MP is largely a myth.

Interesting opinion. But in reality the iincrease in spatial resolution (aka sharpness) going from crop to FF is quite noticeable.  DX as a system needs to be 1.5X better than FX to come out even in an Equivalent situation.

The smaller format needs better system linear spatial resolution (in lp/mm) by the crop factor in order to have the same resolution in the final image displayed at the same size (in lw/ph).

For instance, a 24MP DX camera needs to show an MTF50 of 66 lp/mm at f/5.6 at a focal length of around 35mm in order to have the same spatial resolution in the center of the same-sized displayed image - as a 24MP FX camera mounting a 50mm:1.8D at f/8 (MTF50 44 lp/mm).

If you know of one such lens for budding DX photographers let me know. They do not exist. The very best (those that cost several times as much as the corresponding FF lens) do about 20% less. For the two lenses above mounted on the cameras under discussion DxOmark shows sharpness of 17MP for the D7100+35mm:1.8G vs 12MP for the D610+50mm:1.8D - a ratio of about 1.4X in favor of the D610 mounting a cheaper lens.

The difference in the final image is quite noticeable to me in general. It makes me smile every time I shoot my D610 vs my D90 in equivalent situations. Where's the myth ?

Jack

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