Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

Started Jun 16, 2014 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

Truthiness wrote:

Anders W wrote:

The post of yours that began this exchange in the previous thread was:

"Additionally there is one inherit advantage larger formats have over smaller ones: enlargement factor. A large format image needs to be enlarged less than a medium format image, which needs to be enlarged less than FF image which needs to be enlarged less than APS-C image which needs to be enlarged less than m4/3 image which needs to be enlarged less than cell phone image and when less enlargement is needed, the lens is stressed less, thus the lens can be of lesser quality to achieve the same image quality."

Exactly what do you mean by "stressed less" and "lesser quality" here? And in what way does the "lesser quality" actually translate into an "inherent advantage of larger formats"?

The larger format lens does not have to resolve as many lines per millimeter on the image plane, thus it can be (but need not be) optically inferior to achieve the same output image quality compared to a smaller format lens.

As Ulric has already pointed out, the relevant quantity when comparing resolution across sensor sizes is not line pairs (or lines) per millimeter but line pairs per sensor diagonal. What if we take an FF lens design, say a 50/1.8, and scale it down in all relevant dimensions so as to make a 25/1.8 for MFT. Would the FF version resolve better than the MFT version in line pairs per sensor diagonal at the same f-stop as long as resolution is limited by lens aberrations only?

The reason is in the lesser need for enlargement from the image in the image plane to the output image of arbirtary size.

What about the difference in reduction ratio between larger and smaller sensors at the previous stage, when an image of reality is created on the sensor and that image is reduced twice as much for MFT compared to FF.

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