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

Started 6 months ago | Discussions thread
bobn2
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Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
In reply to Anders W, 6 months ago

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Ulric wrote:

Anders W wrote:

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

http://www.dpreview.com/forums/post/53861976

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

OTOH, what matters is not resolution per millimeter but per image, and the larger format lens has to perform over a larger image circle. It evens out.

In practice, no it doesn't - the advantage is to the larger image circle.

On what grounds?

On the grounds of that's how it is in practice, never mind any theoretical arguments.

OK. What's the evidence?

Plenty of it out there,

I didn't ask how much of it there was. I asked you which evidence.

the larger image circle generally produces higher resolution (normalised to frame size) in practice on most of the lens tests

Based on what statistical analysis of which lens test data?

Based on observation. Which is what we tend to do around here. If you wish to make a counter assertion, do you have a suitable statistical analysis to back that up?

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Bob

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