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

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

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

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.

So you have no data and no data analysis to back up your claim.

If you wish to make a counter assertion, do you have a suitable statistical analysis to back that up?

You made an assertion. I didn't. So you carry the burden of proof. But here is an example as a starting point:

http://www.dpreview.com/forums/post/53893177

Well, I considered picking an example like that, but it takes time and doesn't really 'prove' anything at all, does it?

More than the one you refer to below which is systematically biased.

But, if you are interested in bogus 'statistical' analysis, then try looking at DxOmark rankings. So, for instance if we filter the lens test data by MP, as follows:

Then you'll find that lenses ranked 1-368 are FF lenses, then we get the Panasonic Leica DG Nocticron 42.5mm F1.2 ASPH at 369. There is some duplication there down to same lens different camera, but there's little point spending a lot of time cleaning up an 'analysis' like that.

What is the relationship between those lens rankings and the factor we are trying to isolate in this discussion: Lens resolution.

Resolution is a factpr in those rankings.

Yes. But not the only and as already indicated, the others introduce systematic bias.

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