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

Started Jun 15, 2014 | Discussions thread
eyeswideshut Regular Member • Posts: 333
Re: Handevision Ibelux ?

I get the sense you are inferring from enlargements of film using an enlarger lens?

Truthiness wrote:

texinwien wrote:

Truthiness wrote:

Sergey_Green wrote:

tokumeino wrote:

I was actually thinking of lenses like the Pana 25/1.4 which is 1 stop behind a Sony FE 55/1.8.

Yes, it is 50/2.8 equivalent. An Ok to have, but nothing to give you an edge when it comes to DoF and light. And stopped down to f/2.8 fast FF lenses do usually produce better results, than a wide open on a smaller formats equivalents.

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

This inherent factor is taken into account by switching from "Screen" to "Print" when viewing DXO's measurement graphs.

I wasn't talking about SNR of the signal of such, but about the image as rendered by the lens, before anything sensor does.

and when less enlargement is needed, the lens is stressed less,

What does "the lens is stressed less" mean? Is that accepted optics terminology? Do you have some links to authoritative sources that talk about this in more detail?

I have something better than that - logic:

If you want to produce a 20 cm by 30 cm picture (600 cm^2) from a full frame system where the lens draws you an image of 36 mm by 24 mm, you need to enlarge the image the lens draws to 6940% of the original size, 69 times larger the size the lens draws).

If you system has for example 17.3 mm by 13 mm as in m43 and you want to print the same size (600cm^2), you need to enlarge the image by 26700%, 267 times larger the size the lens draws.

The more you need to enlarge the image, the better quality the image lens draws needs to be for one to get the result one wishes.

If you use the very same lens on both these systems, the aberrations of the lens will be more visible due to the larger enlargement on the system with the smaller image sensor.

thus the lens can be of lesser quality to achieve the same image quality.

Lesser quality in what respect?

It can have stronger aberrations as they (among with everthing else) are enlarged less.

Because of this the very best lenses are in the smallest formats and using lenses meant for larger formats often produce sub-optimal outcome.

Regardless, there is a limit how good a lens can be, thus a larger format in principle has a higher ceiling for image quality in this regard as well.

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Cheers
eyeswideshut

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