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

Started Jun 16, 2014 | Discussions thread
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
3

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

"What is known based on the laws of optics is that if we take a lens design for a certain format, say a 50/1.8 for FF, and scale it down in all relevant dimensions so as to make 25/1.8 for MFT, the two lenses will deliver the same resolution if we measure per image diagonal (and the MFT lens twice as much as the FF lens if we measure per mm) at the same f-stop as long as resolution is limited by lens aberrations only."

There is no such thing as limited by lens aberrations only.

In optical theory there is.

No, there is not.

Yes there is.

You cited a formula yesterday that you do not understand,

What makes you think I do not understand it?

that proves you wrong.

The formula says nothing about diffraction versus aberrations. It just says something about the way lens resolution and sensor resolution combine into image resolution.

Diffraction is always a factor.

Of negligible importance at wide apertures.

On 80mp and m43? Did you just scratch you head again?

There was no need for that.

When we talk about 80mp sensors, it becomes a significant one even at f/1.8.

No, it doesn't.

I take your word for that. Wait, I can actually compute the diameter of the Airy disk (well, I am too lazy for that, so I trusted Cambridge-in-color on that). It is 2.4 microns. An 80mp m43 sensor would have a pixel pitch of about 1.6 microns. Oops!

So what?

And you know that 16mp is enough to tell the difference - how? You just scratched your head?

I know it because the lenses on sale today perform noticeably differently on 16 MP sensors.

And you extrapolate that to MF lens on a hypothetical 16mp MF sensor, and then to m43 lens to a hypothetical 80mp m43 sensor?

There is no need to extrapolate to a 16 MP MF sensor. A comparison between FF and MFT sufficies.

Am I right to assume that your most serious science effort was to post here?

No.

Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
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