MFT zoom VS Full Frame

Physical sensor size has nothing to do with the size of the file produced. My FF camera only has 12mp and I can crop further into my 16mp E-M10 files for the same output size. It would be true for sensors with higher pixel counts regardless of sensor dimensions.

 

16MP m43 is equivalent to 64MP FF. All things being equal to be able to crop an FF image down to m43 size you would need a very high resolution FF sensor.

Or put another way if you had a 200 mm FL FF lens, and you wanted to reproduce the field of view resolution of a 200 mm FL m43 lens you would have to have 4 x the number of pixels available.

This has always been one of the huge advantages of a crop sensor body when shooting telephoto. I first ran into this with the Kodak DCS420 and DCS460 digital backs. The 420 was the choice for shooting subjects that were far away and it was if I remember correctly 1.5 MP.

 

The thing is, all things are rarely equal.

First off you have lens resolution, I've found most of my lenses for my 16MP OMDs kept up with or outresolved my (very good) FF lenses on my Sony A900, which was 24MP. So cropping heavily with a FF camera requires some extremely good optics to keep pace.

Also, when you crop you increase noise as well (when you compare at a fixed output size). Obviously the per-pixel noise level doesn't change, but the amount of noise you see for a given print size does.

So you lose the noise advantage, lose the DOF advantage (if you're cropping heavily you're further back meaning wider DOF), you have to have extremely good lenses to hold up in terms of resolution, you need to have a current generation FF camera (5D2, D700, A900, etc are not much better than current get M43 sensors pre-crop and are worse post-crop), so you're looking at a significantly higher cost, as well as larger size and weight. Heavily cropping any camera with a separate PDAF focusing sensor is going to magnify minor focusing errors which plague pretty much all DSLRs as well (not important for certain types of shooting like landscapes but very important for portraits, wildlife, or anything with narrow DOF).

Certainly a current gen high res FF camera like the D800 gives more options when cropping (when you have a lens sharp enough and have technique sound enough to actually get the detail), but you lose out in so many other areas that I can't really see the argument.

Web resolution and very small prints are probably the only realistic cases where you'll be able to do a 2x crop from a FF camera and match the output of the current 16MP m43rds sensors.

 

Most of these people confuse cropping in achieving the desired equivalent focal length that you can achieve with MFT.

First of all, the focal length of a lens is a measurement of the distance between the optical axis of the lens and the sensor plane of a subject shot at infinity. We associate this focal length to the field of view, but this angle of view is directly correlated with the size of the sensor.

For example, a 80mm full frame 35mm lens is considered a telephoto lens, but the same focal length lens on a 4x5 view camera is considered a WIDE ANGLE lens. What has changed? The angle of view. Also, we know that there are 3 things we associate with depth of field.

1, Aperture
2, Subject distance
3, Angle of View

And how can there be an equivalent focal length of even field of view between full frame and MFT, when even @ 200mm full frame, 3 Nikkor lenses with the 70-300VR, 70-200VR I and 70-200VR II ALL GIVE 3 distinct different angle of view when shot at close focus! Which angle of view of cropping do you choose to based on your MFT equivalent on? The 70-300VR? The 70-200 VR type 1 and 70-200 VR type 2?!? And if you are shooting a Sony A7r with a 35mm lens; which lens do you choose to mimic a 200mm focal length MFT when you crop?

By the way, stock agencies want un-cropped images during submission for a very good reason. They do not want any images cropped even if you can.