Originally posted by kadajawi Large sensors --> large lenses. And large cameras. It also means huge lenses for birders. With something mFT sized you can fit it all into a much smaller package, while doing the same (apart from low light performance). Some people also don't like the super shallow look a FF will give them. Or they want everything to be in focus. If they are stopping down like mad, they may as well shoot with a smaller sensor.
And IMHO APS-C is a good compromise. Not that big lenses, not that big sensor, but also decent image quality and the ability to get relatively shallow DoF AND big DoF. It sits in the middle.
Larger sensors don’t necessarily mean larger lenses. Speaking of a hypothetical future where larger sensors become cheaper and people put more pressure on having a small camera and lens, I don't think it will. Maybe for some, but not all.
Since I love to talk about the technical and theoretical side of it I will, and I start by doing a rather extreme comparison just to show things more clearly then on neighbouring sensor sizes. I have an old 3x4 inch medium format camera with a notably smaller lens (114mm f/4,5) then a Voigtländer 17,5/0,95 on m43 even though the field of view is the same and the MF lens have a larger aperture diameter, passing more light (photons/s) to the film. While I would struggle to compare resolution in a scientifically good way I bet the old MF lens would produce more detail then the m43 lens, if it was used with the same sensor technology. If we get (still in a hypothetical future) a new and comparable lens as the MF lens it would probably be cheaper to produce too (its a simple 4 element lens).
My point with this extreme comparison is that while larger sensor sizes are more expensive, they also give us cheaper, lighter and smaller lenses. IF and only if, we compare lenses with the same field of view, same light capture (photons/s to that reaches the sensor), and same resolution demands.
Even more extreme comparisons like a 1/4" cmos sensor with a f/1,7 normal prime compared to a 1 square meter sensor with a pinhole makes it even clearer.
Here is a reference to that example.
But why doesn't this apply to the mFT, APS-C and FF cameras of today? Its because larger sensors make the cameras much more expensive, targeting people with higher demands, and those people will generally not be satisfied with just comparable lenses. They demand something more, and thus cost more too, weigh more and are larger. So the reason the FF lenses are bigger are not that they have to be, but because its targeting a market with other needs and wants.
Now, if the future becomes as I predict, sensors becoming cheaper per area and more pressure on making smaller lenses, the lens producers will also make smaller lenses for bigger formats to fit that demand. And its not a waste of resources to increase sensors while reducing the lenses because, as I tell in the example, its possible to use less money on the lenses to compensate for more expensive cameras, and at the same time get both more light and better detail.
I must add and underline that I don't expect a fast or huge shift in sensor sizes. Maybe a doubling of sensor area in each price class in a decade or two. For the last decade I have been a APS-C user, for the next probably a FF user and closer to retirement I predict I might increase that to medium format. Assuming lots of if-s.
Last edited by Simen1; 03-03-2016 at 05:54 AM.