BebuLamar wrote:
So why I didn't hear about mirrorless until the 21st century although cameras without mirror were made in the 19th century?
The "mirrorless" designation was meant to imply that the cameras were "SLR-like", but decidedly *not* dSLRs. MILC = Mirrorless Interchangeable Lens Camera. EVIL = Electronic Viewfinder Interchangeable Lens. But for various negative reasons, those acronyms didn't stick!
Consider the evolution of 35mm cameras from the rangefinders (Leica, Contax, Nikon, Canon... and others all made them at least until the late 1950s, and some much later) ...to the SLRs of the late 1950s until around the early 2000s... to the dSLRs we have today.
The dSLR evolved from the SLR. Manufacturers essentially replaced the film transport with electronics and a sensor, and called it digital! They only had to rearrange some things to make it happen. dSLR heritage is an evolution from 35mm film. They even kept the same lens mounts and the reflex mirrors. At first, this made perfect sense, because the technologies for electronic viewfinders had to evolve greatly to make them practical. Heck, the early LCD displays on dSLRs were pretty terrible!
Mirrorless designs came of age when two things happened: The proliferation of digital point-and-shoot and cell phone cameras like the iPhone, which had live view screens, and the development of Micro Four-Thirds, which was a mirrorless evolution of the Four-Thirds platform.
Wonder of wonders... When you get rid of the mirror, you can shorten the distance from the lens flange to the sensor. That makes lens designs smaller, lighter, simpler, and better! AND, there is no mirror slap, no finder blackout at moment of exposure, you can SEE what the camera is doing, instantly, without taking your eye away from the EVF... You can even see in black-and-white or a creative mode.
Getting rid of the mirror means so many things. Most EVFs are pretty good, but some of them still have disadvantages to overcome. Even on the fastest cameras, the EVF still has a lag that puts action stopping at a slight disadvantage to the finest dSLRs. Not everyone likes the "look" of the EVF yet. AF speed needs improvement in several systems.
Still, each of the four non-Canikon brands mentioned has compelling reasons to be attractive. A lot of that attraction has to do with their NEW lens mounts and NEW lines of lenses. Optics designed specifically for these cameras tend to have excellent performance, although there is a wide variety of optics in the field.
Because the flange to sensor distance IS shorter, adapters can fit your older lenses. But as I said earlier, many photographers opt not to adapt their existing optics.
Many who do adapt older lenses are cinematographers working with the Lumix GH4. You can adapter-fit just about any Nikon F/G, Canon EF/FD, Contax G or Contax Yashica, Contarex, Alpa, Arriflex, Leica M or R, Minolta MD, Olympus OM, Rollei QBM, or ciné lens on that camera (and probably quite a few other brands!). Quite often, controls are fully manual, but if you have the lens and don't need it often, an adapter can put it to good use...