DSLR vs. Mirrorless
Everyone always talks about how mirrorless is the new kid on the block, ready to threaten the DSLR market. Whilst that's semi-true, mirrorless cameras have been around for a very long time - in fact, longer than DSLRs. People didn't just design a camera with a mirror to start off with, all cameras were initially "mirrorless", except there were certain severe problems. These problems were then solved by adding a mirror, which is why DSLRs took off and for basically half a century now, they've been the de facto professional camera.
Before we had any of this digital stuff, though, everyone shot film. Anybody who was born in the 1990s or earlier would have come across film SLRs at some point in their lives, some people still shoot with film SLR these days. However, a much less common type of camera is the rangefinder. Rangefinders were the camera of choice before SLRs took the world by storm. Canon, Nikon, LEICA and many other manufacturers who are now defunct all produced rangefinders back in the earlier part of the 20th century. Canon and Nikon eventually jumped ship to the DSLR market, leaving LEICA in the rangefinder market, practically irrelevant in most photography ever since.
With rangefinders, you had to see the world through a little small box on the top corner of your camera. You couldn't view the world through your lens. With that came some inherent problems, most notable of which is that as you focus at different distances, your frame will change due to parallax error, thus, shooting with a rangefinder requires some level of experience. To make it even more difficult, back when everything was film, you couldn't even see your results until you finished the roll and got it developed.
By introducing a mirror assembly into the camera and making lenses slightly more complex (due to the longer flange distance), SLRs were able to solve the parallax issue by allowing viewing "through the lens" (TTL) rather than through a small box near the lens. This was a ground breaking development, which led professional photographers, as well as amateurs to the SLR market. That said, there were trade-offs that had to be made. SLR bodies were heavier, bigger and their lens designs (especially wide angles) became especially difficult to design due to the longer flange distance.
As we moved to digital, for many reasons, we stuck with the SLR format, creating the DSLR. In photography, things move very slowly, people hang onto their old lenses for decades and demand that later bodies continue to work with their library of lenses and accessories. That's what DSLRs became, they were just old SLRs with digital parts built in where the film was meant to go.
In many regards, the mirrorless cameras we see today are the digital reincarnation of the older rangefinder cameras. Many, such as the X-Pro1, even follow similar styling. But unlike their ancestors, they've solved one of the biggest problems with the old rangefinder design - the parallax issue. Because we are now able to feed a live view from the sensor, we can simply feed a digital image to the viewfinder (called an electronic viewfinder) rather than letting the photographer view through the lens as per DSLRs. In other words, we're able to see what the sensor sees, we couldn't do this with rangefinders.
Better yet, this has many benefits over DSLRs. We can now "see what the camera sees" so we can check white balance, exposure and all the technical mumbo-jumbo before hitting the shutter button. We couldn't do this with DSLRs because all we could see was the real world through the lens, not what the camera was seeing.
On top of all that, mirrorless cameras have a weight and cost advantage over DSLRs as well, making them an attractive option for most photographers. That said, there are disadvantages to mirrorless cameras due to their relative immaturity, the most common of which is the issue of autofocus - tracking autofocus especially, is simply not as fast and sure as what most consumer grade DSLRs are capable of.
Before we had any of this digital stuff, though, everyone shot film. Anybody who was born in the 1990s or earlier would have come across film SLRs at some point in their lives, some people still shoot with film SLR these days. However, a much less common type of camera is the rangefinder. Rangefinders were the camera of choice before SLRs took the world by storm. Canon, Nikon, LEICA and many other manufacturers who are now defunct all produced rangefinders back in the earlier part of the 20th century. Canon and Nikon eventually jumped ship to the DSLR market, leaving LEICA in the rangefinder market, practically irrelevant in most photography ever since.
With rangefinders, you had to see the world through a little small box on the top corner of your camera. You couldn't view the world through your lens. With that came some inherent problems, most notable of which is that as you focus at different distances, your frame will change due to parallax error, thus, shooting with a rangefinder requires some level of experience. To make it even more difficult, back when everything was film, you couldn't even see your results until you finished the roll and got it developed.
By introducing a mirror assembly into the camera and making lenses slightly more complex (due to the longer flange distance), SLRs were able to solve the parallax issue by allowing viewing "through the lens" (TTL) rather than through a small box near the lens. This was a ground breaking development, which led professional photographers, as well as amateurs to the SLR market. That said, there were trade-offs that had to be made. SLR bodies were heavier, bigger and their lens designs (especially wide angles) became especially difficult to design due to the longer flange distance.
As we moved to digital, for many reasons, we stuck with the SLR format, creating the DSLR. In photography, things move very slowly, people hang onto their old lenses for decades and demand that later bodies continue to work with their library of lenses and accessories. That's what DSLRs became, they were just old SLRs with digital parts built in where the film was meant to go.
In many regards, the mirrorless cameras we see today are the digital reincarnation of the older rangefinder cameras. Many, such as the X-Pro1, even follow similar styling. But unlike their ancestors, they've solved one of the biggest problems with the old rangefinder design - the parallax issue. Because we are now able to feed a live view from the sensor, we can simply feed a digital image to the viewfinder (called an electronic viewfinder) rather than letting the photographer view through the lens as per DSLRs. In other words, we're able to see what the sensor sees, we couldn't do this with rangefinders.
Better yet, this has many benefits over DSLRs. We can now "see what the camera sees" so we can check white balance, exposure and all the technical mumbo-jumbo before hitting the shutter button. We couldn't do this with DSLRs because all we could see was the real world through the lens, not what the camera was seeing.
On top of all that, mirrorless cameras have a weight and cost advantage over DSLRs as well, making them an attractive option for most photographers. That said, there are disadvantages to mirrorless cameras due to their relative immaturity, the most common of which is the issue of autofocus - tracking autofocus especially, is simply not as fast and sure as what most consumer grade DSLRs are capable of.