So, there’s always a lot of debate about the image quality of the new mirrorless interchangeable lens systems and cameras like the Sony NEX-7 and Fuji X-Pro vs. DSLRs like the Canon 5D Mark III. This video is a simple tour of what the main differences are between the traditional DSLR systems and the newer mirrorless sytems.
Ultimately, the mirror – or the “Reflex mirror” that defines the “DSLR” is the part eliminated by the mirrorless camera designs. Combined with high-quality big sensors and the shorter flange distance or flange-to-focal distance – these small cameras are capable of equal image quality and, in some cases, huge benefits.
The big benefit is in wide angle lens design. As the distance between the flange (where the back of the lens is) and the film/sensor plane INCREASES – the difficulty in making wide angle lenses INCREASES. So does size and price.
This is why wide angle lenses (i.e. 14mm – 24mm) for DSLRs are XBOX HUGE, weigh a ton, have a zillion lens elements and employ all kinds of tricks to correct distortion and other problems. The “retrofocus” or inverse telephoto design required for DSLRs with longer flange-to-focal distances are complex and ultimately expensive.
Meanwhile, Leica and Zeiss have been making epic ultawides and wides for the Leica M system for ages – with fullframe coverage – and they are tiny little suckers.
One of the disadvantages of APS-C sensors was the challenge of making good wide lenses. Think about it. To get an “L” quality wide field of view – say a 24mm equivalent for a Canon APS-C camera, you’d need a 15mm lens. That leaves you with the Canon 14mm f/2.8 II. A monster lens with a rounded front element that BEGS you to bump it against something hard and “scratchy.”
So – while it is generally harder and economically unsound for a DSLR line to have good wide-primes designed for APS-C cameras… the nature of mirrorless systems will make smaller, simpler and high-quality wide optics possible.
The mirror in a DSLR does nothing for image quality and the short flange distance of mirrorless camera bodies offers some unique advantages and flexibility in lens design that can lead to wide angle goodness for consumers.