Why the Canon R5 and why mirrorless system cameras at all?
I consider the mirrorless system cameras to be the natural evolution in digital photography. Similar to the development in software, cameras today should allow you to see as accurately as possible what the final image will look like.
WYSIWYG - What You See Is What You Get
In the days of film, this was the driving force behind the development of the SLR, the single-lens reflex camera. For the first time, this enabled a parallax-free view through the same optics with which the final picture is taken. However, this requires a sophisticated mechanism, which must be extremely precise in order to enable one to set the focus accurately via the groundglass image redirected by the mirror and prism. On the other hand, it must be able to switch very quickly from viewfinder mode to shooting mode and back again, with as few vibrations as possible to prevent camera shake. A second movable auxiliary mirror is even required for the phase contrast distance sensors used in modern DSLR. All this is precision engineering in its purest form!
I have to admit, this is working very well with the current cameras today. The Canon flagship camera 1 DX Mark III reaches up to 20 frames per second in viewfinder mode with autofocus tracking! However, the current cameras also have their limitations due to the built-in high brightness ground glass. The built-in Fresnell lenses in the focusing screens increase the brightness of the viewfinder image, but do not use the full aperture of the viewfinder when using very fast lenses.
So, for example, with the wonderful EF 85mm F1.2L it is not possible to see the exact depth of field in the viewfinder and the manual focus setting becomes a matter of luck. Effectively, the maximum aperture used in viewfinder mode on my 5DS R is just about f/2.8. You can test this by yourself by pressing the stop-down button while looking through the viewfinder: only at apertures below 2.8 the viewfinder image becomes darker. Also shifting with tilt/shift lenses, like my TS-E 17mm f/4L, shows massive vignetting in the optical viewfinder. On DSLR bodies, it is actually only usable in live view.
With conventional film, the SLR would certainly still be the optimal system. In the digital era, however, it is now possible to see the images created instantly. So why should we continue to rely on the complicated and error-prone mechanical mirror system? For several years now, many digital cameras offered a live view on their rear monitors. For static shots on a tripod this was often already a good choice. However, the disadvantage was the low resolution of the image on the small displays, which were hardly readable in sunshine, and the usually very slow autofocus.
The electronic viewfinder
So the development of usable electronic viewfinders was a big step forward. Here Sony has already had experience with SLT cameras since 2010. Since I wanted to have a mirrorless body for my extensive Canon system for a long time and Canon had missed the trend for years, I therefore added a Sony 7R with a Metabones adapter for Canon lenses to my photo backpack in 2013. So I had a high resolution (36 megapixels at that time) for “slow” shots and working with the TS-E was suddenly a lot of fun. The viewfinder resolution in the original 7R was only XGA (1024x768 pixels), but was already usable. One by one I changed to the 7R II and 7R III.
The mirrorless Sony cameras have shown that they offer a very good alternative to the classic DSLR cameras. The initial disadvantages are balanced. Partly the mirrorless cameras already surpass the conventional DSLR. For example, the autofocus on the Sony a9 is now just as fast as on the fastest DSLR bodies, and that at 20 frames per second, with tracking of the AF on the subject and eye recognition with very wide coverage of the viewfinder image. And unlike the 1 DX Mark III, the viewfinder image does not black out!
The electronic viewfinder also got more and more resolution. The current cameras now have a viewfinder resolution of 1,600 x 1,200 pixels, which is hardly distinguishable from an optical viewfinder. And you can see the actual image in the viewfinder, including the over- or under-exposed areas!
The Sony cameras were getting better and better and at Canon - nothing happened.
Then, two years ago, the EOS R finally arrived and shortly afterwards the RP. However, both cameras were still clearly inferior to my Sony 7R bodies, so that with the release of the 7R IV I had already philosophized loudly about a complete change to Sony. Only my existing extensive lens stock, my high-resolution 5DS R and the already overall well working cooperation of my current Sony Alpha 7R III (now with the Sigma MC-11 EF-E adapter) with my Canon lenses (and especially with the Sigma 60-600 HSM) stopped me.
But now the cards are reshuffled again: The Canon EOS R5 is finally up to date and I can fully return to Canon. Not that the Sony 7R III / IV cameras would get worse - but I have a lot of high quality Canon lenses and an EOS 5DS R body and of course a Canon body fits better into my system. Especially the autofocus will with all my lenses natively again. I will ( for now) keep the 5DS R. Which body is better suited for what, I will find out and report here. Nevertheless - if I would already be completely working with Sony, I would certainly stay there.