Originally posted by Michael Piziak But I've read so much about how mirrorless is the future & also read a lot about how flange distance from camera body to lens is a "barrier -"
I believe the "mirrorless is the future" topic has been covered many times in the forum and it's just to do with video, changing mounts to bring in new lenses, cost, etc. These cameras are so cheap to manufacture. Think of them as computers with a sensor. They have to push it to sell, just like any business. I am not against them. I, myself, have been using a mirrorless for 8 years now. DSLRs have matured already, so perceived innovation is with mirrorless.
Originally posted by Michael Piziak Apparently, the flange distance being the reason why Canon and Nikon came out with new mount sizes for their mirrorless.
This one has also been discussed many times in the forum. They change mounts and market them because they will get their loyal users to switch as well. This is just common with many businesses. The marketing is the key.
If you are going to do lens/optical design, the biggest advantage of a mirrorless system over a K-Mount or any DSLR is the design of ultra wide angle (UWA) lenses, which can be quite challenging to the current DSLR mounts, particularly Pentax with it's flange-back distance that it has been keeping since M42. I'll explain this below.
Originally posted by Michael Piziak Addendum: I think also a reason for Canon & Nikon to change their mount size is that with their new mirrorless body designs, they claimed they could offer a superior image with a new mount considering their new flange distances. A personal note, I think the size of the mount hole on the new NIKON cameras, well I think the new mount/hole size looks huge compared to the body of their camera(s)....
Again, the biggest advantage of mirrorless over DSLRs to do with UWA lenses. In optics, and optical engineers know this very well, the mirrorless advantage is up to the 35mm focal length only for any system. Beyond that, the rear projecting element will still have to be pushed forward. Think about the 40mm and 50mm lenses from other companies - their rear elements are already pushed forward away from the sensors. The zooms' rear elements are also pushed way forward so they're almost the size of their DSLR counterparts after 35mm. This is why there isn't really a size advantage with mirrorless lenses beyond 35mm. With this, think about how micro four-thirds can take advantage of this fact. At 35mm, it's already 70mm EFL. Nifty-fifty is already at 25mm in that system. Sigma even mentioned that 35mm limitation way back before they committed themselves to mirrorless lens manufacturing. There isn't really that much difference in lens size after such FL as it's technically dictated by the sensor size.
Nikon's Z-mount still has the 35mm,
however, that extra-wide mount, that big throat, gives optical design a looooot of space to play with. Lens size is a handicap but that throat gives the designers so much freedom.
Regarding your question about the K-01, Pentax has been running the same flange-back distance since M42 and I found out that the reason why many are so loyal to them is that new users are still able to use their lenses from the film era so easily. I am a relatively new DSLR Pentaxian, by the way. I don't think Pentax will leave that feature anytime soon.
These are just thoughts for sharing and discussion but as a relatively new digital Pentaxian, Pentax's strenghts are just so well-defined once one uses it. It's just different. Cheers.
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Originally posted by Wasp Quite a few MILC sensors do have phase detect nowadays, but that would mean doing the R&D to build a body that uses such a sensor. I am not sure where Pentax stand on this front.
Yes, mirrorless started with contrast-detect AF (CDAF) back in the day. CDAF is very accurate. Nowadays, almost all mirrorless cameras have hybrid AF - PDAF and CDAF on-sensor. Even Lumix, with their new S5 II, now has a well-designed PDAF on sensor, to satisfy the gear reviewers. It benefits autofocus in video because the CDAF pulsing is goine.
There is a big, big, big, issue with PDAF on sensor, though, the presence of PDAF lines in the images/videos. It can be mitigated in post but it won't be as clean as one taken with a mirrorless camera with just the CDAF. In the industry, videography and cinematography are done with manual focus, so PDAF on sensor is not necessarily needed. Again, it would satisfy vloggers and gear reviewers so they can run-and-gun. Cheers.