Originally posted by Class A I don't think this downsized format deserves to be called MF*))
So you don't consider the 645z to be a medium formant camera? I think there are only a couple medium format cameras that are using larger sensors. One from Hassey (HC6-100D) and 4-5 from Pahse One. All the other MF cameras use the same size sensor as the Pentax 645, Fuji GFX, Hassy X1D, Hassy HC6-50D, HD-5, HD5X, IQ1, IQ3.....
Most of the MF sensors are this size so the GFX competes sell with most other MF cameras except that is it 1/2 the size and 1/3-1/4 the cost.
Originally posted by Class A BTW, the X-mount has a 44mm diameter. That's bigger than the K-mount's diameter (42mm). Apparently, the shorter registration distance of the X-mount demands bigger throats even for a smaller image circle.
Yes the shorter the register distance the more perpendicular the light needs to be striking the sensor, so the mount has to be larger. BSI sensors help, but its still better to have a lens that doesn't project light at an angle to the sensor. There are also advantages in the sharpness of the image.
Originally posted by Class A I'm sure you will agree that the level of success Fuji has enjoyed with their X-mount is not primarily based on limiting the mount size.
Part of it is. Part of the appeal of the X-mount is the compact size, just as it is for the DA Limited Pentax Lenses. Fuji did what Pentax did well and applied it to a mirrorless system. Designing lenses specifically for APS-C allows them to produce really good optics in a smaller package. That plays a big role in the success. To me the Fuji X-T2 is too small and I need the grip, but for a lot of people with small hands (many women) it is the perfect system.
Originally posted by Class A Currently a full-frame 645D may not be in the same market segment as the Fuji GFX (who knows what Fuji will sell it for, though?), but as the price of a full-frame 645D comes down it will either join the Fuji GFX in the same segment, or the GFX will be pushed to lower margin shores.
Maybe. The 645 system seems to be an after thought to Ricoh. The lenses need to be updated and I don't think Ricoh has the resources to update the 645 line and get the more important FF glass on the market. Hopefully I'm wrong. Hopefully we see more development on the 645 line in the near future.