M42 screw SLR camera has a history of nearly 30 years from 1949 to * * in the late 1970s. It was not until Pentax abandoned the screw and switched to K card eloquence that the fate of M42 ended. The body of the M42 screw can be connected with the M42 screw lens produced by any manufacturer, and all the M42 screw lenses are almost designed in metal, with exquisite workmanship and excellent imaging. However, because the screw lens needs to be screwed on the fuselage like a screw, it will inevitably bring inconvenience to disassembly. Moreover, with the continuous development of SLR cameras, the lens needs to transmit more and more data, and the screws failed to keep pace with the times and were eventually abandoned.
Opposite is a bayonet. Bayonets were not as popular as screws because of their technical patents, so they were not as prosperous as screws in the early days.
At this point, I should probably understand the reasons. The reason why the screw is changed into a bayonet is because it is more convenient and needs to transmit more information. The point is this "information". Different manufacturers have different patented technologies in automatic metering, autofocus and anti-shake, so the designed bayonet also has technical patents and cannot be used universally.
In short, the bayonet is not only responsible for simply connecting the camera body and lens like the previous screws, but also serves as the task of transmitting information, but each manufacturer has its own way of transmitting information, which is not universal.
Now, in order to use different bayonet lenses and fuselage, everyone knows the adapter ring. But we also know that in most cases, we have to sacrifice the autofocus function, and some automatic metering will also fail.
It's a little confusing. It's a good idea to throw a brick at jade. I hope I can help you a little.