We often here that Canon had to ditch the FD mount in order to get AF working, what advantages did the EF mount bring and what exactly are the pros and cons of lens mounts by Nikon, Sony, Pentax and others ?
How does EF Mount compare to other mounts
- Thread starter Haydn1971
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The FD breech lock was slower to mount. It was meant to compensate for wear, but could work loose; it was held fast by friction rather than a locking pin. I guess it was more expensive to produce.
When Canon produced their EF bayonet mount they went for a larger diameter, guess this helps with larger lenses. Also it aligns at the top for mounting and then turns to lock which is quick.
When comared with Nikon and the Pentax K mount these are the only differences that come to mind.
When Canon produced their EF bayonet mount they went for a larger diameter, guess this helps with larger lenses. Also it aligns at the top for mounting and then turns to lock which is quick.
When comared with Nikon and the Pentax K mount these are the only differences that come to mind.
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There are three big things to consider.... size of image circle, focusing distance, and electronics.
Obviously, the larger the image circle, the larger the sensor you can put behind it, plus you can get a more mechanically solid mount. Mechanically, there is not a lot of difference between any of these mounts, just image circle size.
Focusing distance.... The lens is designed to focus at a particular distance behind the mount... once again, not a lot of variation between mounts, most are similar... but there are a few notable variations... Almost all mirrorless mounts are designed for a shorter focus distance that most FF or APS-C size mounts.... that means that mechanicaly, just about any mirrorless camera can use a spacer-adaptor to use just about anyone else's lens.
Electronics... same thing... they all do the same.. You provide power and ground to the lens, usually for the digital logic and another for focusing motors. You send commands to the lens as coded commands over a single pin and get responses back as a coded command over another pin. The lens has a microcomputer on it that interprets these commands, takes the required action, and reports back.
Canon had to ditch the FD mount because there was no way to communicate to a microcomputer on the lens. They could have added pins to the mount like Nikon did, but instead they chose to completely change it for the digital era... no more mechanical bars to operate the iris... placement of contacts better suited for less wear...
Other than larger image circles for larger sensors, there really is not much difference between the newer mounts.
Obviously, the larger the image circle, the larger the sensor you can put behind it, plus you can get a more mechanically solid mount. Mechanically, there is not a lot of difference between any of these mounts, just image circle size.
Focusing distance.... The lens is designed to focus at a particular distance behind the mount... once again, not a lot of variation between mounts, most are similar... but there are a few notable variations... Almost all mirrorless mounts are designed for a shorter focus distance that most FF or APS-C size mounts.... that means that mechanicaly, just about any mirrorless camera can use a spacer-adaptor to use just about anyone else's lens.
Electronics... same thing... they all do the same.. You provide power and ground to the lens, usually for the digital logic and another for focusing motors. You send commands to the lens as coded commands over a single pin and get responses back as a coded command over another pin. The lens has a microcomputer on it that interprets these commands, takes the required action, and reports back.
Canon had to ditch the FD mount because there was no way to communicate to a microcomputer on the lens. They could have added pins to the mount like Nikon did, but instead they chose to completely change it for the digital era... no more mechanical bars to operate the iris... placement of contacts better suited for less wear...
Other than larger image circles for larger sensors, there really is not much difference between the newer mounts.
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The EF mount has a shorter flange focal distance than many other mounts. That's why it's possible to use Canon FD/FL, Nikon F, etc., lenses on a Canon body with an EF mount via an adapter without optics, whereas the reverse isn't the case.
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I haven't heard that they needed to do it to get AF to work, but a complete new design to accommodate the electrical connections and eliminate the unnecessary components, as well as making the mount larger in diameter has proven to be a good choice over the years.Haydn1971 said:
The EF mount was almost certainly less expensive to build, which probably had a lot of influence on the decision to change. Mounting rings are made to incredibly tight tolerances, and the complex mount used on the FD was certainly more difficult to build. It was also a better mount in that it was secure and would not let a lens rotate even a tiny bit when tightened down.
The bayonet mount was larger, and made it a bit easier to fit the electrical contacts into plus, some say it allowed for wide aperture lenses with less viginetting, but I'm not sure that's entirely true.
What is bad about it and all bayonet lenses is that they do not lock a lens securely in place. The lens can rock back and forth due simply to tolerances. My Nikon lenses do the same.
One thing in its advantage is that every EF lens will mount and work on every EF or EF-s mount. I need a book to carry along when looking at used Nikon lenses to see which ones can be mounted and what features can be used. Some of the older ones will cause physical damage to modern Nikon cameras, its a nightmare to those who want to purchase old lenses to use as manual focus lenses on a new digital body.
With Canon, its simpler, just don't do it unless its a lens worth adding a high quality adapter like those Ed Mika makes.
Most of the camera makers have changed mounts one or more times over the years, so you need to be a expert on a particular model. For adapting to Canon, the M42 mounts is very easy, because they had a push in button on the rear that stopped down the aperture, and screwing on a adapter pushes the button in, so that you can manually change apertures easily.
I'm sure there are a ton of details that were argued back when the change took place, I've forgot most, except that photographers were very upset over losing the breech lock mount which was considered to be superior. . There were some lenses that were bridge lenses and did not have all the EF features. Even a couple of electric zoom lenses with push buttons on the side to zoom. That was a bad idea, and quickly went away.
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I should also add this about the control codes....
Everyone has their own control codes... Nikon codes are different than Canon codes are different than Sony codes... You can use an adaptor to mount a Nikon lens on a Canon body (or vice-versa) but that just gives you optics, the control signals are not there, power for IS is not there... you have a completely manual lens.
There is one big exception.... micro four-thirds.... Micro four-thirds is a standardized mount where several manufacturers have agreed to use the same physical mount and the same control codes... A Panasonic micro-four thirds lens will work on an Olympus camera.
Everyone has their own control codes... Nikon codes are different than Canon codes are different than Sony codes... You can use an adaptor to mount a Nikon lens on a Canon body (or vice-versa) but that just gives you optics, the control signals are not there, power for IS is not there... you have a completely manual lens.
There is one big exception.... micro four-thirds.... Micro four-thirds is a standardized mount where several manufacturers have agreed to use the same physical mount and the same control codes... A Panasonic micro-four thirds lens will work on an Olympus camera.
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Sporgon said:
The FDn lenses, 100% interchangeable with FD, have a lock and do not rely on friction. In 25 years of FD and FDn use I never had a lens come close to falling off.
The big thing was the mechanical connections, there was a lever for stopping down the aperture and that lined up with an arm that moved in on the camera body, and there was a pin that told the body the lenses maximum f stop.
Just look at the complete mess that is the Nikon list of limitations, restrictions and non compatibility on their "fully mountable F series mount" to understand why the route Canon chose really was the right one, and I am one who was seriously affected by the change.
http://www.nikonians.org/reviews?alias=nikon-slr-camera-and-lens-compatibility
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Interesting comments - especially about the bayonet mounting being considered superior - it's easy to just get drawn into the brand you own without really considering the limitations or the benefits of other brands - the EF mount does appear to be a flexible solution to accommodating other lens types
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EF is pure electronic, unlike many others, which still kept the mechanical aperture lever.
This made tilt/shift lens easy and consistent to implement.
Take a look at how many mechanical parts in a Nikon zoom lens just to keep the aperture work, and why Nikon PC-E lenses is an exception, you will see that EF mount is superior.
Also, have you seen any Nikon camera that can change Aperture value when recording movie? They can't, because of the mechanical design. To change / step aperture value, they have to activate the aperture lever, which causes the aperture to snap to the fully open value, then re-release the lever again to get to the target value. EF lenses on the other hand, could step aperture value in any direction and steps you want. So EF mount is better for video too.
This made tilt/shift lens easy and consistent to implement.
Take a look at how many mechanical parts in a Nikon zoom lens just to keep the aperture work, and why Nikon PC-E lenses is an exception, you will see that EF mount is superior.
Also, have you seen any Nikon camera that can change Aperture value when recording movie? They can't, because of the mechanical design. To change / step aperture value, they have to activate the aperture lever, which causes the aperture to snap to the fully open value, then re-release the lever again to get to the target value. EF lenses on the other hand, could step aperture value in any direction and steps you want. So EF mount is better for video too.
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