With Nikon and Canon having lately launched model new mirrorless system mounts and speaking about their advantages, there appears to be fairly a little bit of confusion amongst photographers with regard to digital camera lens mounts. That is very true for issues like “throat size” and “inner diameter”, the place totally different measurements are used to wrongly quantify a mount’s potential. Sadly, there’s plenty of misinformation on the market relating to mounts and their actual sizes, which is why I made a decision to put in writing an in depth article speaking about totally different mounts, their variations and take extra exact measurements for various methods to current correct info.
1. What’s a Lens Mount?
Merely put, a lens mount is a gap of a selected measurement on an interchangeable lens digital camera that permits attaching lenses designed for that mount. Though within the early days of images lenses have been solely mechanically hooked up to cameras with none communication between the 2, with the rise of automated metering and autofocus techniques, it was essential to create digital contacts on each cameras and lenses to permit them to speak with one another. In consequence, a lens mount turned greater than only a bodily gap, however extra like an interface between lenses and cameras.
As we speak, virtually each lens mount for images is a bayonet mount (the identify “bayonet” comes from the kind of becoming troopers used on their rifles to shortly mount bayonets), the place three to 4 tabs are used to lock a lens tightly in place, however different lens attachment techniques have been used up to now, akin to screw-threaded lock and breech-lock. With a bayonet mount, one aligns a marked part of a lens (sometimes a coloured dot) with the marked part on a digital camera physique, then after coupling the 2, twists the lens both in clockwise or counter-clockwise path (relying on the model / mount) till it locks into place.
The locking mechanism is mechanical, with a spring-loaded pin locking the lens in place in its correct place, requiring the pin to be retracted when a lens must be indifferent (which is completed utilizing a button subsequent to the digital camera mount). The bayonet mount has a number of benefits in comparison with different mounts, which is why they’re the preferred at the moment. First, it makes it fast and straightforward to connect and detach lenses. Second, it permits for a decent and exact match, which is particularly necessary when capturing with trendy excessive decision cameras, as any type of wobble or play might find yourself negatively affecting elements of the picture. And lastly, a bayonet mount additionally permits for straightforward incorporation of digital contacts between lenses and cameras to allow the 2-approach communication.
Because of the proprietary nature of all digital camera mounts, every considered one of them can differ in mounting path, mount measurement, flange distance, variety of digital contacts and even the place the digital contacts are bodily positioned. Let’s check out every in additional element.
2. Mounting Path
Whereas most lens mounts require attaching lenses by twisting them clockwise, some manufacturers like Nikon have a reversed method of doing it. On one hand, it doesn’t matter which path a lens is mounted or dismounted, however then again, it’d trigger some confusion and may take time to get used to it, particularly for many who determine to modify manufacturers. Under is a desk that summarizes the mounting course of lenses among the many fashionable digital camera manufacturers.
Please notice that the mounting course is relative to the entrance view of the digital camera.
three. Mount Measurement (Throat Measurement, Inside and Outer Diameters)
Relating to mount measurement, there are a number of necessary measurements that must be carried out appropriately, particularly when a lens mount is being in comparison with one other one (as you need to examine apples to apples). There’s throat measurement, internal diameter and outer diameter, and all of them imply various things. Let’s check out totally different measurement standards and their variations.
three.1. Throat Measurement
The throat measurement of a lens mount is the internal diameter of a mount, minus the tabs which are used to mount lenses. Throat measurement provides us a extra correct illustration of the potential of the mount and is necessary for calculating the angle of incidence, which we’ll talk about under.
Check out the under picture to know how the throat measurement is measured on a system:
As you possibly can see, the space measured is between the 2 tabs on the internal aspect of the mount.
three.2. Inside Diameter
The inside diameter of a lens mount represents the dimensions of the lens opening ignoring the tabs on the mount. This measurement is usually offered by digital camera producers to provide us an concept of the general measurement of the lens mount.
Under is the picture of how the internal diameter of a lens mount is measured:
Please word that the measurement is taken of the outermost internal a part of the mount right here. Because of the small further recess inside the inside mount within the case of Nikon F, there’s a further lack of zero.5mm to clear it. Therefore, whereas the internal diameter is 47mm as measured above, it’s technically 46.5mm between the internal elements of the mount.
three.three. Outer Diameter
The outer diameter of a lens mount is the complete diameter of the bayonet mount, which in most cameras represents the top of the metallic mount. The outer diameter of the mount performs an essential position in figuring out the approximate outer diameter of the rear a part of a lens, because it should be capable of wrap itself over the outer diameter.
Right here is the picture of how the outer diameter of a lens is measured:
Once more, there’s one other small recess that’s proper under the outer a part of the mount, however we don’t measure the outer diameter from it.
four. Flange Distance
Flange distance, also called “flange focal distance”, “flange back distance” or just “register”, is the space between the mounting flange (which is the outer a part of the lens mount when seen from the aspect) and the movie / sensor aircraft. Identical to totally different mounts have variations in throat measurement, internal and outer diameters, flange distances additionally typically differ drastically between totally different digital camera techniques.
5. Mount Measurement, Flange Distance and the Angle of Incidence
Now that we’ve outlined the mount measurement and the flange distance, let’s speak concerning the execs and cons of huge vs small mount sizes, in addition to the influence of the flange distance on a system.
The dimensions of the mount is a vital think about a digital camera system. Usually, a bigger mount measurement permits for bigger lenses that may present extra mild to the sensor. Therefore, quicker lenses could be designed by optical engineers. On the similar time, mount diameter isn’t the one variable that impacts lens design – flange distance can also be equally essential. Shorter flange distance permits lenses to be positioned nearer to the sensor, which in itself permits lens producers to start out constructing easier, smaller, lighter and cheaper brief focus lenses as an alternative of the retrofocus varieties. A shorter flange distance additionally permits to design thinner cameras, thus making them smaller and lighter in comparison with cameras with longer flange distances. As well as, it permits lens designers to put a extra highly effective actuator on lenses for quicker autofocusing, and makes it potential to adapt lenses from different digital camera techniques with longer flange distances by way of adapters. Lastly, the throat diameter mixed with flange distance determines the utmost attainable angle of incidence of the marginal rays from the lens, which is essential in designing lenses – usually, the bigger the angle of incidence, the better it’s to make excessive-efficiency lenses.
One draw back of a bigger lens mount is lens measurement and weight points. The bigger the throat diameter, the bigger the lens needs to be at its mount level, which clearly does influence its general thickness and weight as properly. Additionally, the shorter flange distance can result in elevated vignetting or discoloration within the corners of a picture (though this may be mitigated by making the lens design longer to simulate an extended flange distance), as a consequence of sensor microlenses not with the ability to cross sufficient mild at excessive ray angles.
To know the significance of a bigger mount and a shorter flange distance, please take a look at the under video from a Nikon engineer that explains the advantages of the Nikon Z system when in comparison with Nikon F:
When adapting lenses from different mounts, it is very important level out that because of the proprietary nature of autofocus techniques, variations in change of data between digital camera physique and lens by way of digital contacts (the variety of which additionally differ from system to system) and different points, most adapters find yourself being “dumb” adapters with guide controls, manufactured by third social gathering corporations. Digital camera producers themselves typically present adapters with the discharge of shorter flange distance techniques to have the ability to mount lenses from different digital camera mounts that they developed up to now, however they virtually by no means present adapters for competing techniques. As well as, some adapters are able to altering the bodily properties of lenses through the use of glass parts in them, whereas others make it attainable to insert a lens filter (akin to impartial density or polarizing filter), making it attainable to make use of filters on large-angle lenses with outsized entrance parts, with out involving cumbersome filter mounting rigs and enormous filters. When adapting lenses from different methods, it is very important be sure that the goal lens mount has an extended flange distance so as to have the ability to obtain infinity focus. Moreover, the distinction in flange distance between the supply and the goal system needs to be large enough to have sufficient room for an adapter to take a seat between the lens and the digital camera for a dumb adapter. Sensible adapters that may set up communication between the digital camera and the tailored lens should have much more legroom for contacts and electronics to suit between the 2.
6. Digital camera Mount Comparability
Now that we have now gone by way of all of the phrases and definitions, let’s go forward and examine totally different digital camera mounts based mostly on their throat and inside diameters, in addition to flange distance and angle of incidence:
To seek out angle of incidence, I calculated the angle between the throat diameter and the highest middle of every system’s digital camera sensor. I assumed all full-body sensors to be 24mm in peak, the Fuji X digital camera sensor to be 15.6mm in peak, and the Fuji G digital camera sensor to be 32.9mm in peak (notice that different web sites typically do that calculation with internal mount diameter somewhat than the throat diameter, they usually might calculate from a nook or the middle of the digital camera sensor moderately than the highest middle).
Please notice that the above info is predicated on my analysis and submitted knowledge from our readers. For those who use a system that isn’t listed within the desk and want to assist increase it with extra knowledge, please use the pictures on this article to correctly measure the lens mount, then present the knowledge within the feedback part under. We’ll do our greatest to replace the desk as quickly as attainable!