Will Lens X Work on Camera Y?

Simple Answers for Canon

This question comes up a lot in reference to Canon — and Canon has more lens mounts than most — so here's a quick summary.

First, look ahead to "Know Your Lens Mount", and be sure you know what lens mounts you're dealing with. Then if your camera and lens are exactly the same lens mount, you should be OK. Otherwise:

If you have old FD-mount lenses, then they can be used on modern mirrorless cameras (like RF) with the right adapter; but not on EF-mount cameras, because the flange distance of FD is shorter than that of EF. See "Similar but Different" below. Of course those lenses are all manual-focus and manual exposure only; putting then on a modern camera can't change that.

Bottom line (again, for Canon):

• EF (not including EF-S) is the most versatile mount for a lens; it goes on everything
• RF (and RF-S) is the most versatile body; it takes everything, except EF-M
• EF-M is an oddity: it's kind of a dead end, replaced by RF

The Big Lens Matching Issues

Getting a lens to fit — and work well on — your camera, means getting several factors correct. Using a lens with the exact same lens mount as your camera takes care of all of this, so in that simple case you don't need to think about it; but if you're going to get adventurous about adapting different lenses to your camera, then it's worth understanding what all the issues are.

There are 4 main issues; so let's look at them.

Physical Fit

Most lens mounts these days use a bayonet-style attachment, where you push the lens in then twist to lock (either clockwise or anti-clockwise, depending on the make). Unfortunately while the concept is common, each manufacturer has their own specific bayonet design, and they're not compatible. So the first thing you need is for the lens to physically fit the camera. Having the correct lens mount takes care of this.

A typical bayonet mount on a lens.

Flange Distance

Every lens will bring the image to a focus a specific distance behind the lens; this distance is conventionally measured from the rear metal attachment plate, or flange, of the lens, and hence is known as the flange-focal distance, or just flange distance. So to focus properly, the flange of your lens must be the correct distance from your sensor.

Every lens mount has a specific flange distance, so they're not compatible; but if you have a lens and camera with the same lens mount, your lens will be the correct distance from the sensor. By the way, don't try to measure this distance; the thing you see inside the camera is not actually the sensor, it's the block of filters in front of the sensor, and you don't want to scratch it.

You'll find that, in terms of flange distance, lens mounts generally fall into two camps:

• DSLR systems have a long flange distance, to allow for a mirror between the lens and the sensor; so in the region of 44mm to 52mm.
• Mirrorless cameras do away with the mirror to create a smaller, lighter, and cheaper camera system, so flange distance is shorter; generally in the 16mm to 20mm range.

A digital camera sensor — or rather, the filter block. The sensor is behind this.

DSLRs were once the standard for high-end photography; but new technology has allowed cameras to go mirrorless, resulting in more compact and lighter camera systems, and in particular smaller and lighter lenses. This switch is why all the camera manufacturers have brought out new lens mounts in recent years.

Image Circle

Every lens produces a focused image of a particular size, which is usually circular, so the size is known as the image circle. Outside this circle, the image gets darker and then black; how sharply that happens will depend on things like aperture and focal length. The advertised image circle should be filled with a usably bright image under all conditions, though in practice some lenses will show slight darkening in the corners, also known as vignetting.

You want to make sure that your lens's image circle is large enough to cover your sensor. Generally this is taken care of by the lens mount; but only if you have the right lens mount variant. See "Know Your Lens Mount" below.

A lens' image circle can be anything, and likewise there are a lot of camera sensor sizes; but for most photography on interchangeable-lens cameras, sizes fall into three camps:

• Four-thirds sensors are 18mm × 13.5mm, so the image circle is 22.5mm (to cover the diagonal size of the sensor).
• APS-C, a.k.a. "crop", sensors vary somewhat, but are generally around 23mm × 15mm, so the image circle is about 28mm. Super 35 falls into the same camp.
• Full frame sensors are 36mm × 24mm, so the image circle is 43.3mm.

Both APS-C and full frame sizes are featured on multiple lens mounts from different manufacturers; in fact, many manufacturers have cameras and lenses in both APS-C and full frame versions. Four Thirds, and its successor Micro Four Thirds, on the other hand, are specific lens mounts, and the image circle size goes along with that.

Electronic Control

Some lenses are all mechanical, meaning that the focus ring is mechanically geared to the glass elements inside the lens, and the aperture ring is likewise linked directly to the iris blades. But increasingly today, focus and aperture are controlled by motors, which in turn are controlled by a computer inside the lens; and that computer is driven by commands issued by the camera. Those commands are passed over a data link which uses electronic contacts to connect the lens to the camera — you can see these contacts on the back of most lenses.

An all-mechanical RF-mount lens, without control contacts.

An electronic RF-mount lens, showing the control contacts.

An RF-mount camera, showing the electronic control contacts.

The actual communications protocol used by the lens and camera to talk to each other is proprietary, and not compatible between manufacturers; so there's basically no way to use one maker's lens on another maker's camera — if the lens is electronic. If the lens is mechanical, though, and if you can address all the other issues above with an appropriate adapter, then you have no problem. Using mechanical lenses like this is very common in film-making, and most cine lenses are all mechanical.

By the way, if your lens is mechanical — i.e. no electronics — then the camera can't know that there's a lens attached. To use it, you will probably need to tell the camera in its settings; for example, there might be an option called "fire shutter with no lens attached".

Know Your Lens Mount

To get a lens that works for your camera, first, you absolutely need to know the lens mount of your camera, and the lens mount of the lens you're looking at. If you don't know both those things, you're lost before you start. Unfortunately, if you don't already know it, finding your camera's lens mount could take a little digging.

All camera manufacturers have multiple different, and often incompatible, lens mounts; so knowing the maker's name is nowhere near enough. If someone online is advertising a lens as being "for Canon", or "for Nikon", or whatever, don't buy it: if the seller can't tell you what it is they're selling, you certainly should not be giving them your money.

You need to know the specific lens mount, for both camera and lens; this includes both the basic lens mount, and the sensor size variant, if any (see "Image Circle" above). For example, Nikon F-mount lenses come in FX and DX variants, for full-frame and APS-C. Canon's EF, EF-S, and EF-M are all different. And Sony's E and FE are mechanically the same, but with different image circle sizes.

You should be able to find your camera's lens mount on the manufacturer's web page for the camera, as long as you put the pieces together. For example, Nikon's web page for the Z50, in the "Technical Specifications" section, states

so this camera is a Z-mount DX camera, and will natively take lenses described as "Z DX". FX (full-frame) lenses will work, but will be bigger than you need (see "Full-Frame Lens on Crop Camera" below). Similarly, Canon's specification page for their R10 camera says

which of course is true; but it also says that the sensor type is APS-C, so RF-S lenses would actually be the most optimal choice here.

This table shows a selection of common lens mounts, with their variants for different sensor sizes:

Note that Canon has two mirrorless systems; EF-M, which was designed for APS-C cameras only, and RF, which handles both full-frame and APS-C. These are not compatible; see "Canon's EF-M and RF", below. All of Canon's new mirrorless products are based on RF, so EF-M isn't really the best choice for a new investment.

Unfortunately, even all this blurb does not show the whole story. For example, while Nikon have kept their F mount alive since 1959, there are actually many sub-types of the F mount, and not all F-mount lenses and cameras are compatible. Research is required for specific combinations, specially with older cameras or lenses.

Making the Match

So OK, having (hopefully) absorbed the above confusing information, how do you put it into practice? Specifically, how can you know if a given lens will fit your camera?

There are a few scenarios which determine the answer. Let's look at them one at a time.

Same to Same

The simplest way to know that a given lens will work for your camera is to mount same to same: in other words, the camera and lens are the same lens mount, and the same variant. So a Canon EF-M lens, for example, will work on an EF-M camera. If you have a Nikon F-mount DX camera, then a Nikon F-mount DX lens is the simple choice. Easy!

This really is by far the simplest and safest option, and generally you will still have a decent choice in lenses. But one day you may find that you have an investment in gear, and you want to keep that investment alive to work with newer gear — and why not, after all this stuff is expensive. Or you might just want to expand your lens options.

This involves some degree of mismatching, and that opens up some pitfalls. But the good news is that there are real possibilities here; so let's look at them.

Full-Frame Lens on Crop Camera

Generally, a manufacturer's own full-frame lenses will work on a camera with the crop-sensor version of the same lens mount. So in Canon, for example, EF lenses will work on EF-S cameras, and RF lenses will work on RF-S cameras; in Nikon, F-mount FX lenses will work on F-mount DX cameras. But the base lens mount type must be the same — a Canon RF lens, for example, will not work on an EF-S camera.

The drawback here is that you're paying for a lens which covers a larger sensor than your camera has. In other words, you're buying more glass than you're using; so you're getting more size, weight and cost than you need. This isn't optimal, but it's not a real problem, if you're willing to pay the price. And in fact it can be a good investment; if you later upgrade to a full-frame camera with a compatible lens mount, your full-frame lenses will work optimally.

Crop Lens on Full-Frame Camera

Often, a manufacturer's own crop-sensor lenses will work on a camera with the full-frame version of the same lens mount. But not always. Check up on this before buying, as there can be restrictions.

For example, Canon EF-S lenses will not work on Canon EF cameras, as the EF-S lens can stick back into the mirror box, blocking the mirror. With Nikon, on the other hand, F-mount DX lenses will work on F-mount FX cameras. And once again, the base lens mount type must be the same — a Canon RF-S lens, for example, will not work on an EF camera.

The big problem with this is that the lens doesn't cover the whole full-frame sensor. If nothing was done about this, your pictures would all be small circles of image surrounded by black — not what you want. In practice, though, this will usually be OK, as most cameras these days can switch to a crop mode, where they only read out the central part of the sensor; and in many cases the camera can switch to this automatically.

So the real drawback is that you're not using the full resolution of the camera, so this is really not optimal. For example, if you bought a 45 megapixel camera, in crop mode, you might only be shooting 17 megapixels, a significantly lower resolution than you paid for.

Also, your field of view will be narrower; on a full-frame camera, a crop-sensor lens with a 35mm focal length will give you the field of view that a full-frame 50mm lens would give you, because the camera crops the image to a narrower form factor.

DSLR Lens on Mirrorless Camera

So let's say you have a DSLR lens — like Nikon F, or Canon EF — and you want to use it on a newer mirrorless camera, from the same manufacturer. The news here is pretty good.

The issue is that a DSLR lens wants to be farther from the sensor than the camera's lens mount would place it. This can be solved by inserting a tube in between, with the camera's lens mount on one end, and a socket for the lens' mount on the other — in other words, an adapter. The adapter is literally just a tube — there are no optics in it at all — so it won't affect your image quality. Most camera manufacturers make adapters to adapt their older DSLR lenses to their new mirrorless cameras.

This can work very well. However, not all lens combinations will work without issues; some features may be compromised, particularly on older lenses. The speed of burst mode shooting, or autofocus, may be affected. There are many possible combinations, so you'll need to do some research to find out.

Mirrorless Lens on DSLR Camera

So now let's say you want to go the other way — you have an older DSLR camera, and you're tempted by the flashy new mirrorless lenses. Can you use them?

Nope.

Sorry, but that's really it. If you want to use a Canon RF lens on an EF camera, or a Nikon Z lens on an F-mount camera, or whatever, then the answer is just — nope.

If you want to know why, read about "Flange Distance" above. The problem is that your mirrorless lens needs to be close to the sensor, but your camera's lens mount is farther away. There's nothing you can do about this, and no adapter can fix it.

But wait a sec, you say — can't we put optics into the adapter to extend the reach of the lens? Well, technically that's possible, and this would be called a diopter adapter. But all the information I've seen says that the results are poor; you would be better off just buying a compact camera, or using your phone. So I'm going to say that this is not a realistic option.

Similar but Different

What if you have a lens and camera which are of the same type — like a DSLR lens, and a DSLR camera — but different lens mounts. Like, say, a Canon FD lens and an EF-mount camera. Can this work?

Probably not. The issue is that you would need space between the lens and the camera for an adapter to fit in, and there probably isn't enough. Following our example, Canon's FD mount has a flange distance of 42mm, but EF is 44mm; so an FD lens simply can't get close enough to the sensor on an EF camera. (Again, a diopter adapter (with lenses in it) could fix this, but these generally get very bad reviews.)

Even if it seems like there's a few millimetres to squeeze a low-profile adapter in, this still may be impossible in practice... as the following section describes.

Canon's EF-M and RF

Canon have created what I think is a unique situation by having two different mirrorless lens mounts — the older EF-M, a compressed variant of EF, which covers APS-C sensors only; and the newer RF, which is a completely new system, and covers all sensor sizes up to full frame (and even slightly beyond).

Given that these are both mirrorless mounts, from the same manufacturer, it's natural to suppose that you could adapt one to the other. Sadly, though, this is not possible; they are completely incompatible, and no adapter does, or could, exist.

The EF-M lens has a flange distance of 18mm; so it needs to be that close to the camera's image sensor. But an RF camera's front flange is 20mm from the sensor; so there's no way to get an EF-M lens on an RF camera.

Going the other way, with the RF's flange distance being 20mm, it might seem that there's 2mm to fit an adaptor into. This is not true, though, as the bayonet of the RF lens sticks out an additional 6mm, and it's too wide to fit in the throat of an EF-M mount. So, there's no way to fit an RF lens to an EF-M camera.

You might think that optics in the adaptor could fix this; but I think this is a non-starter. See "Mirrorless Lens on DSLR Camera" above.

Foreign Lens on Your Camera

Let's say you want to mount a lens by a different manufacturer on your camera. Will it work?

If the lens has electronic control, the basic answer is no. See the "Electronic Control" section above. There are a handful of exceptions, where a particular adapter can actually provide some degree of electronic lens control, but even then the features tend to be limited. There are a few exceptions, where a particular lens-adapter-camera combination can work well, including full autofocus; but as of now this is a rarity, so proceed with caution.

On the other hand, with an all-mechanical lens, this can work well; as long as the flange distance of the lens is longer than the camera's, and the lens' image circle covers your sensor, as described above. And of course you will need the appropriate adapter.

This is a common way of working for film-makers. You will often see cine PL-mount lenses, or Canon FD lenses, adapted to other lens mounts. Some all-mechanical cine lenses are made in EF mount, and are adaptable to mirrorless lens mounts.

So To Sum Up

If you're careful to match the lens mount of your lenses exactly to your camera, then there really should be no issue, and all of the blurb above can be safely ignored. But you need to be sure that you really know exactly what lens mount your camera and lens conform to. "For Canon" is absolutely not enough information.

Given the price of this gear, it's perfectly natural that you would want to extend the lifetime of your investment by making older and newer kit work together. This is where things can get complicated, and it's worth understanding the issues. The most likely case here is that you have a collection of older DSLR lenses, and you want to upgrade to a newer mirrorless camera; and this is likely to be pretty straightforward, as long as you keep to the same manufacturer, and bear in mind the issues with sensor sizes and image circles.

The farther you get from this simple case, the more pitfalls you are likely to run into; hopefully this article has at least given you a feel for what those might be. And some combinations, sadly, are practically impossible, like adapting mirrorless lenses to an older DSLR camera. If you find yourself wanting that specific combination, your best bet might be to think again.