Lens Compatibility with 5D III - Canon EF-S 18-55mm f/3.5-5.6

[roncrab]

I have just purchased a Canon 5D III. I have a Canon EF-S 18-55mm f/3.5-5.6  that does not fit but my other Canon lenses do. Is it compatible with the 5D III?

[MikeSowsun]

Your 18-55 lens is an "EF-S" lens designed to fit only "Crop" sensor cameras.  It will not fit your 5D Mk  III because it has a "Full Frame" sized image sensor. EF-S lenses usually have their rear element closer to the image sensor and they can interfere with the movement of the mirror when you operate the shutter.  

Your other lenses must be "EF" lenses. "EF" lenses will fit both Crop and Full Frame cameras.  

One more thing to note.  3rd party lens manufacturers like Sigma, Tokina, Tamron etc, make both Crop and Full Frame lenses. They design their crop lenses differently so that they will mount to a Full Frame camera but they will not project a large enough image to cover the entire Full Frame sensor and there is no possibility of them interfering with the mirror. 

[roncrab]

Thanks. You confirmed my suspicion but I was hoping there was something I overlooked.

[ebiggs1]

Not much of a loss as the EF-S 18-55mm is not a worthy candidate for the 5D Mk III. Look for a EF 24-105mm f4 or better, yet, the  EF 24-70mm f2.8 II.

[ScottyP]

NO!!!!!! 🙂

[TCampbell · Accepted solution]

The "S" suffix in "EF-S" is for "Short back-focus".  The lenses have their rear-most element closer to the sensor than the EF lenses.  This is because EF-S lenses are made to work with Canon bodies that have smaller sensors (APS-C size sensors -- roughly the same size as a single frame of negative from an "Advanced Photo System - Classic" size film).  

Since those sensors are physically smaller, there's no need to have a lens that can project the same size image circle into the camera body as it is needed for a camera with a "full frame" sensor (a full frame sensor camera has a sensor roughly the same size as a single frame of 35mm film).  It's noticeably larger.

Since the sensor is larger, the reflex mirror is also larger and that means the larger room needs a bit more clearance when it swings up to take the picture.  That rear-most element on an EF-S lens would be too close... but also since the EF-S lens projects a smaller image circle, you'd have severe vignetting in corners and sides of your image.

So to avoid any possibility of damage as well as very bad images, Canon designs a bit of a step on their full-frame bodies which blocks the EF-S lens from fully seating in the camera.  In short... Canon designed the camera so you cannot accidentally attach a lens that might cause harm (and would not be able to fill the sensor frame anyway.)

You can use any "EF" lens as well as any of the specialty lenses such as the MP-E (extreme macro photo lens) or the TS-E (tilt-shift) lenses.  

You cannot use the "EF-S" lenses (short back-focus lenses designed for APS-C sensor bodies) or the "EF-M" (designed for the EOS-M mirrorless (aka "MILC" Mirrorless Interchangeable Lens Camera).

[mrbodie52]

Thanks for the post about the EF-S lens not working on 5D Mark II camera. It is good to know the lenses will not attach to the camera so it cannot be accidentally used. I was told by someone in my photo club not to use EF-S lens on my 5D Mark II, now I know why

[ebiggs1]

"So to avoid any possibility of damage as well as very bad images, Canon designs a bit of a step on their full-frame bodies which blocks the EF-S lens from fully seating in the camera."

This is true but only in the case of Canon lenses.  Third party DX (crop factor) lenses will mount on a 5D Mk II or any Canon FF camera.  The older ones may even interfere and cause damage.  I do not know of any current off brand lens that does, however.  But they still should not be used as the picture will be degraded like Tim Campbell says.

Most if not all Nikon FF cameras automatically know if you mount a DX lens and then it adjusts the sensor appropriately. Canon does not have this feature.

[Waddizzle]

"Most if not all Nikon FF cameras automatically know if you mount a DX lens and then it adjusts the sensor appropriately. Canon does not have this feature."

Wait a second.  Is that a mechanical adjustment, or an electronic adjustment?  I always thought it was electronic.  Your discussion of physical obstructions almost make it sound like a physical adjustment takes place, instead of an electronic one.

[ebiggs1]

"Is that a mechanical adjustment, or an electronic adjustment?"

It is electronic.  DX format is selected in setup. You will get no vignetting, and the camera will record the innner area.  I must reveal it does so on the models I have.  Since I don't have and have not used all the Nikon camera, unlike Canon cameras, I really shouldn't, or can't, say it is across the line.