Questions and thoughts on EF and EF-S lenses.

[NedM]

So, today I bought myself another APS-C sensor body. Canon 550D to be exact.

I know these cameras have a 1.6x crop sensor.

Questions is:

When I mount an EF lens onto a APS-C sensor camera, such as the Canon 550D or 600D. Let's say a 24mm 2.8 for conversation's sake. Are EF lenses designed so that I will be seeing the true 24mm focal length or would it be cropped because of the 1.6 crop?

 

[xzyragon]

the 24mm ef-s pancake has the same FOV as a 40mm pancake on a full frame camera.

The focal length advertised on EF / EF-S lenses is the focal length of that lens. It doesn't change regardless of the body it's on. All that changes is your field of view (FOV).

 

[Edsport]

EF or EFS lenses will still be cropped...

 

[bratkinson]

A lens does not 'magically' get changed when mounted on an APS-C body. What happens is 'what the camera sees' is narrowed down...aka, field of view (FOV) gets narrowed. I like to think of it as putting horse blinders on the sides and top of a lens.

Imagine the image that comes out of the rear of an EF-S lens were about the size of a saucer (without the cup), and the image from an EF lens the size of a dinner plate. The rectangular APS-C sensor 'just fits' within the size of the saucer image projected by the EF-S lens. On the other hand, the much larger image projected by an EF lens far exceeds the size of the APS-C sensor, with the 'excess' area of the projected image falling on black plastic inside the camera body.

Many feel that mounting an EF lens on an APS-C body is like 'zooming in', making a 24mm lens seem like it's a 38.4mm lens instead (24 x 1.6). No, the sensor only 'sees' what a 38.4mm lens (if such existed) would produce. Where it seems like it is 'zoomed in' happens when the resultant photograph is displayed on your computer. The image from an APS-C camera fills the screen as does the image with the exact same lens but from a full frame camera taken from the same location. The difference? The full-frame image captures much more of the 'surroundings' than does the APS-C produced image...thus making it APPEAR to be 'zoomed in'.

 

[Derrel]

The field of view that is imaged on the APS-C sensor will be identical if a 24mm lens is a Canon EF model, or if it is a Canon EF-S model. When used on an APS-C body, there is no difference in the picture angle of view of a lens that occurs as a result of a lens being labelled EF or EF-S. A 24mm Canon EF lens is the same focal length as a 24mm Canon EF-S lens.

 

[astroNikon]

past posts about it with examples --> So You Wanna See the Difference Between Full Frame and Cropped Sensors? | Photography Forum

 

[astroNikon]

another good article about it --> FX - DX Lens Crop Factor

 

[Lucryster]

In simpler terms, The field of view in the 550, is going to be smaller than a full frame camera, even if you put an ef lense on your 550. Sometimes people on this forum get too involved in the technical details, instead of answering what the original poster was trying to figure out.

 

[KmH]

Anyone not wanting to wade through the technical details can skip over those posts.
The thread starter is not the only one reading the thread.
Others reading the thread may appreciate/want/need the technical details.

I found that the better I understood the technical and artistic details, the better I became at doing photography.

For every member that is logged into TPF at any given moment there are about 10+ 'guests' or non-members reading the forums.
TPF is mostly for the guests, because the guests see (and click on) all the advertising.
A benefit of being a member - in exchange for providing forum content - is members don't have to look at all of the advertising, just some of the advertising.
All of that advertising is what generates revenue for the company that owns the forums (TPF and a bunch of others).

 

[CameraClicker]

So, today I bought myself another APS-C sensor body. Canon 550D to be exact.

I know these cameras have a 1.6x crop sensor.

Questions is:

When I mount an EF lens onto a APS-C sensor camera, such as the Canon 550D or 600D. Let's say a 24mm 2.8 for conversation's sake. Are EF lenses designed so that I will be seeing the true 24mm focal length or would it be cropped because of the 1.6 crop?

APS-C bodies, like the 550D, don't take advantage of the whole EF lens. Lenses designed for APS-C sensor bodies can be smaller and lighter because their image circles can be smaller. Usually that makes them easier to produce and less expensive. Canon's EF-S lenses have a protrusion that keeps them from fitting full frame bodies and teleconverters, but they work fine with hollow extension tubes. Nikon has a neat scheme, you can use most DX lenses with most FX bodies and the body is smart enough to crop for the DX image circle.

Since I have Sigma lenses for my 550D, I put a couple of them on my 5D to see what happens. Not quite what I was expecting, let's look.

This is the whole frame of a 10-20 mm DC lens at 10 mm

Same lens at 20 mm

Just for giggles, I also tried my 18-250 DC zoom, this is what happened:

Full frame at 18 mm

At 50 mm it looked like I was expecting

At 135 mm it gave a surprising result, this is the full frame

And, this is at 250 mm

So they are not great photos, but they are not supposed to be. They do show what happens when you put a lens made for a crop body on a full frame body. Which is much more interesting than putting a lens made for a full frame body on a crop body.

 

[CameraClicker]

In the same vein, this is the 10 mm Sigma, again
and the EFS 16-35 from Canon, both on the 5D

At 100% crops of the same area:

10 mm Sigma and 16 mm Canon

 

[Ido]

EF lenses are simply bigger than EF-S lenses, because they need to cover a bigger sensor. EF-S don't, so they can be smaller so they only cover an APS-C sensor area.

It doesn't matter if you put an EF or EF-S lens on it. If they're identical in the focal length marked on them, they will give an identical field of view.

 

[shaylou]

The lens has nothing to do with the crop factor. The cameras sensor is where the crop factor comes from so as long as you use a camera body with a crop factor regardless of what lens you use the crop factor will always be there.