Does the crop effect still happen with an EF-S lens?

cgtm

cgtm

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Hi all,

I've seen conflicting statements on this around the 'net and wondered if anyone could shed some light?

My guess is that, with an EF-S lens, the crop factor plays no part as that lens has been design for a smaller sensor?

Have at it!
 
If you are referring to the designation of the lens, e.g. 15-85, or a focal length printed on the lens, then those designations and markings will always relate to a full frame camera. So a 15-85 lens would be just that on FF, but will behave like a 24-136 on a 1.6 crop factor camera.

The fact that a lens is designed for a crop sensor means that its optical characteristics can be optimised for that camera and can be built smaller and lighter.
 
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I'm a Nikon shooter, so don't take this as gospel, but I believe that the EF-S lenses are equivalent to Nikon's DX lenses. They are designed for smaller sensors but that just means that they have a smaller image circle. The benefits are that these lenses are typically lighter and cheaper than their full frame counterparts. I'm pretty sure that the figures quoted by Canon for EF-S lenses are the actual focal lengths rather than the 35mm equivalent focal lengths, so crop factor is still a consideration.
 
Munkee has nailed it.. EF-s are designed for and will only work on crop bodies, EF lenses are designed for full frame but will work on both types of body, the crop factor remains the same which ever lens you use on a crop body
 
Ah, OK. So my 18-55 EF-S kit lens is, in real terms to my 400D, actually acting like a 29-88?

Just trying to get a sense of framing. I.e., what I thought was what 55mm looks like is actually what 88mm looks like.
 
The focal length of the lens is the focal length.
It doesn't matter if the lens is in front of a full sized sensor*, crop sensor or held in front of a sheet of paper.
The lens creates an image behind it on the sensor. Cameras can only read the part of the image covered by the sensor, the smaller the sensor the less of the image you get and the higher the crop factor. The lens remains the same.
For a given focal length, the view will be the same if you use an EF or an EF-S lens.

Lenses for crop cameras, EF-S, only need to produce an image big enough to cover the smaller sensor so the lens can be smaller, lighter and doesn't need as much glass so can be cheaper.
Have a look at compact cameras, 4-70mm mega zoom with a tiny sensor so they can use tiny lenses. :)

(* Not all lenses fit all cameras.)
 
cgtm said:
Ah, OK. So my 18-55 EF-S kit lens is, in real terms to my 400D, actually acting like a 29-88?

Just trying to get a sense of framing. I.e., what I thought was what 55mm looks like is actually what 88mm looks like.
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"...actually acting like a 29-88" ...on full frame. If you're going to say 'acting like' or 'equivalent to' then the format must also be specified because you can fit any lens of a given focal length on to any camera, in theory, but the result will be very different in each case.

The focal length is a fixed optical charcteristic, ie if you take a 50mm EF-S lens designed for crop format cameras and a 50mm EF lens designed for full frame, both lenses will give identical framing on the crop format body

Lots of threads on this but here's my explanation. Take a full frame camera with a 50mm lens. Now imagine you have some black tape and have masked off a bit from each side of the sensor to leave a square in the middle the same size as a cropped format sensor.

That full frame camera now has a cropped sensor and will behave exactly like a cropped format camera. In terms of the field of view, that is obviously now narrowed and the image that is captured is equivalent to a 50mm lens multiplied by the crop factor, ie 1.6x, or an effective 80mm lens.

But the focal length has not changed; only the field of view has changed because of the smaller sensor.

Edit: the reason why EF-S and DX lenses exist, is because if they don't need to fill a larger full frame sensor, they can be made smaller/cheaper/better/lighter. Take the 18-55mm kit zoom for example: to make a lens like that for full frame would be very expensive and it would also be much bigger. However, the optical advantages that work for EF-S lenses at shorter focal lengths quickly run out at longer focal lengths, which is why longer lenses are all EF.
 
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cgtm said:
Ah, OK. So my 18-55 EF-S kit lens is, in real terms to my 400D, actually acting like a 29-88?

Just trying to get a sense of framing. I.e., what I thought was what 55mm looks like is actually what 88mm looks like.
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Pretty much, if you've come from compacts/bridge cameras the problem I spose is that they generally deal in "35mm equivilents"(although the actual much smaller focal lenghts are normally on the lens and EXIF).

As has been said the reason for EF-s lenses is to give you the equivlent kind of zoom range to tradisional full frame lenses in a smaller package. Theres no FF lens thats going to give you a 18-55mm zoom range, some ultra wide zooms are similar at the wide end but shorter at the long end plus there alot larger and more expensive.
 
Well that clears that up!

Thanks, everyone, for your kind input. I'm that bit wiser now!
 
I thought the EF-S lenses were different too till I read a review about the 10-22mm EF-S lens and saw that it was supposed to fill the same slot as as 16-35mm on a FF camera :) That made me realise I'd been wrong for a while lol
 
Phal said:
I thought the EF-S lenses were different too till I read a review about the 10-22mm EF-S lens and saw that it was supposed to fill the same slot as as 16-35mm on a FF camera :) That made me realise I'd been wrong for a while lol
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Glad I wasn't the only one that made that assumption! :wave:
 
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