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EF versus EF-S

One of the most confusing things I dealt with first buying a Digital Rebel were the terms EF, EF-S, full frame, and crop factor. It's hard to get through any Canon SLR review without encountering them, so I thought I'd try to clarify them in terms that I at least understand.

The "film" in a Digital Rebel, i.e. the sensor, is smaller than that of actual (35mm film) film cameras (22.2mm wide versus 36mm wide). Imagine taking a photo and trimming a third of it off around the edges. This is what your Digital Rebel is doing and it's what is referred to when people discuss 1.6x crop factor.

Crop factor has it's upsides and downsides:

  • pro: you get extra "zoom."
  • con: it's a lot harder to shoot wide-angle images because you're throwing away the edges of the image.
  • pro: it can improve photos taken with cheaper lenses, which tend to be worse towards the edges.
  • con: the viewfinder for Digital Rebels is smaller because of the smaller sensor size.

Crop factor is also referred to as focal length multiplier, which describes a useful rule of thumb even if it is a bit of a misnomer. A 100mm lens on a Digital Rebel has the same field of view as a 160mm lens on a film camera (100 x 1.6 = 160). It's not the same thing as actually shooting with a 160mm lens on a film camera: as you are just trimming off the edges of the photo, the depth of field is still the same.

How does this relate to EF and EF-S lenses? EF lenses were designed for film. They are built assuming that they are going to focus your image on an area the size of 35mm film. For Digital Rebel owners, this is great if you're trying to shoot telephoto images because you get all that extra artificial zoom for free. This is very bad, though, if you're trying to shoot wide angle. A 16mm lens suddenly acts like a 26mm lens.

Canon's solution to this problem was to design a new type of lens for the smaller digital sensor size and they've called these lenses EF-S lenses. EF-S lenses try to get rid of the major downside of the crop factor: reduced wideangle. They accomplish this by positioning the lens closer to the digital sensor.

Important things you need to know about EF-S lenses:

  • You still use the 1.6x multiplier when evaluating the field of view for EF-S lenses. The 10-22mm EF-S lens gets zoomed up to a 16-35mm lens. You may think it's a bit confusing at first that a lens designed specifically for the crop factor still has to have the multiplier used, but it's consistent: always use the multipler.
  • You (currently) can only use EF-S lenses on Digital Rebels, EOS 20D, EOS 30D, and EOS 40D. You can't use them on Canon's top-of-the-line Digital SLRs, which have different sensor sizes.
  • There is always the possibility that Canon could stop making cameras that support EF-S. However, EF-S lenses tend to be cheaper, as lenses go, and you would only really buy them for wide-angle uses, so it's unlikely that you would ever have many EF-S lenses.

Some other terms:

  • APS-C size sensor: the Digital Rebels (300D and 350D) use a APS-C size sensor, which is 22.2mm wide. This gives a 1.6x crop factor.
  • full frame: A full frame digital camera has a sensor the same size as 35mm film, so there is no crop factor. It's just as if you're shooting with film.

Comments (24)

M Author Profile Page:

The consistent crop factor does explain why my 16-35 EF lens felt like it covered about the identical area as my 18-55 EF-S (at least in the 18-35 range). I never really made the connection until I sat down this morning and tested the mutliplier after reading this entry.

Thanks for posting this useful knowledge. I just got a 300D and am looking around at lenses. This will certainly educate any future purchase.

Jen:

So the EF-S can't be used on my digital rebel 400D?

kwc:

@Jen: You can use it on your Digital Rebel 400D/XTi -- this article was written before that model was released.

Mark:

your camera has a red align dot for installing lenses. if there is a white dot as well, then it can take ef-s lenses

Walid:

if I am using an EF-S 17-85 mm on my 400D, and taking a wide picture of 17mm, does it mean that my photo is at 17mm or 17mm*1.6????

kwc:

@Walid: 17mm * 1.6.

Richard:

Hallo, My friend told me that I can fit a canon lenses from digital to my Eos-1n film camera. But I can`t fit EFS lenses. Why? Or better how I can fit it? Thank you

kwc:

Richard: EF-S lenses are built specifically for digital cameras and cannot be retrofitted onto a film camera. 35mm film is larger than the sensor used in digital cameras, so a digital-specific lenses projects and image that is too small.

Mitch:

I'm about to spring for a Cannon 40D, so this is a very interesting discussion. The 17-85mm is the first lens I'll buy with the camera, and as an amateur who is trying to improve I like the 1.6(17-85) should give me 27.2 - 136 mm performance.

Is there a reasonably priced solution for my occasional long telephoto shots? I've seen prices like $1,700 USD, and that's more than I would like to spend.

kwc:

@Mitch: The Canon 70-200 f/4L is probably what you're thinking of. It's ~$500 depending on what sale is going on, it is L-quality glass, and it's a fantastic lens. It's only real downside is that it is an outdoor/bright-light lens, but that describes most telephoto work. I used it to get my first magazine cover, so it can't be that bad :).

Banson Kat:

I have a Canon EOS 10D. would a EF-S work on this camera? I am new to digital SLR's

kwc:

Hi Banson,

The answer is no, the EOS 10D does not support EF-S. the 20D was the first to add this feature in that line.

Leiman:

So if I have a Canon 40D, I will be able to use EF and EF-S lens?

Ed Cory:

I have a Canon Elan IIe film camera with an EF28-80mm lens AND a Tamron 28-300mm Aspherical telephoto for the same camera. Will these lenses work on either a Rebel XT, XTi or Xsi AND the EOS 20, 30 and 40D? I'm looking at buying one of these DSLRs and would like to know about possibly using my existing lenses. Also, will the Automatic Focus (AF) functions of my existing EF film lenses work properly with the Digitals? Thanks.

Larry:

I have both Xti and Elan IIe. Just took a try. EF 28-80mm lense work on Xti.

Bruno:

Great article - helped clear up a lot!

Is there there is a big difference in quality between EF-S and EF-S IS lenses?

Santhosh:

I think its wrong as per canon site;
Both EF 55 & EF-S 55 will be 88mm.
http://www.usa.canon.com/app/pdf/lens/Lens_Extender_chart_new.pdf

its like.. i m planning to buy a new lens for my 1000D.... i hv EF-S 18-55 lens rite now.. there is only confuses me about EF lens... if i use them on my 1000D.... how will it be different from my EF-S lens ?

and if i get it simple... will i get it all in the image what all i have on viewfinder ?

ranjith:

can I use EF lense on my Canon 350D?

lui:

I see a lot of confusion here, let's try to make things clearer:
never buy ef-s lenses first!
-they are pretty bad built quality, cheap glass and plastic.
-they fit only apsc sensor cameras.
-if you use a EF lens on a 500-50-7D, thanx to the crop factor you will reduce chromatic aberration that usually hits the periphery of the lenses.
if you have bought efs in the kit, fine is a good start to learn but after that invest money in a good glass, ef or even better ef L especially if you consider to buy a full frame camera in the future.

john:

Thanks for the article. One thing though. Isn't it true that while the EF-S lenses look better on the fringe, the full frame will look better in the middle with the same EF lens? In other words I could use a lower class lens on a FF camera and get better results if I cropped and get worse with the crop. Opposite is get worse on the corners with FF but better with Crop.

Sharon:

I have a Canon Rebel Xsi, I'm using my EF lens from my 35mm camera - why can't I use the display on my digital?

Amber :

I currently have a rebel but looking to upgrade to a canon 60D. in looking at lenses, will the 60D take both lenses or just the ef-s. I want to make sure im investing in equipment that will last awhile.

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