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Old 17th of September 2005 (Sat)   #1
T.D.
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Default EF vs EF-S

Can someone put in really simple, layman's terms what the difference between EF and Ef-S is? (Please, no acronyms, abbreviations, etc!)

I have a Rebel XT and want to know what will meet my needs the best. I haven't been able to find out the answer to this question.

Thanks!
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Old 17th of September 2005 (Sat)   #2
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Default Re: EF vs EF-S

The EF-S lenses fit only the 20D and Digital Rebel series of cameras. The distance between the rear of the lens and the sensor is shorter than for EF lenses. It's possible to reduce the distance on those cameras because they have a sensor that is smaller than 35mm, along with a smaller mirror. If it were possible to attach an EF-S lens to a "full size" digital camera, I suspect the mirror would crash into the back of the lens when it comes up.
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Old 20th of September 2005 (Tue)   #3
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Default Re: EF vs EF-S

It would, and you'd also (using mirror lock-up to avoid that) get less than full frame coverage.
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Old 20th of September 2005 (Tue)   #4
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Default Re: EF vs EF-S

If you ever think you'll move up to a 1 series camera or the full frame series, the EF-S is not the way to go. EF lens will work on all bodies and EOS film cameras. Gives way more versatility if you do think you'll get into cameras that would not use EF-S lens.
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Old 20th of September 2005 (Tue)   #5
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Default Re: EF vs EF-S

I am sure I could mod my EF-S 10-22 in such a way as to fit into one of them FF bodies real good, should I ever decide to git it. Heck, in my days I have done much harder make-shift mods while with ole Nor-Con Aircraft Mtce. Dept.
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Old 21st of September 2005 (Wed)   #6
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Default Re: EF vs EF-S

Quote:
Originally Posted by Petkal
I am sure I could mod my EF-S 10-22 in such a way as to fit into one of them FF bodies real good, should I ever decide to git it. Heck, in my days I have done much harder make-shift mods while with ole Nor-Con Aircraft Mtce. Dept.
Maybe you could mod it, but it wouldn't be very useful, because the image circle of EF-S lenses is smaller than that of EF lenses (as Jon already mentioned), which means you will get a black border around your image if you put a modded EF-S lens of a full-frame camera.
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Old 21st of September 2005 (Wed)   #7
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Default Re: EF vs EF-S

Quote:
Originally Posted by Petkal
I am sure I could mod my EF-S 10-22 in such a way as to fit into one of them FF bodies real good, should I ever decide to git it. Heck, in my days I have done much harder make-shift mods while with ole Nor-Con Aircraft Mtce. Dept.
You can always buy a 3rd party wide, wide lens, that would work on all EOS cameras.
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Old 21st of September 2005 (Wed)   #8
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Default Re: EF vs EF-S

Short answer: EF-S is only for small sensor EOS Digital Single Lens Reflex cameras. (Mainly EOS 300, 350 and 20 D models)
EF lenses will work on all EOS cameras, both film and digital.
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Old 22nd of September 2005 (Thu)   #9
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Default Re: EF vs EF-S

EFs lenses are designed so that their rear lens elements closer to the camera.
The whole point of this is because it's cheaper/easier to make wide angle lenses this way
...(and 1.6 crop digital bodies NEED wider angle lenses than normal film cameras because they don't use the full width of the lens)
There are several factors effecting your decision to buy an EFs lens.
Firstly it may be the only affordable choice for wide angle. The 18-55 kit lens is far cheaper than any comparable wide angle normal lens
Or it may be the only way to get the lens you want .
The 17-85 IS lens is an exact 1.6 crop version of the popular 28-135 IS normal lens (that is,it gives the same angle of view when used on the digital bodies as the 28-135 does on a full frame camera)
Or it may be the ONLY way to get a truly serious wide angle lens.
for example the wide angle 17-40 lens only gives a "28mm" angle of view on a 20D etc.
The 10-22 EFs lens gives an angle of view equivilant to 16mm

The other possbly big factor is -should one buy an EFs lens or spend more and get a normal lens that can be used on a possible future full frame digital body?
For the moment it looks like there is absolutally zero chance of canon giving up the 1.6 crop sized digital cameras-i think i've seen them stating that they'll stick with them for entry level bodies at the very least
And besides that the awsome nikon D2x has a reduced sized sensor, so there is still no definite reason to go full frame
And as a last resort-if canon does stop making 1.6 crop bodies at some distant future date ,an EFs lens will still work on older bodies.They wont be worthless


As for the 10-22 lens on full frame idea- It's been tried allready and does of ,course, strongly vignette at the wide end.Plus the rear lens elements and the mirror will have a very expensive meeting when you try to take your first pic .
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Old 22nd of September 2005 (Thu)   #10
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Default Re: EF vs EF-S

^^But the 3rd party guys make EF-S like lens that will work on cameras like 10D's, 1 series. That's one thing Canon made a booboo one. Oh well.
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Old 22nd of September 2005 (Thu)   #11
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Default Re: EF vs EF-S

IF Canon made a mistake with EF-S, it was in not starting that particular line sooner, with the D30. Canon's EF-S design for dedicated mount allows them to design wide angle lenses with less retro-focus (where the focal point of the lens is behind the lens), which makes it easier to design high-performance wide angle lenses that are moderately priced. It also ensures that they won't get disgruntled customers who forgot and tried to mount their "crop" lenses on a 1Ds II and damaged the mirror because of projecting rear elements, or didn't appreciate the circular image because the lens can't cover 35 mm full frame.
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Old 23rd of September 2005 (Fri)   #12
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Default Re: EF vs EF-S

Thank you everyone for your posts. This has been very helpful and educational for me.

Thanks again!
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Old 31st of December 2007 (Mon)   #13
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Default Re: EF vs EF-S

Ok someone tell me if I have this right

The non-full frame cameras (20d, 30d, 40d, XT, XTi) have a smaller sensor. You can put a regular EF lense of them but the sensor will not catch all the light and thus you will get a 1.6x zoom effect. So if I put a 100mm EF lense on an XTi it will essentialy crop the image like I had zoomed 1.6x, however the depth of field and anything else related to a longer focal length would not have changed.

The EF-S lenses are built specific for the smaller sensors. The lense is closer to the sensor, and thus the sensor catches all of the image. However, (and this is what confuses me) I've also read that you still need to use a 1.6x multiplier to get your true field of view even with an EF-S lense. Is that true? Were they just trying to keep things consistent?

Did Canon essentialy create the EF-S line specificly for the smaller sensors so the image from the lense would not be cropped by the sensor. And then rather then labeling them with their true focal length they labeled them with 1/1.6 the focal length(s) so that people could switch between EF and EF-S lenses with out noticing a difference in functionality?

If you still have to mutiply by 1.6 to get the true focal length then what's the point of an EF-S lense? Is it just so you are using more of the lense that you bought?


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Old 31st of December 2007 (Mon)   #14
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Default Re: EF vs EF-S

You're partially correct. Instead of catching all the light, you should say the EF-S lenses don't project an image circle that covers the entire sensor on the full frame and 1.3 crop cameras.

The crop effect comes from the size of the sensor, not the size of the image circle. All it means is that the difference in sensor sizes results in a image on an APS-C sensor that appears to be a crop (a smaller section cut out of a larger image) of a full frame or 35mm film images.

EF-S lenses are closer to the sensor and do project a smaller image circle that still covers the smaller sensor, but the sensor does not "catch" more or less light.

Also, focal length is focal length is focal length - no matter what camera a lens is mounted on, it will only have a set focal length or range of focal lengths, so EF-S lenses are accurately labeled with regard to their actual focal length.

EF-S lenses allow for more affordable wide angle lenses for 1.8 crop cameras.
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Old 31st of December 2007 (Mon)   #15
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Default Re: EF vs EF-S

Eric, the following is something I've posted a few times, but hopefully it will help you understand the EF-S lens concepts.

The APS-C cameras have a smaller sensor than a 35mm film frame. If you limit the lens selection to those lenses designed to fill a 35mm frame (such as Canon’s EF series lenses), you will find that there are no ultra-wide-angle lenses for the APS-C camera. The shortest zoom lens focal length in the EF lens family is 16mm. There are two primes that are a bit shorter, and one of those is a "fisheye" lens. NONE of these lenses are what the average photographer would call "affordable".

To design an ultra-super-wide-angle lens such as a 10mm (non-fisheye) lens for a 35mm camera is a VERY expensive proposition, which is why there are none.

By making some changes to the design criteria - reducing the "film" area to be covered by the lens, and allowing the lens to project deeper into the mirror box (move the rear element of the lens closer to the "film"), it becomes much more economically possible to design lenses for the task. Thus, the EF-S family of lenses was born, the “S” standing for Short back focus. The EF-S lens mount is purposely designed to be different from the standard EF lens mount so that you cannot mount the EF-S lenses on cameras that were not specifically designed for them. If you modified the mount of an EF-S lens to be able to put it on a 35mm film camera, there would be a high probability that the mirror would crash into the rear element of the lens at certain focal lengths (the mirrors in the APS-C cameras are significantly smaller than those in 35mm cameras and “full-frame” DSLR’s). Also, the 35mm film frame would have a dark circle around the edges and the image would be inside the circle (known as severe vignetting).

Now that you have some understanding of what the EF-S lenses are all about - note that there are no long focal length lenses with the EF-S design as they aren't needed - you need to understand that focal length is focal length is focal length. An EF 50mm prime lens designed for a 35mm camera, when used on an APS-C camera, will provide you with EXACTLY the same image size as an EF-S 18-55 lens set to 50mm. If you could cobble together a mount for a Hasselblad 50mm lens and use it on a 20D, you would again have the same size image as a result.

NO CHARACTERISTIC of any lens changes when you mount it on different format cameras. Focal length (or focal length range for zooms) never changes. Aperture range never changes. The only thing that would change is the apparent field of view, and that change is not a function of the lens but it is a function of the size of the sensor or film that will record the image.

EF-S lenses, by the way, will only fit on the Digital Rebel series cameras (300D, 350D, and 400D), the 20D, 30D, and the 40D as of this writing.
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