please explain simple EF-S VS EF

Discussion in 'Digital Photography' started by munkees, Mar 28, 2011.

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  1. munkees macrumors 65816

    munkees

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    #1
    OK

    I have a crop camera and I know it is 1.6x factor on EF. therefore a ef 50mm = 80mm.

    now here is where I do not understand:

    on a EF-S lens is the crop factor still 1.6x the lens value so a ef-s 65mm is really 117mm.

    I just trying to understand what the benefit of crop camera lenses are if the lens has the same focal length as a EF lens.

    my understanding the

    EF-S 10-22mm is the same focal lens as a EF 16-24L lens, why produce a lens EF-S, when on a crop camera you could just add a EF 16-24mm L lens (other than cost).
     
  2. robbieduncan Moderator emeritus

    robbieduncan

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    #2
    EF-s lenses produce smaller image circles. So they are lighter (and cheaper) than a comparable EF lens would be. That's it.

    Note the focal length is always the focal length. A 50mm lens still has a 50mm focal length on a 1.6 crop camera. It has a different effective field of view, but that's not the same thing.

    Also note this has been going on forever: a 50mm lens on a medium format camera (obviously with a bigger image circle) as a different field of view that it does on a "full frame" camera.

    None of this is true. The focal length does not change. The effective field of view (once again not the same thing) of the 10-22 is the same as a 16-35.2mm lens would be on a full frame camera. If you use the 16-24mm lens on a crop camera it will not have the same effective field of view as the 10-22.
     
  3. munkees thread starter macrumors 65816

    munkees

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    #3

    so I understand (sorry, my brain has been damaged), if the 16-24mm is used on a crop it would be 24 - 38. Canon made the 10-22 to give the crop people an equivalent lens like the 16-24 on the FF.

    also the ef-s 18 - 55 would be like a 28 - 90mm on a FF.

    OK this helps,

    I trying to work out what lens I want to purchase, or whether to save my money, and just go FF, and stick with EF lens, just want to make wise investments.
     
  4. thatisme macrumors 6502

    thatisme

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    #4
    EF-S lenses are EF mount lenses that have a smaller element in the rear of the lens that works ONLY on 1.6 crop sensor EF-S Canon cameras. With this design, the glass elements can be smaller and lighter than their EF counterparts, but are only compatible with the 1.6 crop sensor cameras. Design wise, the rear element is placed closer to the sensor than EF lenses.

    DO NOT use an EF-S lens on a 1.3 crop sensor (1D series cameras) or on a Full Frame 1.0 sensor (1Ds or 5D series cameras), as the rear element of the lens will interfere with the operation of the reflex mirror and may/ will cause damage to your camera.

    To the previous post about focal lengths, the difference in perceived focal length comes into account when you factor in the 1.6 cropped sensor. Since the sensor is physically smaller than a Full Frame or 1.3 crop sensor, it is essentially taking the image from the center portion of the lens.

    So, you WILL get different focal lengths from 2 identically marked lenses where one is an EF-S lens and the other is an EF lens.
     
  5. chrfr macrumors 603

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    #5
    No you will not.
    Edit: to clarify, if you take an EF 17-40mm and put it on a 60D, you will get the exact same field of view as an EF-S 17-55mm if both are set to 17mm.
     
  6. thatisme, Mar 28, 2011
    Last edited: Mar 28, 2011

    thatisme macrumors 6502

    thatisme

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    #6
    Well, no, you will not. You are not using the FULL image circle on the EF lens on the 60D. Take that same EF 17-40 and put it on a 5D and your image will be composed differently. NOTE: the Lens has not changed it's focal length, but your image HAS changed.

    The common misconception is that your field of view is what the CAMERA records. In actuality, it is what the LENS TRANSMITS to the camera. Since your 1.6 crop camera does not utilize the FULL lens image circle on an EF lens, it has the effect of zooming the transmitted image. SO your 17mm is not 17mm on a crop camera, it is the equivalent of a 27.2mm (28mm) EF-S lens. 17 x 1.6 = 27.2. On a 1D camera, that same 17mm is the equivalent of 22.1mm, where a 5D as a FULL FRAME camera is using the full image circle from the EF lens, so it is a true 17mm.
     
  7. robbieduncan Moderator emeritus

    robbieduncan

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    #7
    Indeed. Exactly what I said above. But an EF 50mm lens has the exact same effective field of view as a 50mm EF-s lens on a crop camera. I have tested this myself using an EF 50mm f/1.4 USM prime and an EF-s 17-85mm IS USM zoom set at 50mm (as there is no EF-s 50mm prime).
     
  8. Full of Win macrumors 68030

    Full of Win

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    #8
    No. Lens focal length is a function of the lens, not the body. I can take a lens with a focal length of 17mm from a full frame camera and put it on a crop camera, and the lens will keep the same focal length of 17 mm. Now, the amount of the imgae circle recorded on the crop camera vs. the full frame camera will be different. However, this has nothing to do with the focal length of the lens.

    In short. LENS FOCAL LENGHT DOES NOT VARY WITH SENSOR SIZE.
     
  9. cupcakes2000, Mar 28, 2011
    Last edited: Mar 28, 2011

    cupcakes2000 macrumors 6502

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    #9
    I think you both just said exactly the same thing, so I'm not sure why Full of Win is arguing?

    If I shoot my 50mm 1.8 II through my 7d I am effectively multiplying the lenses focal length with the cameras crop factor to give the photographs field of view. ie 50x1.6=80.

    So focal length 50mm= field of view 80mm. (On a 1.6 crop)



    Allthough...This statement from thatisme 'So, you WILL get different focal lengths from 2 identically marked lenses where one is an EF-S lens and the other is an EF lens.' is false.

    You will, in fact, get two different Field of Views but the same Focal Length.
     
  10. John.B macrumors 601

    John.B

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    #10
    ^^^^ This.
     
  11. robbieduncan Moderator emeritus

    robbieduncan

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    #11
    Is not true: a 50mm EF lens and a 50mm EF-s lens will have the same focal length and field of view on a crop camera.
     
  12. cupcakes2000, Mar 28, 2011
    Last edited: Mar 28, 2011

    cupcakes2000 macrumors 6502

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    #12

    I don't think that's true. I pretty much know it's not actually.

    Shooting a 50mm on a 5d will produce a focal length of 50mm and a Field of view of 50mm. (50x1+50)

    Shooting a 50mm on a 7d will produce a focal length of of 50mm and a field of view of 80mm. (50x1.6=80)

    Part of the reason these two cameras exist is because one of them (5d) is full frame, awesome pictures for weddings say. Slow fps but that's not what it's for.

    The 7d however is aimed at sports photogs or wildlife for example. Still an awesome picture, but loses some of it (including aperture, and the fact you can't get as smaller dof, and ISO and the fact you can't get the same low light abilities) for a much faster fps. The focal length multiplier will also help so that you can get closer to the picture with the same lens.

    Same with their top two cameras one is the ultimate full frame camera (the 1D-s mkIII), the other is the ultimate crop (1.3) camera (the 1d mkIV).

    If there was no difference they wouldn't do it.

    it's a smaller sensor, so therefore a smaller field of view.

    Why don't you just google it? Or put in a source that proves you right?
     
  13. thatisme, Mar 28, 2011
    Last edited by a moderator: Mar 29, 2011

    thatisme macrumors 6502

    thatisme

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    #13
    Thanks for the correction, and good catch.

    So, for the OP, the difference between EF-sand EF lenses is that EF-S are lighter and cheaper and are tied to 1.6 sensor cameras. EF is more versatile since they work on all EF mount cameras (including EF-S). They can be very cheap or very expensive(and good) when you get into L series lenses.

    There is really no good reason to compare focal length or field of view between the two since construction wise, they are like apples and oranges.

    Where it becomes relevant, is when you have an EF lens, and you own different format cameras ( like I do). my 400mm 2.8 L IS lens is a true 400mm on my 5D mark II, and 520mm on my 1D mark IIn (1.3) and 640mm on my old 20D. I don't really care about the EF-S mount since it only applies to one of the 3 camera bodies.

    This is not correct.


    A EF-s 50 mm lens is 50 mm on a 1.6 camera. A 50mm EF lens on that same camera is similar in image to a 80mm EF-S lens. The reason for the difference comes into play by the amount of the lens the camera is using to record the image and the proximity of the rear element to the camera sensor.
     
  14. cupcakes2000, Mar 28, 2011
    Last edited: Mar 28, 2011

    cupcakes2000 macrumors 6502

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    #14


    I have a Sigma 10-20mm (EF-s equivalent) for my 7d. It's Focal lenth is 10-20mm. It's field of view is 16-32mm.
    If you could fit it on a full frame (which you can't because of the mirror reflex as explained earlier by someone) but if you could,
    it would still have a 10-20mm focal length. However it would have an increased depth of field (over the crop) of 10-20mm.

    I dont even think you can get that wide on a full frame. I mean you can get a 8-15mm fish eye, but you would have a circular picture at the widest end.
     
  15. arogge macrumors 65816

    arogge

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    #15
    A 50 mm lens has the same focal length as any other 50 mm lens. There is no such thing as a "crop camera". There are differences in film sizes, onto which the lens projects an image. An APS-C recording sensor that is listed as 1.6X will cause the projected 35-mm image to have a smaller field-of-view. The other attributes of the lens, including the depth-of-field and focal length, remain unaltered by the size of the recording sensor.

    A Canon 10-22 EF-S lens is only compatible with specific Canon APS-C cameras. This is because of the Short Back Focus attribute of the EF-S lenses. A Sigma DC lens, which does not use Short Back Focus, is intended only for use on APS-C cameras with 1.5X or smaller recording sensors. The Sigma 10-20 lens, like Canon EF-S lenses, projects a smaller image circle than the 35-mm standard. This is why these "digital" lenses aren't compatible with normal 35-mm cameras. Financial cost and weight were the considerations when developing EF-S, Sigma DC, and similar lenses for APS-C cameras. You do have another ultra-wide option if you don't want to use the smaller APS-C lenses. You can buy the Sigma 12-24 lens.
     
  16. flosseR macrumors 6502a

    flosseR

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    #16
    too much confusion and too many beaters around the bush.
    EF-s and EF is the mount type.
    the focal length of the lenses is exactly the same. Canon cannot mount EF-s lenses on EF only bodies but Nikon full frame bodies CAN mount the smaller image circle lenses and vice versa, so there you CAN compare it.

    The 12-24mm sigma will work on both and its FOCAL LENGTH is 12-24mm on BOTH. On the crop sensor you just SEE less of the whole image. It's like on a full frame camera you see the whole image and on a crop body you see only a largish middle part of the image.
    That is the ONLY difference. No focal length changes no nothing.

    It may APPEAR to be closer shot but it is not. You can take your image shot on a 5d with that 12-24mm and crop it by 1.6 and you will have the EXACT same image as if you take the same lens on your 7d and shoot it.


    it's dead simple...
     
  17. HBOC macrumors 68020

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    #17
    here are some good references to get a grasp of the differences. As others have stated, the lens is the same focal length, but on a smaller sensor body (APC), the image is essentially "cropped". Some websites..

    Site #1

    Site #2

    Site #3

    The second site is a video that is nice. 3rd site has good info.
     
  18. robbieduncan Moderator emeritus

    robbieduncan

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    #18
    I didn't say on different cameras. I said different lenses on the same, crop, camera.

    Look. I own a 7D. I own an EF-s 17-85mm IS USM. I own a EF 50mm prime. I know that if I set the zoom to 50mm and take the same shot as with the prime exact same field of view. EF-s lenses are not corrected for the crop in the way you are saying they are.
     
  19. thatisme macrumors 6502

    thatisme

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    #19
    I'll say it again. You are incorrect.

    See this exerpt from the-digital-picture.com: read the underlined section carefully.

    What affect does the FOVCF have on lenses? None - physically. The lenses are the same and retain all of their same physical attributes. But, there are some differences in how these lenses are used that should be mentioned ...
    *
    First, most lenses produce the highest quality image from near the center of their image circles. Distortion, softness (opposite of sharpness), vignetting ... These issues often show up in the outside portion of the image circle. Since the FOVCF DSLRs utilize only the center portion of a Canon EF Lens, they often avoid a lens' weaknesses. I say "Canon EF Lens" because Canon EF-S Lenses are made specifically for the 1.6x FOVCF DSLR bodies (but still require the same FOVCF to be applied as the standard Canon EF Lenses to get the equivalent focal length comparison). EF Lens hoods are designed for full-frame bodies.
     
  20. thatisme macrumors 6502

    thatisme

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    #20
    FOVCF is the technical term for a crop sensor or crop camera. It stands for FIELD OF VIEW CROP FACTOR, whereby the sensor doesn't see the full image projected from a standard 35 mm format lens (EF lens in this case)

    Nikon also created a FULL FRame camera a while back that also had the ability to create a "cropped" image to increase it's rate of capture to achieve results in FPS that were similar to canon's 1D series bodies. Effectively if it captured less pixels per image, it could do so faster.
     
  21. robbieduncan Moderator emeritus

    robbieduncan

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    #21
    This says exactly what I am saying and proves me right, not wrong: the same crop factor is applied to EF-s lenses as EF lenses. So a 50mm EF lens on a crop body produces the same field of view as a 50mm EF-s lens. Thanks for the proof that I am right :)

    Edit to add: if we look at the only EF-s prime, the 60mm f/2.8, (for simplicity) it states "Its angle of view is equivalent to a 96mm lens on a 35mm camera" showing the same 1.6 crop that would would expect for an EF lens is applied.
     
  22. OreoCookie macrumors 68030

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    #22
    robbieduncan is right-on with his explanation, you're making incorrect claims: focal lengths are independent of the size of the sensor, a 50 mm lens will be a 50 mm lens on a medium format body, a full frame analog body or an APS-C-sized dslr. What changes is the field of view, which is an angle. It is this angle which is different on the above-mentioned cameras. The reason why people write something to the effect `a 50 mm lens on a crop body is equivalent to 75~80 mm lens on a full frame body' is that we've gotten used to associating focal lengths on 35 mm bodies to FOVs. Sort of like Americans got used to measuring distances in miles rather than kilometers.
     
  23. thatisme macrumors 6502

    thatisme

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    #23
    which is why I have not made the claim that 200mm on one lens is not equal to 200mm on the other (by actual measurements). What I have claimed is that the EFFECTIVE (perceived) focal length is different, when angle is taken into effect (the size of the sensor in relation to the size of the rear element).

    YOU WILL GET DIFFERENT IMAGES IF YOU USE A 200mm EF Lens on a 7D (APS-C) and a 200mm EF-S lens on that same camera due to the FOVCF. on the EF lens, the 200mm assumes you are using the ENTIRE image circle of the lens, which you are not. You ARE using the ENTIRE image circle on the EF-S lens, which is a True 200mm for that camera. You have to use the ENTIRE image circle to get a true measure of the focal length. when you use only a portion of that image circle, you have to apply the FOVCF to get the EFFECTIVE focal length.

    Your last 2 sentences actually prove my point for me. Everything in today's photography arsenal (at least in DSLR) is based on the old film standard of 35mm image recording space (or sensor size). It is you standard of measure. It has not changed with Digital. This is why we have conversion factors and have to talk of EFFECTIVE focal lengths.
     
  24. davegregory macrumors regular

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    #24
    Robbieduncan is correct. The only reason the EF-S exists is because it's cheaper for Canon to make wide angle lenses with a short focus back (i.e. that the lens is closer to the mirror than EF lenses). It's purely consumer oriented! Lower-end - mid range cameras use the 1.6 FOVCF, making them inexpensive. Canon wants cheaper lenses so they can sell more lenses and cameras. That's it, plain and simple. They are technically identical to any EF lens in every other way but the mount depth.
     
  25. robbieduncan, Mar 29, 2011
    Last edited: Mar 29, 2011

    robbieduncan Moderator emeritus

    robbieduncan

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    #25
    Go and try it and come back...

    Edit to add:

    Here is a great little one page explanation of EF vs EF-s. I quote from it:

    Which, once again, agrees with me.
     
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