EF vs. EF-S Lens On APS-C DSLR

Discussion in 'Beginner Questions' started by Charles Hamilton, Apr 22, 2022.

  1. Say I have two Canon 200mm lenses-- one EF and one EF-S-- and mount them on two identical model Canon APS-C cameras to shoot a distant light house.

    Because of the crop factor, the subject shot with the EF-S lens will appear closer up. Yes? No?
  2. No. The angle of view for a given focal length is determined by the sensor size. Whether the lens is EF or EF-S has nothing to do with it, assuming that they are the same focal length. EF-S lenses differ from EF lenses in two respects, neither of which is relevant to this: a shorter flange distance (because APS-C mirrors are smaller), and narrower glass (because you don't need the larger image circle that extends beyond the sensor.)

    What generates endless debate and confusion is something different. Suppose that you put a 200mm EF lens on two cameras, one APS-C and one full frame, and take a photo of the same subject at the same distance. The magnification--the size of the projected image relative to the size of the subject--is exactly the same; it's determined solely by the distance and focal length. if you crop the FF image to the size of the APS-C image, the subject would fill the same portion of the APS-C image and the cropped FF image. However, because the frame is smaller on an APS-C camera, if you are not cropping, the subject will fill a larger portion of the frame on the APS-C sensor. This is another way of saying that the angle of view is smaller. That's what people mean when they say that a crop sensor camera has more "reach" or that one gets a similar view with a shorter focal length.
  3. I'll leave this to the lens experts but as far as I know a subject shot with either an EF or EF-S lens on an APS-C camera will have the same focal length of 200mm (taking the sensor crop factor into account) and will therefore appear equally close. The main difference is the that the optical 'field of view' on an EF-S lens is designed for an APS-C camera and will give a wider 'field of view' (say, 100%) on an APS-C camera than an EF lens (62% field of view relative to an equivalent EF-S lens) . So on an APC-c camera, you'd get more in the frame using an EF-S lens than you would using an EF-lens. Whatever is in the frame would appear equally close.
  4. 200mm is 200mm is 200mm. Whether you measure it with a 300mm rule, with a 1 metre rule or with a 10 metre measuring tape.
    The first part of the first sentence is correct, but would you care to reconsider the rest of it Mike?
    Last edited: Apr 22, 2022
  5. This is incorrect. If you put an EF-S 200mm lens on an APS-C camera, you will get exactly the same image as if you put an EF 200mm lens on the camera. I think in using the term "field of view" you may be confusing the size of the image circle captured by the lens with angle of view.

    Because APS-C cameras have a smaller sensor, they don't need as large an image circle, and EF-S lenses, which are designed to cover only that smaller circle, can be smaller (in diameter). But the image cast on this smaller sensor by an EF lens is exactly the same. All that happens is that the APS-C sensor will not see some of the larger image circle created by the EF lens.

    The answer to the OP's question is that the choice between an EF or an EF-S lens has no effect whatever on the image captured by an APS-C camera. The only effect of using an EF lens is that you are carrying a bigger, heavier lens than you need to, all other things being equal.
    NetR, mikemorrell and Jochen like this.
  6. And because they can be smaller , EF-S lenses may not only be lighter, but also may be cheaper.

    There are non-Canon APS-C lenses that will vignette on full-frame cameras even though they, unlike the Canon ones, will mount:
    Sigma 10-20mm APS-C lens on full-frame Canon 5D
    Note that such vignetting will show up on the sensor image,, but may not be seen through the view finder​
  7. So...if I'm understanding.. There would be no difference in how "close" the lighthouse appears in either photo and the same distance of terrain on either side of it-- say 100 yards out each way, though there might be differences in image quality.

    In other words, in a quick, superficial look at the two photos, the subjects would appear pretty much the same-- image quality not withstanding.
  8. In fact, I'd challenge anyone to be able to do better than 50/50 in guessing which was which, unless one of the lenses was known to be an absolute dog.

    Even lenses with distinctive signatures are not easy to identify from real world photos, two short teles will be almost impossible to separate...
  9. Not just superficially. If the two lenses were perfectly accurate in terms of focal length--not generally the case--they would be identical other than image quality. This is not an approximation.

    To put it differently, if the two lenses were exactly the same focal length, then any differences in the images would be a result of something other than the EF vs. EF-S construction. That difference is simply irrelevant to the angle of view (hence "reach) on an APS-C camera.

    The simple answer to your original quesiton is "no".
  10. Thanks all-- I've got it now!
  11. James G. Dainis

    James G. Dainis Moderator

    So if an 8x10 inch photo were made from each the lighthouse would be the same size on each 8x10 photo?
  12. Yes. The distinction between EF EF-S lenses is completely irrelevant to this question. The size of an image projected on the sensor is a function of focal length and distance to the subject. Nothing else. Using different lenses of the same focal length (if they really are the same focal length) will not change this, and EF-S 200m lens has the same focal length as an EF 200mm lens. It's just trigonometry.

    Sensor size, on the other hand, does matter. It doesn't affect the dimensions of the projected image, which are entirely a function of focal length and distance. However, changing sensor size does change the relative size of the projected image with respect to the frame--the smaller the sensor size, the larger the proportion of the sensor filled by a projected image of a given size. This was not the OP's question, and is exactly the same effect regardless of whether one uses an EF-S or an EF lens, but it is a source of considerable confusion when people talk about sensors of different sizes. It's why crop sensor cameras have greater "reach" at a given focal length. This is complicated further by issues of pixel density, but let's not stray to far from the OP.
  13. 1/f=1/v + 1/u
    And m=v/u
    Where f = lens focal length, v = lens (rear node) to image distance, u = lens (front node) to subject distance and m = image magnification.

    Obviously f, v and u must be expressed in the same units.

    Those two formulae tell you all you need to know about conjugate-focii and image size. They take no account of format size or final print size, nor do they need to.
  14. James G. Dainis

    James G. Dainis Moderator

    I thought the OP's question was referring to a projected image of the sensor capture. With a 300mm lens on an 8x10 view camera a photo capture of a house may show the entire house with six windows, each one of which is 36mm on the negative. With the 300 mm lens on an SLR there would only be one window on the film frame and it would be 36mm high. Ergo there is no enlargement because of the different film sizes (or sensor) used, but there is a big difference in the photo produced. .

    I thought that was what the OP was asking about, if there would be a difference in a same size photo not in the sensor capture.
  15. Well, maybe, but their actual wording asked about two different 200mm lenses mounted on identical DX cameras.
    In which case there would be only an insignificant to zero difference, no matter how the images were printed or viewed.

    Once you start altering the field-of-view by changing the format size, then it's an entirely different question.
    Last edited: Apr 28, 2022
    NetR likes this.
  16. The OP asked whether switching from an EF-S to an EF 200 mm lens on an APS-C camera would make a difference. In their question, both the focal length and the sensor size are constant. All that changes is the lens construction (but not the focal length).

    The answer to the OP's question is a simple "no". It makes no difference whatever whether one uses an EF or an EF-S lens on their camera, provided that the focal length is actually the same.
  17. Dustin McAmera

    Dustin McAmera Yorkshire

    In principle, I suppose, not having to cover the periphery of the full-frame image might allow Canon to do an even better job in the centre with an APS-C lens; but I would expect they'd settle for the easy win of the lens being smaller, lighter and cheaper.
    On a full-frame camera body, there's a big difference; the EF-S lens presumably doesn't mount at all. If it does, the picture doesn't go all the way to the edge of the frame. So the APS-C camera user wondering which lens to buy just needs to think 'How likely am I to get a full-frame camera in the next few years?'.
  18. EF-S lenses can't be mounted on a full frame body. The flang distance is too short.

    In the past, Canon devoted a lot more of it's lens budget to EF lenses, so there were far more choices. Even when I shot only APS-C, there were a few times I opted for an EF lens.
  19. Dustin McAmera

    Dustin McAmera Yorkshire

    I didn't suppose they could be mounted - it would be odd to allow it when they won't cover. I only have an APS-C mirrorless (and so far only one full-frame EF lens); but I understood the same adapter will do for EF-S and EF lenses. Is that wrong - would I need another adapter for EF-S lenses?
  20. "but I understood the same adapter will do for EF-S and EF lenses"

    Assuming you are mounting an EF or EF-S lens on a Canon "M" mirrorless, the answer is yes.


    "EF-S lenses can't be mounted on a full frame body. The flang distance is too short"

    Both EF and EF-S have the same 44mm flange focal distance (lens mount to sensor), but some EF-S lenses may have a protruding rear element which may interfere with the mirror operation of an FF camera, so Canon decided that those lenses could not mount on FF cameras (or my ancient Canon D60). I believe only Canon had such restrictions with their APS-C lenses, while you could mount a Nikon APS-C lens on a FF camera and live with the vignetting.

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