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

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

  1. Well...
    Almost everyone was using the same format, no matter what brand, so what would there have been to worry about?
    Some, however, used multiple formats, and they too needed to learn what focal length on what format was good for.
  2. Yes. I think the confusion stems from two different metrics, both of which are relevant:

    1. The physical size of the image cast by a lens of any given focal length. Assuming that the sensor is large enough that the image fits, that size is depends only on the focal length of the lens, not the size of the sensor you put behind it.

    2. The physical size of the image cast by the lens relative to the frame size. Sensor size does affect this because a smaller sensor has a narrower angle of view and hence a smaller frame size. An image that "fills the frame" on an APS-C camera will not fill the frame on a full-frame camera.

    The next logical question is "why would you care about #2 if cropping the FF image gets you the same image you would have from the crop-sensor camera?" The answer is in Ken's post: pixel density. While there are exceptions, in general, smaller sensors cram more pixels into a given area; that is, they have a higher pixel density. In that case, the image from the crop sensor camera will have more detail than the cropped image from the FF camera because the crop sensor is placing more pixels on the image of the subject. This may not matter if you are just displaying on a screen or printing small, but it can matter in some cases.

    This is why I almost always use a crop sensor camera (an old 7D) for chasing bugs rather than my much higher quality FF camera (5D IV). I try to shoot very close to maximum magnification, so the image size on the sensor is the same regardless, but the 7D gives me a lot more pixels.

    This is what people mean when they say that crop sensor cameras have "more reach".
  3. Before digital, or close enough to before, there were APS SLRs that could use the same lenses as 35mm.

    But they might not have been popular enough to make a big deal out of the conversion factor.

    I don't remember half frame cameras with interchangeable lenses, at least not using the same lens mount.

    For cameras with a non-removable zoom lens, most people just zoom and not think about focal length.

    As well as I know the history, before 35mm still cameras, there were 35mm movie cameras with
    (half frame sized) 18x24mm image and 25mm lenses. When 35mm still cameras came along,
    someone doubled that to 50mm, resulting in the popular 50mm lens.

    Do (or did) movie camera uses ever use 35mm (still camera) equivalent?
    For 16mm or 8mm movie cameras?
  4. But high megapixel full-frame (24x36mm) sensors are now turning that on its head. For Example: The 60 megapixel FF sensor of a Sony a7r4 has a higher pixel-density than the fairly common 24 Mp APS-C sensors - i.e. 26 megapixels over a 16x24mm frame area.

    Yes there's a cost penalty versus an APS-C camera, but effectively you have two cameras in one. Full-frame for ultimate IQ and when a shallow depth-of-field is wanted, and an APS frame size when you want more 'reach' and more D-o-F.
  5. As far as I know, Canon full-frame cameras won't mount EF-S lenses.

    Nikon models like the D850 will mount DX lenses, and with the right option set,
    crop a DX sized image and store that. Two cameras in one, without extra work.

    I believe you can also set DX mode with an FX lens, or FX mode with DX lens,
    if you happen to want to do that.

    (As far as I know, DX zooms will fill an FX frame at some zoom settings.)
  6. True, although only for a few camera pairs. For example, it's not true of the Canon R5 and R7. For this reason, I often try to persuade people to think about this in terms of pixel density rather than sensor size, but that's unfortunately more complicated.

    That is correct. EF-S lenses are constructed for a shorter flange distance.
  7. A Canon R7 has the pixel density that would require a FF sensor of 85 Mp to match. That plus the cost difference ($1,500 vs $3,900) make it a more practical option for the bird/wildlife photographer on a budget. Fuji's anticipated 40MP camera would need a 90mp FF to match up in terms of reach. Your run of the mill m43 camera has a pixel density equivalent to 80Mp FF and the Panny Gh6 has the pixel density of a 100MP FF camera. That said, folk who want to bring back the highest quality images of things that are far away can always buy (and carry) the needed optics to do the job. The Canon RF 1200mm F8 L is only $20k and remarkably, only weighs 7.4 lb!
  8. Not so. All this "more reach" is about is angle of view.
    People want long lenses to be able to isolate a part of the scene. A crop adds to what increasing focal lengths achieve. More reach.
    That you may get as many pixels on some crop sensors as on some full frame sensors is something else. And mind you: more pixels on a crop sensor may sound nice. But it only is nice if the lens resolves fine enough detail, and noise levels remain acceptable.
  9. Nothing you wrote actual contradicts what I wrote.

    Take a hypothetical pair of sensors with identical pixel pitches, one crop and one FF. Take the same shot with the same lens from the same location. Crop the latter to the dimensions of the crop. How are the images different? Not at all. You achieve the identical AOV in the completed image, just by different methods.

    So why do wildlife photographers often prefer to use crop sensor cameras? Depends on the circumstance, but one reason is often pixel pitch.
  10. All else equal, the larger sensor will be more sensitive, as it has more area to collect light.

    But sensor technology evolves, so all might not be equal.

    You need a longer focal length lens to get the same field of view with a larger sensor.

    The same f/stop value gives you the same amount of light per sensor area,
    but for a longer lens, you need a larger real, physical lens diameter.

    The lens is now longer, larger around, and a lot heavier.
    It is harder to hold and to move around.
  11. No. It is because of the tighter framing without having to use a longer lens to achieve that. Reach.
  12. The best and most expensive optics in the world are irrelevant if the block of air between camera and subject is polluted, misty, or contains schlieren imhomogenities (turbulence, in short). Depending where you live, perfect 'seeing' may only exist during daylight hours for a few days per month, and then only around dawn or late evening.

    In general: Less distance=less air=better IQ.
    Therefore getting closer is almost always better than fitting a longer lens or using a smaller sensor.
    It's not just the pixel density. Depth-of-field varies approximately as the inverse square of focal length.

    This is the setup from my D-o-F spreadsheet, keeping the aperture @ f/4 and doubling the focal length each row from 100mm:

    And the resulting depth-of-field, assuming the same final viewing size:

    So using a shorter focal length, proportional to the crop or sensor size, gets you far more depth-of-field for a given aperture; as well as allowing a smaller, lighter and cheaper lens.

    It really doesn't matter if you change camera or crop from a larger sensor. As long as the pixel size is small compared with the circle-of-confusion chosen for the final 'print' size.
    Last edited: Aug 13, 2022
  13. They don't allow it because some of the EF-S lenses protrude into the mirror box and the FF has larger mirror that could interfere. Nikon allows you to mount DX lenses on FX body and you can either accept the vignetting or it would automatically crop for you.
  14. William Michael

    William Michael Moderator Staff Member

    Just on the topic of - mounting EF-S and EF Lenses on Canon DSLR Bodies:

    When discussing what lenses mount to what bodies, I think it is important is to understand this concerns the EF-S and EF bayonet mounts.

    Hence importantly differentiating that these are terms for Bayonet Mount Nomenclature and that in other situations, the terms 'EF-S' and 'EF' are often casually used to describe various lens's Image Circle Coverage - i.e. (EF-S) have an APS-C Format Image Coverage; and that lenses (EF) have a 135 Format Image Coverage.

    I think that this casual interchange of terminology "EF-S" and "EF" to describe the Image Circle Coverage can lead to confusion.

    Additionally, for interest's sake:

    - No Canon EF-S Mount Lens will mount on any Canon 'full frame' Format DSLR, (neither will any EF-S lens mount on any Canon APS-H Format DSLR).
    The underlying design feature driving probably is that Canon EF-S lenses have a protruding rear element which might hit the mirror; certainly every EF-S lens I have tested does: but the fact is the, the Bayonet Mounts of the EOS range of 'full frame' cameras only allow the EF Lens Mount, because the bayonet mounts - "EF-S and "EF" are different.

    - The inverse statement to the above is incorrect: i.e. "all Canon EF-S Lenses will mount on all Canon APS-C DSLR bodies" is incorrect.
    Canon developed (many years ago) a few APS-C DSLR bodies which only have an EF Bayonet Mount.

    - It is correct that all APS-C Bodies including and since the EOS 20D, have a dual bayonet mount and will mount both the Canon EF-S and EF Lenses

    - There are Canon (and also third party) accessories, (such as Extension Tubes, Tele-extenders and the like) which also will (should) describe in their specification, whether, on the female end, they accept only EF or both EF and EF-S Lenses

    - There are third party manufactures which make lenses with an APS-C, Image Circle, as far as I have researched each of these lens's release, all made to fit Canon, are supplied with Canon EF Bayonet Mounts, hence these lenses can be mounted and work on canon 'full frame' cameras - albeit with an optical vignette.

  15. There were also, before the DSLRs, actual APS film SLRs.

    I am not sure if they use EF, EF-S, or some other mount.

    (Which mostly matters only if you have some APS film.)
    William Michael likes this.
  16. William Michael

    William Michael Moderator Staff Member

    That's a blast from the past - odd cameras -

    From memory - The EOS IX and EOS IX Lite were the only Canon SLR Advanced Photo System (APS) Format cameras: released circa. 1995.

    I reckon it is very safe to assume both these cameras would have accepted only EF mount Lenses, because,
    1. 1995 was before the EF-S Mount was developed, and
    2. both cameras were part of the EOS Series of Cameras - by definition all in the EOS Series of Cameras must accept the EF Mount.

    Last edited: Sep 16, 2022
  17. Yes, it seems to be EF:

    EOS IX - Canon Camera Museum
    Ken Katz likes this.

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