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

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

  1. OP here; let me clarify what I was actually trying to determine.

    I shoot an APS-C Canon DSLR and have a Canon EF zoom that tops out at 300mm.

    I had the opportunity to buy a righteously-priced Canon EF-S zoom topping out at 250mm. I wanted to know if the focal length of this lens would effectively be 250mm x a 1.6 crop factor giving me essentially a 400mm lens.

    I posted the fixed 200mm lens example in the OP because it was a cleaner, simpler question to respond to. It would yield the same info I wanted— but with less chance of off-topic zoom lens range/image quality/speed/flare, etc. issues muddying the thread.

    Thanks to all the good info I got here, I learned that the 250 lens would in fact NOT get me any closer to the subject I was shooting. So I thanked the guy selling the EF-S lens, told him I wan’t interested and hung onto a few bucks I didn’t need to spend.

    So hey guys, the next round is on me…
    rodeo_joe|1 and Ken Katz like this.
  2. Thanks. I've had my mind set on trying a 50 year old Scotch whisky that costs a mere £4000 a bottle - cheers!

    Only kidding. But spend the money you've saved on something nice for yourself.
  3. Yes Nikon doesn't stop them from mounting.

    For zoom lenses, they might only vignette on some focal lengths.

    Also, you should be able to put one on a teleconverter, which only uses
    the center of the image, without problems. Well, normally a teleconverter
    wastes much of what the lens can do. (Though many aren't as good near
    the edge as in the center.)

    Some Nikon FX models will store a DX sized image from the FX sensor, but
    I believe you can turn that off and store the whole image.
  4. Yes. And your 300mm lens will give the effective focal length of 480mm.

    It is a funny system that we use the 24x36mm frame to judge focal lengths, but as long as
    we do, you have to consider the crop factor.

    Though an EF lens might have better image quality to the edge of the DX image area,
    than it does for FX image area.
  5. It's not funny or strange to use something everybody is familiar with as a reference.
    What is strange, and causes a lot of confusion, is talk about equivalent focal lengths. People will believe that the focal length itself will vary with sensor size.
    We really should find a different way to express the effect of cropping an imaginary reference image to something smaller. Something like, i don't know, crop factor.
    Last edited: May 1, 2022
  6. I agree, "effectove focal length" is a confusing term: it's only the same in one respect, not in others. However, spelling the whole thing out is cumbersome, something like "a 300mm lens on a 1.6 crop factor sensor will give you the same angle of view as a 480mm lens on a FF camera," or "a 300mm lens on a 1.6 crop factor sensor will have the same effect as a 480mm lens on a FF camera in terms of the recorded subject size compared to the frame size".
  7. But not everybody is familiar with it, just 35mm photographers.

    Now, there are a lot of them, but not everybody.

    I presume that there are some medium format photographers who never,
    or maybe only rarely, use 35mm cameras. They would be familiar
    with different numbers.

    Funny thing. I have an eBay saved search for 127 film, which often
    enough comes up with a medium format camera and 127 mm lens.

    I have never used a camera with a 127mm lens (not counting zoom
    lenses that can go to 127mm.)

    But okay, if you consider a 50mm lens as the normal, then it isn't so hard
    to consider ratios. However, the diagonal of a 24x36 frame is closer
    to 43mm, so 50mm should not be the default lens.

    Since 50 is half 100, I can quickly figure out that 135mm is 2.7*50,
    and 35mm is 0.7*50, but it would make slightly more sense if 100
    was the reference.

    But many digital camera uses never used a 35mm film camera, and
    likely don't find it such as useful reference.
  8. Considering that Full Frame is also 'a thing' in the digital world, many photographers need not be familiar with film cameras to be familiar with 35 mm format as a reference.

    Yes, MF and LF photographers also have different references, but still are familiar with 35 mm format too. Shows how this 'equivalent focal length' thing is not needed. Those MF and LF photographers (based on a sample of one, yes) do not calculate equivalent focal lengths using 35 mm format's 50 mm normal lens when selecting lenses to use. You just know your lenses and formats (including their aspect ratios).
    But when using different digital options behind those LF and MF cameras, the crop has to be considered.
  9. Having grown up in the 35mm film world and experienced the impact of focal length to field of view, DOF, and perspective from that standard for decades, it is still how I approach lens section for my 2x crop factor M43 cameras. When using a 12mm focal length, I am thinking 24mm FF in terms of how I approach an image, even though I have not picked up an FF camera for over 2 years. I still use 35mm as the standard of how wide is wide, and how long is long, because it is a standard I am most familiar with over decades of use.

    Perhaps today folks newly introduced to interchangeable lens cameras will think that 26mm (FF Equivalent) is a normal view, and anything wider is a wide angle lens and anything longer is a telephoto, since that is how Apple defines it on their phones.
  10. It almost doesn't matter whether people have had experience with 35mm/FF cameras. This has become the standard for comparing AOV across sensor sizes. You can use it, for example, to compare FLs for MFT and APS-C, albeit with an extra step.
  11. It does seem that Apple gives the 35mm equivalent without even saying that they are doing it.

    And yes it is a 26mm lens, but they do call it wide angle. Then there is also a extra-wide and telephoto lens.

    Samsung gives the angle of view in degrees, so no confusion.
  12. Would that be horizontal (long-side) AoV, vertical (short-side) AoV, or the lunatic diagonal AoV that lens makers are fond of quoting?
  13. Still confused despite all these detailed replies. Let's back to the OP's lighthouse example. Say I have a 200mm EF Canon lens and I place it on both a full frame and then a crop camera and take a picture of the lighthouse. My understanding is that the lighthouse itself will be the same size (not magnified on the crop camera) but the top/bottom and sides of pics taken with the crop camera will simply be "trimmed". If this is correct, why do some folks say they don't need a telephoto lens since the pics taken with say a 100mm EF lens on a crop camera will take images equivalent to a 160mm lens if nothing is magnified?

    Perhaps I need to reread the entire thread.
  14. If you put a 100mm lens on a Canon crop body camera and compare the image to FF camera with a 160mm lens (or a zoom lens set at around 160mm), both cameras will provide the same field of view.

    "Perhaps I need to reread the entire thread"

    Sounds like a wise decision.
  15. Leaving aside compact point'n'shoots and phone cameras, where the focal length(s) stated are usually a tissue of lies.

    The focal length engraved on the lens is the focal length. So if the lettering around the lens says "200 mm" then it's a 200 mm lens whatever the size of camera sensor.

    All that happens between fixing that same lens to a DX or Full-frame camera is that you get a smaller or bigger crop of the image. The image size stays the same - and you're just capturing a smaller or larger section of it.

    This might make it clearer. Here's the full image taken with a 135 mm lens:

    And here's a crop of about 1/20th the width of the frame -
    Same lens, same shot. It's just been cropped to an equivalent view of what you'd get with a 2,700 mm lens. But I didn't use a 2,700 mm lens, and I don't think one is even made. I just cropped the 135mm lens image. Nothing else changed except the amount of image used.

    So when a lens or camera maker states a full-frame or 35mm equivalent focal length, it's as meaningless as that.

    The lens focal length stays the same, and it's just the amount of image that gets captured that changes.
    Perhaps if I draw a little crop-box on the first picture it'll clarify things.
  17. Ken Katz,
    Thanks for replying. An additional question regarding your previous reply to my post:

    "If you put a 100mm lens on a Canon crop body camera and compare the image to FF camera with a 160mm lens (or a zoom lens set at around 160mm), both cameras will provide the same field of view."

    So if I put the 100mm EF lens on a Canon FF camera and photographed the lighthouse and then put the same 100mm (not 160mm lens as you mentioned) EF lens on a Canon crop camera and photographed the same lighthouse, I'm thinking that the size of the lighthouse in the center of the frame would be the same from both camera/lens combinations but the image taken with the crop body would simply "trim out" the bottom and sides of the image.

    Sorry for not understanding this and thanks again for your help.
  18. Friskybongo
    I think I understand your question. If you put a 100mm lens in front of a (i) half frame camera, (ii) full frame 35mm camera, and (iii) medium format camera, and loaded all with Tri-x film, the size of that lighthouse rendered on all 3 pieces of film will be the exact same size. If you print all 3 images so that the larger FF and MF negatives are cropped to provide the same view as the half frame camera, all 3 prints would look identical.

    With current digital equipment though, different sensors can have different pixel densities. A 100mm lens on a 45mp FF Canon R5 would need to be cropped in post to around 17mp in order to render the same field of view as a Canon APSC camera. Put that same lens on a 32mp Canon R7 and resulting image would have almost double the pixels of the cropped R5 image.
  19. JDMvW - thanks for the link to Lens Focal Length Conversions.

    Ken Katz - thanks again for your explanations.

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