EF and EF-S

Discussion in 'Beyond the Basics' started by wiredhernandez, Dec 2, 2009.

  1. wiredhernandez

    wiredhernandez TPF Noob!

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    Hello all, I have been doing a bit of reading and just want to clarify I understand before making my next lens purchase. I am shooting with a 40D which has the 1.6 crop factor. I am looking to verify that comparing any other EF-S lens that I shoot at say 18-20mm for parties etc to be close up with no distortion on the edges is the same reference as would be used on an EF .. They all refer to 35mm for reference.. So if I shoot at 18mm setting with my Tokina I am actually shooting 29mm but if I get an EF 20mm lens I would be just above that at 32mm ... I just want to make sure that the reference is always the same. I am considering purchase of a cannon 20-35mm 2.8 as used the price is good for L glass. When all said and done I am thinking of the following final setup for my shooting needs with a crop sensor. I know where I am and think the following practical budget wise for my hobby. Thanks!

    Tokina 12-24 (current)
    Canon 20-35L 2.8 or Cannon 17-40L f.4
    Canon 70-200L f4
     
  2. Village Idiot

    Village Idiot No longer a newbie, moving up!

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    Correct. The apparent field of view is the same no matter what mount you use. It's based on the focal length of the lens and the crop size of the sensor.

    The focal length of the lens is based physically on the lens properties and not what camera it's on. The field of view that you get with a certain lens is based on the format of a camera. A 50mm lens will always be a 50mm focal length regardless of if it's on a large format, medium format, 35mm, or crop sensor; what changes is the FOV.
     
  3. Derrel

    Derrel Mr. Rain Cloud

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    YES, focal length is ALWAYS the same between EF-S and EF Canon lenses. Focal length is always stated on the lens barrel,and a lens's actual focal length is always the same on every body format it is mounted onto.

    An EF-S Canon lens projects a slightly reduced image circle; the Canon 60mm EF-S macro lens is the same focal length as a Nikon 60mm macro lens, and the same as a 28-70mm zoom set to deliver a 60mm focal length.

    SO, when you multiply the ACTUAL focal length by 1.6x for the Field Of View narrowing, you always use the length(s) provided on the EF-S lens, such as 10-22. You would multiply 10 x 1.6 FOV and 22 x 1.6 FOV to get the "effective" field of view *as if* the lens were being used on a 35mm camera or a Full-Frame Canon body. You would use the same mathematical approach on a full-frame capable Canon lens like the 24mm f/1.4-L, multiplying its actual focal length of 24mm x 1.6 FOV when using it on a 40D.
     
  4. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    The crop factor is just a reference, the focal length listed on the lens, is always the focal length. And yes, it's always a reference back to 35mm film.

    So 20mm should always look the same on your camera, no matter who made the lens or what designation (EF vs EF-S) it has. (of course, listed focal lengths aren't always spot on accurate).
    If you shoot at 18mm, you are actually shooting at 18mm. A 20mm lens would be just about that, but you'd be shooting at 20mm.

    The comparison/reference of the crop factor is meant for comparing one camera to another, not lenses.
    So if you picked up a 35mm film camera (or full frame digital), then a given focal length would look/feel different that it does on your camera. It's not a change perpetrated by the lens, but by the area of the image circle that the camera sees.

    Long story short....unless you are used to shooting with film or full frame, don't give a second thought to the crop factor.

    As for the 20-35mm F2.8 L...I had to look that one up. It's been out of circulation for a long time, and there is probably a reason for it. For one, it doesn't have USM focusing, which practically every modern L lens has (and most non L lenses too). I'd venture a guess that the quality isn't great either (compared to other L lenses)...or else it would still be somewhat popular.
    It was probably replaced by the 16-35mm F2.8 L, which was recently replaced with the 16-35mm F2.8 L II. There is also the 17-40mm F4 L, which is one of the most economical L lenses.
     
  5. wiredhernandez

    wiredhernandez TPF Noob!

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    Thanks for the confirmation and replies. I have read many raving reviews on the 20-35. Definitely an ancient lens as produced in the 90s. Really chewing on which to purchase now.....
     
  6. flightless_beaker

    flightless_beaker TPF Noob!

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    I love shooting crop sensors. Keeps my math skills sharp :) And I thought I never had to use math again as a photographer :(
     
  7. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Why would you have to do any more math when shooting with a crop sensor vs a full frame of film?
     
  8. wiredhernandez

    wiredhernandez TPF Noob!

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    Appears if you dont mind used there are some others out there... Apparently someone liked the 20-35 and bought it...Might keep an eye as I would like the 2.8... Too much thought sometimes...
     

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