Image circle and mirror box protrusion of EF-S lenses

Discussion in 'Canon EOS' started by mark u, Aug 18, 2005.

  1. Does anyone KNOW what the image circle is for each of the EF-S lenses
    currently available? Likewise, the maximum distance between the lens
    mount flange and the rear protrusion of the lens (this will vary with
    zoom/focus distance)?

    It occurs to me that Canon may have designed these lenses so they
    provide adequate coverage on a 1.3 crop sensor, and that a double
    motion mirror (as originally seen on the first Digital Rebel) might
    allow clearance of the rear element. The more complicated mirror
    movement would act as a limitation on maximum frame rate achieveable.
    However, it could allow a 20D successor to remain EF-S compatible
    while having a 1.3 crop sensor. It would also offer some comfort to
    those investing in EF-S glass who feel that they might consider a 1.3
    crop in the future if it is offered (as seems likely from Canon's
    statements about the future of 1.3 crop - it will disappear from the 1
    series, but not completely from the EOS line).
     
  2. If that were so, why wouldn't Canon incliude that in their specs for the EF-S lenses. Don't they clearly state that they are for APS-C sensors?
     
  3. You may be right so far as the non USM 18-55 kit lens is concerned, but close examination of the EF lens chart shows that as the only EF-S lens with a red asterisk:

    http://consumer.usa.canon.com/app/pdf/lens/EFLensChart.pdf

    I think I smell a rat!
     
  4. Short answer, it differs from model of lens and focal lenght.
    Longer answer, (allthough i can not find my notes with the exact measurements) in my experience the 10-22 EF-S covers full frame down to about 15-16 mm and 1.3 crop to around 13-14 mm.
    [​IMG]
    Full frame image from EF-S 10-22 at 14 mm, click on image for full size scan (almost 4 Mbyte). Markings represents 1.3 and 1.6 crop.
    [​IMG]
    Full frame image (EOS 30 slide) from EF-S 10-22 at 12 mm.
    The full frame mirror of my old EOS 30 goes clear of the rear lens element down to about 12 mm, my guess from this is that the lens should be perfectly usable a 1.3 crop body down to the limits of image circle coverage. I should think that the mirror is less of a problem on the 17-85 EF-S (or the 18-55 EF-S for that matter), but i have no information on the image circle of those lenses.
    See also my description on Adapting the Canon EF-S 10-22/3.5-4.5 for use on a Canon EOS 10D
    /Daniel
    Ps. I take no responsibillity for any possible damage caused by this information.
     
  5. jbq

    jbq

    With a fixed pellicle mirror the issue of clearing the mirror disappears. With the 1.3x crop seemingly going toward high-speed shooting and high-ISO noise being under control, I wouldn't be surprised to see a future mark of the 1D use a pellicle mirror.
     
  6. "However, it could allow a 20D successor to remain EF-S compatible while having a 1.3 crop sensor. It would also offer some comfort to those investing in EF-S glass who feel that they might consider a 1.3 crop in the future if it is offered (as seems likely from Canon's statements about the future of 1.3 crop - it will disappear from the 1 series, but not completely from the EOS line)."

    I've read that Canon plans to consolidate the 1D and 1Ds to a single product in the future (perhaps even within the next year?), but I've not read anything about the 1.3x crop surviving this consolidation. In fact, the interview of Canon's CEO in January that I read suggests just the opposite: that Canon plans to eliminate the 1.3x crop.

    Canon never represented the EF-S mount as ever being compatible with anything other than 1.6x bodies beginning with the dRebel. No doubt there will be those who may one day regret their investment in these lenses, probably because the migration to full frame dSLRs happened more quickly than they expected. (These things always seem to have happened more quickly in retrospect, don't they?) But none of those regrets should be based on any illusions of promises broken by the manufacturer.
     
  7. Daniel - thanks for your graphic(!) contribution on the 10-22.
     
  8. Daniel, in you excellent examples on converting the 10-22 lens do you think the that the limiting image circle is in fact not helped by the filter that you have to fit to limit the min focal length?
     
  9. You are of course right, the filter is adding quite a bit of the vingeting at these focal lenghts (as the lens is not constructed for full frame usage). Judging from the viewfinder you might be able to use one millimetre shorter focal lenghts without filter, sorry i did not think of this when I made my test shots.

    /Daniel
     
  10. Jon - maybe you missed this interview with executives from Canon Spain:

    http://www.quesabesde.com/noticias/1_1717
     
  11. ?No hablo Espa�ol, Se�or!
     
  12. (OK, no high-order-bit ASCII characters ...)

    No hablo Espanol, Senor! (Just doesn't look right this way...)
     
  13. My understanding was that canon plans to move to just one pro DSLR, and that it will be
    FF.

    The 1Ds mkII would be fine for most with a higher frame rate.

    If the 5D proves to be true, FF could very well be affordable for serious amateurs within
    about 2 years and then who needs ef-s lenses except entry-level users anyway?

    You're right though, there may be an intermediate step of a 1.3 crop 20D replacement
    before that glorious day dawns :)
     

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