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When Adapting an EF-s Lens to my R6 it automatically switches to only capturing APS-C Format on it's sensor. Is there any possibility to override this and capture the full sensor? Even though it might not be all covered by the lens or have heavy vignetting?

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  • I wonder how the R6 detects that a lens is an EF-S one. Is there any kind of mechanical switch sensing the different mount geometry (e.g. the protruding ring of the EF-S lens) in the adapter, or is it done purely by communication between body and lens? My old EOS 620 film body had a micro-switch in the mount for activating the lens communication (which e.g. M42 adapters didn't engage). Aug 5 at 13:28
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    its electronic communicating to the EOS computer
    – cmason
    Aug 5 at 16:09
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According to the Advanced Users Guide for the R6, page 129, "With EF-S lenses, [1.6x (crop)] is set automatically, and no other option is available."

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  • This is what my experience currently is, correct. But maybe there is a hack to present the EF-s lens is an EF lens or whatever, just like taping over the middle contact of a Magsafe cable will still provide power but not allow the laptop to charge, due to failed communication, thus prolonging battery life on mostly plugged in MacBooks...
    – bardiir
    Aug 5 at 0:22
  • Is the limitation due to the adapter cutting off (vignetting) the corners, using cropping as a way to avoid "peeking through a hole"? Aug 5 at 0:29
  • @DrMoishePippik The limitation is due to the smaller image circle projected by EF-S lenses. In some cases as an EF-S lens is zoomed to longer focal lengths the size of the image circle does increase, but apparently Canon has decided giving the option to use the full sensor with an EF-S lens would be too confusing to many users and cause them to complain that there is something wrong when the image circle doesn't fully cover the full sensor. Either that or the image quality is lower than Canon's standards on the edges of the enlarged image circle.
    – Michael C
    Aug 5 at 18:43
  • @DrMoishePippik The same adapter does not cut off anything when used with EF lenses that project a FF sized image circle.
    – Michael C
    Aug 5 at 18:47
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    @BobMacaroniMcStevens What you are saying it that you can make quality FF lenses for half the weight and half the budget... And Tokina, Tamron and Sigma have not found that out yet?
    – xenoid
    Aug 6 at 8:09
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Not with Canon's own adapter. Perhaps with a third party adapter?

An alternate way is if you covered all the electrical contacts on the lens, so the camera doesn't know what is attached. You'd need to focus manually, and you're stuck at wide open. You also need to setup the camera to allow it to take pictures without a lens attached.

But as mentioned in another answer, the lens isn’t designed for this usage, so you will not get a good image. For a zoom lens you may be able to fill the frame on the narrow end, but most probably it will be extremely soft and heavily vignetted in the corners.

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    Even if you were to fool the camera into shooting full frame, the EF-S lens would not project a full frame, corner to corner image. Some EF-S lenses might reach the corners, but image quality will be poor. Aug 5 at 19:23
  • @MikeSowsun true. But I didn’t address this as it’s already mentioned in another answer. But I updated it slightly ;)
    – Pete
    Aug 5 at 19:52
  • The original idea was more like using a 10-18mm EFs instead of the way more expensive EF Ultrawide and cropping to a square instead of a rectangle then. But overall it's much more of a shower thought question instead of something business critical. Also it could actually be used in an artsy way. It's probably not necessarily a practical thing for "real" usage.
    – bardiir
    Aug 7 at 14:06
  • The image circle of zoom lenses that expand do so on the long end, not the narrow end.
    – Michael C
    Aug 7 at 22:14
  • @MichaelC by "narrow" I mean the opposite of "wide", i.e. the longest focal length of the of the zoom range. Is my terminology wrong? I should believe "narrow" commonly refers to a longer focal length
    – Pete
    Aug 8 at 20:19
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The issue is that an EF-S lens, adapted or not, is going to project a smaller image circle than an adapted EF lens or a native RF lens - one that is suitable for the smaller APS-C sensor that camera bodies designed for the EF-S lens will have installed. Even if you could override the settings to use the full sensor in your R6, that image circle would still not cover the entire sensor, resulting in the appearance of severe vignetting, and probably other aberrations especially toward the limits of the image circle. Overriding that will not actually allow you to use the full sensor to capture a larger image.

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  • You could actually get a larger image if the goal is a square crop ;) But not much I guess.
    – Pete
    Aug 5 at 15:41
  • There's also the consideration that as many EF-S lenses are zoomed to longer focal lengths the image circle size increases, so at the long end of some lenses focal length ranges the image circle might cover the full sensor. But the technical quality of the image projected on those edges might not be up to Canon's standards.
    – Michael C
    Aug 5 at 18:45
  • The image circle will get larger as focus is moved nearer from infinity because (actually or effectively) the lens extends and the inverse square law comes into play. There is nothing inherently wrong with vignetting. It was actually considered an element of "good photographs" at various times historically and nobody dismisses Atget for the vignettes that frequent his pictures. On one hand Canon doesn't want to deal with the customer complaints from the uneducated consumers it targets. On the other, treating vignetting as a character flaw helps lens sales. Aug 5 at 19:06
  • I'm very much aware of this fact, I did even mention it in the original question. It's probably more a "huh I wonder if you could make it work anyway" type of question. :)
    – bardiir
    Aug 7 at 13:59

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