jolyonralph said:I think the lack of a serious range of EF-M prime lenses does tend to point towards the probability of a FF EF-M range of lenses in the future.
Of course, there's no reason that new EF-M prime lenses (eg 50mm f/1.8) couldn't be full-frame capable for when they do eventually launch a FF mirrorless.
Either that, or Canon is having trouble with peripheral illumination on the M series, due to the sharper angle of incidence of light reaching the sensor.
Photozone, in at least one of its lens reviews points to the possibility that Canon may have a problem with its APS-C sensors in that they cannot handle light coming from a very oblique angle of incidence:
[quote author=photozone]Unfortunately vignetting is a massive weakness - again. We have seen this problem in our previous EF-M reviews so by now we are pretty confident to state that this isn't solely a lens issue. It seems as if Canon just took their APS-C sensor developed for some of their DSLRs and this just wasn't the smartest thing to do due to much closer distance to the lens' rear element. It seems as if the sensor doesn't like the more extreme light angles towards the corners.
The "raw" light falloff is shockingly high. At 15mm @ f.3.5, the Canon lens holds the new negative record (again) with a whopping 3.6EV(!!!). This is more than double our usual scale for APS-C format lenses! Even at f/11, you can observe a falloff of ~1.4EV (f-stops). The situation isn't quite as bad at 28mm where f/5.6 is sufficient to solve most of the issue. At 45mm it isn't overly relevant anymore.
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This problem obviously gets worse at larger apertures. This makes me wonder if Canon has a bit of work to do on its sensors before a faster lens is workable. - Hence the research into curved sensors. One of Canon's patents in this area seems to be focused around combating vignetting.
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