Image source : Canon

Although the 40mm EF Pancake STM was a corker of a prime lens, there was something a little restrictive about it's 40mm angle on an APS-C sensor. Sure, the pictures it produced were extremely crisp even at the f2.8 aperture thanks to it using the same UDF like coating found in L lenses, in fact it was even sharper and vastly more capable of retaining more detail than a number of actual L lenses also, there was also no barrel distortion at all with it being an EF lens on a crop sensor. The only problem was that it translated to a 64mm field of view on an APS-C crop sensor which was workable, but more often than not restricted it's use for frame filling people portraits and product photography in my particular case since I didn't have a full frame canon to use it with.  On an APS-C sensor it worked well as sort of short tele lens with extremely crisp and sharp images. For all its compactness and extremely high image quality, it's uses were relatively limited on an APS-C as far as more general photography was concerned.

However, it looks like this hasn't gone unnoticed by Canon and it looks like users that tote their crop sensor DSLR's are likely going to be getting something that's a little more carry everywhere in terms of application. 

It pretty much has the exact same extremely convenient form factor as the 40mm EF STM pancake prime lens, however optically they'll be putting in 24mm EF-S optics instead, the important being that it's an EF-S lens (not a 38.2mm equivalent if it had been an EF lens) meaning that it'll be much more usable in a broader range of general photography situations for owners of APS-C based Canon DSLR's as a 24mm EF-S lens. 

RRP on the 24mm f2.8 EF-S STM pancake is set at 179 quid, hopefully this thing will have the same kinds of optical quality that the 40mm f2.8 EF STM pancake had. I know I keep going on about the 40mm pancake, but the image quality on it is actually that good which I can't emphasize enough.