Edge sharpness is excellent on the Canon 42 because it has field flatteners that actually work, unlike the MHG 😉🤭.
Some Tips on Binocular Edge Sharpness
The only binocular that has sharper edges than the Canon 10x42 IS-L is the Swarovski EL and NL. The EL's edges are just slightly sharper than the NL. The edges are sharper on the Nikon EDG than the Nikon MHG.
Usually the sharper the edges and the flatter the field, the more RB you will see. That is why Swarovski just slightly reduced the field flattening on the NL to avoid RB. The EL has the most RB when panning because it has the strongest field flatteners.
So you can't have your cake and eat it too. Sharp edges and a flat field mean RB is going to be there.
The EL is the 'King' of sharp edges, followed by the NL and then the Canon 10x42 IS-L, and then the Nikon EDG, and then the Zeiss SF and then the Swarovski SLC.
The Swarovski SLC has the least sharp edges of the Swarovski's outside of the Habicht porros.
The Habicht porro has soft edges, but they are not noticeable or distracting in the way that Kowa's are. The Habicht has a more gradual fall off of sharpness at the edge, whereas, the Kowas falloff is more abrupt, making it more noticeable.
With Kowa's you can see a noticeable ring of softness around the edge of the FOV even when you are looking on-axis. I really notice this on the Genesis Prominars.
The older huge FOV porros some having 13 degree FOV's had soft edges in general which I find distracting. FOV can get too large in some of these.
None of the Leica's have sharp edges. They almost always have fall off at the edges, even the Noctivid. The Noctivid though has the sharpest edges of the Leica's. It is Leica's first attempt at Field Flattening. The Retrovid, UVHD and Trinovid all have soft edges.
Sharp edges and flat fields are not a Leica thing. Saturated colors are. Leica has stayed with this design philosophy for years and because of this have not kept up with Swarovski and Zeiss in flat field and large FOV binocular advancements.
Leica's have soft edges, but you do not notice them the way you do Kowa's. If you notice soft edges or not or they are distracting depends on how the optics are designed.
Almost ALL Swarovski's have sharp edges, except for the Habicht porros. Even the compact Curios's 7x21, 8x25 CL-P and the 8x30 CL have sharp edges. That is a trademark characteristic of Swarovski's.
Some binoculars that have soft edges are more noticeable than others. Kowa's in general have soft edges that are more noticeable than say the Nikon MHG.
The noticeably soft edges on Kowa's are a big reason I don't personally care for Kowa's in general. I notice the soft edges on Kowas, and it detracts from the view.
If you like sharp edges, stick with Swarovski's. Some like the EL though will have the Absam Ring which is a slight ring before the very edge that is slightly less sharp. The NL doesn't have the Absam Ring anymore.
The ONLY Zeiss that has fairly sharp edges are the SF's. None of the older Zeiss, including the FL's, HT's or Dialyt's have sharp edges. They all have fall off at the edges.
So if you like sharp edges, the only Zeiss you will like is the SF.
If you like a huge FOV with a flat field and sharp edges, get the Nikon WX. It has the biggest, flattest FOV with sharp edges that you can get, but it weighs 5 pounds, has IF and costs $6000.
The Nikon SE has quite sharp edges for a porro. The E2 less so even though it has a huge FOV. The E2 has considerable fall off at the edges.
Really, the MHG doesn't have very sharp edges for a binocular that is supposed to have field flatteners, but at least they aren't distracting. You don't notice them that much except maybe subconsciously, unless you deliberately look at the edge.
I really like sharp edges, that is why I notice which binoculars have the sharpest. I always look at the edges to see how sharp they are.
This conversation is getting kind of edgy, I think I better leave.😬