50mm

Ok so 48-50mm, seriously there's got to be a way to see focal length on the LCD. Gotta check the manual again.

So this is the good old 18-55 Kit lens vs. the 28-135, vs. the ever popular Canon 50mm "nifty fifty"

I'm too lazy to photoshop this into a series of three side by side, so for all of these I did the 18-55 vs. the 28-135, and then had the "winner" go against the fifty. Embiggen to see metadata.

Edit: Ok so Blogger is broken and won't make the photos bigger. Trust me, the 28-135 wins. The second set of photos is still visible.

The 28-135 finally wins one! So it goes against the 50mm prime 1.8.

And wins that one too!

Ok honestly, the non-scientificness of my testing comes out here. Everyone knows the 1.8 50mm is tack sharp, and most likely it focused a quarter inch forward or behind - it's famously sharp, but also famously janky. Whatever, either way the 28-135 wins this round.

Edge of the frame shots - not much different.