Best Canon APS-C/S35 All In One Zoom Lens Ever.

I've been using the EF-S 18-135mm IS STM (second version) since September. It came with a 70D I bought off eBay and it was so useful I kept it when later upgrading to the M6 Mk II.

Reviews seem to indicate the optical formula did not change from the IS STM to the USM Nano, so optically it seems they should perform about the same.

I found it to be sharp enough for most of what I do. For city-scapes where critical sharpness is important, stopping down to about f8 and cropping to a 4k image just gives sharp enough results at the extreme edges of the frame (see a photo I took tonight at 35mm with this lens). I may have to work a little harder in post-processing, but I can get good images from the lens with some work.

That being said, the 18-135 IS STM is by a little bit my least sharp lens. My copy has some slight field curvature issues wide open where I've seen the center of the frame not quite sharp and the rest of the image sharp for part of the focal length range, but this clears up just one stop down.

When I have more time, I prefer to use my vintage prime Minolta Rokkor lenses (24, 28, 50, and 135) which are sharper than this zoom, and have more pleasing color rendition when used at f5.6 - f8.

At the 18mm end, I've found the EF-S 10-18mm IS STM zoom to be slightly sharper than the 18-135 IS STM. At the telephoto end, I've found the 55-250mm IS STM to be much sharper -- my copy of that lens is tack sharp and contrasty at all focal lengths even wide open

Interestingly, I've found even the much maligned EF-M 15-45mm zoom to have slightly better image quality than, but not by much, the 18-135mm throughout its range.

For me on the M6 Mk II focus on the 18-135 IS STM is very fast and silent. I wouldn't say its instantaneous, but it's fast and precise enough, even in fairly low light, that it wouldn't have occurred to me that I would want a faster focusing lens, if I hadn't read this thread.

It's a great lens for video, it has more than enough sharpness and quality for good 4k video on the M6 II.

I sometimes shoot with my 18-135mm IS STM on an MC7 EF teleconverter. It's easy enough to modify the IS STM version of the lens to become an "EF" lens for that purpose, you just zoom it to 135mm, hook your finger in the back plastic ring that sticks out into the mount, and pull it straight out firmly. It will pop back in, I've done this dozens of times --- but do this at your own risk! The lens works really well with a good MC7 EF teleconverter like Kenko/Tamron/Promaster etc. But be careful, at 18mm the rear lens of the 18-135 may touch or hit the lens of the teleconverter. if used on an EF camera body, the camera's mirror might hit the rear element zoomed to 18mm.

Carrying the camera in a small-ish to medium camera bag with the 18-135 IS STM, 10-18mm IS STM, and a 2x MC7 teleconverter gives me the incredible continuous image-stabilized range of 10mm to 270mm in a small, light package!

I also tried my 18-135 IS STM on a Viltrox 0.71x EF speed booster. At the wide end of 18mm, I had to stop down to f11 to get reasonably sharp images, but there was significant vignetting of course as this lens was not designed for full frame, At 50mm it worked much better, only had to stop down to f8 or so - less vignetting and the image was very sharp, and at 135mm it worked very well with good corner sharpness and almost no vignetting at f8. So, in short, really not much point in using this lens with the VIltrox speed booster, since it only worked well at the longer focal lengths, and the lens itself has the shorter focal lengths you get when using it with the longer focal lengths!

Canon M6 II with Canon adapter and EF-S 18-135mm IS STM at 35mm, f8, 3.2s, ISO 100