The Canon RF 85mm f/2 macro lens represents a potential expansion of the metaphorical color palette available to underwater shooters with Canon mirrorless cameras. At $499.99 is presents a much better price point than the popular Canon RF 100mm macro, which clocks in at $1399. Unfortunately this is a short review. Why? We don't recommend it.
On paper, the Canon RF 100mm macro is enticing. It's a faster lens than the RF100mm at f/2; it has a nice, shorter focal length for blackwater diving; and it's cheap and compact. When combined with a APS-C camera like the Canon R10 or the Canon R7, it's not more expensive than the camera itself (e.g., the R10 retails for $980). But ultimately, by getting this lens, you do your camera a disservice. Here's why:
1. The Autofocus is like Molasses
The autofocus with the Canon RF 85mm was downright unusable underwater...even after using the focus limiter. In a three dimensional, dynamic environment like the ocean, fish are not going to wait for you to take the photo. And no matter how long they waited, we could not get the autofocus to lock onto our subjects. Even with a high-end camera like the Canon R7, we needed to take the camera out of autofocus servo, and shoot old school single autofocus with a single autofocus point. There isn't much reason to upgrade to a nice RF mount camera from a compact system or an older DSLR if you can't use modern features like autofocus tracking or even continuous autofocus.
Much of the reason for this slow autofocus is a design flaw - the moving focusing barrel. When a lens doesn't focus internally, it requires a motor to move the lens itself which greatly reduces the autofocus speed. Although the Canon RF100 mm macro lens is a longer lens, it's so much faster than the 85mm macro that it is worth the upgrade. My keeper rate with the RF100mm macro is about 80% in ideal conditions whereas it dropped down to about 20% with the 85mm macro.
This was our favorite photo captured with the Canon RF 85mm f/2 macro. In this case the image is decently sharp, but it took ten tries with the Canon EOS R7 to get it right. f/16, 1/125, ISO400
2. The Image Quality is Soft (See Point 3)
This may have to do with slow autofocus or it may have to do with the distance of the barrel to the glass in the port, but the image quality with the RF 85mm macro was generally soft. There is also an issue with aberration at wide apertures. While some images did come out to our liking, the minority of the images were sharp.
This photo looked good in camera, but when we blew it up, it was clear that the whole image was soft. We think this is because we were using a Kraken +13 diopter on top of the 85mm macro lens, which was sitting too far away from the port glass.
3. The Moving Focusing Barrel is an Optical Achilles Heel
For ideal image quality, you want your macro lens to be as close to the glass of your port as possible. This is not possible with a moving focusing barrel. When you are focused to infinity, the lens is a lot further away from the glass than when you are focusing at your minimum focusing distance. This reduces image quality and is less than ideal for anyone who wants to shoot with a diopter stacked on top of the macro lens for super macro.
It was fun to shoot these two fighting hermit crabs. However, it's difficult to tell what's going on due to an overall softness in the image. f/16, 1/125, ISO 400
This wouldn't be a review without highlighting some positive aspects of the lens. It's nice to see an optical stabilizer on the lens. For some macro video shooters, if you lock the focus, this can be a benefit to you. It's also nice that there is a focus limiter that allows you choose your focal range. While the lens is still very slow, it does help the autofocus.
While the Canon RF 85mm macro is not an ideal lens for underwater photography, I could see it being a solid lens choice for photographers shooting slow moving topside portraits. Macro photography, it seems, is more of an afterthought with this lens.