April 24, 2023

Canon R5 - the RF 24-105 STM lens (f/4 - f/7.1)

Canon offers two 24-105 R mount lenses. There is this one (which I have) and there is a more expensive L series lens with a constant f/4 aperture. I have taken to calling the one I have the STM and the more expensive one the USM. This refers to the focus motor in the lens, but I find it a handy moniker. I'll also note that although "STM" is short for "stepper motor", my lens is very fast and entirely silent.

You might ask: "What is there to know about using a lens?" This one has a confusing switch on the side with two positions labeled "focus" and "control". I had hoped that moving this switch to "focus" would give me manual focus, but that is not what it does. So, what does it do?

When set to "control" it acts like the usual R series control ring and does whatever you have you program set up to do (typically controlling aperture or exposure compensation).

When set to "focus" it can be used to control focus, but only if the camera is set to use manual focus. So if you want to do manual focus with this lens, you have to move the switch and then do whatever you have set your camera up to do to enable manual focus.

There is more though. When you enable this lens for manual focus (using the two step process just described), the lens with focus a lot closer! Closest focus with AF in control is 20 cm. Closest focus using MF is 13 cm which makes a big difference for macro shooting. The manual warns that if you have the lens set to focus close and switch back to AF, the lens may not respond -- you should move the focus position back towards infinity before switching back to autofocus.

The lens also has the usual switch to enable image stabilization. Canon recommends that you turn this off when shooting from a tripod. Interestingly they say to leave it on when using a monopod.

The Canon RF 24-105 f/4 L

The above table gives some interesting lenses (with weights) for comparison to my 24-105 STM. The weights are quite sobering. I have the last 2 lenses. The 24-70 is in particular "a brick". This is the "fancy" big brother to the lens I have. List price is $1200 (compare to $400 for the STM version). On top of that, the STM is widely available for around $200 used, probably because many people upgrade to the fancy L series lens.

What does the fancy lens offer? Better build quality with weatherproofing. Constant aperture across the zoom range.

Just for the record the 24-105 L series lens has two control rings (one is always the control ring, the other can be enabled for focus). There is a focus switch on the lens with positions AF or MF. In MF mode, the lens performs manual focus without any need to enable it in the camera. Also there is no mention about any closer focusing ability when in manual focus. Apparently AF has access to the entire focusing range of this lens.

Feedback? Questions? Drop me a line!

Tom's Digital Photography Info / tom@mmto.org