EF-S 15-85 on Crop Sensor Camera vs. RF 24-105 on Mirrorless Camera

[Johnny of Cairo]

I have a Canon EOS 550D (T2i) camera with which I mainly use a Canon EF-S 15-85mm f/23.5-5.6 IS USM lens as an everyday lens.

Because I'm planning to buy the Canon R6 Mark II mirrorless camera and a telephoto lens for shooting my daughters' sports activities, I'm wondering whether I ought to hang on to the EF-S 15-85 lens and keep it on the T2i for everyday use or if I should sell the EF-S 15-85 and replace it with the Canon RF 24-105mm f/4 L IS USM lens that I'd use with the Canon R6 Mark II.

I'm trying to figure out if what sorts of advantages there would be to going the more costly route of getting the RF 24-105mm f/4 L and whether the advantages would merit that extra cost.

Thank you for your thoughts about this!

[Mark Keefer]

In the Canon DSLR world you could not physically mount an EF-S lens on a Full Frame EF mount camera, the lens would sit to far back in the camera and I believe would be an issue with the shutter mirror. I don't believe this is an issue with the new R mirrorless cameras using an adapter, but keep in mind the EF-S is a crop lens. While it will probably work,  I don't  believe it can fill the R camera full frame sensor so you will not get the full size resolution images.  That may or may not be an issue for you, but understand that making the decision. You may want to use a full frame lens to take full advantage of your full frame camera. I don't own a R camera yet. I do have a Sony A7RIII with Metabones Canon EF Adapter and that camera has a setting for crop lenses. Again it just uses the crop portion of the sensor and not the full frame. I image it will be similar on the R6 Mk II. Hopefully someone in the forum that owns a R6 or R5 can clarify. 

[Ken Katz]

While the T2i plus EF15-85mm is still a very capable combination, clearly, the R6 mkII will materially outperform it in every possible way, except for size, weight, and cost.  If you just buy the R6ii plus a telephoto lens, do you also want to carry around the T2i outfit just for images requiring a shorter lens?  Your new RF telephoto can't be mounted to a T2i. 

If I was already committed to spend the $2,500 for the R6ii plus the cost of a new RF telephoto, at this point I would likely try to sell the EF15-85, since I don't think the market for used high quality EFS lenses will be improving in the future (unless the R7 really takes off and Canon is really slow providing apsc RF lenses - which is certainly possible).  If you still have the original kit lens for the T2i, you can also use that combination as a knock around, light weight kit.

Edited November 6, 2022 by Ken Katz

[dmanthree]

Replace it. No comparison in image quality and capabilities. To me this is a no brainer.

[wgpinc]

I have a full frame canon RF camera with some very good adapted full frame lenses that I use and enjoy with excellent results. I also have a Canon DSLR T5i along with some nice lenses to go along (10-22mm, the excellent 17-55mm 2.8 and the underrated Canon EF-S 55-250mm f4-5.6 IS STM. I keep this outfit because it is fun to use, worth very little on the used market and produces great images. If I can prioritize an RF 24-105mm some time soon I will get it because it is a great lens with a very good range, but it won't replace my adapted Canon 24-70mm 2.8 EF lens. I don't know much about the R6 II but I read review a while back where the reviewer, a portrait photographer, shot with the then current Canon offerings and stated that without doubt to her the best sensor was on the R5, next in sensor quality was the RP followed by the R and whatever was the remaining Canon RF camera. I'd want to read some reviews of the R6 II before I considered spending  $2500 for it instead of buying up to the R5.

[Johnny of Cairo]

Thank you to everyone for your input in response to my question.

I think that for now it might be sensible (and, of course, a lot cheaper) to hang on to the old camera with the 15-85 lens and use it as a supplement to the Canon R6-telephoto combination when I need the wider angle. I took a look at B&H and KEH online to get an idea of what they'd pay for the Canon 15-85 in very good condition, and I was surprised by how little they'd pay for that lens, given that it's about an $800 lens. 

[JDMvW]

For lenses like the 15-85mm and the 24-105mm (and their equivalents in other mounts) the point is their convenience. If you can't live with anything but the very sharpest, don't use them.