The 135mm f/2 has near-mythical status among event and reportage shooters: it compresses backgrounds, isolates a subject from a crowded room, and lets you work a few rows back without feeling like you’re in someone’s face. But at full-frame prices, it’s a hard lens to justify for a working shooter who doesn’t need it every day. There’s a cheaper way to get most of the way there — and it starts with a lens most people already own.

The math that makes it work. The Canon R100 uses an APS-C sensor with a 1.6x crop factor. Mount the EF 85mm f/1.8 — a lens that’s been around since the film era and can be found used for a fraction of the cost of anything in the RF lineup — via the EF-EOS R adapter, and the effective field of view becomes roughly 136mm. That’s close enough to a 135mm full-frame prime that in practice, on a crowded show floor, you won’t notice the difference in framing.

The image above is a good illustration of what the combination is actually good for. It’s a candid, profile-angle shot at what’s clearly an exhibition floor — a subject’s attention pulled toward something off to the side, background reduced to soft color blocks and blur. That’s the 135mm-equivalent signature: enough reach to work from a respectful distance, enough compression to flatten the background into something that doesn’t compete with the face, and an aperture wide enough to separate the subject from a busy environment without needing to control the light yourself.

Where the substitution actually holds up. The EF 85mm f/1.8 isn’t as fast as a 135mm f/2, and the adapter adds a small tax in AF speed and a bit of extra length to the setup. But for event work — where you’re moving, reacting, and shooting in unpredictable ambient light rather than composing carefully — f/1.8 on APS-C already gives a full-frame-equivalent depth of field close to f/2.9, which is plenty shallow for headshots, candid crowd moments, and stage-adjacent shots where you want the subject to pop without fully melting the background into abstraction.

Where it doesn’t. The R100’s autofocus system is the budget end of Canon’s current lineup, and it won’t track erratic subject movement the way a higher-tier body would. Paired with an adapted EF lens rather than a native RF one, you’re also giving up any in-lens or in-body stabilization advantages RF glass might offer, and you’re carrying a longer, front-heavy setup than a purpose-built RF 85mm would give you. This is a combination for shooters who already own the EF 85mm f/1.8 from a prior body and want a lightweight, cheap way to extend it — not a recommendation to buy into EF glass fresh in 2026.

The takeaway. If the 135mm full-frame look is what you’re after for event and reportage work but the budget doesn’t stretch to a 135mm prime, an EF 85mm f/1.8 adapted onto an APS-C body like the R100 gets you within a few millimeters of the same field of view and a comparable rendering style, for a fraction of the outlay. It’s not a substitute for every use case that lens serves — but for the specific job of working a crowd from a slight distance and coming back with clean, separated portraits, it’s a legitimate budget path to the same result.

• canon
• lens review
• event photography
• aps c
• ef adapter