foathog Loc: Greensboro, NC

I have the EF 100mm 2.8L but it uses the adapter on my R5. I have yet to buy an RF lens and thought this would be an opportunity to do so. I'm pretty sure I can sell the EF since it too is an excellent lens.

Architect1776 Loc: In my mind

It is not variable aperture.
Most primes are that way while most zooms change aperture as one zooms.
It doesn't mean only f2.8 as many here think but that is the maximum opening and can stop down from there as desired.

CHG_CANON Loc: the Windy City

So, you understand the responses so far, right?

This prime lens has a single 100mm focal length. The f/2.8 aperture can vary from f/2.8 to f/32. As others noted, variable aperture lenses are more typical of variable focal-length zoom lens, not a prime lens (aka a fixed focal length). One would not typically identify a prime lens as also having a 'fixed aperture', as that's how a prime lens operates; the focal length doesn't change, and the aperture changes under the control of the photographer or camera, not because the focal length changes.

Blenheim Orange Loc: Michigan

"Fixed" aperture on a zoom lens is pretty standard terminology.

Fixed-aperture lenses vs variable-aperture lenses

These terms apply to different zoom lenses – that is, lenses with variable focal lengths. Fixed-aperture lenses, also known as constant aperture lenses, maintain the same maximum aperture size throughout the entire zoom range. With the Canon RF 24-70mm F2.8L IS USM lens, for example, whether you're shooting wide at 24mm or zoomed in at 70mm, you can still open your aperture to f/2.8. This consistency is an advantage when you're shooting in varying light conditions or when you need to maintain a certain depth of field across different focal lengths. It's particularly valuable in sports or wildlife photography, where light conditions can change quickly and the ability to maintain fast shutter speeds at all focal lengths is essential. Another fixed-aperture lens is the Canon RF 28-70mm F2L USM. This lens is widely used for its fast f/2 aperture across the entire zoom range, making it a powerhouse for low-light photography and providing stunning bokeh.

Variable-aperture lenses offer different maximum apertures as you zoom. For example, on the Canon RF 24-105mm F4-7.1 IS STM lens, at the widest end (24mm), the maximum aperture is f/4. But when you zoom in to 105mm, the largest aperture you can achieve is f/7.1. While this means you may need to adjust your exposure settings when zooming, variable-aperture lenses are often more compact and affordable, making them an appealing option for travel photography or for those on a budget. Another notable variable-aperture lens is the Canon RF-S 18-150mm F3.5-6.3 IS STM. This lens offers an extremely broad, and therefore very versatile, zoom range and image stabilization, making it a solid all-rounder and a favourite among travel and street photographers.

The choice between fixed- and variable-aperture lenses ultimately depends on your shooting needs and style. If consistent exposure and depth of field across a zoom range are paramount, then a fixed-aperture lens would be your best bet. But if portability and budget are key considerations, then a variable-aperture lens could serve you well.

https://www.canon-europe.com/pro/infobank/aperture/#fixed-vs-variable

Blenheim Orange Loc: Michigan

It says it is out of stock.

Also, it isn't a zoom lens, so of course it wouldn't have a variable aperture. "Fixed" doesn't apply.

foathog Loc: Greensboro, NC

LOL. I was questioning why they gave the "impression" that it might be JUST 2.8. I saw other ads for it that said just what you said. (f2.8 to f32) But they didn't mention "fixed f 2.8". If they had mentioned the aperture range I would have bought it. Like I said, I have the EF L version of this lens. I was wondering if this might be something different. Well as it turns out the lens has been sold. I'm out of luck for now. I put my name on a waiting list. Thanks Paul.....and everyone else who helped out.

PHRubin Loc: Nashville TN USA

Check! It has the same wide open aperture available for all zoom settings.

DWU2 Loc: Phoenix Arizona area

It means it's been modified so it can't produce little lenses.

dleebrick Loc: Indian Land, South Carolina

This is a popular macro lens (1:1 image size on sensor). It has fixed 100 mm focal length, but has variable f-stop with 2.8 being the largest opening. And it is image-stabilized.

BBurns Loc: South Bay, California

Thanks, Paul. I can't believe they got 2 pages out of this simple question.

Bill_de Loc: US

Good video for the lens:

https://www.youtube.com/watch?v=76Jfq0VsNy0

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mwsilvers Loc: Central New Jersey

A "fixed" aperture lens refers to a zoom lens where the widest aperture, say f/2.8, is available throughout the entire focal length range. The word "fixed" is irrelevant on a prime lens where there is only one focal length. It was probably simply an error made by whomever wrote the text.

Architect1776 Loc: In my mind

You mean adjustable?

Bill_de Loc: US

..

kddp13 Loc: Wisconsin

Doesn't refurb and fixed mean the same thing ?