The Good And The Bad Of
The Canon RF 100mm Macro SA Lens Control

You're wondering what is SA control on the Canon RF 100mm Lens. It's full name, the Canon RF 100mm F/2.8 Macro IS Lens has a very unique new capability, aptly name spherical aberration or SA for short.

What is RF 100mm macro lens SA controlSA control ring on RF 100mm Macro lens

In this post find out what it is, how it works, and the advantages and disadvantages of using the SA (spherical aberration) control on the Canon RF 100mm macro lens. First we'll look at the pros and cons and then you can view my SA test images.


The first thing we'll look at is the advantages of having SA spherical aberration control feature built into the RF 100mm lens.

  • The SA control ring gives you additional creative control on the size and characteristics of the blur both in front of and behind your subject. This is the first Canon lens with this feature.
  • The SA control ring includes a lock to prevent accidentally using the feature when you didn't want to.
  • This lens gives you the ability for both excellent sharpness and enhanced bokeh.


There's usually a downside, so let's take a look at the disadvantages of having an SA feature in your lens.

  • You could forget to turn the SA control ring back to its neutral setting and effect he blur when you did not intend too.
  • The complexity of the lens design had to increase to include this feature and likely added to a higher price.
  • It's possibly one more thing that could break.

SA Test Results

Soft flat backgrounds will not reveal the effects of the SA control as much as point light sources and backgrounds with contrasty areas, so I set up my test with a string of holiday lights against a dark blanket as the background behind my main subject.

I researched other Canon shooters tests on this lens and it was reportedly found out that the pleasing effects from engaging the spherical aberration are likely to happen in the mid-range of f/stops settings. My test revealed that the effect on the bokeh blur was much more pronounced at f/2.8 than f/5.6.

Moving your mouse cursor overtop the image below shows the image with a full negative spherical aberration engaged. Move your mouse off the photo to see the image with the SA control at the neutral position.

No Spherical Aberration
1/40 Second at f/5.6
Without And With Negative Spherical Aberration

Moving your mouse cursor overtop the image below shows the image with a full positive spherical aberration engaged. Move your mouse off the photo to see the image with the SA control at the neutral position.

No Spherical Aberration
1/40 Second at f/5.6
Without And With Positive Spherical Aberration

Spherical Aberration on Portraits

I also tested using the RF 100mm SA control ring for shooting a headshot portrait. See the comparison below.

Portrait Without SA Spherical Aberration engaged.
Portrait Without And With Negative Spherical Aberration

The SA control ring rotated toward the negative side of the lens markings softened the blur. Turning the SA control ring indicator to the positive side of the lens increased the sharpness. 

SA Control Ring Summary

Is the SA control ring on the Canon RF 100mm f/2.8L macro lens just a gimmick or is it a useful tool?

Like other features and capabilities of lenses, it takes a bit of experimenting to learn how to get the desirable effect that you're looking for. That's because the effect will change depending on the distance to your subject, the f/stop you choose to use, and the characteristics of the background.

I really like this lens a lot. It's sharp. It focuses fast and the 1.4x magnification is a big bonus. I highly recommend the RF 100mm Macro IS highly if you're shooting with any one of the Canon R mirrorless camera bodies. See the related RF 100 articles below my signature.

If you already have the original EF version of this lens, a great performing lens, it may not be enough of an upgrade to justify the investment. You may want to consider one of the other RF lenses.

I'm glad I bought my RF 100mm lens, but not it's not because of the SA feature. I guess I'll have to play around with it more, especially with my macro shooting.

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Author Bruce Lovelace
Bruce Lovelace Signature

Bruce Lovelace is the publisher of Canon Camera Geek. Read more about him on the About Page. He also publishes how to articles and camera gear reviews at the Photography Tips website.

View some of Bruce's photos on Instagram  and Flickr  Join the tribe of followers on YouTube. Visit the Canon Geek FaceBook Page. Bruce also runs photo workshops and provides 1 on 1 digital photography coaching.

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