More thoughts on the Canon RF 50mm f/1.8 STM.

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I got the idea for this post when I was writing another. An update of the RF 85mm f/2 STM Macro.

About that lens I wrote:

I did not expect to buy this lens.

Unlike that lens I did fully expect to like and buy the RF 50mm STM based on my brief, but pleasant experiences with the Canon EF 50mm f/1.8 STM.

RF Blog Post Product Shots

In that recent 85mm post I ended up comparing it to the Sigma 56mm for APS-C, and further I wrote:

…I much prefer the Canon 50mm STM f/1.8 over the Sigma 30mm f/1.4. This is no small feat since I really like the Sigma 30mm. May create a write up like this for these two lenses…

Sony a6000

I really liked the Sigma, but as a spoiler alert this was no contest. Similar to the prior Sigma/Canon comparison I will list the same categories here.

Size and weight.

Unlike the 56mm/85mm match up the Canon is significantly smaller and lighter this time around.

The Canon easily walks away with this one, especially considering that it is a full-frame lens.


Here again things are reversed from the last comparison. The factory, full-frame Canon 50mm is nearly $100 less than the third party APS-C Sigma.

I’ll just say it. This makes no sense to me in the best of ways. Easy win for the Canon.

Optical Specs

When accommodating for focal length and aperture equivalence the Canon is a fair bit faster. As says:

“Your “30mm f/1.4” lens will look like a 45.9mm f/2.14 on a “APS-C” sized sensor.”

Close Focus

While not a macro like the 85mm or 35mm the Canon does still focus a fair bit closer at 0.25x instead of the Sigma’s 0.14x. May not sound like much on paper, but is very noticeable in the real world.

EOS RP - RF STM 50mm f/1.8

Canon for the win.


Check (Sigma)…

Sigma 30mm f/1.4 Contemporary

…and check (Canon).

RF 50mm f/1.8 STM - EOS RP

The Sigma is up two aperture blades at 9 as opposed to the Canon’s 7, but I still give the Canon the lead here. The Sigma is no slouch, but the Canon generates some of the most pleasing bokeh I have seen.

Sharpness and Colors

Check (Sigma)…


…and check (Canon).

RF 50mm f/1.8 - EOS RP

AF Speed and Accuracy

Both focus swiftly and accurately. Both are also silent while they are at it.

Low Light

Here is the only near low light Sigma sample I had. Not terrible, but it struggled more to focus than the Canon.

a6000/Sigma 30mm f/1.4

A big win for the Canon lens likely buoyed by the full frame leg up.

RF STM Lens Samples

And significantly both are capable for…

All Purpose Use


Sigma 30mm f/1.4 Contemporary
Crown Vic
a6100/Sigma30mm f/1.4
Sigma Contemporary 30mm f/1.4
a6000/Sigma 30mm f/1.4
a6000/Sigma 30mm f/1.4
a6000/Sigma 30mm f/1.4


EOS RP - RF STM 50mm f/1.8
RF 50mm f/1.8 STM - EOS RP
EOS RP - RF 50mm STM
EOS RP - RF 50mm STM
RF 50mm f/1.8
EOS RP - RF STM 50mm f/1.8

Unlike the 56mm/85mm comparison where I tried to keep things pretty even, but the 30mm/50mm comparison here is not close at all for my purposes. This is not a ding on the Sigma 30mm. It is still an excellent lens that I would highly recommend if you are already invested in the crop cameras that apply. But side by side the Canon is the clear winner for me here.

  • All other things being equal a factory lens is preferred.
  • I’ll just say it. Canon colors. I shoot RAW which closes the gap regardless of brand sensor wise, but I must admit I have never seen colors out of the Sigma lens like the colors I get out of this Canon lens.
  • As mentioned above at about $100 less for a full frame lens with features like an AF/MF switch and and a control ring the Canon is clearly the better deal.
  • Hit rate. I had the Sigma for quite a while and I got some shots I really like. But the Canon is just a no effort keeper machine.
  • The Canon is lighter, smaller, and better built. Again, not that the Sigma is bad. The Canon just feels better to me with its less shiny surface that feels a bit more rugged.
  • And once again full frame. As mentioned above all things being equal I will take a full frame set up every time. And as good as the Sigma 56mm is it cannot fight physics.

I still say that Sigma really delivered the prime lens goods for Sony crop cameras…

…and because of them I kept Sony crop cameras much longer than I would have otherwise. But I prefer the Canon STM lens trio that has replaced them since.

The 85mm compare well to the Sigma 56mm, but the Canon 50mm outpaces the Sigma 30mm easily. I will not be writing a comparison between the Sigma 16mm


…and the Canon 35mm

Canon EOS RP

because of even though they have different equivalent fields of view, even though focal length aside I do prefer the Canon. The Sigma was very good. But overall I felt it was outmatched by the similarly priced Canon 35mm. The 35mm is a lens I did compare to an also wider lens Leica Q at one point after all and a part of the reason I sold the Q. Add in Macro capabilities and IS and it just tips even more in Canon’s favor here also. But if Canon does ever release a 24mm-ish RF STM lens I imagine it would do just as well as the 50mm and 85mm STM lenses compared directly to the Sigma 16mm.

Back to the main topic lens. I purchased the Canon 50mm STM expecting to like it, but it performed beyond my expectations.

Well done Canon.

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