Canon 50mm f/1.8 STM vs the 50mm f/1.8 II, the 50mm f/1.4 USM and the 24 and 40mm f/2.8 STM lenses.
The new model is offered at the same price as the 50mm f/1.8 II with some important updates- metal mount, 7 aperture blades vs 5 in the older model, much smoother and quieter focus. Overall build quality feels significantly improved with the metal mount and tighter more finished looking construction.
The f/1.8 II didn’t always produce the smoothest bokeh, at times it was possible to see the pentagon shape in the background created by the 5 aperture blades. The new 7 bladed design does eliminate the pentagons and produces slightly smoother bokeh but the difference is slight.
The f1/.8 II version was notoriously loud in focusing and this became even more apparent when using it in live view with the Canon cameras offering continuous AF in live view. The new model offers STM technology which provides smoother, faster and MUCH quieter focusing. It is not silent like the STM kit lenses, it does still makes an audible sound that will be recorded by the on camera mic in quieter environments which is similar in performance to the 24 and 40mm STM primes.
Close focusing distance has been improved slightly which is a nice but again the difference is slight and still not as close as the 24 and 40.
Image Quality remains about the same – at times the new STM version looks to be a tiny bit sharper, especially as you stop down from f/1.8 but if you have the original and you are only looking to get sharper images – I do not recommend upgrading to the new lens.
So who should upgrade? If you want to use the lens in live view and or for video the faster, smoother and quieter focusing is a significant difference, along with full time manual focus makes this a much better experience for folks shooting video.
Who should buy? If you don’t have a prime lens and you are looking for an affordable lens primarily for nice portraits -the 50mm f/1.8 STM lens is an excellent option for crop sensor cameras. However if you are looking for a more general prime, consider the 40mm f/2.8 – it’s slightly wider focal length makes it a little more versatile and at 1/2 the size it is even more travel friendly. Another option is the 24mm f/2.8 prime – a great general walk around prime lens – both the 24 and 40mm are very sharp at f/2.8 and cost only a little more than the 50mm f/1.8 STM
I also want to do a quick comparison of the 50mm f/1.4 vs the 50mm f/1.8 STM
At f/1.8 the 50mm f/1.4 is sharper but the difference only shows up at f/1.8, as soon as you stop down to f/2.8 they appear identical (see below)
The f/1.4 vs f/1.8 difference is very slight in terms of bokeh, and a fairly small difference in light gathering. You also get a focus indicator an even bigger focus ring. Quality wise I find the 50mm f/1.4 soft wide open and often stop down to f1/.8 or smaller to get sharper images and then I find myself doubting the value of this lens. Generally I would skip it and if you really need f/1.4 go for the sigma ART f/1.4 which is an amazingly sharp lens wide open but much more expensive and heavier. And in the other direction, if you want to experiment with a prime but feel $125 is too expensive, get the Yongnuo 50mm f/1.8 for under $70.
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