When mirrorless cameras first started gaining popularity within the industry, brands and photographers were generally discussing the weight and size advantages. This was predominantly true until larger faster aperture lenses were brought into production and the mirrorless weight advantage was supposedly debunked.
Up until quite recently, I, like many others described the weight advantage of mirrorless cameras to be somewhat of a myth. When you start using lenses like the Sony FE 24-70mm f/2.8 GM, then the weight difference becomes mostly negligible. If anything, it's a disadvantage to have a tiny body and a large lens due to how front heavy the system becomes. A combination such as that is rather uncomfortable and to combat that, you need to use a battery grip; then you're back to having a large, heavy system. The alternative would be to use smaller prime lenses and this is where mirrorless holds a significant advantage over DSLR type cameras.
Mirrorless Primes Are Better Primes
Admittedly this subheading is a little incendiary, but in the words of Kevin Hart, let me explain. Chances are you've probably heard several companies talk about the ease of developing lenses for mirrorless cameras. The main reason for this is because of the shorter flange distance. This helps with allowing the optics to sit closer to the sensor and lenses can be more efficient in design. This is especially useful for wider-angle lenses such as the Sony FE 24mm f/1.4 GM. The ability to design efficiently means that you have the opportunity to produce extremely high-quality lenses without them needing to be huge. Another reason mirrorless lenses can be more efficient in design is that they do not necessarily require lens image stabilization. Almost all current Sony cameras offer IBIS (in-body image stabilization) to some degree. The Sony a7R III, for example, offers IBIS that's been rated up to 5.5 stops which is incredibly useful. I compared IBIS from Sony to IS from Canon and found they perform at a very similar level. The huge benefit of this is that you can have your lenses stabilized without any compromises.
Optical performance is another area where many mirrorless lenses perform noticeably better than their respective DSLR counterparts. Personally, I don't think this is because they are for mirrorless cameras but probably due to new methods and technology. Essentially they're more modern lenses and modern lenses tend to perform better.
Smaller, Lighter, and Practical
There are plenty of options currently available for DSLR cameras if you need a small light lens. The most obvious choice that comes to my mind is the Canon EF 40mm f/2.8. Aside from the relatively small aperture for a prime lens, it's actually quite a good performer. Not the best prime lens I've ever used but good enough in many situations. Other than the 40mm from Canon there aren't many other practical lenses available for DSLR cameras that you can use and keep a smaller lightweight setup. Sure there are small and light prime lenses available like the EF 28mm f/1.8, however, the performance is severely lacking. Compare that to the Sony equivalent, which is the 28mm f/2.0. Sure the aperture is ever so slightly smaller, however the performance is significantly beyond that of the Canon lens. The Canon 28mm is pretty poor wide open and comparable performance can only be achieved when you stop the lens down to about f/4.0. The Sony lens is better in almost every regard and has the ability to be stabilized due to IBIS. Not only that but the Canon 28mm is more than 50 percent heavier. A Canon 5D Mark IV with the 28mm lens will weigh 1,110 grams which is more than 250 grams heavier than the Sony setup. This may not seem like a lot but it's actually more than what the Sony 28mm weighs individually.
Another Canon alternative would be the EF 24mm f/2.8 IS. This is a lens I personally own and consider it to be a great option. Even still it's a heavier, more expensive lens and one stop slower than the Sony. Sure it has IS built into the lens, however, as mentioned above, most Sony cameras now offer IBIS which performs similarly to IS.
For portraits, 85mm lenses are quite the common choice and Canon has the EF 85mm f/1.8 as their lightweight option. Unfortunately, the performance of this lens isn't anywhere near as good as the Sony FE 85mm f/1.8. Wide open it's pretty soft and has lots of visible chromatic aberrations. Once again, it's only really comparable when stopped down to about f/4.0 which defeats the purpose of having a wider aperture. The Sony lens on the other hand is superb and offers fantastic image quality, making it practical to shoot wide open. It is the more expensive option although, considering it is lighter and offers much better performance, it can be argued that it is worth the extra cost.
Finally, we have midrange focal lengths like the 50mm mark. Canon has two options available, the EF 50mm f/1.4 and the EF 50mm f/1.8. Once again, performance from these two lenses aren't anything special and they are pretty soft wide open and all the way down to about f/2.8. Sony does have an entry-level FE 50mm f/1.8, although my preferred choice is the Zeiss 55mm f/1.8. Now, this lens doesn't compare well against Canon on paper because it is heavier than the EF 50mm f/1.8 and costs a lot more. The difference is that if you're happy to pay that extra amount you end up with a lens that is significantly better in almost every regard. This lens is one of my favorite lenses to use because it's relatively small and extremely capable. To get this level of quality with Canon you'd have to buy something like the Sigma 50mm f/1.4 Art lens which is significantly heavier and larger, albeit with a wider aperture. What's important to note is that even at f/2.0 the Zeiss is actually a better performer when it comes to detail compared to the Sigma. Sure the 55mm is heavier than the EF 50mm, however when you take into account the weight and size of a camera like the 5D Mark IV then the Sony system is still overall smaller and lighter.
So What's the Point?
It's practical to shoot with mirrorless cameras and use smaller lighter lenses because they don't compromise on image quality. This is not true for DSLR cameras because their smaller lightweight lenses are more of an afterthought. If you want the higher-end quality then you have to upgrade to the much larger heavier lenses, which is not the case with Sony. Compare the FE 85mm to the 85mm f/1.4 GM lens and you'll notice how performance wide open is very similar. The reason why you may want to upgrade is for the wider aperture and the aperture control ring. The fantastic thing about this is that I can have three small prime lenses with me in a small messenger bag with the Zhiyun WEEBILL-LAB and produce high-quality results. With the 5D Mark IV I'd have to use much larger heavier lenses for better quality and this, in turn, would mean I'd have to use a larger gimbal and bigger backpack and so on. That slight difference in weight and size has a significant impact on the overall weight and size of your setup and the kind of accessories you will need.
Sony made sure they worked hard developing high quality, small, lightweight prime lenses early on. This now means we have much more flexibility with Sony mirrorless cameras than we do with many DSLR type systems. Essentially you can have a small, lightweight setup with Sony when required but also use the much larger heavier glass when you need that little bit extra. For this reason, the weight advantage of mirrorless cameras has not been debunked.
Lead image by Reinhart Julian via Unsplash.