I know that this topic comes up time and time again when we discuss larger m43 lenses like the PL42.5, 40-150 PRO, etc., but with the leaked images of the forthcoming O25 PRO, it really brings in to question the value of large aperture lenses in the m43 system, primarily prime lenses. Let me get this out of the way first: I am very pleased to be getting lenses like this in the m43 portfolio. Short of the well matured systems from Nikon and Canon, no other company is releasing the same focal length lenses in faster, "PRO" versions in addition to smaller, slower, inexpensive "consumer" versions. Fuji is also getting on-board with this with their f/2 and f/1.4 series of primes. From what's been seen and compared so far, the O25 PRO will be marginally larger than the 12-40 PRO. The below image compares an E-M1+O25 PRO to an A7II+50/1.8, and D750+50/1.8. Now I know that there will be people who jump out and say "but you're comparing an f/1.2 lens to f/1.8 lenses!" and that's true, but the 1-stop slower FF lenses can compensate the difference simply by increasing their ISO by 1-stop to match the shutter speed of the f/1.2 lens on m43. The benefit in doing so is that the FF lenses still have a more shallow DoF than the m43 lens, but the same shutter speed. Also, there's the weight: The Sony combo weighs 785g, and the Nikon combo weighs 1,026. We can't make any assumptions of the O25 PRO's weight, but with an E-M1 weighing 500g, I think it's safe to say that the O25 PRO will not weigh less than 285g, but will weigh less than 526g, making the Olympus combo weigh somewhere inbetween the Sony and Nikon combo. Now this doesn't account for differences in things like weather sealing or intangibles like comfort & feel or ease-of-use (something I think the E-M1 is fantastic at), but taking a step back from our m43-biased views, and comparing it to FF systems, it's pretty startling to see that the Olympus combo is larger, and should weigh more than the Sony combo. I know there will be people who will buy the O25 PRO, and I hope they do to show Olympus that there is a justification for lenses like these. But compared to my PL25, I don't see the point in upgrading, especially if it's only for 1/3-1/2 stop of light at the expense of the size and weight. I don't mind larger lenses like the 7-14 PRO or the 50-200 SWD that I use with my E-M1's, but when it comes to primes, I love the tiny lenses like my PL15, PL25, P42.5, etc.