You could call this part 2 on my essay on the Sigma 18-35 f/1.8A with a Speedbooster and why I bought it over m43 primes, even if I consider them highly respectible lenses for their performance. A disclaimer: I personally really like the Olympus 17mm 1.8. I like how it has a physical focus scale that lets me manually focus effectively. I like that it is a solid feeling, dense and compact little lens. I would like to own one very much but the price makes it so very hard to justify as a purchase, especially when I have have other, more flexible options avaliable... Prices given in US Dollars, no discounts or sales. Code: Olympus 12mm f/2.0: 130g $800 / $1,100(!) to buy in black Panasonic 14mm f/2.5: 55g $320 Olympus 17mm f/1.8: 120g $500 Panasonic 20mm f/1.7: 87g $385 (II version) Panasonic 25mm f/1.4: 200g $530 592g $2,535 / $2,835 to buy the black 12mm f/2.0 Five lenses, all with autofocus, but I would have to mount and demount to get the 12-25mm focal lengths and the fastest lens is only f/1.4 and the average aperture range is between f/1.7 and f/2.0. Code: Sigma 18-35 f/1.8A: 811g $800 Metabones Speedbooster:<180g $430 <991g $1,230 I really would like to own several of those m43 primes. I really would. But at the prices they're at I really have to make a tough decision, especially when I know how much optics matter. I'll state this clearly: I have already planned to buy a D3s for years and I will not give on that. That means I will not give up my existing collection of lenses at a loss to me and I am given further incentive by Speedboosting to keep them around and use them to their fullest. I don't have autofocus, but I have an effective range between 12.8 to 24.8 = 13-25mm. Its not the 12mm of the Olympus but its not a f/2.5 of the Panasonic 14mm and it goes a little wider. But it is at f/1.2 across the range for about 400 grams of weight difference. I personally don't mind the weight and the lack of autofocus. I come from a D200 so the E-M5 is 270 grams lighter without the grip. With the grip the weight is only approx 40 grams lighter which I pay for with an extra battery but I have a much more usable camera that packs into a bag barely bigger than the D200 yet assembles into a fully gripped camera once I take it out and bolt on the vertical grip. All while I have the same weathersealed build to the buttons and body as I would on the D200 (One of the things I liked about it.) The lack of autofocus is nothing horrible of a loss for me with my personal experiences on the D200, I keep the 14-42PZ with me if I feel that 50mm f/1.2 and manual focus will not allow me to keep up. I keep a focus scale so I can reliably infinity focus or to set the lens to a range and "fire from the hip" so to say. But I get a f/1.2 lens that wide open, will optically outperform everything listed above when they're wide open. If not, a single stop down will keep that optical performance. All with minimal CAs. The distortion from the 18-35 optically is less than the Olympus options which means I have sharper edges and corners. And I have already paid for my Speedbooster when I paired it with my Nikkor 50mm f/1.2. So you could say my second hand $400 Nikkor with my $430 Speedbooster is in a way like a Nokton lens. A $800 dollar, f/0.9 lens that when stopped down will provide some of the sharpest shots out there or blow everything away into a dreamy background while providing a clear enough subject with a dreamy glow. So there goes the sunk cost factor for me. I could of bought a Nokton but that means I wouldn't have anything to mount on a D3s that I have already planned for in the future. For $400 I am getting one of the sharpest lenses that Nikon has ever produced that rivals the Sigma 35mm f/1.4A in center resolution when stopped down. I think that's a personal bargin if anything. I haven't mentioned how much flexibility a Sigma 10-20mm f/3.5 could give me, especially in that I can screw a filter onto it and achieve a 7-14mm f/2.8, as the Olympus 7-14mm f/2.8 has a large, bulbous filter element. Or perhaps I could bring up how a Tokina 11-16 f/2.8 if I need that extra stop for photography in the dark. It turns into a 8-11mm f/2.0 that gives you the extreme "wide" end" and with the Sigma 18-35 f/1.8A paired together, you have a 2mm focal length gap. All of these are within a similiar size as the Olympus 7-14mm f/2.8 announced, perhaps a bit bigger. Or perhaps I could bring up a nice 85mm f/1.4 option from anyone: A 60mm f/1.0. The reach you could achieve with the insane background isolation for those who need it. Even more center sharpness than you would have normally. Need even more isolation and speed? A Sigma 120-300 f/2.8, turning into a dangerous 85-213mm f/2.0. I already posted the results of what happens when you take a Nikon 70-300 f/4.5-5.6 (A fairly soft lens) and then use it at 300mm f/8 (213mm f/5.6). Utter annihilation of the background into pure smooth creaminess. Now imagine what a 106.5-213mm f/2.0 (Think of it as a 105mm-210mm f/2.0 for ease of memory) will do. IBIS is your stabilization and you now have a "very big set of primes" mounted on the camera. A metaphorical big set of primes that costs less than 4/3s lenses with equal or superior optical performance. Less weight than that? Tokina 150-500 f/5.6. A constant f/4 from 106.5mm to 355mm. The current furthest reaching m43 lens only hits 300mm and speeds at f/5.6. You'll have to wait until 2015 to get an Olympus 300mm f/4 and I doubt it'll be as low in cost as the Tokina here. By no means is the Tokina lighter or smaller but it will give you the optical performance, the stop advantage and the zoom. Those are merely a few choices of lenses that currently have no analog on APS-C or 135 format in terms of f-stop, giving me the flexibility to work with higher shutter speeds combined with more depth of field. All while I gain stabilization on all of them. All of this on a camera that turns into a compact, large pants pocketable body with a functional zoom (14-42 PZ or EZ or 12-32) combined with an autofocus. Of that, those lenses and the Speedboosted ones could fit on an even smaller companion body like a GM1. Photography before autofocus has existed for over a century and autofocus has been around for only two decades. It doesn't matter if you've been taking photos for 5 years or 50 years when the fundamentals are still the same. This is still easier than using a FM2n to me with the E-M5's metering and real time view. People still use Leicas today and I think that some of their users would find it troubling that you would want to give them autofocus. (Not that I necessarily prefer the lack of autofocus nor would I agree with the removal of it but it doesn't prevent anyone from taking amazing photos.) I am not advocating for people to become gearheads here. I buy lenses to create a set of focal length ranges that I can bring along to take the photos I want. Speedboosting on m43 gives me the capability to do that.