Lets get this out of the way. I love this lens. I've used it enough over the last eight months to really get to know it. I would consider the 23mm f/1.4 Fuji to be one of the must have lenses for just about any Fuji X system user. This isn't a real review of any sort but there are a few things to consider if you're used to full-frame systems or not used to large aperture wides/semi-wides on APS-C in general. I'll get to those in a minute.
A couple of disclaimers. I'm not a particularly giant fan of the 35mm equiv. field of view compared to what we'll call 35mm lens guys. You know the type I'm talking about right? I did grow to appreciate the field of view as a one-and-only-one lens when using the X100 cameras for a while. It turns out to be an excellent and practical choice if you are only going to have one lens and one field of view and that's it.
I think I'm a little less enamored or mesmerized by a 35 equivalent idue to the fact that I shot Nikon cameras in both film and digital for decades. I swear there was never a 35mm lens for Nikons that I really liked, nor were they in the same league as the Fuji 23mm f/1.4.
I did acquire a fantastic, 35mm lens for the Leica M camera. A 35mm Summicron ASPH. By the time this happened I had grown accustomed to a 28/50 combo as my go-to kit. I really liked my 28mm and my 50mm glass for my Nikons and adored my 50mm and 100mm lens combo for my Hasselblad 500 cameras (which are very close to a 28/50 combo on 35mm film).
How Good Is It?
Now that we have my own bias out of the way I know most of you are asking yourselves; "Is it better than the Summicron ASPH"? The short answer is that I really don't know. I used the Leica exclusively on film. Typically on TRI-X which is a completely different ballgame when trying to evaluate how good a lens is in terms of resolution and all that crap. I can say they are in the same league in terms of macro effects like acutance and micro-contrast.
I've never hesitated to use either wide open. They both are fantastic at their respective widest apertures and the Fuji is a whole stop faster which is always better if you need the speed — which I do on the black/white project. As all the Fuji prime lenses go, they all focus way closer than any of the Leica M lenses and for me that's far better. They go from fantastic to unbelievably good a stop or two down from maximum aperture. Here's something that's way better than the Leica, the out of focus look is more pleasing.
Both are pretty much flawless for any real world picture taking needs. If I absolutely need image quality the 23mm Fuji would be one of the primes I reach for when optimizing for extreme enlargements. That's typically not how I use it for the black/white project though. The included photographs are how I use the 23/1.4 in most cases; Wide open, slowish shutter speeds, super high ISO's. All of these were made at f/1.4, 1/60s, ISO 3200. In other words I use the 23mm when I need it.
If you use any wide or semi-wide lens like the 23mm on APS-C don't expect dramatic subject separation at f/1.4 when used in what I would consider typical situations. Full-length pictures of people with a little environment as context for instance. At six to ten feet which would give you that kind of shot there's really not that much separation at all in typical indoor environments. That's the case with the above photographs.
Here's the thing though, you still have a very narrow margin of DOF at f/1.4 which means there's very little tolerance for focus errors if you want a critically sharp subject or plan on printing big. The translation is you still need to be extremely careful when shooting the 23mm wide open but you're not going to get super blurry backgrounds unless you are extremely close to your subject.
If you are extremely close to the subject then sure, f/1.4 vs f/2 will make a little bit of difference in subject separation but candidly those kinds of effects aren't really that useful as almost nothing will be in focus and the background will be out of focus no matter what aperture you use. Look at the following image as an example of what I am talking about.
This is an extreme example. The above was made an 18mm at f/8 and has far far more background blur even with a shorter lens stopped down a whopping *five whole stops. Sure the 23mm used the same way at f/1.4 would give you much more blur. So much so that Jessica's lips would probably be rendered super blurry.
Doing things like that might be useful or fun every once in a while but not typical. The bottom line is don't get the 23mm/1.4 Fuji with any thought that it's going to give you super bokeh-blurry-ness in all your pictures used in typical ways compared to your X100 23 f/2 or even your 18-55 in the same range. It's not.
Yes you've all seen the 23mm render super blurry backgrounds in all the on-line reviews. You've all seen the huge difference comparisons with the X100 at f/2 but those are all teeny-tiny things shot at about two feet away with backgrounds that are relatively far away. You are not going to see that with typical uses on subjects like people at half or full length. You certainly won't see night/day differences except for a narrow range of very very close subject distances.
Here's a shot about three or four feet away wide-open with some foreground that's super close (aka way out of focus)
This is actually a fairly good image to calibrate your expectations if you are coming from say the 18-55 or the X100 in terms of what to expect that f/1.4 to do for you. The point of true focus is Jeanette's eye on the left. Take a look at the pictures on the wall and some other stuff laying around on the shelf behind her. Take a look at the floor in the foreground. That's about the extreme of it at typical subject distances.
Sure the background would get blurry-er and blurry-er the farther away it gets but don't expect night/day differences compared to what you are using now if you've already got this range covered. Buy the 23mm f/1.4 for it's speed and fantastic IQ not any super-powers of subject separation. Buy it because it really is a one-lens go anywhere, do anything — even in the dark lens.
All images made with the Fuji XT-1 processed in Lightroom CC with VSCO FILM05 BW400CN applied on import. Most images of Jeanette in black made with the Fuji 23mm f/1.4 wide open at 1/60s ISO 3200 others about there check the EXIF if you want. Jessica in the white made with the 18-55mm at f/8 ISO 200 1/180th-ish with strobe.