I'm pretty sure that Nikon 58mm f/1.4 G is in my future at some point. I know it's not now while it's hot and new and going for full price for sure. Even when the street price new or used comes down in a year or so it will still be far more expensive than any of the regular old crappy 50mm Nikon lenses. I also know that it's not going to make one iota of difference in any pictures I will ever make as compared to what I am currently using or have ever used. We all have to have our little photographic fetishes though - part of the fun. I've mentioned on numerous occasions my personal poison is normal-ish primes. I've got a bunch of um. I even have some for cameras that I don't own.
I saw a tweet to me today from a few days ago asking for advise on a Nikon 50mm lens for film cameras. That ones pretty simple to answer - they're all pretty good. For the most part they're all built well and they're all pretty reasonably priced so get all of them if you want. Oh for normal people that would translate into - ummm grab whichever one you fancy at the moment that you have the spare change for. Even the much maligned Series-E 50/1.8 is nice in it's own way - specifically it's tiny. I say maligned because way back in the day you couldn't give them away as they were rumored to have an inferior build to the real Nikkors. They're fine.
Heck I would even say that under 99% of the picture taking conditions you will use any of the Nikkon 50mm family - manual or auto-focus, from $30 series E to crazy expensive 58 1.4G you won't even notice a difference. It's a nit. One won't make great images the other cannot. None of them will turn a great image bad or even a good image great.
You can concoct theories in your head about them and then replay some scenario about a different one providing drastically different results but in reality that's not actually going to happen. Of course AF vs Manual focus is quite a bit different - maybe the biggest difference depending on circumstances. Even if we separate the two categories AF v Manual there's not going to be any sea-change between any of them. Nits. Sure there might be minor differences side by side under magnification - is that how you are going to display your images? take one picture then another with a different lens of the same focal length and show them side by side under high magnification?
Okay with that gross generalization out of the way what are the things to consider? Well lets go through them just looking at the AF options.
- AF speed/convenience. Hmmmm I like the convenience of the AF-S/G lenses in transition between AF/MF will you use that? Speed pretty much only matters on the first shot in any particular focus zone in terms of near/far. Unless you are actually alternating pictures between a subject at infinity and really close up at like 3 feet it doesn't matter they are all REALLY quick to re-focus at same distance range. So where's that important? Big heavy telephoto lenses from far away that need to track with subjects moving toward/away from camera otherwise it's just an exercise to impress yourself as to the difference between two lenses while "testing" them. Oh unless your specialty is grabbing a single shot when you are not actually ready as you pull the camera from your bag and then immediately put it away again - there's that special case - yeah, right, let's optimize for that.
- Bokeh? Well the G's across the board look better to my eye when stopped down across various apertures across a wide variety of non-provocative backgrounds. Wide open they all have various ups and downs. For the most part the one I have a bunch of experience with as of late - the 50/1.4G generally looks pretty good. Let me qualify that - I don't go looking for things that will look bad on purpose and then compare "bokeh quality" as to which lens looks less bad - almost never will you have a case where any of them look great in things/situations that just looks shitty when out of focus. I'll call these provocative backgrounds for discussion. IF, if, if (when) I eventually get that 58mm 1.4G I fully expect it will look about the same on the vast majority of scenes and circumstances with they only way to tell is side by side comparison and even then possibly a hard time for most images. Not a transformative property for the most part.
- Speed as in aperture and very closely related how much out of focus-ness you can get. Well - they are all pretty stinking fast. I'll even include the mythical 1.2 ness factor in there - assuming it's so so so very important you might actually change brands to something like Canon to acquire this magic aperture. If we are comparing 1.4 to 1.2 you aren't going to see anything different. Well I guess you will if you are "testing" side by side and looking really really really really really hard. With most stuff even if you are looking hard you can't tell side by side. Now if we go into a non-testing set of conditions the difference between the two is not even close to being a foot closer or a foot farther away when you shoot close up - no contest. When shooting farther a way even less difference. Half a stop of light? Really in this day and age - how much is that worth and more importantly are you really getting that half a stop? Doubt it but possibly.
- That brings us to fall-off shooting wide open and T-stop or how much of that 1.4/1.2/1.8 is actually getting through in terms of real picture taking light. All lenses are going to have some degree of fall-off. The question is how much and what to do about it. Lens corrections in post will eliminate that if it's actually a factor in a particular image - most of the time it's not when shooting wide open. The case where it is falls into main subject on edge of frame and if that subject happens to be darker than things in the center which also has to do with the lighting of the scene. The other more common factor is shooting a subject on an even toned background - doesn't happen much in wide-open circumstances. Happens way more in the studio. Here's another thought - why would you give a shit if you actually end up adding vingnettes to a lot of your images. The Leica camp treasures some of it's mystical lenses due to the strong vignette - maybe it's a good thing for you? I will be you a the 58mm will have less falloff than the 50mm 1.4G. Ummmm yeah it's huge too.
- Sharpness/resolution. Let's just skip this okay? Are we talking wide open? Really okay let's go there. Ummm ummm - yeah right you are going to know which one is sharper with those razor thin planes of focus. Use a tripod wide open with live view focus at 100% magnification much? really? On live subjects? let me know how that works out. You don't - oh then don't bother contemplating it. You mean stopped down to "optimal" - for the lens or for that shot? They're all the same or just about.
Okay there you have it. Take it for what it's worth. Haven't been through shooting every 50mm on the planet? Go ahead. I have. I even bought a Canon pretty much just to use the 50/1.2 - even though I already knew what the result of my experiment was going to be. Holy shit that lens has some issues I get the same results from my 50mm 1.4G without those issues. Whatever.
I know this flies in the face of my own obsession with buying 50mm lenses. The difference is that I am up-front about what's going to happen as a result of my next acquisition. Would you ever hear me tell anyone that happen to have the 50/1.8G that their images would be a whole lot different - or even materially different due to the 58mm upgrade not a chance. Of course there will be a few differences - they will manifest themselves in a limited number of circumstances - some of which I may never actually shoot unless I am determined to go do so. Will one or the other exhibit some minor degree of improvement on some particular thing that bothers me but makes no real imaging difference - sure. At the same time it might bother me in a completely different way. Yes this happens a lot. There is no perfect.
Shot at top was conveniently located right in front of me during this post so hell - it's the one I am going to use. Shot wide open on the Nikon 50 1.4G. Bokeh? Fine. Liking bokeh or not liking it has more to do with scene, subject relationship/distance to background, and 43 other thing that come before the lens characteristics or 1.4 vs 1.2. As for the amount of out of focus-ness between 1.4 or 1.2… I was over 10 feet from the subject here. If I took a step to the left - heck a half of a step and framed the thing the same way that would have a bigger difference in how out of focus the near/far was. Same with another step forward. At this distance from the subject the OOF-ness doesn't seem too too great. The actual plane of sharpness is still razor thin. The only way to get the background to go all super fuzzy is to move much closer or move the background much farther back NOT 1.4 vs 1.2.
There you have it - pragmatic thought on the 50mm from a self-confessed 50mm fetishist.