Based on my testing, of 5 50 F/1.4s and 7 50 F/1.8 Mk IIs, plus a 50 F/1.8 Mk I, I'd consider the 50 F/1.4 a 50 F/2.8, and the 50 F/1.8 a 50 F/2-F/2.2, from an IQ wide open POV. I am not talking build here, because the obvious winner is the 50 F/1.8 Mk I.
The 50 F/1.8 is very usable from F/2 - F/2.2 (copy variation), the 50 F/1.4 is not great at close distance focusing in mediocre light, and has a weird MTF curve in that it really only is soso at large apertures until it hits F/2.8, where it suddenly jumps through the roof, right to F/8. The F/1.8 focuses well close by, in any type of light, and is quite sharp from wide open, gradually gets better when you close down, gets beaten by the 50 F/1.4 from about F/2.8 to F/5.6, but is equally good again thereafter. At least. that is my experience.
This is something you will also find with most other 50s: the slower ones (F/1.7 - F/2) are good wide open, and get better slowly at smaller apertures, and reach their best somewhere around F/5.6 - F/8. The faster 50s (F/1.4) often are mediocre at F/1.4 - F/2.5, and suddenly becoem excellent at F/2.8, and stay that way until F/8 or thereabouts.
If you are looking for great bokeh, neither will do, BTW. You'll need to get the 50 F/2.5 CM if you want good bokeh. Plus this lens is great wide open already. Pity the AF motor is so noisy <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
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Regarding AF accuracy of the 50 F/1.8: it is IMO a matter of how to apply AF with this little critter. Yes, it tends to get less accurate in lower light, and that may well be a funcion of the relatively large steps of the stepper motor or gears of the AF mechanism. However, the way around this is exactly the same thing as we used to do with MF in a long ago past: focus on something with a good contrast difference at the same distance as your main subject. Black on black, especially in a darker environment, never is a good thing to focus on. It is impossible to do so yourself, and AF systems aren't good at this either. Black on white is a lot better. Always worked for me so far.
The two fast lenses i have come across so far which don't follow the fast 50s trend described above, are the Sigma 50 F/1.4 and the 50L. However, those may well have other problems straight out of the box, if you're unlucky.
Kind regards, Wim
The 50 F/1.8 is very usable from F/2 - F/2.2 (copy variation), the 50 F/1.4 is not great at close distance focusing in mediocre light, and has a weird MTF curve in that it really only is soso at large apertures until it hits F/2.8, where it suddenly jumps through the roof, right to F/8. The F/1.8 focuses well close by, in any type of light, and is quite sharp from wide open, gradually gets better when you close down, gets beaten by the 50 F/1.4 from about F/2.8 to F/5.6, but is equally good again thereafter. At least. that is my experience.
This is something you will also find with most other 50s: the slower ones (F/1.7 - F/2) are good wide open, and get better slowly at smaller apertures, and reach their best somewhere around F/5.6 - F/8. The faster 50s (F/1.4) often are mediocre at F/1.4 - F/2.5, and suddenly becoem excellent at F/2.8, and stay that way until F/8 or thereabouts.
If you are looking for great bokeh, neither will do, BTW. You'll need to get the 50 F/2.5 CM if you want good bokeh. Plus this lens is great wide open already. Pity the AF motor is so noisy <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />.Regarding AF accuracy of the 50 F/1.8: it is IMO a matter of how to apply AF with this little critter. Yes, it tends to get less accurate in lower light, and that may well be a funcion of the relatively large steps of the stepper motor or gears of the AF mechanism. However, the way around this is exactly the same thing as we used to do with MF in a long ago past: focus on something with a good contrast difference at the same distance as your main subject. Black on black, especially in a darker environment, never is a good thing to focus on. It is impossible to do so yourself, and AF systems aren't good at this either. Black on white is a lot better. Always worked for me so far.
The two fast lenses i have come across so far which don't follow the fast 50s trend described above, are the Sigma 50 F/1.4 and the 50L. However, those may well have other problems straight out of the box, if you're unlucky.
Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....