[popo]

You can't please all the people all the time... I think a great 50/1.4 at not too high a price is a good choice over either a mediocre  f/1.2 that's affordable, or a better one people don't want to pay for.

[JJ_SO]

I don't get it. Shall I take those posts seriously, Frank and Rover? One wants 8mm more focal length, the other a bit faster aperture, no matter if it's usable. Those f/1.2 do come from the days when Film was really highspeed with around 6400 ISO. And grainy like a field of rocks. Or one of those early sensors which went beyond 1600 ISO.


With contemporary sensors,

• who needs f/1.2
• and is able to focus that properly
• and is willing to leave resolution, contrast and flare resistance completely on a mediocre side?

any idea why Nikon didn't, nor Zeiss with their latest "around 50mm" lenses? Certainly the price was no limit.

[Scythels]

Zeiss didn't do a 1.2 because they don't like partial stop lenses.  Other than the 18/3.5, they have none.

 

Nikon didn't because they haven't figured out how to make a 1.2AF with decent quality, not that the 58/1.4 should be lauded for quality.

[JJ_SO]

"...they don't like partial stop lenses" ?

 

I recall a Planar 85/1.2 for a Contax RTS jubilee edition (okay, those kind of rare stuff tends to be kept in a wooden box in a safe...), a Tele-Tessar 200/3.5, a Mirotar 500/4.5, a Planar 50/1.7, a Distagon 15/3.5 - Zeiss is not afraid of partial stops...

 

And I agree very much with " they haven't figured out how to make a 1.2AF with decent quality". Other way round: If the 58/1.4 comes for around US$ 1700, how much would they have to ask for 1/2 stop faster?

[peterottaway]

Even with modern cross hair style AF what is the effective f stop they are capable of ? Also to have quickish AF speed there needs to  be an amount of play in lens focus, when you are getting to f 1.4 and f 1.2 with almost no DoF, then most of these things are marketing gimmicks. Look how cute our designers are !

 

The (lack of) quality of Live View on OVF cameras means that you need a lot of practice and luck to get a reasonable  in focus rate.

[JJ_SO]

Jabez02, it's not only the very narrow DOF which makes it difficult for the AF module to focus - given this module is carefully adjusted and the lens reacts always the same on various distances between camera and object.


It's also not only the tolerances between AF module and sensor itself which ideally should be exactly parallel. In reality I've seen the planes not being parallel which lead to slightly different focus results of the left and right outer focus point. And if I have 51 focus points, I'll use them. But with high resolving sensors and just normal manufacturing tolerances tiny differences suddenly start to matter. It's very demanding to manufacture these devices.


A decenterred lens is another failure source.


And at least, in reality we rarely have sensor parallel walls to focus at - this happens just for reproduction tasks and there we close the aperture to the best resolution two or three stops. In reality we do have DOF of what we're aiming at. Look a the topography of an eye - the distance between eyeball and eyebrow is visible with f/1.4, with f/1.2 even more shallow. When aiming the little AF point's frame, to which part of the eye it is referring? The eyelash, the little wrinkles on the skin? If there's some depth in space within the AF point's frame, the AF-module starts to guess - at least, I can't predict, on which point the best focus will be.


With a fast wide angle in combination with Nikon's comparatively big AF point frames (in FX it's better, in DX the frames cover too big areas), almost every focus action becomes a guessing. When Klaus starts to test the Sigma 18-35/1.8, he will notice that, too. I think those fast lenses deserve the best AF and I'm pretty envy on the EOS 70D's modern AF design. DPreview found significantly more keepers because of good sharpness than with other, older AF modules.


I can't blame Nikon - the "fastest widest" wideangle they offer is 24/1.4*, for them there's no need to nourish a strong and partly better competitor. But this is short thinking. If I knew, I like this lens for whatever reasons and would start to buy APS-C DSLR without any or only few lenses and I would know the AF of this particular camera is the best for it - I'd be stupid to go to the Nikon system.


* which costs 260% of the Sigma zoom.

[popo]

Don't forget the depth of field is dependant on things other than focal length and aperture, but also focus distance and sensor format.

 

The depth of field on a 50mm f/1.2 still isn't a problem for AF in most cases. You've got around a couple cm to play with assuming you're shooting wide open at 1m. At worst, you may need a little AF micro-adjust. I tend to find I need to set it on faster primes, but once done the AF is repeatable with a high success rate.

 

A 135mm f/2, or even 300mm f/2.8 would be far worse under similar conditions, but of course they would normally be used at greater distance than a 50mm would be. I don't currently have a super-fast 50mm, but I do have and use 135/2 and 300/2.8 and don't have any problem with AF accuracy.

[thxbb12]

Jabez02, it's not only the very narrow DOF which makes it difficult for the AF module to focus - given this module is carefully adjusted and the lens reacts always the same on various distances between camera and object.


It's also not only the tolerances between AF module and sensor itself which ideally should be exactly parallel. In reality I've seen the planes not being parallel which lead to slightly different focus results of the left and right outer focus point. And if I have 51 focus points, I'll use them. But with high resolving sensors and just normal manufacturing tolerances tiny differences suddenly start to matter. It's very demanding to manufacture these devices.


A decenterred lens is another failure source.


And at least, in reality we rarely have sensor parallel walls to focus at - this happens just for reproduction tasks and there we close the aperture to the best resolution two or three stops. In reality we do have DOF of what we're aiming at. Look a the topography of an eye - the distance between eyeball and eyebrow is visible with f/1.4, with f/1.2 even more shallow. When aiming the little AF point's frame, to which part of the eye it is referring? The eyelash, the little wrinkles on the skin? If there's some depth in space within the AF point's frame, the AF-module starts to guess - at least, I can't predict, on which point the best focus will be.


With a fast wide angle in combination with Nikon's comparatively big AF point frames (in FX it's better, in DX the frames cover too big areas), almost every focus action becomes a guessing. When Klaus starts to test the Sigma 18-35/1.8, he will notice that, too. I think those fast lenses deserve the best AF and I'm pretty envy on the EOS 70D's modern AF design. DPreview found significantly more keepers because of good sharpness than with other, older AF modules.


I can't blame Nikon - the "fastest widest" wideangle they offer is 24/1.4*, for them there's no need to nourish a strong and partly better competitor. But this is short thinking. If I knew, I like this lens for whatever reasons and would start to buy APS-C DSLR without any or only few lenses and I would know the AF of this particular camera is the best for it - I'd be stupid to go to the Nikon system.


* which costs 260% of the Sigma zoom.

 

That's why mirrorless is the way to go: good bye to AF inaccuracies, AF calibration, issues with different wave lengths, etc.

All this crap is history and for the best :-)

[JJ_SO]

I'm not glued to the mirror. It's just, as long the AF of mirrorless (at least the one of the A7R, i.e.) doesn't focus properly in dim light, I have to stick with the inaccuracies of DSLR   It's not helping if I say "sure, it's blurred, but if it would have been more light, it would be razorsharp!"

[Rover]

I don't get it. Shall I take those posts seriously, Frank and Rover? One wants 8mm more focal length, the other a bit faster aperture, no matter if it's usable. Those f/1.2 do come from the days when Film was really highspeed with around 6400 ISO. And grainy like a field of rocks. Or one of those early sensors which went beyond 1600 ISO.


With contemporary sensors,

• who needs f/1.2
  
• and is able to focus that properly
  
• and is willing to leave resolution, contrast and flare resistance completely on a mediocre side?
  

any idea why Nikon didn't, nor Zeiss with their latest "around 50mm" lenses? Certainly the price was no limit.

Sorry, but you've made a few assumptions on my behalf. The 1.2 may not be as cherished as it was in the film days, but nevertheless it was and still is a sign of prestige. Lately, there has been a kind of resurgence in ultrafast lenses (SLR Magic 50/0.95 and the Voigtänders come to mind) so a few people may have been expecting Sigma to jump on this bandwagon. Samyang reps did say something about a 50/1.2 lens down the road as well.

BTW, Fredmiranda "Alternative gear" forum has a thread called "f/1.2 or faster lenses wide open". So it's an elite club nevertheless - though I fully understand Sigma's motivations and what you said as well.

Me, I've never owned anything faster than 1.8, so you missed.