50mm f/1.2 Nikkor vs. 58mm f/1.4 Nokton SL II

[dtcls100]

I have the 50 1.2 ais. It is very good stopped down to f/2 and smaller. Wide open I find it very hard to use on my F2. The rate of misfocused shots is too high in my opinion, even when carefully focusing. I suspect there is some considerable focus shift, given that your viewfinder does not utilize the full aperture (meaning you focus at about f2.8 even wide open). If you hit it, its fun and looks nice. But more often than not, the image has little sharpness due to misfocusing, not due to reduced overall sharpness of the lens (which is to be expected).

Another possibility is that your mirror needs to be perfectly calibrated for this lens. If the angle is not perfect, you can theoretically also get misfocused images... So be aware that using the lens to its fullest capabilities is not easy.

No focus shift on mine, as tested on Nikon film bodies and Sony A7Riii. Takes fine photos even wide-open, although at f1.2, it is a bit dreamy looking, razor sharp at f2

 

[awilder]

Keep in mind than on most Nikon focusing screens with central split image or microprism focus aids, they have a slight focus offset by about 0.06 mm while the surrounding ground glass is calibrated for accurate focus at the film plane. This offset results in a slight back focus shift and is likely designed to compensate for front focus shift of fast (f/1.2 to 2) normal lenses wide open.

 

[lukx]

Interesting bit of information regarding the split prism.

Regarding focus shift: This video illustrates that there is some focus shift with this lens. It moves forward wide open, and backward when stopped down.
https://www.youtube.com/watch?v=2aTKSjMIFyk

From my understanding (which might be entirely false) many fast classic lenses suffer from spherical aberration that gives them a slightly longer focal length in the center, and a shorter focal length at the edges of the glass. If you stop a lens down, you'll have mostly light from the center entering, hence have a slightly longer focal length than wide open. Sonnar lenses are famous for this, but aren't the only lenses with this phenomenon.

This should not be a problem with a camera that is truly what-you-see-is-what-you-get focus wise (EVF for example). But in my experience, when you use a fast lens on an SLR, looking through the finder, pressing the dof-preview button and then slowly stop down the lens, you'll notice that the image only darkens past f2.8. At least with my Nikon F2 this is the case. This would mean that you don't actually focus "wide open, even if your lens opens beyond f2.8. Applying the above logic of focus shift, this might explain why people find it so hard to focus this lens wide open. The focus shift, extremely thin depth-of-field and non-WYSIWYG nature of most SLR finders are working against you...

But there are so many variables to consider (lens, mirror, focus screen, user error) that these discussions don't usually amount to much. It is a nice lens and I wish the OP a lot of fun with his.

 

[awilder]

Nikon's SLR viewfinder optics WRT either the standard microprism or split image focusing aid's prism deviation only uses a section of the lens at f/4.5 (which is why these aids blackout when stopped down below f/4.5) even though your lens may be as fast as f/1.2. The reason these central aids have a deliberate focus offset is to compensate for the focus shift due to inherent spherical aberration at apertures much wider than f/4.5. For precise focus wide open, the surrounding matte/Fresnel field will be best and the subject will be focused at a slightly shorter distance than the central prism aid when confirmed with a 2x eyepiece magnifier. Nikon's B or E screens are optimal because the central spot is fine-ground glass and will accurately focus at full aperture. Of course the drawback is that it can be harder to determine precise focus in low light or without the aid of their accessory 2x eyepiece magnifier. If ground glass is not your thing and you still want a better focusing aid for fast lenses compared to the standard A, K or J screens, consider some of the type G or H screens as these are designed for lenses f/2.8 or faster. Their drawback is lack of DOF preview in the finder and blackout with slower lenses than f/2.8.