Originally posted by robert This lens was designed for film and would be the perfect portrait lens but on and APS-C camera why wouldn't the 50 mm 1.4 be just as good?
Sorry to be so simple, but first of all , you can't compare 77mm and 50mm for portraits as the angle of view / distance, hence result would be fairly different regardless of the quality of the glass.
Now, the reason why the 77 Ltd produces a specific 3D effect versus a similar but newer lens design such as the HD 70mm Ltd, is the gradient of sharpness between the center and the edges. Wide open, the 77 is still resolving a lot of lpmm in the center and gradually gets softer away from the center, which renders high contrast of the subject (when the subject is centered, for instance portrait) with gradually softening bokeh towards the edges. If you consider the 70 Ltd, is a different optical design, the peak sharpness/contrast in the center is less than peak center sharpness of the 77 ltd, but on the edges the 70 Ltd is sharper which render a harsher bokeh and overall less 3D pop effect as the 77 Ltd. Some lenses are better for some applications. You may consider faster lenses, such as 85 f1.2 and you might think that because the lens if faster , it would give you more 3D pop effect, but it does not necessarily render that much 3D pop if the contrast and sharpness of the center decreases as much as the edges when used wide open. You may even find f0/95 lenses they render crappy wide open because both edges and center are softened by the same amount, no sharpness gradient and no much 3D pop effect. Last but not least, the FA Ltd lenses don't have the latest coatings used for digital , so the drawback is that those lenses are more prone to flare and ghosting, but in good lighting conditions they render a colors with some kind of "natural, unfiltered" closer to what it was like in film days, you can't get that rendering with, for instance, the HD coating of the latest lens models.