Is this cheating? Yes, it probably is. Does it matter? No, I don't think so, as in this case there is no loss of image quality: only improvement. There might be a reduction in AF functionality, a reduction in illumination and a reduction in your bank balance, but your pictures should look nicer. So that's a good thing, right? Unless of course you bought the original version last week, and now rather wish you hadn't.
A little extra explanation
* The word 'bokeh', for those who have managed to miss the on-line discussions and re-discussions, refers to the characteristics of out-of-focus highlights – their shape and the tonal transitions within those highlights. 'Good' bokeh describes fully circular highlights with smooth tones, and 'bad' bokeh shows highlights with jagged edges that reflect the number of blades in the aperture iris, highlights that are oval and which have sharp transitions from light to dark. Good bokeh creates a nice smooth background that doesn't distract from the subject, while bad bokeh fights with the subject for our attention. Good bokeh is a genuinely desirable characteristic to strive for.
** The popular meaning of apodisation (or apodization) in optics is the management of light as is passes through an aperture. Here it describes the altering of the effect of the hard edge of an aperture blade, to reduce the contrast in sharpness transition especially in out-of-focus areas. In the case of this lens, and in that of Minolta's Smooth Trans Focus 135mm f/2.8 lens from 1999 (which is still on sale under the Sony brand), an apodisation filter is used to create attractive and smooth bokeh by softening the brightness and focus transitions in high contrast out-of-focus highlights.
The filter takes the form of a circular neutral density filter that is clear in the middle but which darkens towards the perimeter, with the darkening used to mask, or blur, the harsh edges of the iris blades. The heptagonal shape made by the seven bladed Fuji iris diagram when closed down a few stops is smoothed to a more circular appearance by the obstructive interference of the darkened areas of the filter, and hard-edged highlights have their edges blended to a smoother, less distracting, form.
Light intensity is reduced as it passes through the tinted area of the filter, so exposure times need to be extended to compensate, hence the inclusion of T stop markings as well as F stops on this lens.
An inaccurate, but perhaps helpful, comparison to understand the effect might be this: you are holding a large piece of black card parallel to the ground on a sunny day, and a hard edged spotlight is formed within the card's shadow by the sun shining through a hole cut in the middle of the card. You can alter the harshness of the edges of the spotlight by suspending a ring of net curtain, tissue paper, or bubble wrap above the card that just overlaps the edges of the hole. The semi shadow that this material creates softens the edges of the spotlight circle, making the bright area blend more smoothly with the shadow. That, in a crude form, is the principle of how this apodisation filter works.
