The Canon 135mm f/2.8 Soft Focus lens (1987) is even older than the 1996 f/2L USM version. It only stops down to f/2.8 not f/2 and its Soft Focus filter is less relevant in the age of Photoshop, but the filter is optional and it’s possible to use the Canon 135mm f/2.8 Soft Focus as a standard lens, too. So, when we’re all looking to save some cash, how good an alternative is this older lens to the EF 135mm f/2L version?
Well it’s immediately clear that the more expensive f/2 version out performs its older rival in every department. The DxOMark Lens Metric Scores show that it’s sharper, 14P-Mpix to 11P-M-pix, brighter by 0.8Tstop with less Distortion, Chromatic Aberration and Vignetting.
In terms of sharpness the f/2L version is actually sharper at f/2 than the Soft Focus version is at f/2.8. Stop down the aperture on the Canon EF 135mm f/2L to f/2.8 and it also delivers better sharpness across the entire frame without the edge softness evident on the 135mm f/2.8 Soft Focus lens. In fact you need to stop down to f/5.6 on the EF 135mm f/2.8 Soft Focus until you get something approaching edge to edge sharpness, which is not great for a prime lens.
As already mentioned controlling lens shading at f/2 is optically difficult and some heavy shading requiring postproduction correction is inevitable on the EF 135 f/2L. Stop down to f/2.8 however and vignetting is much better controlled on the newer optic compared to its older counterpart, and shooting at apertures of f/4 or smaller with either lens the problem is eradicated.