A STF-lens does not smooth the picture. The 135mm STF is actually super sharp. Its smooths the out of focus area to deliver stunning bokeh - even when you start stopping your lens down.jeffa4444 said:Apodization filters are used to accomplish the following:- "In optics, it is primarily used to remove Airy disks caused by diffraction around an intensity peak, improving the focus".
Sony / Minolta STF 135mm f/2.8 [T4.5] is manual focus only and this is what is said about it:-
Apodization is a process in spatial signal processing which can enhance resolution by reducing the secondary maxima in the diffraction pattern of the lens' aperture. The STF lens features an optical apodization filter in form of a neutral-gray tinted concave lens element near the lens' diaphragm modulating the intensity profiles of the circles of confusion in such a way as to become truly Gaussian. Thereby, it is also deemed to improve the "bokeh" of the lens, that is the character of the image in the out-of-focus areas.
The lens offers two separate diaphragms; one nine-bladed circular diaphragm, controlled by the camera when the lens is set to auto mode ("A"), and one ten-bladed perfectly circular diaphragm, which is controlled by the lens' aperture ring when set to manual settings T4.5 to T6.7.
The f-number in this lens refers to the effective aperture opening and determines the depth-of-field produced by its use. The T-number refers to the amount of light, which passes through the lens and is collected on the film or sensor, as such, transmission stops are used by the camera to calculate exposure. Both values differ significantly, because the tinted glass element remains in the optical path all the time. Fully open, the difference amounts to 1.5 EV, however, the difference will become smaller as the aperture is closed, just as the smoothening effect will become reduced.
This lens use of T numbers mirrors lenses in cinematography which do not have f stops but want accurate transmitted light.
If this is what Canon is working on then I would suggest its aimed at portrait shooters and doesn't have a secondary purpose. Cameras such as the 5DS provide so much resolution that they are not flattering to skin imperfections and an element of "smoothing" would enhance the subject.
Minolta's STF does not have AF. But Fuji has a 56mm that does: FUJINON LENS XF56mmF1.2 R APD
Like the Minolta its a stunning lens. And it has AF - a world's first for this kind of lens.
The ARD is an extra 500$ compared to the standard 56mm FUJINON lens.
Stumbled on a good article about the difference between the two FUJINON-lenses: https://ivanjoshualoh.com/2014/12/13/apd-the-new-king/ Could be the same for the Canon (if its a apodization lens too).
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