Would it be possible to modify a lens to be a STF lens?

And another thought about the STF effect-- why hasn't minolta/sony developed a controlled logarithmic aperture closure during a shot to make all lenses Capable to have an STF effect (basically doing what the film maxxum 7 does without 7 separate shots). Has any tried to simulate this with a manual focus lens with a aperture ring (closing or opening the aperture while taking a shot?)

Those are interesting points. Incidentally that gradient on a transparency is precisely what I have tried as well. I've also thought of doing it on a polycarbonate like a cd-case, but I don't have a good printer for it nor have I found good paint or other dyes to make a good enough gradient pattern. My intention was to test it with cheap materials first, then use whatever method works best to paint a gradient on one of those glass plates you use with microscopes and cut it into shape.

I've also thought about that which you speak of as "controlled logarithmic aperture closure" and I concur that implementing this in firmware would be a great idea.
I haven't come up with any good hacks to make it work with all shutter speeds, but figured that it could be possible to intentionally grease the blades to make them move slowly and then find the shutter speed that matches the closing speed of the blades. That would not be very useful though, since it would mandate a specific shutter speed AND aperture, thus leaving only the sensor sensitivity setting to control exposure.

Implementing such a thing in software though might require hardware changes too, depending on how the diaphragm actuation is done. It might not be possible to control the aperture lever with enough precision and smoothness to create an STF effect without visible steps. Of course, the film 7's method wasn't smooth either, but I haven't seen the results from it.

Creating new lens elements for the 50mm is an interesting idea, but sounds way too expensive and beyond the abilities of most of us so personally I've abandoned such thoughts.

Here are a couple of unprocessed before/after shots:

Without STF


With gradient on transparency


Adjusted fill light/shadows on this one a bit:


EDIT: You can do other interesting things with the aperture besides just STF'ing it...


Edited by Gubbe - 17 January 2008 at 19:15

Nope, STF has nothing to do with soft focus or diffusion. STF is "Smooth Trans Focus" and it's about smoothing the edges of bokeh.

There is no photoshop work.
Those JPEGs are straight from the camera, just resized. The third one had some adjustment to fill and shadows made in Picasa. That's it.
About transparency... think overhead projectors and read laquire's posts again, including the topic of this thread.

Edited by Gubbe - 03 December 2006 at 16:39

I took some sample shots in STF mode on a Dynax 7 today. Samples taken with Min 50 f1.7, 135 f2.8 and berrcan at 70 and 210. I'll get the film processed this week and post the results. I'm interested to see what it looks like vs the stf lens.

The problem with the non linear ND element in the STF is that it interferes with the AF sensor to the point where AF is impossible with the current system used by all SLR cameras. I was thinking that they could use a combination of linear polarizing filters, one group fixed and one that rotates 0-90 degrees. So the lens can turn the nonlinear ND group on and off and every step in between by rotating one of the polarizing filters. This way, the camera can AF with the "STF" turned off and as soon as you take the shot, the "STF" kicks in.

the correct filter needed

would cost quite a bit unfortunately. says minimum pricing is 950$..