Some photo, the Sigma 50mm f1.4 DG with APD filter by handmade.

I tried to create some filters, and I I tried Reverse Bullseye filter. But they are not good enough.

Last year I made one of the best. Now, I put it to inside of Sigma 50mm/1.4 Lens.

Photos in my flickr.

https://www.flickr.com/photos/89411920@N06/albums/72157688141829942

It looks like you placed it pretty close to where the aperture blades go, it that correct?

MediaArchivist wrote:

It looks like you placed it pretty close to where the aperture blades go, it that correct?

Yes, you are right.

I like the last two, they appear to have that STF-style bokeh (which I like). The other ones do not (IMHO). The real STF lens has a apodization lens element, and not just a filter. I wonder if that is what makes it work well in almost any situation, regardless of the characteristics of the scene?

Nonetheless, quite interesting what you have done, and promising. It looks like it improves the bokeh in some situations, while not doing much in others. I have the Sigma 50/1.4 EX, I consider it to have the smoothest bokeh of any lens I own... except the 135 STF and Zeiss 135/1.8 (longer local lengths might have something to do with that?).

d750guy wrote:

The bokeh looks terrible IMO.

Do you mind explaining this further - it looks very smooth to me, which is what is usually said to be desirable. How is this bad?

quadrox wrote:

d750guy wrote:

The bokeh looks terrible IMO.

Do you mind explaining this further - it looks very smooth to me, which is what is usually said to be desirable. How is this bad?

I think it's because the bokeh is just too smooth. To the point where it lacks definition and character.

The Davinator wrote:

The bokeh has lost any character it had...totally lifeless

I would also like you to ask you to elaborate - isn't the bokeh exactly the kind of smooth bokeh everyone (most people) desires?

Tom Axford wrote:

MediaArchivist wrote:

... The real STF lens has a apodization lens element, and not just a filter.

I think that means a filter. A filter is a lens element if it is part of the lens.

It appears to be more than just a flat filter, it looks like a convex lens element:

It serves no other purpose, although it is possible that the lens performance may be very slightly degraded if it is removed because of the change in the light path.

I would think more than "slight", it looks like a thoroughly integrated part of the optical design.

Tom Axford wrote:

It is certainly possible that they would deposit the filter onto an existing lens surface, but it seems unlikely to me as I would expect it to be much more difficult to do that than to deposit it onto a flat sheet of glass as is the case with most filters.

The more difficult construction may have been chosen after experiments demonstrated that simpler solutions were unacceptable. The Sony and Minolta documentation describe it as a lens group, specifically a two element group.

That diagram looks like a highly simplified diagram simply for purposes of explanation. It suggests that the lens consists of only one element, which is obviously a gross over-simplification. I wouldn't place any reliance on it for technical accuracy.

We may have to agree to disagree on the use of the word "obviously". Obviously an even simpler diagram would be a flat filter, yes?

A less simplified diagram:

Or, this:

More detail: http://www3.xitek.com/testreport/xitek/135stf.htm

I am ever more convinced that the use of a apodization element (more than a flat filter), placed near the aperture, is an essential part of the "special sauce" to get the bokeh effect for OOF scene elements regardless of their location (near, far, center, edge) or shape or contrast. The experiment by the OP is impressive, and I think demonstrates the effect very well when the scene allows for it, but other scenes (backgrounds) are not handled as well as a lens with a more complex apodization element.

Tom Axford wrote:

Very interesting!

Indeed! I became fascinated (obsessed?) with the 135STF the first time I read about it, and bought into the A-mount system specifically for it. I am gear nerd guilty.

The fuller diagram convinces me that you are right!

Until recently, it was the only lens of its type, so it is a little odd to conceptualize (or, rather, the concept is a little odd).

It appears that they have made the filter from a concave element of absorbent glass so that the varying thickness of glass provides the required variation in filter density.

I can tell you that the lens is big, and very heavy. There is a lot of pixie dust in there

I made it like a sandwich.

I have one of 135STF, I love it of Bokeh. But I will not take 135STF when I travel.

I often use 50mm / 1.4 more. So I hope that there is a 50mm STF lens.

The 135STF & 100STF is the only lens that has no cat's eye effect. So it is so beautiful bokeh.

There are still flaws in edge of my 50mm/1.4 lens.

my 50mm/1.4 with APD filter.

Compare with 135STF:

135STF with A900

135STF with A900

Any other lens with APD filter can not replace 135STF or 100STF.

Handmade filter is hard to uniform. Compare night shooting of three lens.

Maybe my 135STF is flawed

Tom Axford wrote:

Very interesting!

The fuller diagram convinces me that you are right!

It appears that they have made the filter from a concave element of absorbent glass so that the varying thickness of glass provides the required variation in filter density.

After my various experiments
This is indeed the only method, and retains good optical properties.

vfan wrote:

I have one of 135STF, I love it of Bokeh. But I will not take 135STF when I travel.

I use the 135STF where I probably shouldn't, like outdoor concerts. It is a beast to carry around, but the results are different than any other concert photo.

I often use 50mm / 1.4 more. So I hope that there is a 50mm STF lens.

The Sigma 50/1.4 EX (same one you were using) is my "most used" lens. I love the bokeh, and 50mm is (for me) the perfect single focal length. A 50/1.2 STF (maybe T/2?) would be killer.

MediaArchivist wrote:

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The Sigma 50/1.4 EX (same one you were using) is my "most used" lens. I love the bokeh, and 50mm is (for me) the perfect single focal length. A 50/1.2 STF (maybe T/2?) would be killer.

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Want a roXplosion!?

The 50mm/1.2 STF must be super super big lens!

I want the one, too.