[LennyBloke]

It may have been suggested before (but I've never noticed it) and I certainly don't have the skills to even attempt it but would it be possible to re-shape the aperture blades in some older lenses to "curve" them so they resemble the blades in newer lenses and give the more rounded Bokeh effect?

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Last edited by LennyBloke; 11-26-2021 at 11:26 AM. Reason: wrong word used

[c.a.m]

would it be possible to re-shape the aperture blades in some older lenses to "curve" them so they resemble the lenses in newer lenses and give the more rounded Bokeh effect?

Interesting idea.

I'd say I'm fairly handy with restoring older lenses and using tools in general. I've removed and restored only two sets of diaphragm blades -- both successful jobs, but didn't require any physical modifications!

The blades are extremely delicate and must be handled with care. It might be possible to restrain a blade in a cushioned clamp jig of some sort, and use a high-speed rotary tool (aka Dremel). Even a slight deformation of the blade would render it useless.

Also, I would think that changing their physical dimensions or shape would create a problem with the aperture and exposure setting -- the blades are designed with close geometrical tolerances.

It will be interesting to hear other peoples' impressions. I'd be glad to hear if someone has done this.

- Craig

[pschlute]

Grab yourself a 50mm M series f2.0 and give it a try for fun. Unless you want to have a go at one of your A* lenses John ?

[LennyBloke]

Grab yourself a 50mm M series f2.0 and give it a try for fun. Unless you want to have a go at one of your A* lenses John ?

...Great Advice Peter - I'm just unscrewing the A*200 Macro now......

[Lowell Goudge]

The problem is that I am not sure when it comes to exposure accuracy, without replacing the blades with new ones, you will have the correct exposure, a hexagon or octagon does not have the exact same area as a circle when you consider the measurement across the flats compared to a diameter of a circle, close but not exact, and if you”sculpt” the blades your aperture may become inconsistent

[tuco]

Do you mean remove the aperture blades, clamp one up in your bench vise and take a file to it? Or, perhaps, modify them with expensive machines/processes that none would likely afford?

[kypfer]

Surely if any material is removed from the aperture blades the resultant aperture will always be larger than the original, so without some clever rejigging of the aperture closure mechanism the lens will always over expose at the indicated aperture, unless all metering is done manually (the K-3iii maybe an exception to this).
Any depth of field scale would also become redundant and the minimum aperture will no longer be very small, unless the mechanism can be modified to cause the blades to travel further than the original design.
To ensure symmetry all of the blades would need to be clamped together and modified as a unit.
As for the plotting of the curve required to achieve suitable results … you'll need some fairly specialist software or be particularly competent on a drawing board!
Good luck

[kiwi_jono]

Interesting. Not sure it would make much difference to bokeh (even stopped down a bit) - except for converting hexagon to round highlights.
Some lenses used for video have some pretty funky aperture shapes and could imagine someone modifying for that (although you can get a similar affect by using lens wide open with a cap with a shaped opening on it.

[Apet-Sure]

I would think that anyone willing, and competent, to make this kind of modification would charge big bucks. And the results may not be as desired due to reasons mentioned above. It would most probably be cheaper, and certainly easier, to just buy a lens with curved blades. That way you can be certain the design is optimized for those blades.

[Michail_P]

That’s an interesting idea but I don’t think it’s doable. Firstly it would require really precise equipment for trimming the blade and reshaping it. It’s not just a matter of skill. Secondly, as well mentioned above, you would actually alter your lens’ exposure capabilities (EV, Dof). Would a round bokeh be worth the hustle? Imho no. I like polygons anyway...

[house]

It seems to be that, in addition to the aperture issues, it would be *very* difficult to ensure the blades don't snag at all after removing material from the them.

[c.a.m]

On further thought, I wonder whether the blades could be shaped by a CNC laser cutter. The machine could be programmed from a design profile. A challenge might be securing each blade to the cutting bed.

I don't know whether laser cutting can be done on such delicate pieces.

- Craig

[stevebrot]

All it will take is one simple touch to bring home the folly of the attempt. They are flexible.


Steve

[Lord Lucan]

would it be possible to re-shape the aperture blades in some older lenses to "curve" them so they resemble the blades in newer lenses

The short answer is no.

[shyrsio]

It may have been suggested before (but I've never noticed it) and I certainly don't have the skills to even attempt it but would it be possible to re-shape the aperture blades in some older lenses to "curve" them so they resemble the blades in newer lenses and give the more rounded Bokeh effect?

I don't know if you ever held an aperture blade in your hands but they are fragile. they look like plastic at first but they are super slim metal sheet, it is impossible to alter them without braking them imo.