Add aperture blades to old manual lenses

neil bayin wrote:

I wonder if anyone has tried this before, some old Minolta prime lenses are really sharp and nice, for example 50/1.4, problem is bokeh is kind of bad. But if we are more blades to it, would that improve the bokeh?

This is very hard in the old slr world because it will add weight and slow down the shutter speed, but for most of the ppl nowadays using as adapted lens, I don't think it's a problem anymore, just wonder if anyone has tried before and how hard it is.

I have cleaned several lens' aperture, take off all the blades and wipe off the oil stains and put them back, from what i imaging, all you need is buy two of the same lenses, drill holes on one of the plates, put the diaphragms in the new holes, that is it. One think I think will cause problem is it will increase the thickness and may cause diaphragm stuck,

Quite a few of my adapted lenses don't have an aperture control.

I've used paper discs up against the front element (with both circular & shaped apertures) and have tried an iris in front of the lens. In a few cases I've ended up with noticeable vignetting (usually when the lens has a long built in hood) but many have been OK.

Here's a quick example of shaped bokeh via a paper disc https://flic.kr/p/27KRhGp

For lenses with more space between the rear element & the camera I'm planning on experiments with my iris there, and then might end up buying some of the adapters that have an iris built in.

I personally wouldn't attempt to modify the aperture mechanism in a lens my DIY skills are definitely not up to it. Cutting a slot to allow a waterhouse style aperture to be inserted is a possibility, but I'd only consider that if I cant arrange something outside the lens.