Reshape Aperture Blades on Canon 50mm f18 ?

chadh · Joined: 01 Jan 2013 Posts: 5

Yes, I know reshaping blades may sounds silly, but here is my logic. Like most I shoot the Canon nifty between 1.8 and 2.8 (80% of the time). So, why cant I reshape the blades where they overlap, but only between 1.8 and 2.8? I've thought about it and when I'm shooting above 2.8, it's always for a large group shot, and I don't think the new blade shape will will change my image when focused so far way.

Dose anyone has words if wisdom for me before I throw my $99 away?

David · Expire: 2013-01-25

I would expect that results in aperture jamming 100% of the time. If you're using it on a camera with electronic feedback, you may even get error messages with the lens and be unable to use it.

ZoneV · Expire: 2011-12-02

These blades are very thin, I think it is hard to get them in another shape without .
Probably with Laser? Or with a scissors, and afterwards sanding the ridge.
Risk is high, I think you have to disassemble the the iris, and somehow have a setup to get the same shape on all blades.

Remember afterwards f-stops are a bit faster than they should - automatic exposure will be a bit off.

bugbait · Joined: 27 Sep 2013 Posts: 4

Interesting. I think a lot of us have thought of doing it, but I haven't heard of anyone following through. Polishing pins are the first things that come to mind to me. If they are metal as I would expect you would have to insure you ended with a black surface, not easy that.

Here are polishing pins, for jewelers.
Three tries and no go, inserting the link. Anyhow, go to riogrande . com and search for polishing pins. Other vendors have them as well.

soikka · Joined: 11 Jun 2008 Posts: 534 Location: Finland

bugbait · Joined: 27 Sep 2013 Posts: 4

No problem, makes sense. And thanks for the welcome. One of this forums members has already helped me elsewheres. http://www.riogrande.com/Search/polishing-pins Polishing Pins. I have them and use them occasionally for very oddball tasks, on metals and plastics. Oh and polishing too. A rotary tool like a Foredom or Dremel is used with them, but a stationary hand drill can work in a pinch. The color coding refers to the various abrasiveness of the silicone tips. If the aperture blades are a ferrous metal they might be too hard to be cut by them. Silver is what they are usually used on. Guess trying would be the only way to find out, preferably on a lens you don't care about. I don't have any old unused lenses. But I imagine a gentle hand and a fine miniature stone might work as well.

Excalibur · Expire: 2014-04-21

Couldn't you use an old manual focus lens with more blades?

ZoneV · Expire: 2011-12-02

I am a bit unsure wheter such a Dremel tool would work well.
The material is thin, I could imaging that the Dremel tool easily bends the iris blades.
But better testing it on a cheap lens, than too much thinking and guessing Smile

Dogtag · Joined: 27 Jul 2013 Posts: 164 Location: Holland del norte

DaveBob · Joined: 14 Mar 2019 Posts: 3 Location: Oregon, USA

A good number of years later... But here's my experience. All you need is a jig and you can cut any shape you want (carefully), with a rotory tool.

1. Grab a piece of thin sheet metal and bend it in half. Clean up the edges opposite the fold so they're even and smooth.

2. Drill locating hole or holes for the blade pins. This is easiest if you're hacking up old style blades with a pin on either end, but one pin style still works as long as you make sure of the next step.

3. Place folded end of jig in vice. You need to make sure the (top) edges come together firmly for at least 1.5 to 2 cm. The whole trick to making this work is in keeping the blade locked into place and firmly backed by the jig material... Any gaps or loose spots will shatter the blade when you cut it. Do whatever it takes to bend your jig so that when in the vice it's clamping evenly where it needs to clamp.

3. Trace your blade on the outside of the jig so you have a good reference, then scribe the new profile you want to cut. I won't talk to what shapes work... I made a square aperture with mine.

4. Now that it's marked out, clamp up the jig low in the vice so it doesn't vibrate horribly, then grab your rotory tool with cylindrical stone grinder and slowly go to town until your be profile is nicely shaped. Finish with a file and paper as needed.

5. Doublc check you cut the right shape by clamping a blade into the jig. You only get one chance so make sure it's pretty. Once satisfied, double check the blade is totally backed by the jig (except where the material is getting removed), then proceed with the rotory. Personally I used a high speed die grinder for the sheet metal jig and an itsy bitsy little Chinese dremel copy for the blade work.

6. The trick is to let the stone do the work and for the love of God, stay completely parallel to your work (or you'll wreck it all), and wear a face shield! Really, it cuts like butter so do take it easy. Once the bulk of the material is removed, go back and lightly clean up the edge of the profile. With a gentle touch you should be able to get a nice clean edge without removing hardly any of the jig material... Remember you've got more blades to cut and they should be identical!

6. Clean up any roughness on the profiled edges. I used a razor blade myself but there are a number of ways this can be done. End of the day, you need to them to remain perfectly flat while getting the edge baby butt smooth... without having to apply blacking or chemically dipping anything... Unless that's your bag and I salute you if that's the case.

Hope this helps anybody who's fool enough to toy with wrecking a lens in the pursuit of bokeh dragon. My first attempt was rather presumptuously made on a pristine helios 44-3 and it worked out perfectly... I just thought it up and did it. I wish everyone else the same good fortune!