2nd pinhole attempt!
Here's my 2nd pinhole drilling attempt. I think I actually had the hole rounder than this but I managed to screw up the burnishing at one point by letting the needle go too far in and tilt sideways. Anyway, here are the parameters I'm going on based on mrpinhole using 4.25" x 3.25" (polaroid pack film dimensions):
Pinhole Specs 1.jpg
I cut a square out of a soda can using a box cutter. I tried to flatten it out by rolling it against things of various diameters but didn't do such a good job. Hopefully I got it flat enough. I then sanded off the silkscreening on the label side of the aluminum and attempted to "dimple" it with a rather blunt sewing needle. Not sure if the needle I used was still too sharp, or if the cardboard I was using was too soft but I didn't do that good of a job with the dimpling.
I set my ancient, somewhat beat up, 1920s micrometer to 0.019" and stuck the thinnest needle I have into it. It didn't go in that far, so I put the needle in the chuck of my Dremel tool and lathed it against some 1500 grain sandpaper (which worked on it very slowly). I measured it now and then to see when enough of it had been tapered to my satisfaction. I then stuck it into the micrometer and marked the spot where it stopped with a sharpie. I decided that wasn't good enough though, and not having a pin vise at this time I put the pin in my dremel again, loosened the chuck so it would slide a bit, then stuck it into the micrometer gap so that the smallest part that wouldn't fit was right up against the chuck.
So then I just used the Dremel like a pin vise, without turning it on, to poke a hole in my not-so-deep dimple.
I then sanded both sides with both 600 and 1500 grain sandpaper. (The 1500 was going frustratingly slow, maybe due to my less than sharp and deep dimple.)
Then I decided that was still going too slow so I decided to try experimenting with a grinding stone on the dremel to see what I could do. It wasn't a disaster but it probably wasn't the best idea.
I also tried using the polishing wheel on the dremel with some abrasive compound (jeweler's rouge, basically) and that seemed to be ok but the surface was still a bit uneven. Not sure if the grindstone screwed it up or if I just didn't get the aluminum square all that flat.
Looked at it with my standard 10x jeweler's loupe, saw some burrs, and burnished it with my lathed-down needle. Repeated the sanding and burnishing a couple of times, but the last time I did the burnishing I did a rather sloppy job. (All the burnishing was done just holding the needle by hand without using a pin vise or using the dremel like a pin vise. I just used the makeshift pin vise technique to punch the initial hole.)
At some point I got tired of messing with it further, and in the loupe it looked pretty good. So I stopped.
Here are photos that I took of it using my iPhone with a 10x loupe held in front of the lens. (Yea, that actually works.) I don't have a scanner handy at the moment. All of the photos are a bit oversharpened to enhance detail at the expense of aesthetics.
The photo above shows the pinhole with a ruler. That's the metric side of a cheapo wooden ruler showing mm.
The one above shows the lathed-down needle next to the pinhole with the part of the needle that the micrometer says is the right width right next to the hole. It's very faint but there's a little sharpie mark on the pin at that point. NOTE: the needle is not actually bent. Since it's not exactly photographic grade glass, the loupe isn't corrected for astigmatism and thus exhibits a good bit of barrel distortion.
That's my attempt to compare the hole to the micrometer gap. Of course the shaft of light shining between the gap isn't the actual size of the gap, which is pretty difficult to see, and the lighting and DoF are horrible, but I gave it a shot anyway.
That's the pin placed over the hole. Difficult to tell, but maybe the hole is actually a little narrower than it looks. The mark on the pin is the sharpie mark showing the part that wouldn't go into the micrometer gap. (That part of the pin should be a little too wide anyway, so shrug.)
These two are my attempts to photo light shining through the hole. I think in the one on the left I just held it up toward the room lighting, and in the one on the right I placed a paper towel on top of a flashlight (to act as a diffuser) then set the pinhole plate on top of the paper towel and photographed it.
Not sure but perhaps these might be the photos that best show the real shape of the pinhole.
Anyway, I'm thinking that this isn't too bad but I'm betting I could actually do a little better next time.
What do people think? Is it possible to do better, and is doing any better beyond this worth anything in image quality terms?