Homemade pinhole, focal length 40mm, estimate f/400

[KeithM]

OK, so this isn't really a serious lens test but since I finally got round to trying some more pinhole photography, it seemed the right place to post the first results of my efforts !! :)

It's hard to measure the diameter of the hole but I estimate it to be around 0.1mm and mounted in a M42-Nikon adapter ( which places it slightly inside the throat of the camera ) it gives a focal length of about 40mm.

The shots below we're taken as Raw images, exposure of 15 seconds in slightly overcast but bright conditions - using Raw gave me a bit of latitude in exposure. The images were converted with s7raw, adjusted a little for colour temperature, resized down to 720, then.... OK I applied a little USM to add a bit of definition to the detail and then resized down to a realistic size... - OK - resized to a size where the images stop looking too soft :)

Keith.

[KeithM]

The photo below is a rear view of the pinhole in it's mount. The M42-Nikon adapter as supplied has an 'infinity focus' correction lens - I took this out and replaced it with the pinhole. The pinhole was made in a piece of soft-drink can and sandwiched between two pieces of matt black plastic ( a chopped up, black, 3.5" floppy disk ) to cut down on reflections. A 20mm long M42 extension tube was screwed to the front as a lens hood !

The pinhole is made by punching a dimple into the metal ( but not piercing it ) and then filing the other side until a small hole appears.

Keith.

[KeithM]

I don't think the hole could be usefully any smaller - in the image below, there are ( well, what appears to me to be ) diffraction artifacts around the highlights of the spokes in the front wheel.

The bike is a 3" long model btw.... :)

Keith.

[KeithM]

First, with an equivalent angle-of-view to a 60mm lens ( in 35mm terms ), this isn't going to give that ultra-wide pinhole look ! I don't think you can get much shorter thanks to the mirror. You do get nice even illumination though.

Second - small sensor means small pinhole but that then suffers from diffraction effects. I think I'm going to try making another pinhole in slightly harder metal and see if it works any better ( drink tin aluminium is a bit soft and I suspect 'tears' too easily when filing, making a ragged hole ! )

And finally - and this is a big bugbear - dust ! Any foreign object on the CCD surface just casts a nice sharp ugly shadow of itself. No escape from the ugly truth of just how much dust there is on the sensor :rolleyes: - just break out the healing/cloning brush.

So...

Have I enjoyed myself doing this ?? .... yep.

Will I do some more ?? .... yep.

Is it a waste of time ?? .... ! :)

Keith.

[ianmcc]

Great fun!.. I can see why people order up the laser drilled holes, you'll get a sharper image....

[KeithM]

Hi Ian.

"I can see why people order up the laser drilled holes" - me too Ian - I'm going to have another go at homemade and then see about getting a commercial pinhole.... the one good thing about the mount is that I can fit any disc upto 30mm diameter so swapping is a cinch.

Keith.

[S_Leeper]

On trick to consider... after punching the hole & filing the hole take some wet & dry sandpaper to smooth the filing.
Start with 400, then 600 & finally 800.

If you are really energetic(sp???) you might also consider painting with sandable primer then sanding (use 600 then 800) after about 5 - 10 cycles of priming & sanding (try not to sand down to the metal after the 2nd or 3rd coat) shoot a coat of paint (gloss black) then use some rubbing compound to smooth it out & dull it some.

Alternatively, one place to buy pinholes.
http://www.zoerk.com/

[KeithM]

Sam,

I agree totally with the finer wet&dry to get the hole smoother - I only had some coarse grade to hand so that won't have helped !

I did consider painting the metal to get a dull matt finish but for one, I was impatient to get going :) and second I wanted to avoid ( with extreme prejudice ) the possibility of anything foreign getting into the S2 - and using the two plastic disks gives me a convenient carrier with fast swapping of pinholes !

Thanks for the link to zoerk... I was seriously looking at Lenox Laser - their pinholes look really good in very thin metal - but the cost of shipping bloated the cost into orbit ! There are suppliers in the UK of pinholes, and metal shim, so I'm probably edging toward a packet of shims, a punch, wet&dry, binocular microscope and a bottle of Guiness :beerchug: - I love a challenge :)

If I get a move on, I'll be able to join in on Pinhole Day (http://www.pinholeday.org/) with a decent aperture !! :)

Keith.

[S_Leeper]

Pinhole Day sounds interesting...

Actually the paint was to give a coating to the surface so as to sand a smoother hole.
Do you mount your pinhole "plate" onto an extension tube???

[KeithM]

Ah - I see what you mean ! - my apologies...

I am a total newbie at this so I've been trying to gather as much info as I can on making pinholes. Given the small size I want to achieve, the technique I've tried is to punch a dimple into the metal but not pierce, then gently file/sand the protruding dimple until a hole appears - the theory being that you should be left with a very thin edge to the hole ( good for reducing diffraction effects ). I guess this depends very much on the type of metal but also very careful selection of punch - a shallower angle than a pin but with a good sharp point. I've placed an order for a 0.2mm pinhole and pack of 10 silver shims from Pinhole Solutions (http://www.pinholesolutions.co.uk/) here in the UK - this will give me a known good pinhole against which to compare my efforts ! :) - so I'm totally open to any advice to improve my chances of getting a good hole.

Regarding the mount - the Nikon-M42 adapter I use has an infinity focus correction lens to the rear of the adapter which is slightly inside the throat of the camera body - the pinhole replaces that lens to give me a slightly shorter focal length ! It's not a cheap option but gives a nice way of mounting the pinhole. It also lets me use an M42 extension tube on the front as a lens hood - I thought it must be a good idea to keep as much unwanted, non-image forming light from illuminating the pinhole as possible.


Keith.

[HulaMike]

Keith,

Have you considered locating machine shop with lasar cutting capability? Maybe a sign or engraving shop that uses lasar CNC routing. They could burn a pretty small hole, .002" maybe, and it would be perfectly round with no dimple in the metal.