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Home-made pinholes

dudler

Time for an update: I still use film, though. Not vast quantities, but I have a darkroom, and I'm not afraid to use it.

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Home-made pinholes

2 Aug 2020 9:05AM   Views : 539 Unique : 340

11864_1596355366.jpg

I hope youíre going to find this distressingly simple. There isnít a big secret, so all you need to do is get on and try it, if you want to.

You will need one camera body cap, a three-quarter-inch square of aluminium kitchen foil, and some glue. Evo-Stik or Bostik is good, superglue will do fine. The only tools you will need are a drill to make a quarter-inch hole in the middle of the body cap and a sewing needle with a fine point.

Ready? Drill through the body cap, roughly in the middle. Itís worth going all high-tech and using a penknife of craft knife to remove any swarf round the hole, so that it doesnít fall onto your sensor.
Put the foil on an old newspaper and make the smallest hole you can manage in the middle of it.

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Glue the foil onto the body cap, with the pinhole roughly in the middle. Donít worry too much about accuracy: you can always remove your Ďlensí from its mount and replace it with a new piece of foil.
Attach the body cap to a camera and set the ISO to 12,800 or higher, and the mode to Aperture priority, and experiment in bright light: you should, just about, be able to use handheld exposures.

Please note a few things that may make it less simple. I use Sony Alpha 7 bodies which are mirrorless, and give a reasonable viewfinder image with a pinhole, as well as operating satisfactorily in Aperture priority mode. They need to be set to ĎRelease without lensí in the menu, as they do for Lensbabies and other non-electronic lenses. Other brands may need to be set to Manual exposure mode, though the meter should still give a reasonable guide to exposure.

Contrast will be low and exposures may be rather dark: Iím not sure why this happens, but it seems to be consistent.

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Dust on the sensor shows up better with small apertures, and a pinhole is smaller than anything youíve used before. Donít panic about all the marks which are suddenly visible Ė if they donít show up with proper lenses itís not worth cleaning the sensor. Use the Spot Healing Tool in processing. You may well get light leaks around the body cap (as in the picture above this paragraph) - try holding a finger around the edge nearest the light source.

If you drill an off-centre hole, you will create a shift lens, capable of giving correct perspective with the field shifted up, down, or to the side. Iíve not tried this, but the possibility existsÖ

Putting a body cap directly onto a mirrorless body will give you a wideangle view. Extension tubes will allow you to vary the focal length.

Strictly, you can calculate the size of the pinhole to get the best balance between unsharpness caused by the pinhole being too big and allowing light from a point source to form a disc on the sensor and unsharpness caused by diffraction, where light rays are bent by the edge of the pinhole. Perfectionists worry about this, as they worry about making the pinhole perfectly round and smooth to reduce diffraction effects. You can worry about this later, if you want.

For now, get on with it and you can have your first pinhole picture in half an hour from reading this blog: less time than it took me to write it, because I had to take the pictures to illustrate it!

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Comments

PaulCox Avatar
2 Aug 2020 9:31AM
Will have to that a go!!!!!! Paul
woolybill1 Avatar
woolybill1 Plus
17 39 79 United Kingdom
2 Aug 2020 11:05AM
This is really worth trying; thanks for your help and encouragement with the initial stages, John. I have had some fascinating results both with 'your' pinhole and one I made myself, tripod-mounted and hand-held between ISO 400, in bright sunlight, and 3200. It does pay to experiment.

Subjects need to be selected with care. A bright red bus and the brass radiator on an Edwardian vehicle at Beamish museum last summer really stood out:
49816_1596362077.jpg

49816_1596362101.jpg

I might get round to uploading those two to the Gallery when I'm next in the mood for colour.
A frame full of clutter, such as a packed bookcase, really doesn't work:
49816_1596362481.jpg

There is therefore a simple recommendation:
KEEP IT SIMPLE!
49816_1596362685.jpg


Bill

AltImages Avatar
AltImages 3 4
2 Aug 2020 11:20AM
It's something that I've always meant to get round to doing. However, there's one refinement that might be worthy of people's consideration. When I was looking into it a few years ago there was a website which gave the optimum pinhole diameter (playing off sharpness against diffraction for any given focal length). Anyway I realised that the required diameter range was similar to the range diameters that acupuncture needles are sold in, which are typically £6 for a box of 100 on eBay. So that was my plan.
dudler Avatar
dudler Plus
20 2.2k 2064 England
2 Aug 2020 1:27PM
Thanks to all - particularly to Bill for the pictures and practical advice on choosing subjects.

Paul - I'm honestly not sure how much the size of the pinhole affects results in practice. I am pretty sure that making sure the pinhole has no rough edges is as important. The perfectionists therefore make pinholes by putting a dent in a sheet of metal, then filing away material on the outward bump, then fine-finishing the edges so the 'pinhole' is smooth and circular. There have been firms offering ready-made pinholes, too.

The big problem will be what to do with the other 99 needles...
philtaylorphoto Avatar
philtaylorphoto 22 334 2
2 Aug 2020 7:07PM
See, comments on your practice blog. I also used to show students pinhole work.

Loads easier on digital, as you don't have to calculate reciprocity law failure, as on film.

I used to use sticky tape to hold my tinfoil on my body cap. Of course, Canon body caps are perfect, as having odd numbers of letters, the centre is in the n.

Don't forget to press the stop down lever to check your depth of field😀
dudler Avatar
dudler Plus
20 2.2k 2064 England
2 Aug 2020 9:09PM
A prize to the first person to check their DoF!
AltImages Avatar
AltImages 3 4
2 Aug 2020 9:15PM

Quote:Paul - I'm honestly not sure how much the size of the pinhole affects results in practice. I am pretty sure that making sure the pinhole has no rough edges is as important. The perfectionists therefore make pinholes by putting a dent in a sheet of metal, then filing away material on the outward bump, then fine-finishing the edges so the 'pinhole' is smooth and circular. There have been firms offering ready-made pinholes, too.

The big problem will be what to do with the other 99 needles...



Well John, there's only one way for me to find out! 😊 There's reckoned to be quite a difference, but I don't yet have any practical experience.

As for the needles don't you yet know how my models suffer for my art? Lol
philtaylorphoto Avatar
philtaylorphoto 22 334 2
2 Aug 2020 9:17PM
You need to be careful with chromatic aberration. I understand you can solve this by injecting apochromatic gases via the pinhole.
dudler Avatar
dudler Plus
20 2.2k 2064 England
3 Aug 2020 7:42AM
I'm not sure what Mr McDuell, my chemistry teacher, would make of the idea of injecting apochromatic gases...

But it's a possible use for hollow needles. Possibly not acupuncture needles, though!
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