June 18, 2018, 07:27:04 PM

Author Topic: Kickstarter: Pinhole Pro S | World's Widest Professional Pinhole Lens  (Read 6507 times)

AlanF

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Re: Kickstarter: Pinhole Pro S | World's Widest Professional Pinhole Lens
« Reply #15 on: December 17, 2017, 08:51:10 AM »
Graham
You got me thinking about this, but I am sure it is the school textbooks of the 19th century. Straight out of my head and it could be very wrong, I intuit the following.

A hole through a thick sheet will cause a small exit pupil and huge vignetting as the light has to pass through a tunnel, and the light rays going straight through will be OK but those at an angle will hit the sides. So, the ideal pinhole should have just atomic thickness at the edges and you should chamfer the edges to give the angle of entry you want.

The next problem is the diameter of the hole.  If you want to optimise resolution you have to balance two effects; the size of the hole and diffraction. The sensor will not be able to resolve objects closer than the diameter of the hole so you want the hole to be small.  But, the smaller the hole, the greater of Airy disk of diffraction. My intuition is that optimal resolution at the centre of the sensor is when the diameter of the hole is equal to the diameter of the Airy disk. (And this resolution is at the centre but gets worse to the edges.) If d is the diameter of the hole, and the wavelength of the light is L, and the distance to the sensor is F, using standard formulae, 1.22LF/d = d. Using a flange-sensor distance of 44mm for the EF mount and 400nm light, this gives d = 0.146mm, which leads to an f-number of 300.

You might wish to lower resolution by having a wider hole to reduce exposure time.

A 0.146mm hole with the effects of the size of hole on the two aspects of resolution, would give an effective pixel size of about 0.2mm. So, a 24x36mm sensor would have an effective resolution of about 22kpx, not too dissimilar from the first Casio digicam.

Please correct me if I am wrong.
« Last Edit: December 17, 2017, 08:57:12 AM by AlanF »
5D IV, 5DS R, 400mm DO II, 1.4xTC III, 2xTC III, EF 1.8 STM,  EF 24-105, 100-400 II, EF-S 15-85, Sigma 150-600mm C, EOS-M5 15-45, f/2 22, 11-22, Samyang 8mm f/2.8 fisheye: sold 7D II, EOS-M, Powershot G3 X,  Sigma 10-20, EF 300/2.8 II, 70-200/4 IS.

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Re: Kickstarter: Pinhole Pro S | World's Widest Professional Pinhole Lens
« Reply #15 on: December 17, 2017, 08:51:10 AM »

Valvebounce

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Re: Kickstarter: Pinhole Pro S | World's Widest Professional Pinhole Lens
« Reply #16 on: December 17, 2017, 09:07:38 PM »
Hi Alan.
Wow, thanks!
I have no idea if you are wrong, but I’m not sure I have long enough for an f300 exposure, (how many stops past f22 is that, 3 and a bit?) should give lovely smooth water and clouds! Also I think my drill sets stop at 1/16” and 1mm respectively, my specialist drill assortment may get to somewhere around number 68-72. I might have to try piercing the hole with a bit of 0.6mm (no 73) welding wire with an edge dressed on to it!  ??? :) If that is too big I’ll just have to leave it for now!

Thank you for taking the time to write such a detailed response, much appreciated.

Cheers, Graham.

Graham
You got me thinking about this, but I am sure it is the school textbooks of the 19th century. Straight out of my head and it could be very wrong, I intuit the following.

A hole through a thick sheet will cause a small exit pupil and huge vignetting as the light has to pass through a tunnel, and the light rays going straight through will be OK but those at an angle will hit the sides. So, the ideal pinhole should have just atomic thickness at the edges and you should chamfer the edges to give the angle of entry you want.

The next problem is the diameter of the hole.  If you want to optimise resolution you have to balance two effects; the size of the hole and diffraction. The sensor will not be able to resolve objects closer than the diameter of the hole so you want the hole to be small.  But, the smaller the hole, the greater of Airy disk of diffraction. My intuition is that optimal resolution at the centre of the sensor is when the diameter of the hole is equal to the diameter of the Airy disk. (And this resolution is at the centre but gets worse to the edges.) If d is the diameter of the hole, and the wavelength of the light is L, and the distance to the sensor is F, using standard formulae, 1.22LF/d = d. Using a flange-sensor distance of 44mm for the EF mount and 400nm light, this gives d = 0.146mm, which leads to an f-number of 300.

You might wish to lower resolution by having a wider hole to reduce exposure time.

A 0.146mm hole with the effects of the size of hole on the two aspects of resolution, would give an effective pixel size of about 0.2mm. So, a 24x36mm sensor would have an effective resolution of about 22kpx, not too dissimilar from the first Casio digicam.

Please correct me if I am wrong.
7DII+Grip, 1DsIII, 7D+Grip, 40D+Grip, EF 24-105 f4L EF-S 17-85, EF-S 10-22, EF 70-200 f2.8 L IS II, EF 1.4xIII, 2xIII, EF 100-400 f/4.5-5.6l IS II, Σ17-70 f2.8-4 C, EF 50mm f1.8, YN600EX-RT, YN-E3-RT, Filters, Remotes, Macro tubes, Tripods, heads etc!

1DsIII, 20D, 24-105, 17-85, Nifty 50 pre owned

AlanF

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Re: Kickstarter: Pinhole Pro S | World's Widest Professional Pinhole Lens
« Reply #17 on: December 18, 2017, 03:08:45 AM »
Your drills would seem to too big, though I have some watchmakers tiny ones. You could try punching through with a needle. But, better still, you could drill a 3 mm hole or so in the centre of the body cap, stick some thin black tape over that and poke a needle through the centre. That way, you would have a thinner membrane, easier to punch through, and you could quickly change it to try different sized pinholes.

Hey, let's use Kickstarter to set up a company to sell the kit.
5D IV, 5DS R, 400mm DO II, 1.4xTC III, 2xTC III, EF 1.8 STM,  EF 24-105, 100-400 II, EF-S 15-85, Sigma 150-600mm C, EOS-M5 15-45, f/2 22, 11-22, Samyang 8mm f/2.8 fisheye: sold 7D II, EOS-M, Powershot G3 X,  Sigma 10-20, EF 300/2.8 II, 70-200/4 IS.

Valvebounce

  • Canon EF 400mm f/2.8L IS II
  • *********
  • Posts: 3758
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Re: Kickstarter: Pinhole Pro S | World's Widest Professional Pinhole Lens
« Reply #18 on: December 18, 2017, 03:57:36 AM »
Hi Alan.
Thanks for the heads up on the size, I have just remembered I have a tin with some special bits, a couple of tiny ball bearings, some custom hand made tool-steel boring tips and an assortment of tiny drills. No idea how small they go, I will report back later. If I don’t have a suitable drill I will have to see about getting one after the festive season.
Just a thought, but if I drill the hole a bit off centre will I have a fixed ‘shift’ lens?  ???  :)

Cheers, Graham.

Your drills would seem to too big, though I have some watchmakers tiny ones. You could try punching through with a needle. But, better still, you could drill a 3 mm hole or so in the centre of the body cap, stick some thin black tape over that and poke a needle through the centre. That way, you would have a thinner membrane, easier to punch through, and you could quickly change it to try different sized pinholes.

Hey, let's use Kickstarter to set up a company to sell the kit.
7DII+Grip, 1DsIII, 7D+Grip, 40D+Grip, EF 24-105 f4L EF-S 17-85, EF-S 10-22, EF 70-200 f2.8 L IS II, EF 1.4xIII, 2xIII, EF 100-400 f/4.5-5.6l IS II, Σ17-70 f2.8-4 C, EF 50mm f1.8, YN600EX-RT, YN-E3-RT, Filters, Remotes, Macro tubes, Tripods, heads etc!

1DsIII, 20D, 24-105, 17-85, Nifty 50 pre owned

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Re: Kickstarter: Pinhole Pro S | World's Widest Professional Pinhole Lens
« Reply #18 on: December 18, 2017, 03:57:36 AM »