Pinhole Camera Test

[JimFox]

Okay, so I got the Body Caps in and tried my first pinhole shots. I don't think I did too well.

First, since I had 2 caps, I decided to get clever (usually a bad thing ) and I heated up the needle and let it poke (melt) a hole in the cap. I barely pushed in through.

I then went outside and tried 2 shots, both near and far were blurry.

Any ideas @Graeme F ?

I will try it next with the aluminum foil over the hole and just barely poke through it with the needle. Maybe the hole I made was too big? Even though it sure looks small.

 

[Ken Rennie]

Okay, so I got the Body Caps in and tried my first pinhole shots. I don't think I did too well.

First, since I had 2 caps, I decided to get clever (usually a bad thing ) and I heated up the needle and let it poke (melt) a hole in the cap. I barely pushed in through.

View attachment 37286

I then went outside and tried 2 shots, both near and far were blurry.

View attachment 37284

View attachment 37285

Any ideas @Graeme F ?

I will try it next with the aluminum foil over the hole and just barely poke through it with the needle. Maybe the hole I made was too big? Even though it sure looks small.

A dressmakers pin is too large so try just pushing it in so that it just breaks the surface of the foil. Problems occur if the hole Isn't smooth. I remember that a company used to sell body caps with laser cut holes of various sizes. Short flange distances ( mirrorless cameras) give you longer "focal lengths" and brighter images although they are still dark. Using extension tubes will give you wider "focal lengths". Ken

 

[Graeme F]

@Jim i think the hole might be too big. I found the smallest pin i could find and barely broke the foil with it. on the plus no vignetting which i found to be an issue

 

[JimFox]

A dressmakers pin is too large so try just pushing it in so that it just breaks the surface of the foil. Problems occur if the hole Isn't smooth. I remember that a company used to sell body caps with laser cut holes of various sizes. Short flange distances ( mirrorless cameras) give you longer "focal lengths" and brighter images although they are still dark. Using extension tubes will give you wider "focal lengths". Ken

Thanks Ken, I think I made the hole too big even though it seems small. I will try it again this afternoon.

 

[JimFox]

@Jim i think the hole might be too big. I found the smallest pin i could find and barely broke the foil with it. on the plus no vignetting which i found to be an issue

Yeah, I will try an even smaller hole. Hopefully that works.

what did you find with DOF, how close was your focusing?

 

[Ken Rennie]

This is indoors and just to see if it works, tinfoil wrapped across an extension tube. 15s exposure at ISO 100. I pushed the pin all the way through so tomorrow in daylight I will try again with a much smaller hole. I also need to find a way of smoothing the tinfoil without it hitting the contacts. The picture on the wall is an ICM shot Ken

 

[Graeme F]

i was about 6ft from main subject in the wall shot I took and then in the seascape maybe about 10ft to nearest large rocks? I think this pinhole work tho is never going to be sharp

 

[Ken Rennie]

This is pinhole 2 with a barely visible hole, it requires about 1minute exposure indoors. Much sharper but I am definitely into diffraction here. The smaller the hole the sharper it should be using a simpe geometry model but the greater the diffraction. When the hole is tiny any "chads" will cause odd problems. I think that I could produce a decent image with this setup tomorrow will tell. Lots of light fall off but easily cured in ACR. This setup with 16mm extension tube gives a focal length of approx 50mm. Oh and I have clearly visible dust spots, I will calculate the aperture tomorrow. Ken

 

[JimFox]

Looking good Ken. I will definitely go smaller hole in a few. Thanks for helping out. Don’t forget this weekend I will do a Community Challenge thread for Pinhole photos.

 

[Graeme F]

I think I read somewhere on the net a pinhole camera something like f/200!

 

[JimFox]

I redid mine, and I made the smallest of holes, I just barely poked the aluminum and I think it's better. I will look closer at them tomorrow, but its funny, on the back of my 3" lcd display it looks sharp, until I zoom in to 100%...

 

[Ken Rennie]

Simple calculations focal length is the distance from tinfoil to sensor. My version is 40mm approx. Aperture= focal length (in mm) divided by diameter of hole in foil ( in mm). The difficult part is measuring the hole diameter. The calculations can be done in inches. I will work out my aperture using a lightmeter today but I suspect it is approx f80. I could calculate the optimal size of hole but unfortunately couldn't produce that size so little point in doing the calculation. This takes me back to university and firing lasers through various holes and slits to produce interference patterns. Calculated at approx f80, this makes my hole slightly larger than optimal but producing a smaller one is difficult. Other problems, light leakage through the foil, leakage around the foil I have this with repeated mounting of the extension tube. Roundness of the hole and more importantly removing the tiny shards of foil produced by the pin pushing through the foil. Good cheap fun but I need to clean my sensor. Ken

 

[Graeme F]

@Ken haha yes. I was somewhat dismayed what the pinhole showed me in terms of dust and nonsense on the sensor! Booked in dslr for a thorough clean next week!

 

[Ken Rennie]

I started to work out the mathematics behind resolution, pinhole size, focal length using my mostly forgotten physics knowledge but before going too far decided to hit the net and of course the answer or fairly close to the answer is there. Firstly before before we rush off and get precision laser cut hole in tin foil the maximum theoretical resolution is close to 720px by 480px for a full frame camera. It is inversely related to pinhole size, however you can't just make the hole smaller as a limit is reached where diffraction starts to overcome everything. With my setup of a 40mm distance between sensor and foil the optimal hole has a diameter of 0.15mm and it must be round with smooth edges and this gives the 720px by 480px which is very close to the resolution of the rear screen of my Sony A7R4 giving the impression that you have a reasonably sharp image. If anyone is lucky enough to have a Fuji GFX irrespective of resolution you could get 880px by 720, owners of phase one could get 1070 by 800. So no matter how good your camera you will not get up to old tv standards of resolution. Now if you want to go back to 5 by 4 or 10 by 8 film then pinhole cameras could produce fairly good results but calculating reciprosity rates for unknown apertures costing upwards of $5 an image and a week turn round rates could take a few years and very deep pockets. If you can get the ditance of sensor to foil down to 20mm then the theoretical max resolution will rise to 1020px by 680px. Ken