Building a Pinhole Camera - Page 2

DLM · 06-24-2009, 04:46 PM

At some of the art supply stores, Ive seen some of the balsa in thicker sheets, so that may be an option. I think I might look for some to make one, or just use foamcore since it's easy to glue together and is really light.

ralnphot · 06-24-2009, 04:56 PM

I too have been bitten by the pin-hole camera bug. This is a project for my 11 year old daughter and self. we are using a left over Christmas popcorn tin- 9.5in.diameter by 10.5in. tall. By my calculations, we can get a 5x7 negative using the bottom for the pin hole and the lid for the negative . this is dictated by the lid size. However, we can get an 8x10 panorama using the side forour set up.
Rick

jnanian · 06-24-2009, 05:14 PM

if you want to do it the easy way ...
go to pinhole resource . com

or look for pinholebilly on eBoo they make custom laser cut holes ...

the easy rule of thumb for pinhole coverage is 3 or 3 1/2" x ( relative) focal length of lens will tell you coverage / image circle.

have fun!
john

bdial · 06-24-2009, 05:49 PM

Yes, I found the Pinholebilly method much easier. For 25 or so bucks you get a stack of them in different sizes.
You do miss out on the cutting up pop cans, or going to the hardware store and asking for "shim stock" and getting blank stares part.
And the figuring out how to just dimple the metal and sanding it just right part.

But there is plenty fun to be had in building the rest of the camera or fitting one of the holes onto a suitable camera body.

WGibsonPhotography · 06-24-2009, 05:51 PM

Thanks for all the replies. The more I think about building a pinhole camera, the more I want to do it. Hopefully I'll have a rough sketch of my camera and the dimensions later tonight

Darkroom317 · 06-24-2009, 06:02 PM

Any idea what size pinhole I would need for 6 x 9 120?

WGibsonPhotography · 06-24-2009, 06:33 PM

I used the pinhole calculator here http://www.mrpinhole.com/holesize.php to find what the image circle and the f/stop would be. Using the focal length of 746.5 that I came up with earlier, the calculator told me the image circle diameter would be 1433mm and the f/stop would be 648. What caught my eye was the pinhole size. According to my formula (which I'll post at the bottom), the pinhole diameter should be 1mm. According to the calculator, the pinhole diameter should be 1.15mm.

The calculator must be using a different formula than me. What formula is the calculator using, and is that more accurate than mine?

the formula I use is "pinhole diameter=0.0366(square root of the focal length)"

I know I posted my formula on my first post. If someone knew the answer to my question, I didnt want that person to have to go to page one of the thread to find it

Edit:

I played around with the focal length on the calculator to find what focal length I sould use if I have a pinhole of 1mm. The calculator told me 565mm. I know that would be a freaking huge pinhole camera, and I really have no intention of building one this big. I'll just use a smaller pinhole and make a smaller camera. I'm just using the measurments I came up with earlier as an example

BetterSense · 06-24-2009, 06:45 PM

Quote:

Yes, I found the Pinholebilly method much easier. For 25 or so bucks you get a stack of them in different sizes.

I might pay 25 dollars for an assortment of pinholes, but pinholebilly isn't selling any on the auction site right now.

jnanian · 06-24-2009, 08:45 PM

Quote:

Originally Posted by BetterSense

I might pay 25 dollars for an assortment of pinholes, but pinholebilly isn't selling any on the auction site right now.

the other nice thing about a laser-cut hole
is the pinhole is exact and "relative to f16" so you can
take a light meter reading and figure out the exposure ...

i am sure if you go to a completed auction
and ask a question of the seller
you can find out when his next auction will be ..
or you can ask him what his email address is
and buy from him directly ...

making the hole is kind of fun, but billy makes it painless ...
i bought mine from him pre-ebay .. he has been making
these a very long time, and he is a very nice guy.

DWThomas · 06-24-2009, 10:08 PM

Quote:

Originally Posted by WGibsonPhotography

The calculator must be using a different formula than me. What formula is the calculator using, and is that more accurate than mine?

the formula I use is "pinhole diameter=0.0366(square root of the focal length)"

Methinks accuracy is a somewhat subjective term here.

One of the formulas often referenced is:

d = c * sqrt( f * l)

Where d is the pinhole diameter
c is a constant (that's where the trouble starts)
f is the focal length
and l is the wavelength of the light (more trouble)

Folks seem to use 0.00055 for the light wavelength (which might be a green) but the spectral sensitivity of the film could come into play. Ortho film would likely produce sharper results if one optimized for the appropriate wavelength.

The constant --- oooh --- I think Lord Rayleigh, an early tinkerer with these matters, came up with 1.9. But I've seen people using numbers as low as 1.5. Obviously this cauld bend the results quite a bit. In my quick perusal of the MrPinhole calculator, I didn't see an indication of what he used, although it may be lurking there somewhere. Pinhole Designer defaults to .00055 for the light wavelength and 1.9 for the constant, but gives a user the option to edit those values.

Edit: The 0.0366 is simply bundling numbers, the product of the constant, c, and sqrt( wavelength) for metric values; 0.0073 for inches.

When one considers the issues of fabrication, pinhole cutting, reciprocity failure and possible film flatness problems, it's probably not worth doing three decimal place calculations here.

DaveT