I am using this website to do the maths for me: http://www.mrpinhole.com/calcpinh.php
So I researched about f-stop scale and wherever I find it they only show until f/256. While the f-stop of my camera is 339. I would like to find out the nearest f-stop to the one I got or even adapt it to a full stop but I don't know to do the maths. I know the maths formula but I don't know calculate it.
Does anybody can help me on this? :)
If you print this and put it together (I used heavier paper - cardstock - so it would last better) - http://www.ilfordphoto.com/Webfiles/...6152612113.pdf You can take a reading (or guess based on weather) and then adapt it to whatever pinhole you have. It's not meant to be exactly exact, but neither is pinhole photography. This saves me from having to do math.
Now I would like to talk about how to make the hole. Should I open an other topic?
I am using a knife to make a hole in a can but it is hard to mesure the mm of the aperture so maybe I should make a test before open more?
I'd recommend using a needle instead of a knife. Sand down the location till it's as thin as possible, and gently use the needle to create a hole. If you have a scanner available, you can scan the hole and use your favorite photo editing software to measure it.
The scanner is a good idea...
I printed the Ilford dials on glossy paper, sprayed the printed surface with clear adhesive and attached them to clear acrylic (very thin) sheet that I pre-cut to match the dials. Use a hole punch if possible and connect all with stainless steel bolt/ washers and non-slip nut (with nylon interior). I take either an incident or spot meter reading as the subject calls for. Then use the dials as per their instructions. I have found the readings to be very accurate. I use Delta 100 and HP5 and so far my shortest exposure has been two seconds with most in the thirty second -
eight minutes. With longer exposures being off a few seconds probably doesn't make a noticeable difference. I'm using PMK Pyro developer and have printed in silver gelatin, pt/pd and scanned and printed digitally as well. The results have been great and pinhole shooting has been a fun experience. I posted my int'l pinhole day submission on their website and on the APUG one also. I'm on my laptop and don't have them on this computer.
Regarding f-stops, another quick way to think of it is that they found by doubling these two series of numbers:
1 2 4 8 16 32 64 128 256 512 1024 2048... ( find more by doubling )
1.4, 2.8. 5.6, 11, 22, 45, 90, 180, 360, 720 ... ( find more by doubling )
So all the "standard" f-stops are found by alternating the values from these two lists.
When I make a pinhole camera, I often figure out which one of these numbers it is closest to, which gives a ballpark place to start for exposures.
But quite honestly, each camera is a little different ( internal reflections, shape of film plane, etc... ), and even though this calculation will be about right I always make a series of quick tests to get my "full sun" sunny 16 exposure by testing the camera. Then you can take that exposure and change it depending on the available light.
If nobody else has answered, I'll try to come back by and write how I make my pinholes. Gotta get back to work now!
If your pinhole is f339, then the closest equivalent would be f360, or one stop slower than f256. So you could use the f256 times and add one stop to be on the safe side.
You can use a nice & free programm to calculate pinhole size, f-stop, make exposure charts, etc.
But how to check that the hole is round and with a nice clean edge ?
Originally Posted by Klainmeister
For that, pop it on a glass carrier inserted in to an enlarger - With the column racked up high, focus a nice sharp image on the baseboard. You might be surprised at how rough the hole is.