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1. After a few months of inactivity, i've finally made some way on the project. Its now become a 4X5 instead of 8X10.

All I have left to do now is make the actual pinhole and tape up the joints!

2. Yay! Looks great to me. Have fun with it!

3. Cool! Looking good.

Yesterday I was in an art and craft store (A.C. Moore) and happened to notice they had what appeared to be 1/2 inch thick black foamcore, black skin, black foam. Might be handy stuff for a large pinhole machina fotografica if one doesn't want to go with wood. Alas, I did not check the price.

4. My 8x10 is made from black double weight mat board, and it is starting to wear out. The top is warping a little and I suspect it will develop a light leak around the lid eventually. It's been a lot of fun and I'm really glad I made it but next time I'm going to make something sturdier, probably from wood. I could imagine 1/2" thick foam core might be pretty good too!

5. Ok, one more question re the actual pinhole. If I use an enlarger to measure the hole...how exactly do I calculate or figure out the enlargement? Sorry if that is such a stupid question.

6. Howto: measure a pinhole

Originally Posted by edcculus
Ok, one more question re the actual pinhole. If I use an enlarger to measure the hole...how exactly do I calculate or figure out the enlargement? Sorry if that is such a stupid question.
1) Take a piece of clear film and make a mark of 1 cm on it with a pen like this |----|.
2) Put it in your enlarger and project the line. Now measure the line on the base board (lets say 8 cm).
3) Calculate the enlarging factor for this line: 1 cm/8 cm = 1/8 or (0.125).
4) Put the pinhole in your enlarger and measure the diameter of the projected circle (lets say 1.2 cm).
5) Multiply this factor with the measured diameter: 1/8 x 1.2 cm = 0.15 cm.

Now you know your pinhole diameter is 0.15 cm.

Note:
* it doesn't matter how high you turn your enlarger: but use the same hight for both measurements!
* it also works with inches ;-)

7. oh awesome. I knew it would be something simple. I'll stick to metric. its easier!

Thanks!

8. Put a plastic ruler in the negative stage of your enlarger and use another ruler to measure the degree of enlargement.

9. Originally Posted by NormanV
Put a plastic ruler in the negative stage of your enlarger and use another ruler to measure the degree of enlargement.
Yep, this is what I do. But then I just measure how many mm in 2cm, and do just what Bert said.
And if you are aiming at a particular diameter, you need to make it slightly too small and then slowly expand the pinhole until it's just right.

Honestly, I've only done this a few times. Usually I just make several pinholes and hold them next to a ruler with mm markings, look through a hand lens, and pick one that's close and looks clean. You might find different pinholes do have different character. Occasionally there will be one that makes particularly nice pictures, and it's not always just about sharpness... sometimes there is just a "certain something" and it is hard to say what it is.

I've swapped out the pinhole in my instant film camera several times. The first few looked perfectly round and clean and the right size, but were unsatisfying. The one that is in it right now was a little too small and close but not perfectly round, but it's my favorite so far. I used paper negatives in it to test the different pinholes quickly without wasting film. You could try that if you want. Quick and easy.

( Okay, actually now that I think about it, that's not totally true. I did use paper negatives and picked the best, and it looked really good, but ended up swapping it again after that... the color instant film pictures were not as good as the b/w paper. That could have been because the paper is not sensitive to the same range of wavelengths, or just something subjective about instant color film, I don't know. So I'm not sure the paper negative advice is good after all. )

10. Thanks guys!

One more thing. For the actual pinhole material. I have access to aluminum offset printing plates. The thinnest we have is .2mm. I guess I'm assuming its mm because the other dimension on the label are in mm as well (340 X505 x.2). Will that be thin enough?

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