We don't have "hobby lobby" here, but I've seen those paper photo/video boxes at our local craft store. They were on sale for less than $4 each a couple weeks ago. I don't know if the version I saw has felt or not. I measured 7.5 inches wide, and gave up on it without considering that the photo paper could be curved a little. I made my 8.5 x 10.5 x 5 box on Saturday out of 6 pieces of black mat board... so totally homemade, but it probably took me 2 hours of time to make it. The lid is attached on only one side like a hinge, and then I made a simple cover ( like those video boxes have ) that fits tightly over that. The combination of the lid and cover seems to be light tight so far. It is totally fun and I was thrilled to see what an 8x10 paper negative looks like!!!
Here's the one from yesterday, with the mat board box held to pine board with t-nut on tripod with Joe's hooks+bungee! This negative looks really neat.
Ned, that's a fine image, you should be proud. It's amazing what a simple pinhole box and paper can do in the hands of someone talented.
Joe, that means a lot to me coming from you. Thank you.
Ned, thats a great image!!! Is that a scan of the paper negative and reverse it in the computer, or did you contact print it onto paper for the positive image?
Joe, thanks for the idea of the photo box. I may have to try that out since its essentially a cheap "off the shelf" pinhole box. Any idea on where to start with pinhole size?
Thanks! That one is an inverted scan, but I do like contact prints. I just got a new contact frame ( the photographers formulary one ) and my first impression is that it will work really well. I've had trouble with softness ( and a weird sort of "swirlyness" that's hard to describe ) when using a thin piece of glass from a cheap picture frame.
Originally Posted by edcculus
I put a couple photos of my camera on my flickr page.
Sounds good. I have a Print File "custom proofer" that I use to make contact prints off of regular negs. No troubles with that so far, so hopefully it will work with paper negs too.
I ended up getting some cheap 4X5 holders, so I'm changing this build to the smaller format.
With the film holders in hand, I'm basically going to follow this tutorial. http://www.stanford.edu/~cpatton/foamcore.html
-what is a good focal length to start with on 4X5?
-on this build, what is the purpose of the foam core back? Also pictures of it at the end of this link http://www.stanford.edu/~cpatton/dai.htm. If I'm using a film holder, do I need it?
Once I get these questions answered, I'll hopefully draw this out in my CAD program and cut it at work at the end of the week. Then all I have to do is assemble the pieces and make the pinhole.
That back is like a "window frame" for the film holder to rest against. It provides 1/2" of support on all four sides of the film holder. Does that make sense? The first page also mentions that you can make a second one to press against the film holder from behind... that would be for applying some pressure to hold the filmholder tightly in place. I haven't done this myself so can't offer any other comment...
I really like the wide angle field of view on my 8x10 camera with a 5" "focal length". The equivalent on a 4x5 would be 2.5 inches. Others might have a different idea what a nice focal length would be.
In re-reading this thread I realized I might mention something for future readers. My 5x7 camera has a mat board "window" that holds the paper in place on 3 sides. That seemed to work pretty well. But when I did the same thing on the 8x10 camera, the paper fell out inside the camera. Now it is is held in place on all 4 sides by strips of mat board about 3/8" wide. Even this is not ideal.... I've noticed that the center of the paper still has a tendency to warp out and I don't get nice straight border lines, but slightly curved ones. I don't own any 8x10 film holders, so I don't know how they manage to keep the film flat, but I think Joe's suggestion of a couple pieces of two-sided tape, not too sticky, is a good one and I will try it soon myself.
Thanks Ned, that makes sense about the film back.
I plugged in a 2.5" focal length to the pinhole calcuator, and it looks like it won't give me enough coverage. I increased it to 3.5" and here is what I got:
Focal lenght: 3.5"
pinhole diameter: .016" (.4mm)
film dimension 6.4
angle of view 84.9
Does all of that look good? I basically tried to get the coverage larger than the film dimension.
I'm not sure how the program computes coverage. On my calculator I just verified all the other numbers... if I assume a "daylight" wavelength of 550nm and a "user constant" of 1.8 it's very close to a 0.4mm pinhole.
That angle of view will be similar to a 24mm lens on 35mm film. Which is pretty nice, I think. ( I'm biased... 24mm is my favorite lens :) )
Since I use paper negatives, I usually use 500nm or even 475nm for the wavelength, because paper is so sensitive to blue light. And I tend to use a smaller "user constant" of 1.56. If I was making that camera for paper, I'd start with a 0.33mm pinhole. But I think your 0.4mm will probably work well for film. If you will be mostly using paper, I think you could get away with a smaller pinhole.