# Easiest way to make a simple viewfinder?

• 07-07-2012, 11:43 PM
aterimagery
Easiest way to make a simple viewfinder?
As part of my pinhole camera making, I want to make one of those simple lensless "wire" viewfinders like the ones you see on the old press cameras. Basically, the ones that are just a little frame in the front with another one in the back that you look through and line up sort of like the iron sights on some sort of gun.

I realize that I probably just need to do some trigonometry to match the size and distance of the "sights" to the angle of view of the camera, and I know I won't easily be able to come up with any sort of parallax correction scheme (if pinholes have that problem), but anything better than guessing would be helpful for aligning a pinhole camera.

Does anyone have recommendations on how to make one of these?
• 07-08-2012, 01:05 AM
Bill Burk
Go somewhere with obvious landmarks, set the camera up on a tripod with the back off and note which landmarks hit the corners of the frame.

With those landmarks in mind, make a wire frame, or paint an outline on a piece of acetate...
• 07-08-2012, 02:29 AM
andrew.roos
I think the trig is as follows:

width_of_big_rectangle = width_of_little_rectangle + 2 x distance_between_rectangles x tan (horizontal_angle_of_view / 2)
eye_relief = distance_between_rectangles * width_of_little_rectangle / (width_of_big_rectangle - width_of_little_rectangle)

The aspect ratio of both rectangles should be the same as the aspect ratio of your film.

You can use any unit for the distances, provided you use the same unit throughout. The angle unit should be as required by your calculator (or trig tables) - probably degrees.

Parallax is an issue for any camera where the viewfinder does not see from the same point as the lens (i.e. not in LF cameras and SLRs but pretty much everything else). If you mount the viewfinder directly above the pinhole (i.e. not to the left or right of it) then ant least you won;t have to worry about parallax in the horizontal direction. If necessary you could use multiple horizontal wires in the big rectangle to demarcate the close and far focus frames.

Bill's suggestion is probably easier though :)
• 07-08-2012, 03:02 AM
Matthew Rusbarsky
Having said all that, one of the pleasures of pinhole is that it's down and dirty in a fun way. If you are sweating framing, angle of view, etc, you might be better served by just pointing the box in whatever direction suits you and pushing the little button. If you are going to worry about something, worry about exposure and reciprocity.
• 07-08-2012, 11:18 AM
neelin
When you get to the mechanics, here's my sportsfinder "proof of concept" that I want to do someday with nitinol memory wire.
• 07-09-2012, 05:16 AM
xxloverxx
Quote:

Originally Posted by Matthew Rusbarsky