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murrayatuptowngallery
08-26-2005, 02:55 PM
I borrowed a Leonardo or Michaelangelo...I forget (but I remember the names Pinhole Resource & Tom Renner).

It has viewfinding lines drawn on top & side.

If I want to draw my own on my own camera, particularly a longer f.l. one where one's aim is more critical, is it simply a matter of determining the angle of view from a pinhole calculator and drawing the lines on top? Is the dependency on format addressed by just using a calculator that gives you a format-related angle-of-view?

Thanks

moot
08-26-2005, 04:44 PM
I don't see why not, just be sure the calculator is giving you the right angle. I use Balihar's PinholeDesigner and the angle of view is for the diagonal, so that would not be right for either horizontal or vertical orientation.

It's probably easiest do it graphically. Measure the length and width of the part of the film that gets image and lay out two triangles with those lengths as the bases, then the pinhole-to-film separation is the height. Connect the points to complete the triangle and you have it. If you lay the lines out on the camera you don't even need a protractor.

Tom Persinger
08-26-2005, 04:58 PM
i think, though could be totally wrong, you're over-complicating the "view lines" idea. if you merely draw lines from (if looking at the side) the vertical loation of the pinhole (in sketch centered) to the top corner and to the bottom corner of your camera back (or where the film sits) you'll effectively achieve everything all that math does.

Attached files http://f295.f295.org/uploads/viewsketch_7242.gif (http://f295.f295.org/uploads/viewsketch_7242.gif)

earlj
08-26-2005, 05:57 PM
The angle of view calculations show the circle of light that the pinhole throws, but it doesn't do any good if the film is not there to receive it! I use TP's method. Just connect the location of the edge of the image area on the film to the location of the pinhole.

Daryl
08-26-2005, 08:51 PM
A good multi-format number cruncher is fCalc.
Available at http://tangentsoft.net/fcalc/
It is good for angles of view,
fields of view at a distance,
and distances between f/stops
(and a bunch of |_3||$ type functions too).

moot
08-27-2005, 12:28 AM
All that math? *Ummm, maybe I didn't state it too clearly, but Tom drew a nice picture of exactly what I was talking about. *The second triangle I was referring to goes on the side of the camera to give you the angle for the other dimension, assuming a rectangular film format. The "measuring" part was just to be sure you are actually using the area of the film where the light hits, not hidden by the film holder, as Earl pointed out.

Sorry if my post didn't make sense. Easier to do than say, I guess ::)

JoeVanCleave
08-27-2005, 05:46 PM
I've used a variation of Tom's sketch on several of my cameras. Instead of actual lines, I install "viewing dots" on the top and side surfaces of the box. These dots protrude above the surface. Metal "acorn nuts" work well, especially on my aluminum box cam.

The front dot is positioned adjacent to where the pinhole is located, and the rear two dots are located adjacent to the film's edges, thus forming a triangle of dots on the top and sides.

You line up a rear dot with the front dot, which defines one of the edges of the film's field of view.

I check both left and right angles for the top dots, which defines the horizontal limits of the scene, and then the up and down angles on one of the sides, defining the vertical limits of the scene.

I've achieved some remarkably accurate compositions using this method.

I also have an idea for a "viewing pyramid" scheme, useful for extreme close-up compositions. I'll post more about this at a later date.

dvoracek
08-28-2005, 12:47 PM
On my foarmcore cameras I use white map tacks for these viewing dots.

Nick

ImageMaker
08-28-2005, 02:37 PM
I also have an idea for a "viewing pyramid" scheme, useful for extreme close-up compositions. I'll post more about this at a later date.

That sounds similar to the framing aids I've seen on underwater close-up cameras, where you can't get your eye to a conventional viewfinder (for taking portraits of little tiny fish, I guess). This attaches to the lens or ring light, and has a frame on four legs, just barely larger than the FOV of the lens in use, and at the correct distance (corrected for underwater optics) for the preset lens focus. When the fish you want to photograph is in the plane of the frame, push the release, and you get a perfectly framed, focused, and exposed image.