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summerbee
1-Sep-2011, 06:51
Hallo dears,
i am drawing my first own made camera, a 24 mm pinhole one, based on a 4" * 5" film holder.
I was wondering if there is a way to calculate the correct dimension of a frame to be used as a viewfinder on top of the camera.
thxalot, and have a nice day

Robert Hughes
1-Sep-2011, 06:57
You could make a sports finder with a coat hanger that will show you the frame lines.

summerbee
1-Sep-2011, 07:09
mmmh, i'd rather make it from thin wood, i forgot to mention it will be a wooden one. But what about dimensions? any way to calculate? or could someone simply measure his own one?

E. von Hoegh
1-Sep-2011, 07:17
If 24mm is the focal length of your pinhole, simply take a 4x5 frame and place an aperture 24mm behind it, you now have a frame finder.

Any arrangement of identical proportions will work.

summerbee
1-Sep-2011, 07:31
If 24mm is the focal length of your pinhole, simply take a 4x5 frame and place an aperture 24mm behind it, you now have a frame finder.

Any arrangement of identical proportions will work.

an aperture of what measure? sorry but can not figure out... or am I missing a meaning of the word "aperture"?

E. von Hoegh
1-Sep-2011, 07:42
an aperture of what measure? sorry but can not figure out... or am I missing a meaning of the word "aperture"?

Aperture = hole.

Try 1/4". It doesn't really matter, as long as you can see through it. What is important is that the distance between the aperture and frame (as long as your frame is of identical dimensions to your film) be equal to the focal length of your lens or pinhole.

summerbee
1-Sep-2011, 07:56
Aperture = hole.

Try 1/4". It doesn't really matter, as long as you can see through it. What is important is that the distance between the aperture and frame (as long as your frame is of identical dimensions to your film) be equal to the focal length of your lens or pinhole.

oh okies, finally got it! but this would mean having it some 20 mm "away" from camera edge.
i should find a way to move it forth those 24mm (so it would be in line with film and more safe on the camera and i could easily manage to have it removeable), and proportionally reduce it in size.

cyrus
1-Sep-2011, 08:10
Best thing to do: position your camera in front of something like a wall, as level as you can get it, take a picture, and without moving the camera from that place, develop the shot and see what falls inside the frame. Then, adjust your frame/aperture to match what's on the film.

ic-racer
1-Sep-2011, 08:26
Hallo dears,
i am drawing my first own made camera, a 24 mm pinhole one, based on a 4" * 5" film holder.
I was wondering if there is a way to calculate the correct dimension of a frame to be used as a viewfinder on top of the camera.
thxalot, and have a nice day

The equation is as follows:

Distance from pinhole to film = distance from view frame to your eye

So use a 4x5 view frame about 24mm from your eye. Or a frame half that size about 12mm from your eye etc. As has been pointed out.

summerbee
1-Sep-2011, 12:56
The equation is as follows:

Distance from pinhole to film = distance from view frame to your eye

So use a 4x5 view frame about 24mm from your eye. Or a frame half that size about 12mm from your eye etc. As has been pointed out.

you made it really more clear. thank you very much!