In 3DJournal you can read about basic principles of making 3D photos. Here we take a much more detailed look look at it - and we add some more principles which can help you to make really good 3D photos.
Our first rule is about the distance between two cameras (for the left and the right photo; if you use only one camera then it's about the shift between it's left and right position).
We've said this distance should be around 7 centimeters (2.5 inches). But the precise rule is this: use the distance equal to 1/30 of the nearest object on the pfoto (see our picture - the object is in a distance A, the cameras have a distance A/30). If - for example - is the nearest object 2 meters from the camera and all the other objects are behind it, the shift between the left and right camera should be 2 meters / 30 = 200 centimeters / 30 = 6,66 centimeters.
This shift isn't an accident - human eyes can comfortably focus to objects (on one scene) from 2 meters to infinity - for nearer objects they have to refocus. We want to make a good visible 3D photo (stereophoto) - our eye shouldn't refocus between objects on this photo. The nearest object should be no nearer than 2 meters - and we expect eye distance around 6,66 cm (an international standard for stereopictures is 63,5 mm).
(And one more thing - this rule of 1/30 is good for a 35mm film and a focal length of 35 mm. For bigger focal length (zoom - the scene is nearer) it's necessary to slightly change the rule - for example for focal length 70 (2x35) is the rule not 1/30 but 1/(30x2) = 1/60. If you don't use zoom you don't need to bother with this.)
If the nearest object of the scene is nearer than 2 meters then the eyes (cameras) should be nearer as well. When we watch the photo made this way the object should appear as in longer distance - at the best in 2 meters.
If the nearest object is further than 2 meters it's a good idea to use a longer distance between the left and right camera. The 3D effect will emphasise. If you take - for example - a photo of a castle and between you and the castle is a tree in the distance 30 meters from you (and no object is nearer than the tree) then you could use the distance between the left and right camera 1 meter (30/30=1).
If the nearest object is in 90 centimeters distance then you should use maximal distance between the cameras 3 centimeters (90/30=3). If the object is nearer than 20 centimeters then the 1/30 rule changes - the distance between the two cameras has to be even shorter. For 10 cm it's 2,5 mm, for 5 cm only 1/2 mm.
In our first article about 3D photography we've said you can make the left and right image in two ways - you can direct the cameras to one direction (parallel view) or to one point (you can see here the picture from our first article once again) - the first way is marked as B the second one as A).
The truth is this: The best way - and the best photos you should get - with the way B. If you use the way A, your photos will be little bit distorted. But it's true what was said in the previous article - if the point you direct the cameras to is in a long distance the distortion won't be visible. But if the point is very near (or there is a near object between you and the point) it could be a problem. If you choose the way B then it's necessary to use a bigger horizontal shift when you create the anaglyph from the left and right picture - the nearest objects should have the same position then.
For international competitions it's often required all the objects on stereoimage to be behind the stereo window (for example behind the screen). Nothing can go "out" of screen (we've written about this possibility in our text about painting 3D pictures in the July issue of 3DJournal). To be honest: We think sometimes it could be a very nice effect.
If an object goes out of the picture (to an observer) it's necessary to place it not to cross the border of the stereo window (monitor screen).
If your 3D picture seems not to be 3D as much as you want then try to convert it to black and white (in the 3DJournal software). If the black and white picture is OK then just try to lower saturation of your image. You should do it in your graphical editor, but don't forget: Do it on your left and right image, not on the final (3D) one. Then make the 3D picture from the two changed ones.
If you use these rules (and the ones we'we mentioned in our previous articles) your 3D pictures should be the best ones.