Focus at some point in the canon bp-608a battery distance, depth of field the other extreme just for infinity, the infinity within the scope of the depth of field to recent photography distance, called "super focal distance". If you focus will be set as the focal distance, the focal distance of half the start, into the infinite distance, falls within the scope of the depth of field.

Because of the lens of the depth of field after is larger, people say the focus on after the distance to imaging can clear the focal length. A fool is using the camera the focal length, the use of short focal lens at a distance of the scenery after can clear imaging characteristic, save focus function, so, generally cheap cameras and can't af, just use the super focal length just. As mentioned before, the "clear" is not an absolute concept, the focal length within the scope of the scenery is not a real clear imaging, not because of the focal point, affirmation is fuzzy,, but the canon bp-412 battery extent of the fuzzy ordinary people can accept it, this is a fool cameras film can't enlarge too big reason.

The focal length of the calculation of the original formula is:

The focal length = focal length of the lens + (focal length of the lens of the square divided by c, F of the product). F for aperture coefficient, not much said. The results show that the summer wear women's new public praise discharge makeup oil which good acne removing bbshuang frost is what chamfer toothpaste teeth cleaning products what good look line eye drops eye wash what brand good c for diameter circle of confusion, the early textbooks as 0.05, namely 1/20 mm, old lens are all is according to the view of 1/20 mm painted, not letter you as you have to calculate the lens. Nowadays are as 1/30 mm, and set 1/40 mm. I want to put a few inches photos need a relationship.

Due to the focal length of the lens is far less than (focal length of the lens of the square divided by c, F of the product),

A general formula for remember The focal length of the focal length of the lens = c, F divided by the square of the product canon bp-308b battery