A focusing lens after the pair of flats would produce an inverted image of the source if the flats were not present; all light emitted from a point on the source is focused to a single point in the system's image plane.
32.
By the 17th century, Rene Descartes had shown how light rays entered the lens at the front of the eye and was " brought to a focus on the back surface of the eyeball, the retina, to form an inverted image ."
33.
Then, as the inverted image traversed the screen, the instants of contact with the wires of the sun's limbs and of the spot-nucleus to be measured were severally noted, when an easy calculation gave its heliocentric position ( ib . xiv . 153 ).
34.
Shen Kuo also responded to a statement of Duan Chengshi in " Miscellaneous Morsels from Youyang " written in about 840 that the inverted image of a Chinese pagoda tower beside a seashore, was inverted because it was reflected by the sea : " This is nonsense.
35.
The arrow at ( 4 ) is a ( notional ) representation of the original image; the arrow at ( 5 ) is the inverted image at the focal plane; the arrow at ( 6 ) is the virtual image that forms in the viewer's visual sphere.
36.
In it, Kepler set out the theoretical basis of double-convex converging lenses and double-concave diverging lenses and how they are combined to produce a Galilean telescope as well as the concepts of virtual images, upright vs . inverted images, and the effects of focal length on magnification and reduction.
37.
A focusing lens produces what would be an inverted image of the source if the paired flats were not present; " i . e . " in the absence of the paired flats, all light emitted from point A passing through the optical system would be focused at point A '.
38.
:: A complication is that astronomical telescopes usually show an inverted image, because this requires the least amount of lens glass ( or number of mirror surfaces ) in the optical train, thus maximising the brightness of the image and minimising its degredation, given that no lens or mirror is perfect.
39.
Or do the same with " CMY " instead of " RGB " and use the " Multiply " blend mode . ( This will give you an inverted image . ) The latter may work better if the colors you want to remove are indeed close to the additive primaries.
40.
Double Porro prism systems are used in small optical telescopes to re-orient an inverted image ( an arrangement is known as an " image erection system " ), and especially in many binoculars where they both erect the image and provide a longer, folded distance between the objective lenses and the eyepieces.
