I didn't realize that the entire experience of shooting with one lens gave me a lot of learning about focal length
and how it would affect the image.
Although monocentric, orthoscopic, and Plossl eyepieces all provide decent eye relief, about 70% to 80% of their focal length
, the short focal lengths
required for planetary observing involve squinting through tiny eye lenses located a small fraction of an inch from your eye.
3: Experimental setup of Sony G camera with four lenses of different focal length
and a chessboard pattern (1830 x 1330)
5 wide-angle lens, thinking that this will be closest to your own vision, consider this: the measured focal length
of the eye isn't what determines the angle of view of human vision
It has a 30x zoom lens which in terms of focal length
This research indicates that the focal length
of molded microlens acts as the goal.
One would expect that reducing the focal length
of the objective lens in this manner would reduce the distance between the red and blue focus as a proportion of the cut off or remaining focal length
of the objective lens over the short focus of the reducer, but not so
Folding the optic increases the effective focal length
without increasing the distance from the front of the optic to the image sensor.
But as recently as 20 years ago the standard lens supplied with a 35mm camera had a fixed focal length
of 50mm, which captured the scene being photographed pretty much as the eye saw it.
angle lens equivalent to a 24mm focal length
or wider is absolutely essential for controlling perspective.
Questar's motorised StepZoom 180 is an 8:1 variable focal length
lens with what the company describes as the longest focal length
available in an optic of its size.
It was built in a mahogany housing for stability and had an adjustable width entrance slit, a 20-cm focal length
quartz collimating lens, a Comu quartz prism, a 20-cm quartz camera lens and a plate holder for a 3.