Iris needs one more definition:
5. A variable opening for a camera lens to alter the amount of light being admitted as well as to adjust the depth of field available for the image.
good catch! the iris diaphragm, i think it is exactly
Thanks Lloyd,
I was hoping some photography buff would add this definition. You did a much better job then I would have! It always fascinated me that the iris in the camera affected both the amount of light and therefore the required exposure time AND the depth of field.
I had to look at a lot of diagrams to understand that concept and it has been a long time, so I do not understand it anymore. I just know it is true.
Frank
humans can do that too--squinting, changes the amount of light, and the size of the opening (pupil)--this changes the focal lenght of the image (and sometimes makes it appear clearer/sharper.
Hey, we do, don't we? Thanks, Helen. And welcome to all you new folks!
DON'T DO IT! It causes wrinkles.
<- see?