STG Studios

Digital photography devices contain a pinhole at the point light is focuses, right?

In order for the CCD to capture light from a single direction, there has to be a small hole at the focal point or the image will be flew. But all the diagrams I looked at didn't show it
ok I think I didn't explain myself quite right.

Thanks Geoff.
That's the whole point of a lens..it forms a sharp image. What each cell sees is it's own bit of the image,nothing else. It doesn't need a pinhole in front of it. Each pixel, or cell, is it's own seperate bit...it's own 'sensitive pinhole' if you like. The object is focussed by the whole area of the lens onto each point of the image. If you cover bits of the lens with small pieces of black paper randomly stuck all over it you still get a whole image but fainter, because less of the area of the lens is contributing to the image.
When the Yerkes 40" refractor was first demonstrated to it's sponser, the staff actually put over a dozen postage stamps on the front of the objective to prove it to him,after comments he made when he saw the polishing process,which can get very messy. They showed him after he had already looked through the telescope and exclaimed what a wonderful lens it had.
In a digital camera the image is focussed onto the sensor, allowing each pixel to be activated by the light of a particular part of the image falling on it. The same with film cameras. Each grain of a film emulsion gets exposed with the light focussed onto that grain,nothing else,apart from stray reflections which is why the insides of cameras are black,to cut down stray reflections and so not lose contrast.
The image consists of a number of image points ...actually called 'Airy Disks',or for out of focus images,'circles of confusion'..but this is getting confusing enough already, of a size determined by the diameter and optical quality of the lens. The wider the lens the smaller the theoretical limit of the 'point',the Airy Disk...which is the difraction limit for resolution, called Dawes Limit for telescopes and microscopes, but measured as line pairs per millimeter in the image for camera lenses. 30-40 line pairs per millimeter is the lower end of average these days for cheap or lower mid-price cameras. Expensive lenses can get well over 100.
That's why big telescopes are made for astronomy, not only to get more light,the main reason, but to increase the resolution. The same with radio telescopes. If each point in the image wasn't from the whole area of the lens,then making the lens bigger wouldn't increase it's light-gathering power or resolution, so it would be senseless making bigger ones.
It's easy to make a lens with image points, ie Airy Disks, small enough that sharp results can be got from digital sensors or film. . http://hyperphysics.phy-astr.gsu.edu/Hbase/phyopt/cirapp2.html . . .
http://www.dofmaster.com/digital_coc.html . . .

MASTER SERIES: Matthew Jordan Smith diagrams lighting for Tyra Banks photo shoot

Light It, Shoot It, Retouch It: Learn Step by Step How to Go from Empty Studio to Finished Image (Voices That Matter) £16.63 ...

Light & Shoot: 50 Fashion Photos £8.23 ...

The Off Camera Flash Field Guide This guide walks you through the step by step process towards mastering off camera flash. With 60 pages of easy to read instruction, Sam Adams takes you through shot setups, lighting diagrams, and camera settings to help you build the basic knowledge necessary for expanding your photographic creativity. With over six years in the wedding industry, Sam has written this book so that even a novice ph...

Tags:   blog · digital photography lighting diagrams · lighting · photography · studio · tutorialNo Comments