I was reading ...somewhere ...that f8 on a dig can be out there with f32 odd on a film camera. I have always wondered why my camera...fixed lens..can only go to f8 , but this may explain things.


Ta ..humungus

Originally Posted by Humungus I was reading ...somewhere ...that f8 on a dig can be out there with f32 odd on a film camera. I have always wondered why my camera...fixed lens..can only go to f8 , but this may explain things. Ta ..humungus

My response from another thread...

The articles at http://www.photodo.com/nav/artindex.html that Patch recommended are much more suitable, particularly the Resolution, contrast, MTF article that he mentions. It is important to realize that diffraction distortion is tied to the absolute physical diameter of the aperture and that the f-number is the ratio of that aperture to the focal length. Thus f8 on a 50mm lens might be optimum but on a digicam with a 8mm-24mm zoom, f8 is so bad that that the lens is not even allowed to stop down that far.

For the beginner, I highly recommend Canon's EF Lens 101 pages. The focal length comparisons, the lens care artcle and the glossary are all worth the visit.

Originally Posted by Humungus I was reading ...somewhere ...that f8 on a dig can be out there with f32 odd on a film camera. I have always wondered why my camera...fixed lens..can only go to f8 , but this may explain things. Ta ..humungus

I don't think that statement holds true when it comes to depth of field. My CP950 will stop down to f8. Even stopped all the way down, the CP950 doesn't give me enough depth of field for some of my table-top still life work. On the other hand, shooting on film at f32 I get more than enough depth of field.

Who knows, maybe my CP950 is just a piece of junk.

Originally Posted by cletus I don't think that statement holds true when it comes to depth of field. My CP950 will stop down to f8. Even stopped all the way down, the CP950 doesn't give me enough depth of field for some of my table-top still life work. On the other hand, shooting on film at f32 I get more than enough depth of field. Who knows, maybe my CP950 is just a piece of junk.

The thing is that DoF is just an artificial construct based on our acceptance of a certain size circle of confusion (the size of a point image when almost focused on the imager) The DoF is the distance in front of and behind the best focus where the CoC is still within our accepted limitations.

Ta cmr....i was fearfull it was too tech for me. I will persist. So just how much brighter is my f1.8 over say a f2.8 ?

Originally Posted by Humungus Ta cmr....i was fearfull it was too tech for me. I will persist. So just how much brighter is my f1.8 over say a f2.8 ?

The best way for you to get a handle on this is to see the differences in shutter speed. Those are a lot easier to comprehend than powers of the squareroot of two.

Set your camera into aperture priority mode and point it at the wall. Now see the shutter speed at different f-stops. Think of it like a homework assignment :) Tell me the shutter speeds you see on the same patch of wall at f1.8 , f2.8 , f3.5, f4.0, f5.6, f8.0

Anyone can answer. Doing the experiment will give you a better feeling for light and by contemplating the shutter speed, a better feeling for action.