Loren; Your post to Jessica puts me in mind of to things. What you
stated about using smaller f-stops (larger numbered ones) is
correct. The smaller the aperture (larger the f-stop number) the
greater the depth of field. When I made my original post, I assumed
that Jessica had read the instruction manual and knew about the
relationship between f-stop and depth of field.
But having read some recent instructions that basically said buy
(and install) batteries, open lens cover, point at object to
photograph, push button - I could have been wrong. I am properly
mortified at my own ignorance, please forgive me Jessica.
Anyhow , Jessica, make sure that you have your camera adjusted to
obtain the greatest depth of field.
If, you have plenty of depth here are a couple of other hints.
Adjust the f-stop so that what you want in focus is covered and no
more. A good camera will have a depth-of -field preview button on
it. This does two things. One, it allows you to shoot at the fastest
speed, which minimizes things getting blurred because of camera
movement. Second thing: lens usually image their sharpest (have
their best resolution) a couple stops down from the smallest aperture
I am sorry to inform you, but you are incorrect in stating that the
f-stop is the diameter of the lens aperture in inches with f2
equaling 1/2", f5 equaling 1/5", etc.
Logically, most, if not all lens (excluding view cameras and older
film cameras) are measured in millimeters. 50 mm, 100 mm, etc. Why
would they, in essence, measure their length in millimeters and their
width in inches?
Here is the correct
The f number is the reciprocal of the ratio of the lens length to
the aperture diameter. For instance: if the lens is a 100 millimeter
lens and the diameter of the aperture is 50 mm the diameter is 1/2
the length. This gives an f-stop of 2. With the same 100 mm lens,
if you adjust the aperture to 25 mm, it is 1/4th the lens length.
This works out to a f-stop of 4.
In case you are wondering why the numbers are so odd, (1.2, 1.4, 2,
4, 5.6, 8, 11, 16, etc.), here is why.
The lens aperture is set up to give you exposure changes of twice as
much or half as much with each full change between the listed
numbers. The odd series results because these numbers, to give that
result, have to vary with the square of the aperture.
Hope this helps. Any questions, please ask. I obtain so much
from all you people I love it when I can chime in on
something I know about.