# Will the Nikon D80 or D200 do this?

Discussion in 'Nikon' started by E. E. Herbert, Sep 26, 2006.

1. ### Bill FunkGuest

The f/number is really easy; it's just a ratio of the lens focal
length to the aperture opening.
For example, let's use a 50mm lens. If the aperture is 25mm, the
f/number is 2, because the ratio of the focal length to the aperture
is 1:2. With the same lens, an aperture of 12.5mm would be f/4,
because the ratio of the focal length to the apertire is 1:4.
Why the odd numbers then? ASAAR covered the math, but the reason is
because we are dealing with the area of a circle (the ideal aperture
opening is a circle), thus the need to use square roots.
The end result, though, is simple. Each established f/number is 1/2 or
twice (depending on whether you're going *up* or *down* the f/number
scale) the exposure of the preceding one. Thus, for example, f/4 will
let twice the light through that f/5.6 does, and f/2.8 will let in
twice as much light as f/4 will.
It can be confusing, because a larger f/number means a smaller
aperture.

Bill Funk, Nov 30, 2006

2. ### Thomas T. VeldhouseGuest

And for simplicity, each full stop is 1.4 (square root of 2) times the
previous full stop.

f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32

These full stops should really be memorized. Makes manual exposure much
easier.

Thomas T. Veldhouse, Nov 30, 2006

3. ### Bill FunkGuest

Simplicity?
How many people can do that math "simply"?
I sure can't.
Agreed, wholeheartedly!

Bill Funk, Nov 30, 2006
4. ### Thomas T. VeldhouseGuest

You don't find it simple to multiply by 1.4? I didn't say to do it in your
head. In fact, that is why I said that one should memorize the whole stops.

Thomas T. Veldhouse, Nov 30, 2006
5. ### CynicorGuest

If you're American, just do exposure in two touchdown increments.

Cynicor, Nov 30, 2006
6. ### Bill FunkGuest

No, actually, I don't. I'm math challenged. :-(
I carry a PDA with me with the calculator on speed-button.

Bill Funk, Nov 30, 2006
7. ### ASAARGuest

Nah. Before multiplying by 1.4 most Americans would just punt.

ASAAR, Nov 30, 2006
8. ### ASAARGuest

Bill didn't make that f/8 comment. I did. You can figure it out
by counting the number of ">" characters at the beginning of each
quoted line. It's a pun, sort of, with f/8 falling halfway between
f/2.8 and f/22. Have you heard of the Golden Mean, or learned the
difference beteen "average" and "mean" in high school math classes?
You don't have to even know the actual definition of "mean" to get
it, you only need a slight familiarity with the term. And btw, my
name is Bill too, so you actually got it right!

ASAAR, Nov 30, 2006
9. ### Thomas T. VeldhouseGuest

I am curious. A D200 seems like a rather large purchase for somebody that
doesn't understand apeture and f/stop. I am glad to see you have an
interested in learning it though and I am sure the D200 won't limit your
progress. I just picked up mine last week (moving from a D70) and absolutely
love the camera myself.

Thomas T. Veldhouse, Dec 1, 2006
10. ### Thomas T. VeldhouseGuest

f eight = "fate"?

Thomas T. Veldhouse, Dec 1, 2006
11. ### VXGuest

Actually things haven't really changed, its just that they developed
electronic cameras, so that opened up a lot of options that can be confusing
if you didn't follow the gradual changes of camera design as they occurred.
For example you say there are more f-stops, but there aren't. The range you
saw on a manual focus camera a couple of decades or so ago would have been
something like f2.8, f4, f5.6, f8, f11, f16, maybe f22. f8 lets in twice as
much light as f11, and so on throughout the range. But an electronic camera
such as a digital SLR can display the in-between aperture values also. These
were there all along in between the marked positions on the aperture ring of
the lens you held long ago, but they weren't indicated because that would
have been too complex and confusing to put on a small aperture ring, and
unnecessary anyway. But now since the aperture display can be on an LCD there
is no reason why it cannot display the in-between settings.

If you want to try a photographic tool that could really help you understand
these exposure settings in an obvious and accessible way, I would recommend
finding an old Weston Master 5 exposure meter. It should be the 5 or later
since the earlier ones did not use ASA/ISO values and would confuse things. I
have used one many times to see graphically where a particular aperture
number fell into the whole range when comparing maximum f-stops, etc. it is
also very useful for learning about exposure in a number of other ways. Now
that I say that, I remember I lost mine a while ago so I will now go about
getting another one. These are great learning tools. Basically an analog
exposure meter that shows ALL the aperture numbers including fractions of an
f-stop on one rotating ring makes it all clear. The Weston Master 5 is the
one I'd suggest.

VX, Dec 7, 2006
12. ### VXGuest

They can be. If you know anywhere that sells used or "classic" equipment,
that would be the place to look for a used one. KEH in Atlanta (they have a
web site) is generally recommended for ordering used camera gear by mail
order. Although I think I saw that they were strill making these not so long
ago! A web search might be a good way of researching where to find one of
these. Or Ebay:

http://search.ebay.com/weston-master-invercone_W0QQfnuZ1

-but do bear in mind that these are generally quite old and so try to ensure
you are buying one that is working.

VX, Dec 7, 2006
13. ### VXGuest

In fact on this Ebay entry this photograph actually shows you most of what
you need to know- all the apertures are visible and the whole stops (the
values that are half or double the light of the next whole stop along) are
highlighted in black. I'm going to print this image out and keep it, it will
be useful to me too....

http://imagehost.vendio.com/bin/viewimage.x/00000000/vanhook/west3.JPG?vvid=30
691004&sp=1

or look for the last pic here:

http://cgi.ebay.com/Weston-Master-V-mod-748-w-case-invercone-etc-
NR_W0QQitemZ150067068704QQihZ005QQcategoryZ4702QQssPageNameZWDVWQQrdZ1QQcmdZVi
ewItem

or look at the pics on the Ebay page I quoted in my previous post:

http://search.ebay.com/weston-master-invercone_W0QQfnuZ1

The second entry, last picture, is the one. At least until that page changes.

VX, Dec 7, 2006