| Author |
Message |
none
Guest
|
 Posted:
Mon Oct 31, 2005 3:52 am Post subject:
"1:" on lens label -- what does it mean? |
|
|
On the front of my P/S lens, there is a label that says:
5.8-32mm 1:2.6-5.5
And on the front of my film SLR lens, the label says:
35-80mm 1:4-5.6
My question is, what does the "1:" in front of the aperture mean?
Thanks,
-Mike
|
|
| Back to top |
|
 |
Patrick Cleburne
Guest
|
| Posted:
Mon Oct 31, 2005 4:04 am Post subject:
Re: "1:" on lens label -- what does it mean? |
|
|
"none" <none@nowhere.invalid> wrote in message
news:Hgb9f.5029$UW5.886@trndny09...
| Quote: | On the front of my P/S lens, there is a label that says:
5.8-32mm 1:2.6-5.5
And on the front of my film SLR lens, the label says:
35-80mm 1:4-5.6
My question is, what does the "1:" in front of the aperture mean?
Thanks,
-Mike
|
It's a carry over from expressing the f stop or how wide the lens can open
as a ratio. On most contemporary zoom lenses, the maxim aperture or f stop
gets smaller as the lens zooms out. In your case, at 35mm focal length, the
maximum f stop is 4 but as you zoom out to 80mm, the f stop is smaller
(higher number, huh) meaning that less light passes through the lens. Other
things being equal, you need brighter light to shoot when you have the lens
zoomed out to telephoto. You need more light to shoot with a "slow" lens
tha thas a max aperture (opening) of f/4 or f/5.6 than you woule for one
with f/1.8 or 2.8.
Pick up a beginner's book on photography-- or find a website-- that will
explain it in more detail if you're interested.
Pat |
|
| Back to top |
|
|
Stephen M. Dunn
Guest
|
| Posted:
Mon Oct 31, 2005 4:13 am Post subject:
Re: "1:" on lens label -- what does it mean? |
|
|
In article <Hgb9f.5029$UW5.886@trndny09> none <none@nowhere.invalid> writes:
$On the front of my P/S lens, there is a label that says:
$5.8-32mm 1:2.6-5.5
$
$And on the front of my film SLR lens, the label says:
$35-80mm 1:4-5.6
$
$My question is, what does the "1:" in front of the aperture mean?
It's just a different way of writing f/, expressing it as a ratio
rather than by division.
f/x means the size of the aperture is the focal length divided
by x; in optics, the letter f is used to denote focal length (and
on some lenses, you'll actually see the focal length shown in the
form "f=50mm").
1:x means that the ratio of the aperture to the focal length is
1:x.
--
Stephen M. Dunn <stephen@stevedunn.ca>
| Quote: | ----------------> http://www.stevedunn.ca/ <----------------
------------------------------------------------------------------ |
Say hi to my cat -- http://www.stevedunn.ca/photos/toby/ |
|
| Back to top |
|
|
|
|
|
|
FAQ
Memberlist
Register
Profile
Log in to check your private messages
Log in