What is the difference between "Aperture" and "F-Stop"

Archived from groups: rec.photo.digital (More info?)

In looking at the EXIF headers of my pictures, I notice separate entries
for "Aperture" and F-Stop". Sometimes these entries are the same, and
sometimes they are different. I have tried looking it up in several
glossaries, but haven't found anything that really explains the
difference.

Thanks, Gary

--
Gary Edstrom <gedstrom@pacbell.net>
Visit my Midway Island home page at http://gbe.dynip.com/Midway
My reality check bounced!
The above tagline is number 328 in a series of 547. Collect them all!

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Gary Edstrom wrote:

> In looking at the EXIF headers of my pictures, I notice separate entries
> for "Aperture" and F-Stop". Sometimes these entries are the same, and
> sometimes they are different. I have tried looking it up in several
> glossaries, but haven't found anything that really explains the
> difference.


Aperture is the diameter of the opening, f/stop is aperture divided by
focal length.

But I think what you are looking at is "maximum aperture of the lens"
and "f-stop used for this photo".


--
Paul Furman
http://www.edgehill.net/1
san francisco native plants

Archived from groups: rec.photo.digital (More info?)

Another way to explain is:
aperture vs. f-stop is like
length vs. inches

"Gary Edstrom" <gedstrom@pacbell.net> wrote in message
news:qbkt7112vboacpt02ok9r9n73ueo8qejf3@4ax.com...
> In looking at the EXIF headers of my pictures, I notice separate entries
> for "Aperture" and F-Stop". Sometimes these entries are the same, and
> sometimes they are different. I have tried looking it up in several
> glossaries, but haven't found anything that really explains the
> difference.
>
> Thanks, Gary
>
> --
> Gary Edstrom <gedstrom@pacbell.net>
> Visit my Midway Island home page at http://gbe.dynip.com/Midway
> My reality check bounced!
> The above tagline is number 328 in a series of 547. Collect them all!

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Jim Townsend wrote:
> Gary Edstrom wrote:
>
>
>>In looking at the EXIF headers of my pictures, I notice separate entries
>>for "Aperture" and F-Stop". Sometimes these entries are the same, and
>>sometimes they are different. I have tried looking it up in several
>>glossaries, but haven't found anything that really explains the
>>difference.
>
>
> F stop and aperture are essentially the same thing.. The aperture is
> measured in stops. The more stops, the smaller the opening.
>
> Many cameras have duplicate fields in the EXIF info.. For example, my
> Canon 10D has both "Exposure Time" and "Shutter Speed".
>
> I don't know why they do this I'm guessing it's done to maintain
> backwards compatibility with earlier EXIF standards.

Moreover, they aren't always exactly the same, at least on my camera.


--
Ron Hunter rphunter@charter.net

Archived from groups: rec.photo.digital (More info?)

Ok, I think I have found the answer to my own question:

And it involves MATH!

Take the square root of 2.

Raise it to the power of the aperature.

The result is the F-Stop.

I have tried this on several of my pictures and it works very precicely.

Example: Aperture=6.9189 F-Stop=11

(Sqrt(2))^6.9189 = 11.00014

I have tried it on other pictures and it seems to work.

On Mon, 09 May 2005 02:59:22 GMT, Gary Edstrom <gedstrom@pacbell.net>
wrote:

>In looking at the EXIF headers of my pictures, I notice separate entries
>for "Aperture" and F-Stop". Sometimes these entries are the same, and
>sometimes they are different. I have tried looking it up in several
>glossaries, but haven't found anything that really explains the
>difference.
>
>Thanks, Gary

Archived from groups: rec.photo.digital (More info?)

Always wondered the same thing...Thanks for the info.


--
Jack M
------------------------------------------------------------------------
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View this thread: http://thephotostation.net/forums/ [...] hp?t=12692

Archived from groups: rec.photo.digital (More info?)

Here is a conversion table to convert from Aperture to F-Stop. This
seems to match the EXIF data generated by my Canon EOS 20D. Fractional
apertures would of course fall somewhere between 2 F-Stops. The term
"Aperture" as used in the EXIF header seems to be a much different
aperture than we would normally think of. It is a logarithmic scale.
Each increase of 1 unit on the aperture scale results in a cutting in
half of the light to the CCD.

Gary

Aperture F-Stop

0 1
1 1.4
2 2
3 2.8
4 4
5 5.6
6 8
7 11
8 16
9 22
10 32
11 45
12 64

On Mon, 09 May 2005 15:47:41 GMT, Gary Edstrom <gedstrom@pacbell.net>
wrote:

>Ok, I think I have found the answer to my own question:
>
>And it involves MATH!
>
>Take the square root of 2.
>
>Raise it to the power of the aperature.
>
>The result is the F-Stop.
>
>I have tried this on several of my pictures and it works very precicely.
>
>Example: Aperture=6.9189 F-Stop=11
>
>(Sqrt(2))^6.9189 = 11.00014
>
>I have tried it on other pictures and it seems to work.
>
>On Mon, 09 May 2005 02:59:22 GMT, Gary Edstrom <gedstrom@pacbell.net>
>wrote:
>
>>In looking at the EXIF headers of my pictures, I notice separate entries
>>for "Aperture" and F-Stop". Sometimes these entries are the same, and
>>sometimes they are different. I have tried looking it up in several
>>glossaries, but haven't found anything that really explains the
>>difference.
>>
>>Thanks, Gary

Archived from groups: rec.photo.digital (More info?)

"Gary Edstrom" <gedstrom@pacbell.net> wrote in message
news:5a1v71htt97mkh44asas09v2ie5pis5tnu@4ax.com...
> Ok, I think I have found the answer to my own question:
>
> And it involves MATH!
>
> Take the square root of 2.
>
> Raise it to the power of the aperature.
>
> The result is the F-Stop.
>
> I have tried this on several of my pictures and it works very precicely.
>
> Example: Aperture=6.9189 F-Stop=11
>
> (Sqrt(2))^6.9189 = 11.00014
>
> I have tried it on other pictures and it seems to work.

I'm not sure what you're doing there, but the standard f-stop series is
based on multiples of the square root of 2, such that each higher number
represents half the *area* of the aperture opening and thus passes half as
much light in the same period of time. (If it were half the *diameter* it
would have only one-fourth the area and thus pass one-fourth the amount of
light.)

Starting with 1, the series is 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16 and so on.
Thus f/2.8 passes half as much light as f/2 but twice as much as f/4, four
times as much as f/8 and so on. There are in-between stops of course.

N.

Archived from groups: rec.photo.digital (More info?)

In message <117tmn15ogtv7c6@news.supernews.com>,
Jim Townsend <not@real.address> wrote:

>F stop and aperture are essentially the same thing.. The aperture is
>measured in stops.

Not exactly. When aperture is referred to by an f-stop, you have to
know the focal length to know what the aperture actually is. Aperture
is measured in millimeters' f-stop is a ratio of focal length to
aperture.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><

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"Paul Furman" <paul-@-edgehill.net> wrote in message
news:uLGdnTGcEaHffh7fRVn-oA@speakeasy.net...
> Nostrobino wrote:
>> "Paul Furman" <paul-@-edgehill.net> wrote in message
>>>
>>>Aperture is the diameter of the opening, f/stop is aperture divided by
>>>focal length.
>>
>>
>> Other way around. Focal length divided by size of aperture.
>>
>> For example, f/8 says the aperture size is f (the focal length) divided
>> by 8.
>
>
> Ah, thanks, that explains the fractional expression of f-stop. Isn't that
> nice when things make sense.

You're welcome, and yes it is. ;-)

N.