# Formula?

Discussion in 'Digital Photography' started by Jim, Jan 25, 2004.

1. ### JimGuest

My niece is taking a Digital photography class. The teacher is trying to
teach the students how to figure out the f-stop without using a meter. He is
giving them the lighting condition and the film ISO. (I know he is teaching
them film photography first!) Is there a easy formula for this? My niece
says the teacher ran through it so quickly she does not understand how to do
it. Thanks for any help

Jim, Jan 25, 2004

2. ### WebrositaGuest

>"Jim" wrote:

>My niece is taking a Digital photography class. The teacher is trying to
>teach the students how to figure out the f-stop without using a meter

If I remember correctly it is called the Sunny 16 Rule and it used to be
included in the print insert for all Kodak film. I did a Google search and came
out with this url:

http://www.camerareview.com/templates/sunny16.cfm

Webrosita, Jan 25, 2004

3. ### KBobGuest

On Sun, 25 Jan 2004 12:53:00 GMT, "Jim" <> wrote:

>
>My niece is taking a Digital photography class. The teacher is trying to
>teach the students how to figure out the f-stop without using a meter. He is
>giving them the lighting condition and the film ISO. (I know he is teaching
>them film photography first!) Is there a easy formula for this? My niece
>says the teacher ran through it so quickly she does not understand how to do
>it. Thanks for any help
>

She's better off if left to work this out for herself--otherwise, how
will she learn this? In any case the basic formula is:

Film sensitivity X Illuminance = Aperture X Exposure Time

and for convenience these quantities are usually expressed in terms of
their Log2 values (and choosing a suitable starting value). When this
is done, the formula becomes:

Exposure Value = Film Value + Brightness Value
-or alternatively-
Exposure Value = Aperture Value + Time Value

where
Exposure Value (EV) is 0 at T=1 sec, Aperture (f/#)=1, and ASA=3

To simplify things the "Sunny 16" method can often be used, and I
suspect the "lighting condition" you refer to may be covered by this.
For example:

Shutter setting = 1/ISO at f/16 for midday sun

where "midday sun" might be assumed to be about 10,000 foot candles.
Add a couple stops for shade, subtract a stop or two for sand or snow,
and there you have it!

KBob, Jan 25, 2004
4. ### JC DillGuest

On Sun, 25 Jan 2004 14:41:16 GMT, KBob <> wrote:

>To simplify things the "Sunny 16" method can often be used, and I
>suspect the "lighting condition" you refer to may be covered by this.
>For example:
>
> Shutter setting = 1/ISO at f/16 for midday sun
>
>where "midday sun" might be assumed to be about 10,000 foot candles.
>Add a couple stops for shade, subtract a stop or two for sand or snow,
>and there you have it!

1/400 shutter with 400 iso at f16 = 1/400 shutter at 200 iso at f 11,
= 1/400 shutter at 100 iso at f8, = 1/800 shutter at 100 iso at f 5.6?

jc

JC Dill, Feb 5, 2004