Exif data and EV calculation

Why the Exif data (version 2.1.0) does not show the Exposure Value?

I have taken, for example, two identical pictures at ISO 100 with the following settings:

1. Shutter 1/350s and aperture f8.0
2. Shutter 1/250s and aperture f6.7

As may be seen picture 2 had a higher exposure than picture 1 but by how much?

Many of us can calculate the EV but what about our other colleagues that are not maths experts.

Having aperture, shutter speed and ISO number this is a simple mathematical calculation that adds some more information to the photographer so why not have it on the Exif list?

Josh

there is a brightness value in the exif - for some reason minolta decided not to show it with Dview - there is a lot more in the exif than what they show.

try something life exifread to view the exif data - shows the whole file

http://www.takenet.or.jp/~ryuuji/minisoft/exifread/english/

also, picture 2 is one fstop brighter, isn't it? f8.0 to f6.7 = 1/2 stop brighter and 1/350 to 1/250 = 1/2 stop brighter, so total is 1 stop brighter?

--
Minolta D7i
http://www.pbase.com/ukbuckeye
http://www.nickyandjeff.dsl.pipex.com/weather/weather.htm

Hi Jeff,

Thanks for the information. On a second look the Dimage Viewer includes in the Exif data a Brightness Value but with my confusion I was looking for the Exposure Value.

What is actually the difference between BV and EV?

Thanks, Josh

Jeff/UK said:

there is a brightness value in the exif - for some reason minolta
decided not to show it with Dview - there is a lot more in the exif
than what they show.

try something life exifread to view the exif data - shows the whole
file

http://www.takenet.or.jp/~ryuuji/minisoft/exifread/english/

also, picture 2 is one fstop brighter, isn't it? f8.0 to f6.7 =
1/2 stop brighter and 1/350 to 1/250 = 1/2 stop brighter, so total
is 1 stop brighter?

--
Minolta D7i
http://www.pbase.com/ukbuckeye
http://www.nickyandjeff.dsl.pipex.com/weather/weather.htm

Click to expand...

fraid i can't answer that one

all i know about it is that +1.0EV = 2X light = 1 fStop

maybe brightness is some average of the histogram curve?

how different is the value listed in the exif for your examples?

--
Minolta D7i
http://www.pbase.com/ukbuckeye
http://www.nickyandjeff.dsl.pipex.com/weather/weather.htm

Hi Jeff,

Just to clarify the difference between Brightness and Exposure Value I have done some bracketing experiment and you may see it posted to both the Minolta and the Open Talk forums. It will be very interesting to read the comments.

Regards,
Josh

Jeff/UK said:

fraid i can't answer that one

all i know about it is that +1.0EV = 2X light = 1 fStop

maybe brightness is some average of the histogram curve?

how different is the value listed in the exif for your examples?

--
Minolta D7i
http://www.pbase.com/ukbuckeye
http://www.nickyandjeff.dsl.pipex.com/weather/weather.htm

Click to expand...

Josh Halberthal said:

................
Having aperture, shutter speed and ISO number this is a simple
mathematical calculation that adds some more information to the
photographer so why not have it on the Exif list?

Josh

Click to expand...

Looking at the Exif 2.1 standards, Brightness Value is shown as being a part of the formula to compute the exposure value. The formula in the standards does not make sense to me (see second equal sign below):

Ev = APEX aperture value + APEX shutter speed value = APEX brightness value + Film Sensitivity (not used in Exif 2.1 standards)

I'm not sure if Brightness Value replaces film sensitivity or is now included with film sensitivity as part of the formula.

The Exif 2.1 standards says brightness value can range from -99.99 to +99.99, but indicates in a chart that it is an APEX expression of foot lambert:

APEX Brightness Value -2 represents 1/4 foot lambert
APEX Brightness Value -1 represents 1/2 foot lambert
APEX Brightness Value +0 represents 1 foot lambert
APEX Brightness Value +1 represents 2 foot lambert
APEX Brightness Value +2 represents 4 foot lambert
APEX Brightness Value +3 represents 8 foot lambert
APEX Brightness Value +4 represents 15 foot lambert
APEX Brightness Value +5 represents 30 foot lambert

See Appendix C (APEX Units) in the Exchangeable Image File Format for Digital Still Cameras: EXIF 2.1 Standards

APEX (Additive System of Photographic Exposure)

I am assuming the camera is storing APEX values for shutter speed and aperture, and Dimage Viewer and other programs are using table similar to following to show actual shutter speed and aperture. I am under the impression that the APEX values need to be added to compute Exposure Value.

APEX Values for Aperture: (these values may be different for EXIF Standards 2.2)

0 = aperture 1
1 = aperture 1.4
2 = aperture 2
3 = aperture 2.8
4 = aperture 4
5 = aperture 5.6
6 = aperture 8
7 = aperture 11
8 = aperture 16
9 = aperture 22
10 = aperture 32

APEX Values for Shutter Speed:

-5 = shutter speed 30 seconds
-4 = shutter speed 15 seconds
-3 = shutter speed 8 seconds
-2 = shutter speed 4 seconds
-1 = shutter speed 2 seconds
0 = shutter speed 1 second
1 = shutter speed 1/2 second
2 = shutter speed 1/4 second
3 = shutter speed 1/8 second
4 = shutter speed 1/15 second/
5 = shutter speed 1/30 second
6 = shutter speed 1/60 second
7 = shutter speed 1/125 second
8 = shutter speed 1/250 second
9 = shutter speed 1/500
10 = shutter speed 1/1000
11 = shutter speed 1/2000

The Exif 2.1 standards says brightness value can range from -99.99
to +99.99, but indicates in a chart that it is an APEX expression
of foot lambert:

APEX Brightness Value -2 represents 1/4 foot lambert
APEX Brightness Value -1 represents 1/2 foot lambert
APEX Brightness Value +0 represents 1 foot lambert
APEX Brightness Value +1 represents 2 foot lambert
APEX Brightness Value +2 represents 4 foot lambert
APEX Brightness Value +3 represents 8 foot lambert
APEX Brightness Value +4 represents 15 foot lambert
APEX Brightness Value +5 represents 30 foot lambert

William West said:

See Appendix C (APEX Units) in the Exchangeable Image File Format
for Digital Still Cameras: EXIF 2.1 Standards

Click to expand...