Questions re: Photo Info

[windrunner]

i am trying to make sense of the following photo information provided by iphoto (Apple format):

shutter speed 1 over 40
Aperture f4.0
Max Aperture f3.0
Exposure Bias 0.33
Focal Length 7.30mm

shutter speed is self explanatory as is aperture and exposure bias...

no clue as to max aperture and focal length...

i suspect a relationship exists amongst these values...

would like to know how this information (feedback) can assist me to take better pictures (for example, some pictures the difference between aperture and max aperture is one f stop, while on others it may be as wide as 4 to 5 stops)...

any information along these lines would be appreciated...

thanks in advance...
windr

[robertwgross]

I suggest that you find a basic tutorial on digital exposure.

The camera is choosing different apertures for different shots, and you sure would not expect it to use the maximum aperture for everything.

---Bob Gross---

[DavidW]

The maximum aperture is simply the maximum aperture of the lens. It may be camera dependent as to whether the maximum aperture is the maximum aperture of the lens at all focal lengths, or at that focal length (I'm too tired to jump into the EXIF specifications to find out, and both my DSLR lenses are constant aperture zooms).

Focal length is a measure of how zoomed you are - for want of a better term.


As Bob says, hunt around for tutorials on digital exposure. The small focal length tells you this was a digital compact camera (the wide end of the lens of the Ixus 700 on the desk in front of me is 7.7mm), and these small sensor cameras have higher depth of field at wide (small f number) apertures than a digital SLR would.



David

[PhotosGuy]

i suspect a relationship exists amongst these values... These should help you figure it out:
Virtual Camera
Cameras Interactive aims to help novice photographers grasp the main concepts of SLR photography.
http://www.camerasinteractive.com/index.php#
Exposure explained: Three gateways for light.
http://www.canon.co.jp/Imaging/enjoydslr/p_2_005.html
Exposure - Low Tech Tips
http://www.photonhead.com/exposure/
SimCam
http://www.photonhead.com/exposure/simcam.php