Steven060 wrote:
> I am looking for a small pocket camera (say Canon IXUS 60 /
> PowerShot SD600 or Panasonic Lumix FX01 size, not say Canon
> PowerShot S3 IS or Panasonic Lumix FZ7) that allows you to change
> the aperture settings easily. DPReview describes these as
> "ultra-compact", not the ones it describes as "compact".
>
> I normally shoot with a Canon 20D but I want a very small point and
> shoot camera that I can carry around with me at all times (in my
> pocket) but that will allow me to change the aperture to wide open
> to get a shallow depth when the shot / composition requires it.
> Similarly I want to set the smallest aperture when required
> (normally you can do this via the landscape mode on most pocket
> cameras).

As Petteri mentioned there is so much depth of field available across the aperture range that aperture adjustments alone will only have a minimal impact on DoF. Changes in focal length and lens to subject distance (magnification) will have a much greater impact.

Also, due to the shorter focal length lenses that these cameras have, the useful aperture range is fairly minimal. Due to size constraints, it's rare to find a digicam lens with a maximum aperture greater than f/2.8, if even that. Stopping the aperture down below about f/5.0 will usually begin to introduce diffraction artifacts that in turn will decrease overall sharpness beyond any apparent gains seen through increased Dof as a result of stopping down.

Effectively, there is seldom more than a three stop range of useable apertures with these cameras and with many of them, that range is closer to two stops. So, while many of these cameras do let you choose an aperture and then adjust shutter speed/ISO around that, and while there are benefits to having that capability, DoF control isn't terribly high on the list.


--
Tom Young
http://www.pbase.com/tyoung/