Re: Exposure confusion...

KC wrote:
> I have a Canon S3 which does a great job setting exposure (outdoors).  
> So that I could take better pictures of objects, I recently purchased 
> both a light box and a six foot wide white backdrop.  I have two 85 watt

> photo light sources.  I tripod mount my camera.

Manual exposure is the way to get studio tripod shots right. Check the 
histogram and adjust.

> What I want to get is a low-noise, adequately exposed image that needs 
> minimal photoshop touch up for improvement.
> 
> I am baffled that using the 85 watt lights and backdrop (or lightbox), 
> the Canon S3 underexposes all shots and requires use of additional 
> lighting to get proper exposure.  White backgrounds appear gray.  If I 
> have the camera bracket exposure, the longer exposure is light enough 
> which shows there is enough light for the camera to get a good shot, but

> it just isn't calculating things correctly.
> 
> Because there are so many settings, I used menu/reset to reset to 
> factory. Set the ISO to AUTO, and took photos in both P and AUTO mode.  
> I still get the same result.  Gray whites.
> 
> Loading an image into photoshop shows the shutter speed of 1/60 second. 

> F stop of 3.2 (seems high since the camera supports 2.7).  I can't tell 
> what ISO the S3 used for the shot.
> 
> Since the Canon can adjust aperature, shutter speed and ISO, why would 
> it constanly underexpose these images?