Newsgroup: it.arti.fotografia.digitale
Titolo: canon A40 e A20

Ho ordinato la Canon A40.
Ho avuto modo di provare una A20 prima di ora.
Le foto che ho fatto in interni con la A20 non sono mai uscite sfuocate.
La Canon A40, in automatico, non è uguale alla A20?
Se si, allora anche le foto con la A40 non dovrebbero uscire sfuocate.
Chi mi sa dire qualcosa al riguardo?
Maurizio
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 ha scritto nel messaggio
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dipende in quale modalità intendi operare.. se in automatico o in
manuale!!!!

 wrote in message
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Leggi qui.
http://www.powershot.inxtec.net/showthread.php?s=6130838169f40a8feb20d272b12
1eeea&threadid=926
Ciao
:-)
Red.

Meglio se te lo riporto tutto...
If you know what you are doing, you will not have any problems with locking
focus, even in low light,
The only caveat is you have to ANALYZE any situation where the camera
doesn't give you the "green square" that says you are focused locked. For
example, one situation I found where I cannot get a lock is when I try to
focus in low light upon any flat, uniform colored surface.
To be specific:
1) I aim the camera at the carpet in a room with only one overhead light.
There are no shadows or anything crisscrossing the frame. Focus will not
lock. If there is a shadow or anything in the frame, it will lock fine (and
fast).
2) I aim the camera at a plain white wall. Focus will not lock, I get the
dreaded "red square". The focus assist light is on, I can see the little
pattern of light on the wall, but it will not give me a lock.
3) I have a large armoire that is painted a very dark blue. I am the camera
at the side, which is very smooth. I cannot get a lock in low light.
Of course, I am being facetious because I KNOW how autofocus works and these
situations are KNOWN problems for ALL autofocus cameras that use the
passive/contrast detection way of autofocusing.
Here is a quote from 
http://www.howstuffworks.com/autofocus3.htm
"Passive autofocus must have light and image contrast in order to do its
job. The image needs to have some detail in it that provides contrast. If
you try to take a picture of a blank wall or a large object of uniform
color, the camera cannot compare adjacent pixels so it cannot focus.
There is no distance-to-subject limitation with passive autofocus like there
is with the infrared beam of an active autofocus system. Passive autofocus
also works fine through a window, since the system "sees" the subject
through the window just like you do.
Passive autofocus systems usually react to vertical detail. When you hold
the camera in the horizontal position, the passive autofocus system will
have a hard time with a boat on the horizon but no problem with a flagpole
or any other vertical detail. If you are holding the camera in the usual
horizontal mode, focus on the vertical edge of the face. If you are holding
the camera in the vertical mode, focus on a horizontal detail.
Newer, more expensive camera designs have combinations of vertical and
horizontal sensors to solve this problem. But it's still the camera user's
job to keep the camera's sensors from being confused on objects of uniform
color. "
So what this means is that you have to find a work-around to deal with your
particular focus "problem". Like if I REALLY REALLY needed to lock focus on
that carpet, I might toss some object in the middle of the scene, get my
focus locked on the object (use the focus lock feature to keep the focus
set), remove the object, and snap away. For the white wall, I probably would
estimate the distance, focus on something equal distance away, lock down the
focus, and turn back to the white wall and shoot.
Now, if you are getting the green square, and your scene is uniformly
blurry, then that usually means your hands were too shaky for the shutter
speed your camera chose in that light. Put the camera on a flat surface and
use the timer, or get a tripod
http://www.howstuffworks.com/autofocus3.htm

Ti ringrazio
Maurizio
"Redshift" <"Redshift"> wrote in message
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noncediché
:-)