What you need to know
The two primary reasons photography is not allowed during the service:
1. It's considered "work" to take pictures on Shabbat (this is primarily the case in Conservative/Orthodox synagogues).
2. The clergy feels it's too disruptive to the service.
If your synagogue does not allow photography during the service or rehearsal (and you'd like to try and change that), here are a few facts you can share with your Rabbi and/or synagogue staff:
No loud clicks.
Professional photographers who use the latest digital equipment are no more disruptive to the service than a videographer. For example, I use a Canon 5dMkIII pro camera which has a virtually silent shooting mode - no loud shutter clicks here! If your synagogue allows videography, there's a great case for allowing photography as well.
No flash required.
Again, the newest cameras allow us to shoot quality images in the dimmest of lighting conditions with no flash.
Out of sight.
We primarily shoot on a tripod from a stationary position in the back of the synagogue. If allowed, we may come off the tripod to shoot the Torah processional, still from the back. Using professional long telephoto lenses allows us to shoot from a distance, yet still get those key closeup shots.
Sensitive to the service.
Professional photographers who are familiar with the nuances of a Bar/Bat Mitzvah service will instinctively know not to shoot during sensitive times (ex. Amidah - silent prayer, Mourner's Kaddish, etc...).