3 questions ?

[yb98]

1. I have read that the captor of the Rebel has 6.5 millions of pixel but the images are only 6.3 millions. why ?

2. Is it true that the rebel can not activate the flash at the end of the time exposure ?

3. What is the difference between activating the flash at the beginning and the end of the time exposure ?

Thanks in advance for your answers.

Yacine.

[RichardtheSane]

I honestly don't know the 1st two, but I wouldn't worry about .2 of a megapixel, it is virtuallty nothing.

The second curtain flash is useful for creative effects on long exposure as just one example. If I wanted to make a cyclist look sharp int he fram but still give motion blur then I would use a slower shutter speed (1/8th second to 1/30th second) and second curtain flash. Then there would be the blur of the cyclist but the flash at the end of the exposure would freeze the motion - meaning the cyclist is fairly sharp but with motion blur behing them.

Did I explain that well? I don't think I did because that is just one example.

[scottbergerphoto]

Richard,
I believe the main difference between 1st and 2nd curtain sync flash, is that in 1st curtain, the motion trail is in front of the subject and looks unnatural, and in 2nd curtain sync the motion trails are behind, and look more natural.
Scott

[nosquare2003]

For the first question, 0.2m pixels is nothing important. Anyhow, I try to explain it.

The total pixels of Drebel are 3,152 x 2,068 = 6,518,336 pixels. In other words, there are 6,518,336 photo detectors in the sensors.

However, the aspect ratio is 3:2. As you can see from the above, the 3,152 vs 2,068 is not in a ratio of 3:2. It is listed in the menu that the effective pixels are 3,072 x 2,048 = 6,291,456 effective pixels. And it is in the ratio of 3:2. In other words, some of the photo detectors (approx. 0.2m) has not been used for the generation of the images.

[CyberDyneSystems]

RE: Photocells and megapixles,...

The seemingly "Unused" photosensors that we assume just go to waste actually don't.

There is a thin border of photocells that surround the part of the sensor we do use for out images,. this frame of sensors are used however,.. they record information that helps to establish your images black point.

Combine this whith Nosquare's answer and you get the whole picture.. or should I say,. the whole Image sensor.

[Jesper]

I don't know why, but on all digital cameras (not only the Digital Rebel) there's a slight difference between the number of pixels on the sensor and the "effective" number of pixels.