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Canon REBEL TI Flash Sync Speed Question



 
 
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  #1  
Old July 29th 04, 11:05 PM
William Graham
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Posts: n/a
Default Canon REBEL TI Flash Sync Speed Question


"Dr. Slick" wrote in message
om...
Hi,

I ended up getting the Rebel TI kit obviously.

But i was wondering about using the built-in flash.

In the "P" mode, you can see how the shutter speed
is always set to the sync speed, which is 1/90 for the
Rebel TI. However, the aperture always stays the same,
because it is automatically set by the TTL exposure
program, or something like that.

In the "Tv" or "Av" modes, whether or
not the flash is popped out or not, the exposure
reading (flashing numbers mean under or over
exposure) never seems to change. The only thing
which will certainly happen when you pop the flash up,
is that the shutter speed will be set to 1/90 if it was
anything faster...

If the shutter speed is slower than 1/90,
then the EXPOSURE SETTINGS STAY THE SAME IN "Tv" or "Av".

Why is this? I understand why the shutter speed
must be 1/90 or slower, but why doesn't the "Tv"
mode, for example, select a smaller aperture
automatically when i pop up the flash? To compensate
for the extra light from the flash?


Probably because with today's electronics, the light from the flash can be
extinguished to automatically limit the amount the film or sensing plane
gets. The camera knows you want to use a given aperture (probably for depth
of field reasons) so it chooses to quench the flash sooner to limit the
light, rather then closing down the aperture.


  #2  
Old July 29th 04, 11:05 PM
William Graham
external usenet poster
 
Posts: n/a
Default Canon REBEL TI Flash Sync Speed Question


"Dr. Slick" wrote in message
om...
Hi,

I ended up getting the Rebel TI kit obviously.

But i was wondering about using the built-in flash.

In the "P" mode, you can see how the shutter speed
is always set to the sync speed, which is 1/90 for the
Rebel TI. However, the aperture always stays the same,
because it is automatically set by the TTL exposure
program, or something like that.

In the "Tv" or "Av" modes, whether or
not the flash is popped out or not, the exposure
reading (flashing numbers mean under or over
exposure) never seems to change. The only thing
which will certainly happen when you pop the flash up,
is that the shutter speed will be set to 1/90 if it was
anything faster...

If the shutter speed is slower than 1/90,
then the EXPOSURE SETTINGS STAY THE SAME IN "Tv" or "Av".

Why is this? I understand why the shutter speed
must be 1/90 or slower, but why doesn't the "Tv"
mode, for example, select a smaller aperture
automatically when i pop up the flash? To compensate
for the extra light from the flash?


Probably because with today's electronics, the light from the flash can be
extinguished to automatically limit the amount the film or sensing plane
gets. The camera knows you want to use a given aperture (probably for depth
of field reasons) so it chooses to quench the flash sooner to limit the
light, rather then closing down the aperture.


  #3  
Old July 31st 04, 02:30 PM
Dr. Slick
external usenet poster
 
Posts: n/a
Default Canon REBEL TI Flash Sync Speed Question

"William Graham" wrote in message news:%[email protected]_s03...

In the "Tv" or "Av" modes, whether or
not the flash is popped out or not, the exposure
reading (flashing numbers mean under or over
exposure) never seems to change. The only thing
which will certainly happen when you pop the flash up,
is that the shutter speed will be set to 1/90 if it was
anything faster...

If the shutter speed is slower than 1/90,
then the EXPOSURE SETTINGS STAY THE SAME IN "Tv" or "Av".

Why is this? I understand why the shutter speed
must be 1/90 or slower, but why doesn't the "Tv"
mode, for example, select a smaller aperture
automatically when i pop up the flash? To compensate
for the extra light from the flash?


Probably because with today's electronics, the light from the flash can be
extinguished to automatically limit the amount the film or sensing plane
gets. The camera knows you want to use a given aperture (probably for depth
of field reasons) so it chooses to quench the flash sooner to limit the
light, rather then closing down the aperture.



Well, to put it in another way, in the "Tv" and Av"
modes, the exposure settings DON'T CHANGE when you
turn on/pop-up the flash. My digital Powershot G3,
on the other hand, will show a faster shutter speed
when i add the flash (in the Av mode), as I would
suspect it should do, as there will be more light
obviously.

Maybe the Rebel TI is also doing this, except
it doesn't show it in the chosen exposure settings?


Slick
  #4  
Old July 31st 04, 02:30 PM
Dr. Slick
external usenet poster
 
Posts: n/a
Default Canon REBEL TI Flash Sync Speed Question

"William Graham" wrote in message news:%[email protected]_s03...

In the "Tv" or "Av" modes, whether or
not the flash is popped out or not, the exposure
reading (flashing numbers mean under or over
exposure) never seems to change. The only thing
which will certainly happen when you pop the flash up,
is that the shutter speed will be set to 1/90 if it was
anything faster...

If the shutter speed is slower than 1/90,
then the EXPOSURE SETTINGS STAY THE SAME IN "Tv" or "Av".

Why is this? I understand why the shutter speed
must be 1/90 or slower, but why doesn't the "Tv"
mode, for example, select a smaller aperture
automatically when i pop up the flash? To compensate
for the extra light from the flash?


Probably because with today's electronics, the light from the flash can be
extinguished to automatically limit the amount the film or sensing plane
gets. The camera knows you want to use a given aperture (probably for depth
of field reasons) so it chooses to quench the flash sooner to limit the
light, rather then closing down the aperture.



Well, to put it in another way, in the "Tv" and Av"
modes, the exposure settings DON'T CHANGE when you
turn on/pop-up the flash. My digital Powershot G3,
on the other hand, will show a faster shutter speed
when i add the flash (in the Av mode), as I would
suspect it should do, as there will be more light
obviously.

Maybe the Rebel TI is also doing this, except
it doesn't show it in the chosen exposure settings?


Slick
  #5  
Old August 2nd 04, 02:10 AM
Dr. Slick
external usenet poster
 
Posts: n/a
Default Canon REBEL TI Flash Sync Speed Question

Hi,

I ended up getting the Rebel TI kit obviously.

But i was wondering about using the built-in flash.

In the "P" mode, you can see how the shutter speed
is always set to the sync speed, which is 1/90 for the
Rebel TI. However, the aperture always stays the same,
because it is automatically set by the TTL exposure
program, or something like that.

In the "Tv" or "Av" modes, whether or
not the flash is popped out or not, the exposure
reading (flashing numbers mean under or over
exposure) never seems to change. The only thing
which will certainly happen when you pop the flash up,
is that the shutter speed will be set to 1/90 if it was
anything faster...

If the shutter speed is slower than 1/90,
then the EXPOSURE SETTINGS STAY THE SAME IN "Tv" or "Av".

Why is this? I understand why the shutter speed
must be 1/90 or slower, but why doesn't the "Tv"
mode, for example, select a smaller aperture
automatically when i pop up the flash? To compensate
for the extra light from the flash?

I'm pretty certain there is nothing wrong with
my camera, but i just wanted to be sure.

Any information greatly appreciated in advance.


Slick
 




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