"P" mode and "Av" mode..whats the difference on a Canon 400d?

As per title, what is the difference between these 2 shooting modes?
According to the manual, both allow you to define or set your own aperture
whilst the camera sets a shuuter speed to deliver a correct exposure...if
thats the case, then why are there 2 modes ro do almost the same thing?

Thanks!!



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the_niner_nation wrote:
As per title, what is the difference between these 2 shooting modes?
According to the manual, both allow you to define or set your own aperture
whilst the camera sets a shuuter speed to deliver a correct exposure...if
thats the case, then why are there 2 modes ro do almost the same thing?

"P" mode makes an initial selection for you of both aperture and speed
(based on metered light, ISO setting, max lens aperture and Canon's
particular P algorithm) and then lets you "program shift" as desired in
either aperture or speed.

"Av" locks the exposure speed according to your chosen aperture (and ISO
setting). You vary the aperture only.

On top of both of the above is the exposure-compensation that you enter
to offset for the metering.

Cheers,
Alan.

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the_niner_nation offered these thoughts for the group's
consideration of the matter at hand:

As per title, what is the difference between these 2 shooting
modes? According to the manual, both allow you to define or
set your own aperture whilst the camera sets a shuuter speed
to deliver a correct exposure...if thats the case, then why
are there 2 modes ro do almost the same thing?

P generally meaning "programmed auto", attempts to reach a best
compromise between shutter speed and aperture so that you don't
get camera shake from a too low shutter speed nor too shallow DOF
due to a too wide aperture. But, it is a compromise.

Av means "aperture priority" which assumes you know that you know
the correct aperture for the effect you want, e.g., really broad
or really shallow DOF, and it adjusts shutter speed to create a
correct exposure.

Tv means "shutter priority", which assumes you know what effect
you want from shutter speed, e.g., some blur to show motion or
absolute stop-action, and it adjusts aperture accordingly.

To use Av and Tv effectively, you have to keep a close eye on the
shutter and aperture shown in the viewfinder to ensure that it
will be "correct" for what you want to achieve. It REALLY helps
if you have a good founding in the principles of photography so
that you can reasonably estimate the shutter speed or aperture to
any given effect you want to achieve. Could they be combined?
Yes, but it is simpler to think in terms of what you want to
control and let the camera do the math on the other setting. A
true combination does exist - P.

I find with my Rebel XT that when I try to out-think the camera
with Av, I usually blow it, so about the only time I use it is
when I have a specific DOF effect I want to achieve. I don't
shoot things that move, so I've never tried Tv. All things
considered, I think the Rebel does a damn fine job of balancing
shutter and aperture on P.

--
HP, aka Jerry

Alan Browne offered these thoughts for the group's consideration
of the matter at hand:

the_niner_nation wrote:
As per title, what is the difference between these 2 shooting
modes? According to the manual, both allow you to define or
set your own aperture whilst the camera sets a shuuter speed
to deliver a correct exposure...if thats the case, then why
are there 2 modes ro do almost the same thing?

"P" mode makes an initial selection for you of both aperture
and speed (based on metered light, ISO setting, max lens
aperture and Canon's particular P algorithm) and then lets you
"program shift" as desired in either aperture or speed.

"Av" locks the exposure speed according to your chosen
aperture (and ISO setting). You vary the aperture only.

On top of both of the above is the exposure-compensation that
you enter to offset for the metering.

I added Tv because it is a natural adjunct to the OP's overall
question. You correctly amplified my remarks by noting that ISO
modifies how all 3 modes will compute, and the camera's AE can be
overridden to at least +/- 2 stops. I don't do that much, but isn't
that EV?

--
HP, aka Jerry

HEMI-Powered wrote:
Alan Browne offered these thoughts for the group's consideration
of the matter at hand:


the_niner_nation wrote:

As per title, what is the difference between these 2 shooting
modes? According to the manual, both allow you to define or
set your own aperture whilst the camera sets a shuuter speed
to deliver a correct exposure...if thats the case, then why
are there 2 modes ro do almost the same thing?

"P" mode makes an initial selection for you of both aperture
and speed (based on metered light, ISO setting, max lens
aperture and Canon's particular P algorithm) and then lets you
"program shift" as desired in either aperture or speed.

"Av" locks the exposure speed according to your chosen
aperture (and ISO setting). You vary the aperture only.

On top of both of the above is the exposure-compensation that
you enter to offset for the metering.


I added Tv because it is a natural adjunct to the OP's overall
question. You correctly amplified my remarks by noting that ISO

eh? I answered first, so you're the one amplifying... ;-)

modifies how all 3 modes will compute, and the camera's AE can be
overridden to at least +/- 2 stops. I don't do that much, but isn't
that EV?

I didn't mention Tv as I thought the OP could make that leap of
connection by himself...

In the Canon world EV seems to be what everyone else calls "exposure
compensation". In the real world EV is "Exposure Value" which is
basically aperture & speed for ISO 100. (eg: Sunny-16 is EV 15
regardless of actual aperture and speed combo to achieve it).

Your post correctly pointed out that P sets the shutter speed (or
should) to reduce camera shake as well as the other factors I mentioned.

Every time I use a Canon camera I am frustrated by its exposure system
and it takes me many minutes to adjust. Minolta and Nikon is straight
nuts and bolts terminology and usage. Pentax too IIRC.

Cheers,
Alan.

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.

"Alan Browne" wrote in message
...
HEMI-Powered wrote:
Alan Browne offered these thoughts for the group's consideration
of the matter at hand:
the_niner_nation wrote:

As per title, what is the difference between these 2 shooting
modes? According to the manual, both allow you to define or
set your own aperture whilst the camera sets a shuuter speed
to deliver a correct exposure...if thats the case, then why
are there 2 modes ro do almost the same thing?

"P" mode makes an initial selection for you of both aperture
and speed (based on metered light, ISO setting, max lens
aperture and Canon's particular P algorithm) and then lets you
"program shift" as desired in either aperture or speed.

"Av" locks the exposure speed according to your chosen
aperture (and ISO setting). You vary the aperture only.

On top of both of the above is the exposure-compensation that
you enter to offset for the metering.


I added Tv because it is a natural adjunct to the OP's overall question.
You correctly amplified my remarks by noting that ISO

eh? I answered first, so you're the one amplifying... ;-)

modifies how all 3 modes will compute, and the camera's AE can be
overridden to at least +/- 2 stops. I don't do that much, but isn't that
EV?

I didn't mention Tv as I thought the OP could make that leap of connection
by himself...

In the Canon world EV seems to be what everyone else calls "exposure
compensation". In the real world EV is "Exposure Value" which is
basically aperture & speed for ISO 100. (eg: Sunny-16 is EV 15 regardless
of actual aperture and speed combo to achieve it).

Your post correctly pointed out that P sets the shutter speed (or should)
to reduce camera shake as well as the other factors I mentioned.

Every time I use a Canon camera I am frustrated by its exposure system and
it takes me many minutes to adjust. Minolta and Nikon is straight nuts
and bolts terminology and usage. Pentax too IIRC.

Cheers,
Alan.


Pentax now also has two more modes on the K10D, Sv and TAv.

Alan Browne wrote:
HEMI-Powered wrote:
Alan Browne offered these thoughts for the group's consideration
of the matter at hand:

the_niner_nation wrote:

As per title, what is the difference between these 2 shooting
modes? According to the manual, both allow you to define or
set your own aperture whilst the camera sets a shuuter speed
to deliver a correct exposure...if thats the case, then why
are there 2 modes ro do almost the same thing?

"P" mode makes an initial selection for you of both aperture
and speed (based on metered light, ISO setting, max lens
aperture and Canon's particular P algorithm) and then lets you
"program shift" as desired in either aperture or speed.

"Av" locks the exposure speed according to your chosen
aperture (and ISO setting). You vary the aperture only.

On top of both of the above is the exposure-compensation that
you enter to offset for the metering.


I added Tv because it is a natural adjunct to the OP's overall
question. You correctly amplified my remarks by noting that ISO

eh? I answered first, so you're the one amplifying... ;-)

modifies how all 3 modes will compute, and the camera's AE can be
overridden to at least +/- 2 stops. I don't do that much, but isn't
that EV?

I didn't mention Tv as I thought the OP could make that leap of
connection by himself...

In the Canon world EV seems to be what everyone else calls "exposure
compensation". In the real world EV is "Exposure Value" which is
basically aperture & speed for ISO 100. (eg: Sunny-16 is EV 15
regardless of actual aperture and speed combo to achieve it).

Actually, on a Rebel XT the button is labeled Av+-. And the manual
describes it as the Av/Exposure Compensation button. In manual mode it
is used to change aperture, and in other modes it's used to change EC.

I don't see EV mentioned anywhere.

Greg
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G.T. wrote:
Alan Browne wrote:

HEMI-Powered wrote:

Alan Browne offered these thoughts for the group's consideration
of the matter at hand:

the_niner_nation wrote:

As per title, what is the difference between these 2 shooting
modes? According to the manual, both allow you to define or
set your own aperture whilst the camera sets a shuuter speed
to deliver a correct exposure...if thats the case, then why
are there 2 modes ro do almost the same thing?


"P" mode makes an initial selection for you of both aperture
and speed (based on metered light, ISO setting, max lens
aperture and Canon's particular P algorithm) and then lets you
"program shift" as desired in either aperture or speed.

"Av" locks the exposure speed according to your chosen
aperture (and ISO setting). You vary the aperture only.

On top of both of the above is the exposure-compensation that
you enter to offset for the metering.


I added Tv because it is a natural adjunct to the OP's overall
question. You correctly amplified my remarks by noting that ISO


eh? I answered first, so you're the one amplifying... ;-)

modifies how all 3 modes will compute, and the camera's AE can be
overridden to at least +/- 2 stops. I don't do that much, but isn't
that EV?


I didn't mention Tv as I thought the OP could make that leap of
connection by himself...

In the Canon world EV seems to be what everyone else calls "exposure
compensation". In the real world EV is "Exposure Value" which is
basically aperture & speed for ISO 100. (eg: Sunny-16 is EV 15
regardless of actual aperture and speed combo to achieve it).


Actually, on a Rebel XT the button is labeled Av+-. And the manual
describes it as the Av/Exposure Compensation button. In manual mode it
is used to change aperture, and in other modes it's used to change EC.

If you have and Av mode then it should mean that and having another
button labeled "Av+/-" seems like poor UI to me.

I may have made an error above, but the point remains that Canon have
one of the strangest exposure nomenclatures. Minolta had it just right:
A,S,M,P and exp-comp for both available light and flash. What more does
one need? (Drop the "P" and I'd be just as happy).

I don't see EV mentioned anywhere.

HEMI wrote:
""modifies how all 3 modes will compute, and the camera's AE can be
overridden to at least +/- 2 stops. I don't do that much, but isn't
that EV?""

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.

Alan Browne wrote:
G.T. wrote:
Alan Browne wrote:

HEMI-Powered wrote:

Alan Browne offered these thoughts for the group's consideration
of the matter at hand:

the_niner_nation wrote:

As per title, what is the difference between these 2 shooting
modes? According to the manual, both allow you to define or
set your own aperture whilst the camera sets a shuuter speed
to deliver a correct exposure...if thats the case, then why
are there 2 modes ro do almost the same thing?


"P" mode makes an initial selection for you of both aperture
and speed (based on metered light, ISO setting, max lens
aperture and Canon's particular P algorithm) and then lets you
"program shift" as desired in either aperture or speed.

"Av" locks the exposure speed according to your chosen
aperture (and ISO setting). You vary the aperture only.

On top of both of the above is the exposure-compensation that
you enter to offset for the metering.


I added Tv because it is a natural adjunct to the OP's overall
question. You correctly amplified my remarks by noting that ISO


eh? I answered first, so you're the one amplifying... ;-)

modifies how all 3 modes will compute, and the camera's AE can be
overridden to at least +/- 2 stops. I don't do that much, but isn't
that EV?


I didn't mention Tv as I thought the OP could make that leap of
connection by himself...

In the Canon world EV seems to be what everyone else calls "exposure
compensation". In the real world EV is "Exposure Value" which is
basically aperture & speed for ISO 100. (eg: Sunny-16 is EV 15
regardless of actual aperture and speed combo to achieve it).


Actually, on a Rebel XT the button is labeled Av+-. And the manual
describes it as the Av/Exposure Compensation button. In manual mode
it is used to change aperture, and in other modes it's used to change EC.

If you have and Av mode then it should mean that and having another
button labeled "Av+/-" seems like poor UI to me.

I completely agree.


I may have made an error above, but the point remains that Canon have
one of the strangest exposure nomenclatures. Minolta had it just right:
A,S,M,P and exp-comp for both available light and flash. What more does
one need? (Drop the "P" and I'd be just as happy).

I don't know why Canon has to do the Av, Tv thing, and why T instead of
S anyway?


I don't see EV mentioned anywhere.

HEMI wrote:
""modifies how all 3 modes will compute, and the camera's AE can be
overridden to at least +/- 2 stops. I don't do that much, but isn't
that EV?""


Can't speak for HEMI but I was just talking about the manual.

Greg

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In article , G.T.
wrote:

I don't know why Canon has to do the Av, Tv thing, and why T instead of
S anyway?

aperture value, time value