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

On Sun, 27 May 2007 12:59:16 -0700, G.T. wrote:

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

S(hutter) makes more sense, but maybe T(ime) was the intent.

G.T. wrote:
Alan Browne wrote:

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?

Exactly what I was getting at...



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.

Ah.

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.

ASAAR wrote:
On Sun, 27 May 2007 12:59:16 -0700, G.T. wrote:


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


S(hutter) makes more sense, but maybe T(ime) was the intent.

Probably. That's what I mean about Canon's offbeat exposure nomenclature...

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

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

S(hutter) makes more sense, but maybe T(ime) was the
intent.

Probably. That's what I mean about Canon's offbeat exposure
nomenclature...

I agree it doesn't make sense, but why argue with reality? Just go
with the flow, pick the setting that does the job for you, and just
ignore Canon's nomenclature. But, again, Alan, it is when I think
I'm getting smarter than the camera and switch off P to T or A that
I tend to get worse results. My Rebel XT does a damn fine job of
setting a good compromise shutter and aperture with P, so why risk
failure. The ONLY time I switch to Av is when I KNOW I'll have a
DOF problem. e.g., suppose I am shooting a car in the foreground
and there's a building or foliage in the background I also want in
focus. I MAY switch to Av and go to f/11 or f/16 and even up the
ISO from 100 to 200. But, those situations are rare for me.

--
HP, aka Jerry

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


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

S(hutter) makes more sense, but maybe T(ime) was the
intent.

Probably. That's what I mean about Canon's offbeat exposure
nomenclature...


I agree it doesn't make sense, but why argue with reality? Just go
with the flow, pick the setting that does the job for you, and just
ignore Canon's nomenclature. But, again, Alan, it is when I think
I'm getting smarter than the camera and switch off P to T or A that
I tend to get worse results. My Rebel XT does a damn fine job of
setting a good compromise shutter and aperture with P, so why risk
failure. The ONLY time I switch to Av is when I KNOW I'll have a
DOF problem. e.g., suppose I am shooting a car in the foreground
and there's a building or foliage in the background I also want in
focus. I MAY switch to Av and go to f/11 or f/16 and even up the
ISO from 100 to 200. But, those situations are rare for me.

In using Av / Tv you really need to understand the meter of the camera.
What area it's covering and what is the relative reflectance of the
part being metered. From there using exposure compensation comes in.

OTOH, P is likewise affected, but it probably weights strongly to the
overall scene as a starting point so whatever errors get biased out
fairly well in "average" scenes. In Av/Tv start with scene evaluative
metering (whatever mode in the camera meters all over the scene) and
then work towards more spot metered areas using exposure compensation.
Look up all the meter offset values (ashphalt is 0, grass is -1, skin
(palm of hand) is +1, yellow is +1, red is 0, etc. .. use a gray card as
a target and then build your own table of what EC's to use.... Use the
histogram..

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

I agree it doesn't make sense, but why argue with reality?
Just go with the flow, pick the setting that does the job for
you, and just ignore Canon's nomenclature. But, again, Alan,
it is when I think I'm getting smarter than the camera and
switch off P to T or A that I tend to get worse results. My
Rebel XT does a damn fine job of setting a good compromise
shutter and aperture with P, so why risk failure. The ONLY
time I switch to Av is when I KNOW I'll have a DOF problem.
e.g., suppose I am shooting a car in the foreground and
there's a building or foliage in the background I also want
in focus. I MAY switch to Av and go to f/11 or f/16 and even
up the ISO from 100 to 200. But, those situations are rare
for me.

In using Av / Tv you really need to understand the meter of
the camera.
What area it's covering and what is the relative reflectance
of the
part being metered. From there using exposure compensation
comes in.

Yes, e.g., the 3 available modes of metering light. In my case, I
almost always use Evaluative.

OTOH, P is likewise affected, but it probably weights strongly
to the overall scene as a starting point so whatever errors
get biased out fairly well in "average" scenes. In Av/Tv
start with scene evaluative metering (whatever mode in the
camera meters all over the scene) and then work towards more
spot metered areas using exposure compensation. Look up all
the meter offset values (ashphalt is 0, grass is -1, skin
(palm of hand) is +1, yellow is +1, red is 0, etc. .. use a
gray card as a target and then build your own table of what
EC's to use.... Use the histogram..

I would probably agree, Alan, if I had the faintest clue what
you're talking about! grin Well, I have some clue ... But, as
you've been following along in my comments in this and other
threads, getting an absolutely, precisely accurate exposure isn't
really an issue for my car pictures - usually. The bigger problem
is uneven exposure and dynamic range problems that are really
difficult to easily fix. e.g. suppose it is daylight, I am in P
mode on Evaluative, I do an AF lock and allow the camera to
simultaneously do the AE lock. Rare for me to need to pick a
different sample point for AE, which is so common is flash
situations. At car shows, the hoods are almost always up because
the judges need to see that and because the owners like to show
off their hard work. When the car is reasonably well exposed and
there are no serious backlight problems, the engine will be
almost black. And, the interior will also be quite dark, but not
as dark as the engine. To fix that. I tweak the entire scene in
PSP 9 using the usual techniques, then do individual selections
on area(s) that are either too bright or too dark and adjust them
until I have a good compromise.

The main reason I have never taken the time to develop custom WB
and exposure settings, as you describe, and/or using an image
already in memory as the base point, is that from car to car to
car, the problems vary too much to try to diddle around with
multiple custom settings. And, even with the LCD set all the way
to bright, in daylight, it is virtually impossible for me to read
the menus unless I crouch down in a shadow on the car, not to
mention that there seldom is enough time to be all that careful.

If that makes me a fool in the eyes of some folks, so be it. I
think I've clarified my position enough that it isn't what other
folks think is "right" or "wrong", what the camera books say, or
what teachers in a photography class say - although I do place
weight on those things - it only matters what the photographer
thinks is important and right, for them.

--
HP, aka Jerry

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


I agree it doesn't make sense, but why argue with reality?
Just go with the flow, pick the setting that does the job for
you, and just ignore Canon's nomenclature. But, again, Alan,
it is when I think I'm getting smarter than the camera and
switch off P to T or A that I tend to get worse results. My
Rebel XT does a damn fine job of setting a good compromise
shutter and aperture with P, so why risk failure. The ONLY
time I switch to Av is when I KNOW I'll have a DOF problem.
e.g., suppose I am shooting a car in the foreground and
there's a building or foliage in the background I also want
in focus. I MAY switch to Av and go to f/11 or f/16 and even
up the ISO from 100 to 200. But, those situations are rare
for me.

In using Av / Tv you really need to understand the meter of
the camera.
What area it's covering and what is the relative reflectance
of the
part being metered. From there using exposure compensation
comes in.


Yes, e.g., the 3 available modes of metering light. In my case, I
almost always use Evaluative.


OTOH, P is likewise affected, but it probably weights strongly
to the overall scene as a starting point so whatever errors
get biased out fairly well in "average" scenes. In Av/Tv
start with scene evaluative metering (whatever mode in the
camera meters all over the scene) and then work towards more
spot metered areas using exposure compensation. Look up all
the meter offset values (ashphalt is 0, grass is -1, skin
(palm of hand) is +1, yellow is +1, red is 0, etc. .. use a
gray card as a target and then build your own table of what
EC's to use.... Use the histogram..


I would probably agree, Alan, if I had the faintest clue what
you're talking about! grin Well, I have some clue ... But, as

It's very simple: 18% grey is about the middle of the exposure range.
All the relfective parts of the image lie on each side of that. Near
white is about two stops above (add +2 compensation as the meter thinks
that white is 18% grey). Dark clothes lie at about -2 to -2.5 so set -2
to -2.5 (the meter thinks that dark stuff is 18% grey, so it tries to
open it up to make the dark stuff grey ... you adjust -2.5 to compensate).

Run the exercise for a bunch of colors v. a grey card reference and
you'll see what I mean.

Or with digital, use its built in "white" card. Put a white card in the
scene and shoot a test shot. Look at the histo. If it shows info all
the way to the right without overflowing (creating a sharp spike at the
right), then you're bang on. Underexpose that same scene by two stops
(the white turns grey) and the histo will be blank from the right to
about the middle...

you've been following along in my comments in this and other
threads, getting an absolutely, precisely accurate exposure isn't
really an issue for my car pictures - usually. The bigger problem
is uneven exposure and dynamic range problems that are really
difficult to easily fix. e.g. suppose it is daylight, I am in P
mode on Evaluative, I do an AF lock and allow the camera to
simultaneously do the AE lock. Rare for me to need to pick a
different sample point for AE, which is so common is flash
situations. At car shows, the hoods are almost always up because

We've gone over this before ... you can't get 10 Lbs of **** into a 5 Lb
bag. The first thing to do is to control the lighting. If you're
shooting digital outdoors in mid day with strong shaddows there is NO
WAY a digital image can fit in all the detail. Use flll flash to
lighten up the shaddows, but shoot for the daylight.

Or use negative film and overexpose it a little. You'll get tons of
detail. (Portra 160 VC would be a good choice exposed at 100).


the judges need to see that and because the owners like to show
off their hard work. When the car is reasonably well exposed and
there are no serious backlight problems, the engine will be
almost black. And, the interior will also be quite dark, but not
as dark as the engine. To fix that. I tweak the entire scene in
PSP 9 using the usual techniques, then do individual selections
on area(s) that are either too bright or too dark and adjust them
until I have a good compromise.

The main reason I have never taken the time to develop custom WB
and exposure settings, as you describe, and/or using an image
already in memory as the base point, is that from car to car to
car, the problems vary too much to try to diddle around with
multiple custom settings. And, even with the LCD set all the way
to bright, in daylight, it is virtually impossible for me to read
the menus unless I crouch down in a shadow on the car, not to
mention that there seldom is enough time to be all that careful.

Here is where Manual shooting can save your day. Once you figure, for a
scene, what the exposure should be, set the aperture and speed manaully.
This will give you shot to shot consistency without the meter making
errors based on each new scene.

The point is: the light is constant, so should be the exposure.

Fill flash will need to vary due to distance.

If that makes me a fool in the eyes of some folks, so be it. I
think I've clarified my position enough that it isn't what other
folks think is "right" or "wrong", what the camera books say, or
what teachers in a photography class say - although I do place
weight on those things - it only matters what the photographer
thinks is important and right, for them.

That's not the point at all. By using P (ot Tv or Av) you're letting
the camera evaluate the exposure from shot to shot. But in a given
scene with available light you can find one exposure value that will
give you consistency for every frame. In manual mode your camera
probably has a button you can hold while changing aperture that will
make the reciprocal change in speed (or v-v).

For a mid sunny day at ISO 100, if you set f/8 @ 1/500 and the flash at
-1.5 (for fill light when needed) I would bet you'll get very good
results and a lot more consistency shot to shot. (adjust the shutter
speed with something matt white in the scene to fill the histo to the
right without overflow).

If shooting the "open shade" side of the car, then you will need more
exposure (by about 1.5 stops, but sunlit parts will blow out) and you
may want to set the color temp higher (8,000 - 10,000 K). (If you shoot
RAW then you can do this on importing the images into the computer).

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

I would probably agree, Alan, if I had the faintest clue what
you're talking about! grin Well, I have some clue ... But,
as

It's very simple: 18% grey is about the middle of the
exposure range. All the relfective parts of the image lie on
each side of that. Near white is about two stops above (add
+2 compensation as the meter thinks that white is 18% grey).
Dark clothes lie at about -2 to -2.5 so set -2 to -2.5 (the
meter thinks that dark stuff is 18% grey, so it tries to open
it up to make the dark stuff grey ... you adjust -2.5 to
compensate).

You're forcing me to try to remember my Photography 101 from 40
years ago! grin

Run the exercise for a bunch of colors v. a grey card
reference and you'll see what I mean.

Or with digital, use its built in "white" card. Put a white
card in the scene and shoot a test shot. Look at the histo.
If it shows info all the way to the right without overflowing
(creating a sharp spike at the right), then you're bang on.
Underexpose that same scene by two stops (the white turns
grey) and the histo will be blank from the right to about the
middle...

Please excuse my denseness here, Alan, but what question are you
answering? I can follow the quotes that you're commenting on how
to put more science and less seat-of-the-pants into the decision
which exposure mode to use and how best to use them wrt building
custom WB and EV settings. Beyond that, I'm not following you.
Maybe you're replying in general and not to my particular set of
strange problems ...

you've been following along in my comments in this and other
threads, getting an absolutely, precisely accurate exposure
isn't really an issue for my car pictures - usually. The
bigger problem is uneven exposure and dynamic range problems
that are really difficult to easily fix. e.g. suppose it is
daylight, I am in P mode on Evaluative, I do an AF lock and
allow the camera to simultaneously do the AE lock. Rare for
me to need to pick a different sample point for AE, which is
so common is flash situations. At car shows, the hoods are
almost always up because

We've gone over this before ... you can't get 10 Lbs of ****
into a 5 Lb bag. The first thing to do is to control the
lighting. If you're shooting digital outdoors in mid day with
strong shaddows there is NO WAY a digital image can fit in all
the detail. Use flll flash to lighten up the shaddows, but
shoot for the daylight.

10 pounds of **** into a 5 pound bag is what used to be called a
"blivet". I understand your point, which is that it is patently
impossible to get anywhere near 100% correct exposures across the
entire dynamic range of a pathological case like my example. As
for me, I am not really complaining, I know how to "fix" the dark
engines and interiors, I was simply pointing out that it isn't
always possible to "do it right the first time".

Or use negative film and overexpose it a little. You'll get
tons of detail. (Portra 160 VC would be a good choice exposed
at 100).

I think my film days are long gone, and not coming back. But, if
you've followed my general theses wrt car photography, I am NOT
all that concerned with 100% correct results on each and every
photo. I am a documentary photographer interested in the car, and
less so the technical quality of the image. Other people feel
differently, and that is their right.

The main reason I have never taken the time to develop custom
WB and exposure settings, as you describe, and/or using an
image already in memory as the base point, is that from car
to car to car, the problems vary too much to try to diddle
around with multiple custom settings. And, even with the LCD
set all the way to bright, in daylight, it is virtually
impossible for me to read the menus unless I crouch down in a
shadow on the car, not to mention that there seldom is
enough time to be all that careful.

Here is where Manual shooting can save your day. Once you
figure, for a scene, what the exposure should be, set the
aperture and speed manaully.
This will give you shot to shot consistency without the
meter making
errors based on each new scene.

The point is: the light is constant, so should be the
exposure.

First, the light is not constant; it varies throughout the day,
sometimes literally in minutes if clouds are moving. Second, the
degree to which an engine or interior is in the shade is highly
dependent on where the car is wrt the sun. e.g., the Walter P.
Chrysler Museum where the CEMA show will be held on June 9, faces
exactly E-W, which means that I shoot one series of photos with
one set of views in the AM and another set in the PM. As the sun
rises, peaks at around noon, then begins to sink, lighting
changes dramatically, as does its temperature as well as how much
the car is actually lit.

With the number of cars I would like to shoot - can't always do
what I like, but I try - there simply isn't time to take the
"correct" approach, and using full manual is problematical for
many people, including me. If done well, it may save the day as
you describe. Done not so well and the images will be total junk.
So, again, P mode is the best all around compromise for me for
the average car show in daylight.

Fill flash will need to vary due to distance.

Haven't been too successful making fill flash do what it is
intended to do. I need to do more practicing at home before the
big shows start.

If that makes me a fool in the eyes of some folks, so be it.
I think I've clarified my position enough that it isn't what
other folks think is "right" or "wrong", what the camera
books say, or what teachers in a photography class say -
although I do place weight on those things - it only matters
what the photographer thinks is important and right, for
them.

That's not the point at all. By using P (ot Tv or Av) you're
letting the camera evaluate the exposure from shot to shot.
But in a given scene with available light you can find one
exposure value that will give you consistency for every frame.
In manual mode your camera probably has a button you can hold
while changing aperture that will make the reciprocal change
in speed (or v-v).

For a mid sunny day at ISO 100, if you set f/8 @ 1/500 and the
flash at -1.5 (for fill light when needed) I would bet you'll
get very good results and a lot more consistency shot to shot.
(adjust the shutter speed with something matt white in the
scene to fill the histo to the right without overflow).

If shooting the "open shade" side of the car, then you will
need more exposure (by about 1.5 stops, but sunlit parts will
blow out) and you may want to set the color temp higher (8,000
- 10,000 K). (If you shoot RAW then you can do this on
importing the images into the computer).

I appreciate you many good pieces of advice,Alan. I'm sorry that
I won't be able to follow you direction however, for the reasons
I have stated. There is a continuum between two extremes where
one is lesser quanitity but much higher quality, and the other is
quantity enough to try to at least get SOME image on a really
large number of cars, but sacrificing quality to the point where
it may get pretty dismal at times. Forget me, and just think of
the general cases I describe. Each photographer has to decide
where in the continuum they want to be, or can be, and adjust
their technique(s) accordingly. There are times when I think I
might be better off giving up my DSLR and going back to a
"snapshot camera", i.e., a small P & S. It annoys me that I
cannot take advantage of better methodologies, but that's the way
the cookie crumbles.

Have a great holiday!

--
HP, aka Jerry

HEMI-Powered wrote:

Snipped bits out

Have a great holiday!

Thanks; I will. Finals of NCAA D-1 lacrosse start in an hour or so.

Jerry-

Alan has given a splendid discourse on it, while I've previously
suggested you use manual, in a very few words. It's not so difficult as
you seem to make out.

In any event, it looks like you have had your mind made up some years
ago on this, and naught's going to change it.

Happy shooting!

--
john mcwilliams

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

HEMI-Powered wrote:

Snipped bits out

Have a great holiday!

Thanks; I will. Finals of NCAA D-1 lacrosse start in an hour
or so.

Jerry-

Alan has given a splendid discourse on it, while I've
previously suggested you use manual, in a very few words. It's
not so difficult as you seem to make out.

In any event, it looks like you have had your mind made up
some years ago on this, and naught's going to change it.

It isn't that my mind is made up, although it is, it is more that
I just don't see the benefits of doing it "right" vs. the effort.
That is not in any way an insult to Alan or anybody, just how I
feel. I use examples of my personal experiences to illustrate my
realist and pragmatist approach to everything in my life,
including photography, cars, PCs, etc. People on this and
rec.photo.digital apparently confuse my comments as complaints,
they are not, or requests for help in solving my problems, which
they also are not. I pretty much gave up asking for specific help
because my philosophy of doing things is incompatible with
people's recommendations, which inevitably leads to bad blood. I
don't want to see that, so I'm just "taking an even strain."

As to RTFM, I have, but it is like most manuals, poorly written
and indended to be a reference manual, not a tutorial. If you
believe manuals are easy to glean information from, I am happy
for you. I find it extremely difficult and thus extremely
frustrating.

In conclusion, again, I do NOT want to insult anyone or diss them
by appeearing to ignore their advice. Responders to all OPs in
this NG tend to be more experienced and much more interested in
superior results than I am. That's fine by me. I wish that people
would cut me a little slack and allow me to feel the way I do, if
I am happy and satisfied with my results. Now, if I could improve
my percentage of first-time good images, I surely would - but it
has to be with a good eye on the cost-benefit curves. There are
just so many other things in life more important to me than
photography of any subject that I have to prioritize my time, and
that leaves out learning the more esoteric aspects of digital.
However, I DO keep a folder of what people say, whether to me or
in general, that I can always print if I want to try my hand at
improving.

Let me comment on one aspect of this and rec.photo.digital. OPs
that are newbies of one sort of another more often than not put a
couple of paragraphs in that do not have nearly enough detail for
anyone to respond intelligently. When the thread goes toward the
highly technical, high quality end, I suspect that the OP doesn't
want to look stupid, so they simply don't come back in. It has
been said that beauty is in the eye of the behold, and I would
submit that so is image quality and print quality.

Thanks for your comments.

--
HP, aka Jerry