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Evaluative metering is mostly extra center weighing

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marscalls

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I think I have figured out a quick and dirty but practical understanding of what "Evaluative" metering really does — at least on the Pro1.

Effectively, "EVALUATIVE" SEEMS TO OPERATE LIKE "CENTER WEIGHTED AVERAGE" WITH EXTRA CENTER WEIGHTING.

Applying this SIMPLISTIC view for a high contrast shot:

• "Center Weighted Average" — use when exposure balance of the whole field is more important than just the subject.

• "Spot" — when proper exposure of the main subject completely trumps the rest of the field. May require several readings of different parts of the subject.

• "Evaluative" — use when the subject is clearly more important than the rest of the shot, but you still want the background have consideration. That’s why if you insist on using only one setting, this should be it.

The above assumes that when necessary, you place the subject in the center for AE lock, then recompose.

Once again — shoot the marketing people and let the engineers write the manuals (bad grammar and all).
 
http://web.canon.jp/Imaging/pspro1/206-e.html#02

This is what I understand these modes to entail...

Evaluative....looks at the entire scene and picks out a balance.
(kind of works like AiAF)

Center weighted...looks at the entire scene, but gives more priority towards what is in the center.
(kind of works like AiAF, but with priority towards whats in the center portion)

Spot...meters a small area in the center or your AF frame (depending upon which you choose)
(kind of works like using a single focus point)
marscalls said:
I think I have figured out a quick and dirty but practical
understanding of what "Evaluative" metering really does — at least
on the Pro1.

Effectively, "EVALUATIVE" SEEMS TO OPERATE LIKE "CENTER WEIGHTED
AVERAGE" WITH EXTRA CENTER WEIGHTING.

Applying this SIMPLISTIC view for a high contrast shot:
• "Center Weighted Average" — use when exposure balance of the
whole field is more important than just the subject.
• "Spot" — when proper exposure of the main subject completely
trumps the rest of the field. May require several readings of
different parts of the subject.
• "Evaluative" — use when the subject is clearly more important
than the rest of the shot, but you still want the background have
consideration. That’s why if you insist on using only one setting,
this should be it.
The above assumes that when necessary, you place the subject in
the center for AE lock, then recompose.

Once again — shoot the marketing people and let the engineers write
the manuals (bad grammar and all).
Click to expand...
--
My Pictures
http://www.pbase.com/absurd_username
 
I find that what the manufacturer says is not always correct. I've used Canon cams and now a Pentax DSLR, and made the same observation as Marcalls. The difference between evaluative and center-weighted is so slight that I cannot tell them apart. :)
 
I did a couple more experiments and found:

• Contrary to Canon’s inflated doubletalk, the Evaluative metering on the Pro1 works like a MORE HEAVILY CENTER-WEIGHTED averaging mode even when the AF/AE spot is moved off-center. In other words, manually moving the rectangle (Pro1 doesn’t have AIAF) definitely does move the AE point in Spot mode, but not in Evaluative mode.

• Canon shouldn’t be ashamed of telling what Evaluative really does, because once you know how it works, it is very effective.

• I just now compared Evaluative with Center Weighted Average on the SD300. It works the same as on the Pro1.

• On the SD300, AIAF has no effect — the heavy weighting remains in the center regardless of the focus point.

• As an aside, the term “Artificial Intelligence” as in AIAF is also inflated rhetoric. It is simply focusing on the closest spot that it can get a focus lock. This feature can also be helpful when the user actually knows what is happening.

Evaluative mode works JUST LIKE ITS DISPLAY SYMBOL IMPLIES--very Center Weighted, but certainly not Spot..
 
One would hope, that evaluative actually divides the scene up into N rectangles, and looks at the exposure values in each of them, and tries to keep whatever is the brightest area from blowing out.

So, in a more complex scene, with say relatively fairly bright areas in an otherwise darker scene, the evaluative will differ more from center weighted.

Also, note that spot metering can be quite useful, even without metering on the subject. If you use the AE lock, or half press the shutter to lock focus and exposure... Just meter on some object that you want to be mid-grey equivalent...

I almost never turn evaluative off. But I do dial in compensation on a regular basis.

Don

--
Don Erway
http://www.pbase.com/derway/kona_underwater_g2
 
center weight -

based on absurd_username, I agree these definitions. I think the first two are very close together.

sue anne
gee-six
-------------------------------------------
absurd_username said:
This is what I understand these modes to entail...

Evaluative....looks at the entire scene and picks out a balance.
(kind of works like AiAF)

Center weighted...looks at the entire scene, but gives more
priority towards what is in the center.
(kind of works like AiAF, but with priority towards whats in the
center portion)

Spot...meters a small area in the center or your AF frame
(depending upon which you choose)
(kind of works like using a single focus point)
marscalls said:
I think I have figured out a quick and dirty but practical
understanding of what "Evaluative" metering really does — at least
on the Pro1.

Effectively, "EVALUATIVE" SEEMS TO OPERATE LIKE "CENTER WEIGHTED
AVERAGE" WITH EXTRA CENTER WEIGHTING.

Applying this SIMPLISTIC view for a high contrast shot:
• "Center Weighted Average" — use when exposure balance of the
whole field is more important than just the subject.
• "Spot" — when proper exposure of the main subject completely
trumps the rest of the field. May require several readings of
different parts of the subject.
• "Evaluative" — use when the subject is clearly more important
than the rest of the shot, but you still want the background have
consideration. That’s why if you insist on using only one setting,
this should be it.
The above assumes that when necessary, you place the subject in
the center for AE lock, then recompose.

Once again — shoot the marketing people and let the engineers write
the manuals (bad grammar and all).
Click to expand...
--
My Pictures
http://www.pbase.com/absurd_username
Click to expand...
 
When there is a much brighter center to an otherwise dark scene, Evaluative will set a shorter exposure/smaller aperture than will CWA.

When there is a much darker center to an otherwise bright scene, Evaluative will set a longer exposure/larger aperture than will CWA.

In either case, when the bright or dark object is moved to the side of the field, Evaluative and CWA give about the same exposure.

These are my actual observations with two very different but current Canons. Perhaps the true black magic of matrix metering would show up in much more complex scenes, but those characteristics (if they really do show differences in complex scenes ) would be impractical to master. You would just look at your shot and then compensate or switch to Spot.

Forget the marketing BS in the manuals and try a few test shots or readings.

Now that I understand it, I will use all three settings. Before, I only used Evaluative and Spot.
 
Sigh. I had hoped for a simulated zone system, or something...
marscalls said:
When there is a much brighter center to an otherwise dark scene,
Evaluative will set a shorter exposure/smaller aperture than will
CWA.

When there is a much darker center to an otherwise bright scene,
Evaluative will set a longer exposure/larger aperture than will CWA.

In either case, when the bright or dark object is moved to the side
of the field, Evaluative and CWA give about the same exposure.

These are my actual observations with two very different but
current Canons. Perhaps the true black magic of matrix metering
would show up in much more complex scenes, but those
characteristics (if they really do show differences in complex
scenes ) would be impractical to master. You would just look at
your shot and then compensate or switch to Spot.

Forget the marketing BS in the manuals and try a few test shots or
readings.

Now that I understand it, I will use all three settings. Before, I
only used Evaluative and Spot.
Click to expand...
--
Don Erway
http://www.pbase.com/derway/kona_underwater_g2
 
Don Erway said:
Sigh. I had hoped for a simulated zone system, or something...
Click to expand...
Don’t sweat it. In tough metering situations, only the photographer knows what compromises to make.

“AI”, all AI, is more Artificial than Intelligence. Firmware is fast, wetware is good.
 
marscalls, you are right. I did a limited and informal test this morning and found that if you shoot an evenly lighted scene, evaluative and center-weighted will give you identical results. But if part of the scene is much more brightly lit and this light source is not in the center of the frame, then center-weighted will actually account for this brighter area better and choose a higher f-stop than evaluative metering, resulting in less blown highlights. Anyone can do the same test by shooting an interior with a brightly lit window off to one side, confined to one of the outer thirds (or less) of the frame.

Now this behavior is very counter-intuitive and contradictory to the camera's icons and manual's description. It's very odd. But if you look at the icons, they seem to logically depict how the camera actually works.

IOW, [ ] really is evaluative and NOT center-weighted and [o] is really center-weighted... just as the icons would suggest. It's reversed in the manual which seems to be wrong, and Canon should be spanked for this oversight! So perhaps some marketing person just got mixed up and no one ever bothered to correct it?

Bottom line: follow the icons, and not the manual.

Thanks for bringing this to our attention. It will help me use my camera better.

--
Pat
marscalls said:
I think I have figured out a quick and dirty but practical
understanding of what "Evaluative" metering really does — at least
on the Pro1.

Effectively, "EVALUATIVE" SEEMS TO OPERATE LIKE "CENTER WEIGHTED
AVERAGE" WITH EXTRA CENTER WEIGHTING.

Applying this SIMPLISTIC view for a high contrast shot:
• "Center Weighted Average" — use when exposure balance of the
whole field is more important than just the subject.
• "Spot" — when proper exposure of the main subject completely
trumps the rest of the field. May require several readings of
different parts of the subject.
• "Evaluative" — use when the subject is clearly more important
than the rest of the shot, but you still want the background have
consideration. That’s why if you insist on using only one setting,
this should be it.
The above assumes that when necessary, you place the subject in
the center for AE lock, then recompose.

Once again — shoot the marketing people and let the engineers write
the manuals (bad grammar and all).
Click to expand...
 
I made some test in my room a few moments ago, and it seems to be true!
Pat said:
Now this behavior is very counter-intuitive and contradictory to
the camera's icons and manual's description. It's very odd. But if
you look at the icons, they seem to logically depict how the camera
actually works.

IOW, [ ] really is evaluative and NOT center-weighted and [o] is
really center-weighted... just as the icons would suggest. It's
reversed in the manual which seems to be wrong, and Canon should be
spanked for this oversight! So perhaps some marketing person just
got mixed up and no one ever bothered to correct it?

Bottom line: follow the icons, and not the manual.

Thanks for bringing this to our attention. It will help me use my
camera better.

--
Pat
Click to expand...
--
Ciao, Filippo.



http://xoomer.virgilio.it/sosrah/gallery.htm
 
Would this mean the manual is wrong for the S1 as well?
sosrah said:
Pat said:
Now this behavior is very counter-intuitive and contradictory to
the camera's icons and manual's description. It's very odd. But if
you look at the icons, they seem to logically depict how the camera
actually works.

IOW, [ ] really is evaluative and NOT center-weighted and [o] is
really center-weighted... just as the icons would suggest. It's
reversed in the manual which seems to be wrong, and Canon should be
spanked for this oversight! So perhaps some marketing person just
got mixed up and no one ever bothered to correct it?

Bottom line: follow the icons, and not the manual.

Thanks for bringing this to our attention. It will help me use my
camera better.

--
Pat
Click to expand...
--
Ciao, Filippo.



http://xoomer.virgilio.it/sosrah/gallery.htm
Click to expand...
 
Pat said:
IOW, [ ] really is evaluative and NOT center-weighted and [o] is
really center-weighted... just as the icons would suggest. It's
reversed in the manual which seems to be wrong, and Canon should be
spanked for this oversight! So perhaps some marketing person just
got mixed up and no one ever bothered to correct it?
Click to expand...
FWIW ...
seems to be wrong in the Dutch translation as well ..
 
Don Erway said:
Really Amazing!

I wonder what the 2 of them do, in a complex backlit scene - light
say a sunset behind trees, or something like that. I would sure
hope that in some scenes, the evaluative would give a better
exposure than center weighted!

Don
Click to expand...
Yes, you can bet that evaluative WILL outperform centre-weighted averaging in certain tricky lighting conditions. Centre-weighted averaging doesn't care about positions of light sources or whether the camera is held horizontally or vertically, etc. It just does a really simple thing: averaging the frame with more emphasis on the centre. Evaluative is a different, more complicated beast... It's pointless to try to determine how it works by doing simple tests.

Costas
 
Costas, yes evaluative is smarter and should do a better job in a tricky situation such as Don described.The problem is that for the G6 and Pro 1 at least, what the manual calls evaluative acts instead like center-weighted and vice versa. IOW, Canon seems to have messed up or switched their descriptions of the two metering methods in their manuals. I suspect many if not all their digicams have this fault in their manuals. And thus, countless legions of Canon owners have been using the metering methods incorrectly.

Despite the fact evaluative is more tricky, one should be able to predict the way it meters relative to center-weighted in known lighting situations. If not, why use it at all? In my tests, I got the same results that marscalls did. His findings have also been confirmed by thw and sosrah. I think Canon has screwed up here.

--
Pat
Costas Vlachos said:
Yes, you can bet that evaluative WILL outperform centre-weighted
averaging in certain tricky lighting conditions. Centre-weighted
averaging doesn't care about positions of light sources or whether
the camera is held horizontally or vertically, etc. It just does a
really simple thing: averaging the frame with more emphasis on the
centre. Evaluative is a different, more complicated beast... It's
pointless to try to determine how it works by doing simple tests.

Costas
Click to expand...
 
Pat said:
Costas, yes evaluative is smarter and should do a better job in a
tricky situation such as Don described.The problem is that for the
G6 and Pro 1 at least, what the manual calls evaluative acts
instead like center-weighted and vice versa. IOW, Canon seems to
have messed up or switched their descriptions of the two metering
methods in their manuals. I suspect many if not all their digicams
have this fault in their manuals. And thus, countless legions of
Canon owners have been using the metering methods incorrectly.

Despite the fact evaluative is more tricky, one should be able to
predict the way it meters relative to center-weighted in known
lighting situations. If not, why use it at all? In my tests, I
got the same results that marscalls did. His findings have also
been confirmed by thw and sosrah. I think Canon has screwed up
here.

--
Pat
Click to expand...
Thanks Pat, I see what you mean. I did some tests last night with my G2 (indoors, using a desk lamp to simulate backlighting). Here's what I observed (I used aperture priority at f/2.0):

Light source at the centre of the frame:

Evaluative: 1/250 sec
CWA: 1/125 sec

Light source at the top-right corner of the frame:

Evaluative: 1/5 sec
CWA: 1/10 sec

This shows that Evaluative varies exposure more (1/250 sec to 1/5 sec) than CWA (1/125 sec to 1/10 sec). One stop above, one below. BTW I used the [o] icon for Evaluative and [ ] for CWA. So are you saying that in the G6/Pro1 [ ] is actually Eval. and [o] is actually CWA? If that's the case then yes Canon has screwed up big time! As for Evaluative, I think the purpose is to just point'n'shoot and not think about it too much, so in that sense it's not too bad to be a little unpredictable.

Costas
 
center weight [ ] so actually 'when' I did a switch I'm really at evaluative still if the manual is switched as you say??? LOL

I thought the manual said evaluative is [@] eye in the middle
center weight is [ ]
spot [o] filled dot in middle

sue anne
---------------------------------------------
Costas Vlachos said:
Pat said:
Costas, yes evaluative is smarter and should do a better job in a
tricky situation such as Don described.The problem is that for the
G6 and Pro 1 at least, what the manual calls evaluative acts
instead like center-weighted and vice versa. IOW, Canon seems to
have messed up or switched their descriptions of the two metering
methods in their manuals. I suspect many if not all their digicams
have this fault in their manuals. And thus, countless legions of
Canon owners have been using the metering methods incorrectly.

Despite the fact evaluative is more tricky, one should be able to
predict the way it meters relative to center-weighted in known
lighting situations. If not, why use it at all? In my tests, I
got the same results that marscalls did. His findings have also
been confirmed by thw and sosrah. I think Canon has screwed up
here.

--
Pat
Click to expand...
Thanks Pat, I see what you mean. I did some tests last night with
my G2 (indoors, using a desk lamp to simulate backlighting). Here's
what I observed (I used aperture priority at f/2.0):

Light source at the centre of the frame:

Evaluative: 1/250 sec
CWA: 1/125 sec

Light source at the top-right corner of the frame:

Evaluative: 1/5 sec
CWA: 1/10 sec

This shows that Evaluative varies exposure more (1/250 sec to 1/5
sec) than CWA (1/125 sec to 1/10 sec). One stop above, one below.
BTW I used the [o] icon for Evaluative and [ ] for CWA. So are you
saying that in the G6/Pro1 [ ] is actually Eval. and [o] is
actually CWA? If that's the case then yes Canon has screwed up big
time! As for Evaluative, I think the purpose is to just
point'n'shoot and not think about it too much, so in that sense
it's not too bad to be a little unpredictable.

Costas
Click to expand...
 
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