G1 Focus Hocus Part 2: Conclusion

First off, I don't mean to be redundant in creating this new thread; I just though this info is so helpful to G1 users that it shouldn't get lost in the long, long original thread.

From part 1, looks like there is no dispute that position matters, as illustrated by the original 5 pictures of the cake I posted.

Then the debate is whether the entire frame or just the center is used by the camera for focusing. To clear this unsettling question I added 3 more shots to the test, please take a look.

http://www.ofoto.com/I.jsp?m=25101888103&n=569919155

Picture 8 (# sign on paper) clearly indicates that the G1 will evaluate the entire frame and will focus on the corner if sufficient contrast cannot be found elsewhere. Any disgreement?

Picture 6, the cake is VERY near edge causing my G1 to shift focus to the wall. Like Bob W. noticed, the G1 actualy focuses on the wall texture and not just arbitrarily throws long -- it's darn sensitive!

Picture 7, the cake is also near edge but closer to center than in pic 6, and now my G1 shifts focus back on the cake.

Evidently both the cake and the wall texture provide adequate contrast. The cake has more contrast but is at edge, the wall texture has less contrast but covers the center. Combining this information with what we saw in the original 5 pictures, it is so clear to me that the G1 indeed scans the entire frame, but it also gives more weight to subjects which are closer to the center and/or more contrasty. This behavior can be quite properly called "Center-Weighed" focusing after all. The Canon Rep who talked to Don T is correct (my personal conclusion); whether he realy knows or just got lucky is irrelevant.

If I design an autofocus system, I probably would do the same thing. In otherwords, the autofocus scheme is very good in my opinion -- if you know how it works. The main problem is that Canon does not provide adequate documentation, leading to the massive confusion when your G1 fails to focus on the object you want it to.

One thing bothers me though: there is no spot focus in M mode!

--Michael

Let me see if I have this right..

The G1 has center weighted exposure AND center weighted focusing? Are they somewhat independent? That is, when pushing the shutter half way down (forgettign for a moment automatic exposure lock), one is locking in both exposure (within the other parameters of other settings like wb, ev, etc) and focus as you have explained below? That is asking alot from one half shutter depression..lol

Also, does spot metering also provide spot focusing? Can this get around some of the trouble people are having?

Perhaps one way of approaching many difficult shots might be to use spot metering for exposure.. set the ev and wb as required by the conditions.. lock in the exposure with the auto exposure button (star button).. then go back and use spot metering for focus lock by depressing the shutter half way down then recomposing.

Does any of this make sense?

Steve D

Michael W. said:

First off, I don't mean to be redundant in creating this new
thread; I just though this info is so helpful to G1 users that it
shouldn't get lost in the long, long original thread.

From part 1, looks like there is no dispute that position matters,
as illustrated by the original 5 pictures of the cake I posted.

Then the debate is whether the entire frame or just the center is
used by the camera for focusing. To clear this unsettling question
I added 3 more shots to the test, please take a look.

http://www.ofoto.com/I.jsp?m=25101888103&n=569919155

Picture 8 (# sign on paper) clearly indicates that the G1 will
evaluate the entire frame and will focus on the corner if
sufficient contrast cannot be found elsewhere. Any disgreement?

Picture 6, the cake is VERY near edge causing my G1 to shift focus
to the wall. Like Bob W. noticed, the G1 actualy focuses on the
wall texture and not just arbitrarily throws long -- it's darn
sensitive!

Picture 7, the cake is also near edge but closer to center than in
pic 6, and now my G1 shifts focus back on the cake.

Evidently both the cake and the wall texture provide adequate
contrast. The cake has more contrast but is at edge, the wall
texture has less contrast but covers the center. Combining this
information with what we saw in the original 5 pictures, it is so
clear to me that the G1 indeed scans the entire frame, but it also
gives more weight to subjects which are closer to the center and/or
more contrasty. This behavior can be quite properly called
"Center-Weighed" focusing after all. The Canon Rep who talked to
Don T is correct (my personal conclusion); whether he realy knows
or just got lucky is irrelevant.

If I design an autofocus system, I probably would do the same
thing. In otherwords, the autofocus scheme is very good in my
opinion -- if you know how it works. The main problem is that Canon
does not provide adequate documentation, leading to the massive
confusion when your G1 fails to focus on the object you want it to.

One thing bothers me though: there is no spot focus in M mode!

--
Michael

Click to expand...

So, to get "correct" exposure does one spot meter to the darkest part of the shot or to the "desired in focus" part of the shot?

Logically I say metering and focusing SHOULD be independent Steve, but since they're both coupled to the half-pressed shutter we're having a little trouble here. Now I understand the focusing behavior better, but still don't know how I will cope with this from now on... I'm sure we'll be exchanging ideas on how to deal with this. May be better answers will come with time.

My old Minolta Maxum 5000 uses center spot focus. You would half-depress the shutter to get the focus to lock (on the Maxum that does not lock the exposure like the G1), then recompose and shoot (that's when the Maxmum set the exposure). I find that a lot more reliable than the way the G1 works, but for point & shooters that's too complicated, they just want to... point & shoot! Apparently Canon couple both metering and focusing together to cater to point & shooters. Like they say, if it's one-size-fits-all it doesn't fit anyone.

But at least now I feel more comfortable with the camera than before.

Michael

Steve D said:

Let me see if I have this right..

The G1 has center weighted exposure AND center weighted focusing?
Are they somewhat independent? That is, when pushing the shutter
half way down (forgettign for a moment automatic exposure lock),
one is locking in both exposure (within the other parameters of
other settings like wb, ev, etc) and focus as you have explained
below? That is asking alot from one half shutter depression..lol

Also, does spot metering also provide spot focusing? Can this get
around some of the trouble people are having?

Perhaps one way of approaching many difficult shots might be to use
spot metering for exposure.. set the ev and wb as required by the
conditions.. lock in the exposure with the auto exposure button
(star button).. then go back and use spot metering for focus lock
by depressing the shutter half way down then recomposing.

Does any of this make sense?

Steve D

Click to expand...

But whatever, I'm off to Siggraph in L.A. for the week! Adios

So Michael..

does that say that what i described is right? In your view should we be locking exposure in with the star button based upon exposure conditions (color and light conditions with required ev and wb) and THEN go back and lock focus in with the half depressed shutter before recomposing? And should we be using spot metering as an adjunct to each of these.. exposure and focusing .. independently and when center weighting might confuse the camera (like in backlit conditions for exposure and off center contrast areas for focusing)? I'm not trying to push.. just understand..

Steve D

Michael W. said:

My old Minolta Maxum 5000 uses center spot focus. You would
half-depress the shutter to get the focus to lock (on the Maxum
that does not lock the exposure like the G1), then recompose and
shoot (that's when the Maxmum set the exposure). I find that a lot
more reliable than the way the G1 works, but for point & shooters
that's too complicated, they just want to... point & shoot!
Apparently Canon couple both metering and focusing together to
cater to point & shooters. Like they say, if it's
one-size-fits-all it doesn't fit anyone.

But at least now I feel more comfortable with the camera than before.

Michael

Steve D said:

Let me see if I have this right..

The G1 has center weighted exposure AND center weighted focusing?
Are they somewhat independent? That is, when pushing the shutter
half way down (forgettign for a moment automatic exposure lock),
one is locking in both exposure (within the other parameters of
other settings like wb, ev, etc) and focus as you have explained
below? That is asking alot from one half shutter depression..lol

Also, does spot metering also provide spot focusing? Can this get
around some of the trouble people are having?

Perhaps one way of approaching many difficult shots might be to use
spot metering for exposure.. set the ev and wb as required by the
conditions.. lock in the exposure with the auto exposure button
(star button).. then go back and use spot metering for focus lock
by depressing the shutter half way down then recomposing.

Does any of this make sense?

Steve D

Click to expand...

Click to expand...

Try using continuous AF and spot metering. The focus changes as you move from subject to subject, but sometimes you can see it hunt when you depress the shutter. Exposure doesn't seem to change--at least you can't see it in the lcd. I think it sets exposure, then focus, but both are independent functions.

I usually spot meter the brightest area and then recompose, because it's easier to bring the detail out of the shadows. But I can also think of situations that would go the other way.

ms

Steve D said:

does that say that what i described is right? In your view should
we be locking exposure in with the star button based upon exposure
conditions (color and light conditions with required ev and wb) and
THEN go back and lock focus in with the half depressed shutter
before recomposing? And should we be using spot metering as an
adjunct to each of these.. exposure and focusing .. independently
and when center weighting might confuse the camera (like in backlit
conditions for exposure and off center contrast areas for
focusing)? I'm not trying to push.. just understand..

Steve D

Michael W. said:

My old Minolta Maxum 5000 uses center spot focus. You would
half-depress the shutter to get the focus to lock (on the Maxum
that does not lock the exposure like the G1), then recompose and
shoot (that's when the Maxmum set the exposure). I find that a lot
more reliable than the way the G1 works, but for point & shooters
that's too complicated, they just want to... point & shoot!
Apparently Canon couple both metering and focusing together to
cater to point & shooters. Like they say, if it's
one-size-fits-all it doesn't fit anyone.

But at least now I feel more comfortable with the camera than before.

Michael

Steve D said:

Let me see if I have this right..

The G1 has center weighted exposure AND center weighted focusing?
Are they somewhat independent? That is, when pushing the shutter
half way down (forgettign for a moment automatic exposure lock),
one is locking in both exposure (within the other parameters of
other settings like wb, ev, etc) and focus as you have explained
below? That is asking alot from one half shutter depression..lol

Also, does spot metering also provide spot focusing? Can this get
around some of the trouble people are having?

Perhaps one way of approaching many difficult shots might be to use
spot metering for exposure.. set the ev and wb as required by the
conditions.. lock in the exposure with the auto exposure button
(star button).. then go back and use spot metering for focus lock
by depressing the shutter half way down then recomposing.

Does any of this make sense?

Steve D

Click to expand...

Click to expand...

Click to expand...

I am off to shoot a three hour Alabama concert in daylight
tomorrow at Six Flags. I will be playing with a Zyykor 2x tomorrow
morning getting ready. I tried to get step up rings here in town,
but no such luck. I was going to buy the Tiffen after I couldn't
find the stepup rings. Instead we went to the boat, so I will not
be buying the Tiffen now! Just for the heck of it, I decided to
try the old Casio make do rubber mount. It fits perfectly over the
Tiffen tube, and is maybe more solid than a stepup would be, and
believe it or not, it actually looks better than using a step up also.
In a quick experiment today, the G-1 does fine with the Zykkor
lens, but it causes vignetting until almost full zoom. That won't
be a problem at the concert.
The problem with the macros and missed focus seems to be
that you set up the tripod, and the camera is focusing so that you
can see in the LCD. Then you zoom in on a rose to frame the shot.
There is not enough contrast in the rose sometimes to break, or
change the focus. It stays where it was when it was looking at the
whole scene, before you tried to focus. You can break the focus
by either moving a blank sheet of paper or something else between
the lens and the rose. The camera tries to focus on the object,
and then has to re-establish focus after you remove it. Sometimes
that is enough. The other side of this is what Michael was referring
to. In a case of not enough contrast in the middle of the frame,
it sometimes focuses on contrasty other parts of the frame. If it
doesn't get a good focus once you have passed something
between the rose and the lens, you can almost bet it is picking
something else up. The way to defeat that with macro is to use
a small contrast target on a stick. I am using a fourth of July bottle
rocket stick, with a green piece of paper with bold black cross
hatching on it. Reach into the shot and place the target on the
rose, focus and remove it. This works well for macro, but doesn't
answer the problem of normal shots. That will always take focus
recompose I guess.
Thanks for listening and checking it out Micheal.

Kevin Bjorke said:

But whatever, I'm off to Siggraph in L.A. for the week! Adios

Click to expand...

Bob Williams wrote:
The way to defeat that with macro is to use

Member said:

a small contrast target on a stick. I am using a fourth of July
bottle
rocket stick, with a green piece of paper with bold black cross
hatching on it. Reach into the shot and place the target on the
rose, focus and remove it. This works well for macro, but doesn't
answer the problem of normal shots. That will always take focus
recompose I guess.

Click to expand...

Wouldn't it still be easier here to use the MF?? If you do the long way (RAW to jpeg/set and 2x or 4x digital zoom/MF/back to original/menu and to RAW---which I can do really quickly and without looking at the buttons). I found that with a dark cloth over my head for just a moment, I could easily see the LCD in bright sunlight and focus. I use reading glasses while using the LCD, so other than the sweat drops, it works great LOL.

I'll have to try the paper trick though. Is there a reason you are using green paper---and what shade is it and what hue? Does that make a difference??

Diane

Michael W. said:

Picture 8 (# sign on paper) clearly indicates that the G1 will
evaluate the entire frame and will focus on the corner if
sufficient contrast cannot be found elsewhere. Any disgreement?

Click to expand...

I disagree.

You can easily do a test to see where the camera looks for contrast. Take a sheet of blank white paper. Cut out a 1/2" square from one of the corners. Mark a bold X on the square and then lay it in the middle of the sheet of paper.

Put the camera in macro mode and zoom in on the X until you can see it clearly and the entire image consists of only the sheet of paper. Turn on spot metering to easily determine the center of the image and center the X there.

You don't have to take any pictures. Gradually move the X in one direction and see if you can focus on it using the LCD. It helps to use a tripod if you have one. Do this several times starting with the X in the center of the image and moving it in different directions and you will see where the camera is looking for focus.

Michael w said:

One thing bothers me though: there is no spot focus in M mode!

Click to expand...

There is no spot focus in any mode. Using the above test, nudge your target until it is just out of focus in spot metering mode. Then turn off spot metering and autofocus. It will still be out of focus. This must be done with a tripod to make sure the camera doesn't move.

gc said:

So, to get "correct" exposure does one spot meter to the darkest
part of the shot or to the "desired in focus" part of the shot?

Click to expand...

Spot metering has nothing to do with autofocus except that the spot metering box roughly corresponds to the autofocus area.

I'm confused by your question because you are asking about exposure and focusing and they are not related. If you want to spot meter to determine exposure you need to have a good understanding of what a meter is telling you. Some good info on that is available here:
http://www.cliffshade.com/dpfwiw/exposure.htm

Thanks for taking the time to answer. My question was not about focus but simply: what part of the shot do YOU spot meter to get the desired exposure?

GC

Peter T said:

gc said:

So, to get "correct" exposure does one spot meter to the darkest
part of the shot or to the "desired in focus" part of the shot?

Click to expand...

Spot metering has nothing to do with autofocus except that the spot
metering box roughly corresponds to the autofocus area.

I'm confused by your question because you are asking about exposure
and focusing and they are not related. If you want to spot meter to
determine exposure you need to have a good understanding of what a
meter is telling you. Some good info on that is available here:
http://www.cliffshade.com/dpfwiw/exposure.htm

Click to expand...

Diane B Fields said:

I found that with a dark cloth
over my head for just a moment, I could easily see the LCD in
bright sunlight and focus. I use reading glasses while using the
LCD, so other than the sweat drops, it works great LOL.

Click to expand...

That's a great idea and it also makes you look like a really serious photographer.

gc said:

Thanks for taking the time to answer. My question was not about
focus but simply: what part of the shot do YOU spot meter to get
the desired exposure?

Click to expand...

It depends on the scene and how I wish to render it. Usually when spot metering I also use exposure compensation. There is no simple answer. Spot metering is not for P&S type shooting.

To get a better understanding see the link I recommended.
http://www.cliffshade.com/dpfwiw/exposure.htm

Yes thanks I did read that article quickly. I'm trying to learn to use the pro 90's capabilities, and was just wondering if you any short insights to offer on spot metering beyond what the manual offered, i.e., spot meter on the part of the frame you want properly exposed.

GC

Peter T said:

gc said:

Thanks for taking the time to answer. My question was not about
focus but simply: what part of the shot do YOU spot meter to get
the desired exposure?

Click to expand...

It depends on the scene and how I wish to render it. Usually when
spot metering I also use exposure compensation. There is no simple
answer. Spot metering is not for P&S type shooting.

To get a better understanding see the link I recommended.
http://www.cliffshade.com/dpfwiw/exposure.htm

Click to expand...

Diane B Fields said:

Wouldn't it still be easier here to use the MF?? If you do the
long way (RAW to jpeg/set and 2x or 4x digital zoom/MF/back to
original/menu and to RAW---which I can do really quickly and
without looking at the buttons). I found that with a dark cloth
over my head for just a moment, I could easily see the LCD in
bright sunlight and focus. I use reading glasses while using the
LCD, so other than the sweat drops, it works great LOL.

I'll have to try the paper trick though. Is there a reason you are
using green paper---and what shade is it and what hue? Does that
make a difference??

Diane

Click to expand...

Diane,

I hope Ichabod Crane never runs into you during one of your photo sessions!

Doug

Decide which part of an image is the most important to expose correctly. Spot meter that area. The exposure will render that area a medium tone. If you want to render that area to be a different tone then use exposure comp to get what you want.

Let's say you have an image with a white cat and the cat is most important. Spot meter the cat and open up by 1 and 2/3 stops. If it was a light gray cat you might only open up 1 stop. If it was a black cat you would stop down by 1 and 2/3 stops. A dark gray you stop down 1 stop.

gc said:

Yes thanks I did read that article quickly. I'm trying to learn to
use the pro 90's capabilities, and was just wondering if you any
short insights to offer on spot metering beyond what the manual
offered, i.e., spot meter on the part of the frame you want
properly exposed.

Click to expand...

That's helpful. Thanks.

Peter T said:

Let's say you have an image with a white cat and the cat is most
important. Spot meter the cat and open up by 1 and 2/3 stops. If it
was a light gray cat you might only open up 1 stop. If it was a
black cat you would stop down by 1 and 2/3 stops. A dark gray you
stop down 1 stop.

gc said:

Yes thanks I did read that article quickly. I'm trying to learn to
use the pro 90's capabilities, and was just wondering if you any
short insights to offer on spot metering beyond what the manual
offered, i.e., spot meter on the part of the frame you want
properly exposed.

Click to expand...

Click to expand...

Michael W. said:

Picture 8 (# sign on paper) clearly indicates that the G1 will
evaluate the entire frame and will focus on the corner if
sufficient contrast cannot be found elsewhere. Any disgreement?

Click to expand...

I disagree.

If I place a high-contrast object in a corner (well away from the centre), my G1 will not focus on the object. I used a plain, untextured white sheet as the background and raised the object about 8" above the plane of the white sheet background.

The high-contrast object does not pop into focus until it is near the centre of the picture. I have found that this centre focus area is perhaps 2x the length and width of the spot exposure meter rectangle. I have also found that it makes no difference (re focus) if you have the spot meter exposure on or off, although it (the rectangle) is an aid in determining the centre of the pic.

Could you repeat your test with the target raised above the background? That would conclusively tell where the camera was focusing.

Michael w said:

One thing bothers me though: there is no spot focus in M mode!

Click to expand...

I don't really think there is a spot focus area that coincides with the spot exposure rectangle area. See above remarks.

Doug

I agree with your conclusions. But I'm puzzled as to why you feel it's important for the test object to be raised above the sheet.