iESP Auto Focus Mode

[Moshe Ronen]

Hi,

I don't understand the rationale behind the iESP AF mode in C4040z (I think it is also availabele in C3040z, but I'm not sure). I always regarded focusing as a 'spot' operation. In all the traditional focusing methods, in viewfinder or SLR cameras, you always focused on something, and then, if necessary corrected. I don't understand how can iESP determine an 'average' focus, and what does an average focus mean.

If anyone can clarify it for me, I'll appreciate it.

Moshe

 

[misha]

Hi,

I don't understand the rationale behind the iESP AF mode in C4040z
(I think it is also availabele in C3040z, but I'm not sure). I
always regarded focusing as a 'spot' operation. In all the
traditional focusing methods, in viewfinder or SLR cameras, you
always focused on something, and then, if necessary corrected. I
don't understand how can iESP determine an 'average' focus, and
what does an average focus mean.

If anyone can clarify it for me, I'll appreciate it.

It probably measures focus distance at several points rather than one and chooses a point that is closest. This can be helpful occasionally for off-center subjects or for the common situation of the camera focusing past the subject on the background (like when you give the camera to someone to snap your picture, and end up with your blurry likeness against a tack-sharp wall). By and large, the spot focus offers better control.

Misha

 

[PFR]

I can't speak for the 4040, but on the 2100 the iESP is used to measure average exposure over the entire frame. Centre weighted and spot metering are also available options. It does not do anything for focus.

From my understanding and experience, the autofocus point is located in the center of the small frame you can see in the viewfinder.

This applies to the 2100, but I can't see Oly going to a completely different system for the 4040.

Hope this helps.

PAT

Hi,

I don't understand the rationale behind the iESP AF mode in C4040z
(I think it is also availabele in C3040z, but I'm not sure). I
always regarded focusing as a 'spot' operation. In all the
traditional focusing methods, in viewfinder or SLR cameras, you
always focused on something, and then, if necessary corrected. I
don't understand how can iESP determine an 'average' focus, and
what does an average focus mean.

If anyone can clarify it for me, I'll appreciate it.

Moshe

 

[Russ Yost]

I believe Misha has it correct. Auto focus works by a cut and try process (I think) where "contrast" is measured in a small region of the image and the result is compared at a number of trial focus settings, the one with the highest contrast being selected as optimum for that small region. In the iESP, I think, this process is repeated at a large number of different small regions of the image. The optimum focal settings are then averaged, with those from the central region being weighted highest. (Weighting? Say the setting from the center region is repeated 10 times in making a list of focus settings for averaging.) This approach works well for the "point and shooter" who could care less about focus - just wants "everything sharp"! The problem is the "contrast" for a region depends on not only focus, but object contrast. Also, contrast is measured along a horizontal axis. If the subject comprises only horizontal lines, NO contrast! This can cause trouble in AF and it means that a background region of high contrast can "attract" the focus away from a low contrast subject you intend to focus on. Foliage behind a baby is a prime example.

For all the above reasons, I much prefer spot AF, which is available on many of the Oly cameras. It's set from the menu, mode settings, AF mode = "normal" or "spot". The setting is retained on power-off. (The preceding aapplies for my c2040z, at least.)

Don't confuse exposure and focusing. They're separate operations and either can be set to spot or average (normal), separately.

I can't speak for the 4040, but on the 2100 the iESP is used to
measure average exposure over the entire frame. Centre weighted and
spot metering are also available options. It does not do anything
for focus.

From my understanding and experience, the autofocus point is
located in the center of the small frame you can see in the
viewfinder.

True if you select AF mode = spot, but not for the default "normal"
setting.

This applies to the 2100, but I can't see Oly going to a completely
different system for the 4040.

Hope this helps.

PAT

Hi,

I don't understand the rationale behind the iESP AF mode in C4040z
(I think it is also availabele in C3040z, but I'm not sure). I
always regarded focusing as a 'spot' operation. In all the
traditional focusing methods, in viewfinder or SLR cameras, you
always focused on something, and then, if necessary corrected. I
don't understand how can iESP determine an 'average' focus, and
what does an average focus mean.

If anyone can clarify it for me, I'll appreciate it.

Moshe

 

[dick52717]

I can't speak for the 4040, but on the 2100 the iESP is used to
measure average exposure over the entire frame. Centre weighted and
spot metering are also available options. It does not do anything
for focus.

PAT

Well, Pat, I can't speak for your 2100 manual, but mine reads like this -

Page 96." iESP: Focus selection is based on the entire range on the screen (factory preset)."
****

 

[PFR]

I'll have to look into this. It could explain some of the focus difficulties I have been having lately. I always though iESP was exposure related only.
:-( (shade of red)

You learn something new every day.

PAT

I can't speak for the 4040, but on the 2100 the iESP is used to
measure average exposure over the entire frame. Centre weighted and
spot metering are also available options. It does not do anything
for focus.

PAT

Well, Pat, I can't speak for your 2100 manual, but mine reads like
this -
Page 96." iESP: Focus selection is based on the entire range on the
screen (factory preset)."
****

 

[PFR]

OK guys. I stand corrected. Just read up on the spot focusing option in Phil's review. I guess I got confused because ESP is also associated with exposure.

Apologies and thanks for the eye opener.

PAT

You learn something new every day.

PAT

I can't speak for the 4040, but on the 2100 the iESP is used to
measure average exposure over the entire frame. Centre weighted and
spot metering are also available options. It does not do anything
for focus.

PAT

Well, Pat, I can't speak for your 2100 manual, but mine reads like
this -
Page 96." iESP: Focus selection is based on the entire range on the
screen (factory preset)."
****

 

[Moshe Ronen]

Thanks everyone for the replies. I think it convinced me that the default setting should be 'spot' and iESP should be used only for special circumstances.

Thanks,
Moshe

Apologies and thanks for the eye opener.

PAT

You learn something new every day.

PAT

I can't speak for the 4040, but on the 2100 the iESP is used to
measure average exposure over the entire frame. Centre weighted and
spot metering are also available options. It does not do anything
for focus.

PAT

Well, Pat, I can't speak for your 2100 manual, but mine reads like
this -
Page 96." iESP: Focus selection is based on the entire range on the
screen (factory preset)."
****

 

[Allen53219]

I think you'll find that most of the people on this forum use spot because of the control or because that is what they are used to on SLR's.

I used my 2100 on spot for a while but was having trouble getting the proper focus (mainly because I didn't know what I was doing). So I switched to iESP and have been happily using it ever since. Most of my photos turn out perfect now. It doesn't seem to use an average focus, rather it tries to determine what the main subject if the photo is and focus on that. If it can't determine a subject then I guess it uses an average, like in a landscape photo of distant objects.

I have a great photo a of person where an object in the foreground is blurred and the background is blurred, but she is in perfect focus, really stands out.

On the other hand I have a photo where my subject fills a smaller portion of image than a tree that is off to the side. The tree is in focus, but she isn't. So, iESP is not a mindreader and spot would have worked better in that situation.

I would post the photos to show the difference but don't have them here right now.
Al

Thanks everyone for the replies. I think it convinced me that the
default setting should be 'spot' and iESP should be used only for
special circumstances.

Thanks,
Moshe

Well, Pat, I can't speak for your 2100 manual, but mine reads like
this -
Page 96." iESP: Focus selection is based on the entire range on the
screen (factory preset)."
****

 

[Russ Yost]

So, Allen, your two examples, even the first, would have as good or better with spot AF. Why take a chance with "normal" iESP?

Thanks everyone for the replies. I think it convinced me that the
default setting should be 'spot' and iESP should be used only for
special circumstances.

Thanks,
Moshe

Well, Pat, I can't speak for your 2100 manual, but mine reads like
this -
Page 96." iESP: Focus selection is based on the entire range on the
screen (factory preset)."
****

 

[Steve Weisel]

I'm glad you brought this up, Moshe. I was just wondering about it myself, and changed my camera's setting to spot focus a day or two ago. I haven't had time to test the results yet, but I suspect it may well explain some problems I had foccussing.

I'm embarrassed to say it took me several months to realize that the camera was not actually focussing on what I pointed at in that little square in the middle of the viewfinder. Sheesh. Hundreds of photos, and I didn't catch on!!

I thought it was focussing and taking exposure settings from that area.

It does make you wonder why Oly had that non-intuitive setting as the factory default.

BTW, I also learned that I may not have been using manual focus properly. You are supposed to, and may have to press the OK button after choosing your manual focus range. Then a red "MF" comes on to indicate that it is locked. Does that mean that noneof my manual focus choices were ever registered, because I never hit OK and got the red MF? Hmmmm.

Luckily, I didn't use MF much, and many of my other photos came out looking outstanding to my untrained eyes.

If anyone with a greater understanding and more experience would care to explain the various exposure settings in detail, but using simple, non-technical terms and examples, it would probably help a lot of people on this board.

For instance, when using multi-metering, how do you choose several spots, (how do you make the camera do that?), and how would you decide whether to include a spot in your frame or not? If you have, let's say, a house, a mountain, some sky, a tree, and a deer, would there be any advantage in choosing each and every one of these into the meter's memory? If not, why, and how would you decide which ones to include and which ones to leave out?

Simple, non-technical answers, please. Thanks. ; - )

 

[Jay Siegel]

I find automatic focusing, especially on digital cameras, to be one of the most "difficult" aspects to use reliable. I have a C-2500L which ONLY has spot focusing and both the Oly C-2020z and C-21. My experience is that I have to use the C-2500L very deliberatively (not sure that is a word) to get accurate focus. If I use it as a fast camera/point and shoot, then I have too many out of focus shots for all the reasons mention in this thread. My experience leads me to support Oly's default focus setting for the "point and shoot" cameras. I include all their non-slr cameras as point and shoot.

One can argure that auto-focusing is the weakist link in the digital camera chain. Just check all the posts in the Oly SLR forum on focusing difficulties and how they had to be dealt with. Experienced SLR photographers can make good use of the spot focusing and other options in Oly cameras for excellent photos. But I like the statement in this thread that referred to handing your camera to another to take your family portrait only to discover that it is the objects behind you (that were in the middle of the frame) that are in focus, not the people!!

To sum up---I'm looking forward to taking pictures with the D-40z and expect that I will keep it on the overall focus setting, as I will be taking what I call "fast" pictures -- capturing the moment and usual don't have time to point the autofocus spot in the right position before framing the shot.

Jay http://www.carr-siegel.net

I'm glad you brought this up, Moshe. I was just wondering about it
myself, and changed my camera's setting to spot focus a day or two
ago. I haven't had time to test the results yet, but I suspect it
may well explain some problems I had foccussing.

I'm embarrassed to say it took me several months to realize that
the camera was not actually focussing on what I pointed at in that
little square in the middle of the viewfinder. Sheesh. Hundreds of
photos, and I didn't catch on!!

I thought it was focussing and taking exposure settings from that
area.

It does make you wonder why Oly had that non-intuitive setting as
the factory default.

BTW, I also learned that I may not have been using manual focus
properly. You are supposed to, and may have to press the OK
button after choosing your manual focus range. Then a red "MF"
comes on to indicate that it is locked. Does that mean that noneof
my manual focus choices were ever registered, because I never hit
OK and got the red MF? Hmmmm.

Luckily, I didn't use MF much, and many of my other photos came out
looking outstanding to my untrained eyes.

If anyone with a greater understanding and more experience would
care to explain the various exposure settings in detail, but using
simple, non-technical terms and examples, it would probably help a
lot of people on this board.

For instance, when using multi-metering, how do you choose several
spots, (how do you make the camera do that?), and how would you
decide whether to include a spot in your frame or not? If you have,
let's say, a house, a mountain, some sky, a tree, and a deer, would
there be any advantage in choosing each and every one of these into
the meter's memory? If not, why, and how would you decide which
ones to include and which ones to leave out?

Simple, non-technical answers, please. Thanks. ; - )

 

[Forrest41926]

If anyone with a greater understanding and more experience would
care to explain the various exposure settings in detail, but using
simple, non-technical terms and examples, it would probably help a
lot of people on this board.

Focus and exposure are completely different. One can be perfect while the other is way off...

Spot focus means the camera will focus on what's in the center of the frame in the little [ ] box. I think iESP focus means the camera reads the whole frame, and focuses on whatever the closest subject is. Full-time AF does either constantly ... not using full-time AF seems to only focus when you press the shutter half-way down.

For instance, when using multi-metering, how do you choose several
spots, (how do you make the camera do that?), and how would you
decide whether to include a spot in your frame or not? If you have,
let's say, a house, a mountain, some sky, a tree, and a deer, would
there be any advantage in choosing each and every one of these into
the meter's memory? If not, why, and how would you decide which
ones to include and which ones to leave out?

I've never used multi-metering. Here's the thing: no camera is terrific at capturing a lot of contrast. If there's really strong and really weak lighting, you're either going to capture one or the other, but not both. You can decide yourself ( manual exposure, or auto with spot metering ), or let the camera average them for you ( ESP or matrix metering ). Averaging puts what you capture in the middle, between the brights and the darks, and usually doesn't do a great job of either. When you multi-meter, you're also taking an average, but instead of the whole frame, you're deciding which parts are important, and averaging them.

It's usually better to look at the scene and decide whether you want to get detail in the shadows or the highlights, and then spot meter that part of the picture.

 

[Steve Weisel]

I posted that message just before Jay's and waited, and waited for it to render. After almost 5 minutes of my browser spinning its wheels, I hit "cancel", copied the text, re-worded it so my questions were more clearly stated, and started a new thread, "focus & metering strategies".

You can answer it at http://www.dpreview.com/forums/read.asp?forum=1008&page=1&message=1561691&posted=1 if you like.

I thought that naming the thread "focus & metering strategies" might bring more people from this board into the discussion. Sorry for the double post.

 

[Marty Schultz]

It's usually better to look at the scene and decide whether you
want to get detail in the shadows or the highlights, and then spot
meter that part of the picture.

One thing to keep in mind with digital is that for darker areas there is usually information there that can be made visible with software later. So for scenes with too much dynamic range for the camera if you under expose you can bring out the shadows later. There's nothing you can do for overexposed areas, once you get to all 3 colors reading 255 you're stuck. Of course if you underexpose too much you don't have enough info to work with either, usually -.7 or -1 does the trick. I've found spot metering is really tricky in high contrast situations, you either overexpose the bright areas or underexpose the shadows, if you don't have a good area to meter on let the esp set the exposure and compensate with the left arrow button.

 

[Marty Schultz]

BTW, I also learned that I may not have been using manual focus
properly. You are supposed to, and may have to press the OK
button after choosing your manual focus range. Then a red "MF"
comes on to indicate that it is locked. Does that mean that noneof
my manual focus choices were ever registered, because I never hit
OK and got the red MF? Hmmmm.

I don't think you have to hit the OK button, I've taken shots with the manual focus scale still displayed and the focus was good. If you are in full manual mode you need to hit OK so you can get the up/down arrow buttons to switch from focusing to changing the shutter speed (or is it f-stop?).

 

[Moshe Ronen]

I agree with Marty (regarding exposure): if the situation is complicated, let the camera use its algorithm, iESP, which probably is better than you can do yourself.

One spot metering is fine if you can find one representative point, or you know which brightness level you want to assign to this spot, for instance choose a point in deep shadow and set cpmpensation to -3.

Multi point metering may be very tricky because of the averaging, if you chose two bright points and one dark, the bright gets double weight.

As for focusing, we tend to prefer spot because we are used to it from SLR days, but we forget that it was manual focus, and when we shot landscapes, we set the lens at infinity and forgot about it. With spot auto focus, if the [ ] area happens to be on the sky, sea or any distant objects without distinct contrast, what will it focus on?

So probably, like with everything else in life, there is no simple answer and one must decide according to the circumstances.

Moshe

It's usually better to look at the scene and decide whether you
want to get detail in the shadows or the highlights, and then spot
meter that part of the picture.

One thing to keep in mind with digital is that for darker areas
there is usually information there that can be made visible with
software later. So for scenes with too much dynamic range for the
camera if you under expose you can bring out the shadows later.
There's nothing you can do for overexposed areas, once you get to
all 3 colors reading 255 you're stuck. Of course if you
underexpose too much you don't have enough info to work with
either, usually -.7 or -1 does the trick. I've found spot metering
is really tricky in high contrast situations, you either overexpose
the bright areas or underexpose the shadows, if you don't have a
good area to meter on let the esp set the exposure and compensate
with the left arrow button.

 

[Allen53219]

Thankyou!

I posted earlier on this string that I thought most of my photos looked sharper using iESP, while some of my spot focused photos were not perfectly focused. I couldn't think of a logical reason why though. As you suggest below, there might not have been anything in [ ] area to provide enough contrast for an accurate focus.

As for focusing, we tend to prefer spot because we are used to it
from SLR days, but we forget that it was manual focus, and when we
shot landscapes, we set the lens at infinity and forgot about it.
With spot auto focus, if the [ ] area happens to be on the sky, sea
or any distant objects without distinct contrast, what will it
focus on?

So probably, like with everything else in life, there is no simple
answer and one must decide according to the circumstances.