G2 Focus?

That's a BS response Robert. Many have documented issues with the G2 focusing on who-knows-what. I've seen it myself with my own pics where I shot pics of the same house at 15 meters. There was nothing else in the frame other than the house yet the camera's subject distance EXIF data reported values ranging from 9 to 66 meters. All while focusing on the same cross hatch, high-contrast window pane, standing in the same position. Try it sometime. The G2 clearly has some focus issues that one needs to be aware of so why not keep the sanctimonious responses to yourself?

Kristian-

Search and read the threads of focus issues, you will find some good tips to help keep the autofocus from getting confused. There are some limitations as to how well the auto focus does. The more you know about those limitations, the better you will be able to minimize them and take great pics-

--
Eric
http://www.pbase.com/haglunde
Hello you G2 owners. G2 has the same internals as the S30/40. Do
you have the same focus problem that is discussed in this thread:

http://www.dpreview.com/forums/read.asp?forum=1010&message=2906914

--
---
http://www.iki.fi/steelduck
The focus problem lies behind the camera rather than inside it
 
I've seen it myself with my own pics
where I shot pics of the same house at 15 meters. There was nothing
else in the frame other than the house yet the camera's subject
distance EXIF data reported values ranging from 9 to 66 meters. --
Thank you Eric. That is exactly the problem I had with the S40 and many have according to the S40 Focus thread. I think Canon should act on this.

One quick and dirty (temporary) solution would be to have the manual focus slider visible also when you shoot with auto focus, so you could check what the camera "thinks" the distance is.

Robert: Check the "subject distance" of your pictures EXIF data. Many times you can see that the camera has focused to 66meters or some odd distance, even with the subject just few meters away.

---
http://www.iki.fi/steelduck
 
98% of the time I have seen this there either has not been enough contrast or the contrast was in the wrong axis. People have a very convoluted idea of contrast sometimes on this forums. They say "but I pointed it right at his face." The G1/G2/S30/S40 simply do not have this much resolving power.

How about this, someone post there full size out of focus picture where they had a high contrast item as the target?

Jason
I've seen it myself with my own pics
where I shot pics of the same house at 15 meters. There was nothing
else in the frame other than the house yet the camera's subject
distance EXIF data reported values ranging from 9 to 66 meters. --
Thank you Eric. That is exactly the problem I had with the S40 and
many have according to the S40 Focus thread. I think Canon should
act on this.

One quick and dirty (temporary) solution would be to have the
manual focus slider visible also when you shoot with auto focus, so
you could check what the camera "thinks" the distance is.

Robert: Check the "subject distance" of your pictures EXIF data.
Many times you can see that the camera has focused to 66meters or
some odd distance, even with the subject just few meters away.

---
http://www.iki.fi/steelduck
 
I don't have a great eye at these things, but that looks like it is in focus to me...Maybe the right arm of the child on the left is out a little, but other than that?

-Ben
http://www.pbase.com/maverick55
How about this, someone post there full size out of focus picture
where they had a high contrast item as the target?
Here is one with a S40 where I focused on the checkered shirt and
the Exif data says 66meters.

http://www.pp.htv.fi/ksalo/s40

Kristian
---
http://www.iki.fi/steelduck
 
I don't have a great eye at these things, but that looks like it is
in focus to me...Maybe the right arm of the child on the left is
out a little, but other than that?
I posted an other pic with "subject distance" 1.23 meters. You can see that it is much sharper. You can even see the hair on the arms.

Try both images at 100% and apply UnSharp Mask, then you really see the difference. The point is that the camera was many times quite clueless what the actual distance was and then the pictures are unsharp. I used used 5.6 aperture. That is the reason why the difference is not so obvious.

Kristian
 
Exif data concerning focus distance isn´t correct. i don´t have zoombrowser installed so i can´t tell for sure, but i guess that Canon doesn´t report subject distance. Breeze Browser does it, but numbers are almost asways wrong, altough pictures are well focused.

So, it´s wrong to say that a picture is unfocused by numbers if evidence says that it is focused.

Focus issues have been reported for long time but i still mantain my first opinion that is based on the 1900 pics i have from G2: i can count less than 10 unfocused pics and on those, and that´s mostly from my fault.
Regards,
How about this, someone post there full size out of focus picture
where they had a high contrast item as the target?
Here is one with a S40 where I focused on the checkered shirt and
the Exif data says 66meters.

http://www.pp.htv.fi/ksalo/s40

Kristian
---
http://www.iki.fi/steelduck
--
Paulo Abreu
http://www.pbase.com/psergio
 
1. Do NOT trust the EXIF data for subject distance.
2. Read below.....

From http://www.dpreview.com/forums/read.asp?forum=1010&message=2710820

The following was posted ,by cronostvg, concerning the autofocus mechanisim in the G2. It is VERY useful information. I thought it deserved it's own thread

==============================================
Forum Canon Talk
Subject Re: Question on G2 AF performance in AUTO mode
Posted by cronostvg [CLICK FOR PROFILE]
Date/Time 9:46:31 AM, Tuesday, February 26, 2002
==============================================

How many here truely understand G2's AF mechanism? Many in this forum complain about G2 focus, but offer no theory why it is. So here is my input.

Start reading here: http://www.howstuffworks.com/autofocus.htm
http://www.howstuffworks.com/autofocus4.htm

Active or passive test: Here's a quick test to tell which autofocus system is in use in your camera (some cameras may have both systems):

1.Go outdoors and aim the viewfinder at an area of the sky with no clouds, power lines or tree limbs. Press the shutter button halfway down.

2.If you get a "focus okay" indication, it's an active autofocus system.

3.If you get a "focus not okay" indication, it's a passive autofocus system. 4.The CCD cannot find any contrast in a blue sky, so it gives up.

My test:
Pointed G2 at blue sky, G2 gave up, so it is passive.

-------------------------------------------------------------------------------------------------

Section about passive auto focus: http://www.howstuffworks.com/autofocus3.htm

The microprocessor in the camera looks at the strip of pixels and looks at the difference in intensity among the adjacent pixels. If the scene is out of focus, adjacent pixels have very similar intensities. The microprocessor moves the lens, looks at the CCD's pixels again and sees if the difference in intensity between adjacent pixels improved or got worse. The microprocessor then searches for the point where there is maximum intensity difference between adjacent pixels -- that's the point of best focus. Look at the difference in the pixels in the two red boxes above: In the upper box, the difference in intensity between adjacent pixels is very slight, while in the bottom box it is much greater. That is what the microprocessor is looking for as it drives the lens back and forth.

Passive autofocus must have light and image contrast in order to do its job. The image needs to have some detail in it that provides contrast. If you try to take a picture of a blank wall or a large object of uniform color, the camera cannot compare adjacent pixels so it cannot focus.

Passive autofocus systems usually react to vertical detail. When you hold the camera in the horizontal position, the passive autofocus system will have a hard time with a boat on the horizon but no problem with a flagpole or any other vertical detail. If you are holding the camera in the usual horizontal mode, focus on the vertical edge of the face. If you are holding the camera in the vertical mode, focus on a horizontal detail.

My test:

I tested the vertical detail or horizotal detail, by photo graphing one my dorm's huge radio tower. G2 able to focus better when photographing the to tower, as a portrait/horizontally. What I did is focus lock horizontally, then rotate camera 90 degrees and snap picture. One of the difficulty is holding the shutter release button half way while doing the rotation. On my first try, I misfired, deleted the diagonal picture, and retake.

I pointed my G2 at the top corner of my bathroom door. It had a shadow of the wall next to it. Positioning G2 vertically/portrait, I got back a flashing yellow, and a yellow retical, meaning focusing difficulty. Positioning G2 horizontally/landscape, G2 successfully focus lock!!!

-------------------------------------------------------------------------------------------------

I photographed my student advisor twice, vertically to photograph entire body. The edges are blurry, maybe is my shaky hand; or to G2 his office is dark; he is wears black and white, while the background is white; or the property of jpeg (TIFF from RAW is 22+ MB, would easily overwhelm my free 3GB of HDD workspace).

Conclusion, G2 is passive, reacts to vertical detail not horizontal detail. If need to photograph a horizontal object, tilt the camera 90 degrees get focus lock, while maintaining focus lock rotate G2 back to horizontal position, and snap.

------------------------------------------------------------------------------------------------

Request for comment.
--
TVG riding a Train à Grande Vitesse. Life is fast.
Photography skill: Newbie/Novice/Point and shoot
Own: Canon PowerShot G2
 
What you're seeing here is mega depth of field on a slightly OOF shot.

I would say if those kids were sitting still, in that light the S40 should have focused. Were they moving at the time?

If so, it's very difficult to keep the focus on exactly the same spot while people are moving. Even if you do that, there are other variables that are very hard to quantify. For instance, what do you think the shutter speed would have been if you hadn't used flash? Let's say it would have been 1/30? While you're panning, the focus frames can easily have a little bit of motion blur (as the photo seems to) and it can confuse the camera into thinking a frame taken a infinite focus has more contrast than another closer up.

Also, part people don't seem to understand is that the maximum number of lines that the camera can use for high speed focusing is about 120 in AF2 mode. So, basically the camera is looking at a downsamples image to determine focus, then you're blowing it up. Notice that your photo doesn't really look out of focus if you shrink it down some? That's what the camera is seeing.

It's not that bad really. I got a D60 recently, and although it's focus is 10 times more accurate, it needs to be at least 5 times more accurate just to make up for the difference in depth of field.

Jason
-Ben
http://www.pbase.com/maverick55
How about this, someone post there full size out of focus picture
where they had a high contrast item as the target?
Here is one with a S40 where I focused on the checkered shirt and
the Exif data says 66meters.

http://www.pp.htv.fi/ksalo/s40

Kristian
---
http://www.iki.fi/steelduck
 
Well I agree with you a bit but you're definitely wrong that the Exif data is wrong. The exif data is where it focused. Due to the large DOF it sometimes doesn't seem that way, but it's right. I've heard this explanation before and it's totally wrong.

Jason
How about this, someone post there full size out of focus picture
where they had a high contrast item as the target?
Here is one with a S40 where I focused on the checkered shirt and
the Exif data says 66meters.

http://www.pp.htv.fi/ksalo/s40

Kristian
---
http://www.iki.fi/steelduck
--
Paulo Abreu
http://www.pbase.com/psergio
 
It appears to me, that the 'out of focus' picture is focused on the toy in the background ....

--
jbstrick
http://jbstrick.com
 
Please learn to use the forum search feature before posting well worn topics like this one. Use at least 2 words in your search and search just subject lines.
Mike K

Hi,

I consolidated all the info I could find on the forum
on getting sharp pictures from the G2. Though a lot
of the tips could apply to any digital camera. The list
is for beginner's like myself so I only went as far
as using P mode and didn't bother going farther than
using Breeze Browser. I apologize to anyone who should
get credit but didn't.

Please feel free to correct or add to the list since
I'm just regurgitating all this. I'll re-post after a
lot of corrections and additions have been made.

TIP 01.
-------------------------------------
Learn to use Autofocus (AF) and how it works.

If you don't know how to use AF read this:
http://www.howstuffworks.com/autofocus6.htm

If you don't know how AF works in the G2 read this:
http://www.howstuffworks.com/autofocus3.htm

TIP 02.

The G2s autofocus uses contrasting vertical (up and down) lines to focus, this means ...

Don't use a person's face to focus! Instead lock focus on their clothing then re-compose and take the shot.

Reason:

Most of a person's face is made of horizontal lines - the eyes, eyebrows, mouth, the bottom of the nose etc. In addition,

most people's faces don't have a lot of contrasting colors because their skin tends to be the same color all the way across

their face. Putting somebodies face in the shade might help this situation.

TIP 03.

The G2s autofocus uses contrasting vertical (up and down) lines to focus, this means ... You might have a better chance of getting focus lock on a person's face if you turn them sideways or shine a light on them, creating contrasting vertical lines.

TIP 04.

The G2s autofocus uses contrasting vertical (up and down) lines to focus, this means ... If you're having trouble getting a focus lock, try rotating the camera 45-90 degrees, lock focus, rotate back and take the shot.

Reason:

This might work with a person's face because when you turn the G2 90 degrees the eyes, eyebrows, mouth and bottom of the nose

become contrasting vertical lines to the camera. Also can work when you're trying to take a picture of something on the horizon. When turned 90 degrees the horizon becomes a contrasting vertical line.

TIP 05.

For Landscape photos - Don't focus on the horizon. Lock your focus 1/3 of the way into the final photo, then re-compose and take the shot. If you're using manual focus set the focus for approx. 40 feet.
Reason:

When you lock focus on a subject 1/3 of the in-focus area is in front of the object and 2/3 of the in-focus area will be behind the subject.

Explanation:
Hyperfocal distance: http://www.nyip.com/tips/tip_hyperfocl898.html

TIP 06.

Once you've locked focus ... don't take your finger of the shutter button, it unlocks your focus.

TIP 07.
Once you've locked focus ... don't use the zoom, it unlocks your focus.

TIP 08.
If possible, use a tripod

TIP 09.
If you use a tripod, use the remote - so you don't shake the camera

TIP 10.

Use the flash when the background is very bright and your subject is dark or to help fill-in shadows from a bright light.
Generally using the flash helps create a sharper photo.

TIP 11.
Use P mode with the light meter/automatic exposure

In P mode, you can have the G2 take a light meter reading and automatically give a set of shutter/aperture values (exposure) that are appropriate for your particular photo. This helps you get sharper photos because you can select a smaller apertureso that more objects in the photo are in focus, or you can select a faster shutter speed so that moving objects in your photo don't blur.

Step 1: Put the G2 in P mode

Step 2: Press the * button, wait for the G2 to take a meter reading and automatically set exposure values (shutter/aperture)

Step 3. Use the right/left arrows on the omni controller to select a good aperture OR shutter value. This feature is called Program Shift.

TIP 12.
Try to use apertures between f4.0 and f5.6
Reason:
This is the sweet spot for this lens.

TIP 13.

If you want the least amount of hassle and just want the sharpest pictures you can get right out of the G2 - set the picture

format to jpeg and set the Contrast, Saturation, and Sharpness in your G2s menu to +1. That's it, all you need to do now is
download the pictures so you can distribute or print them out.

TIP 14.

If you want a little more control over your photos, set the picture format to RAW and set the Contrast, Saturation, and

Sharpness in your G2s menu to -1. You can set the Contrast, Saturation, Sharpness and White Balance when you convert the RAW
images to jpeg or tiffs in Breeze Browser.

TIP 15.

If you want the most control over your photos, set the picture format to RAW and set the Contrast, Saturation, and Sharpness

in your G2s menu to -1. You can then convert the RAW photos and edit them in your favorite imaging program.

More:
http://www.dpreview.com/forums/read.asp?forum=1010&message=2890738

And more general advice for beginners:
http://www.dpreview.com/forums/read.asp?forum=1010&message=2276317
 
Thanks John. I have read that, and it helped alot. The point is that I do not think it is acceptable for a 1000euro camera to have this poor autofocus, when the competion focuses just fine.

Start rant mode:

It is not very nice that I have to babysit the autofocus all the time, when I know that it could be better. I just sold my S40 and bought the G2 knowing that it has the same issue. I loved the S40, but I wanted the 420EX and the flipping LCD. I know how to minimize the AF issue, but I wan't Canon to come out and do something if there is something to do.

What I do not understand why people are OK with this. All of us regognize that the G2/s30/s40 autofocus needs some babysitting. Some of you think that both of my pictures are sharp, but that is because of the huge DOF and the fact remains that the G2 was clueles about the subject distance.

Everybody is giving these expanations: "The subject is this or that or the lightning was bad". How come the competion can do it? I do not wan't make my subjects to hold still and keep vertically striped black and white papers in their hands while the G2 autofocuses.

It would be nice if Canon would give us a AF improved microcode so that the G2 could "grow up". But if we as consumers just let it be, they will not put any resource into it.

There is allways something you can do with clever software engineering :)

End rant mode:

Kristian "the frustrated Finn" Salo ;)
1. Do NOT trust the EXIF data for subject distance.
2. Read below.....
---
http://www.iki.fi/steelduck
 
Saying this means you have no concept of the depth of field of a camera with an imager the size of an S30s. If it's this much out of focus at f/5.6 (which is not that much), it means it's WAY off on the distance. A distance of even 5 meters would have given a tack sharp photo.

Jason
It appears to me, that the 'out of focus' picture is focused on the
toy in the background ....

--
jbstrick
http://jbstrick.com
 
You act like your camera NEVER focuses right. If so, get a new camera. I have 5,000 pictures from .8m to infinity that are dead on for distance. About 10% are out of focus for a reason. About 3% are actually just out of focus for various reasons that are related to going beyond the camera's limitations.

There are complaints in every forum of bad focusing, the G2 is worse than average but to say none of the others have problems is silly.

Jason
Start rant mode:

It is not very nice that I have to babysit the autofocus all the
time, when I know that it could be better. I just sold my S40 and
bought the G2 knowing that it has the same issue. I loved the S40,
but I wanted the 420EX and the flipping LCD. I know how to minimize
the AF issue, but I wan't Canon to come out and do something if
there is something to do.

What I do not understand why people are OK with this. All of us
regognize that the G2/s30/s40 autofocus needs some babysitting.
Some of you think that both of my pictures are sharp, but that is
because of the huge DOF and the fact remains that the G2 was
clueles about the subject distance.
Everybody is giving these expanations: "The subject is this or that
or the lightning was bad". How come the competion can do it? I do
not wan't make my subjects to hold still and keep vertically
striped black and white papers in their hands while the G2
autofocuses.

It would be nice if Canon would give us a AF improved microcode so
that the G2 could "grow up". But if we as consumers just let it be,
they will not put any resource into it.

There is allways something you can do with clever software
engineering :)

End rant mode:

Kristian "the frustrated Finn" Salo ;)
1. Do NOT trust the EXIF data for subject distance.
2. Read below.....
---
http://www.iki.fi/steelduck
 
OK, yeah, you're right......
 

Keyboard shortcuts

Back
Top