I suppose it's only fitting...#@$%%# BACKFOCUS!!!

[DavidP #28649]

How do you know that? (Hint, you don't).

It could just as easily be that it found contrast somewhere else, but misfocused.

With low contrast objects, these cameras CAN and DO achieve focus, albeit inaccurately. This particular example can't show that . . but for the same reason, it can't be shown that it was focusing on the area that appears to be in focus.

But it has found enough contrast in the log directly below the
chain saw.

--
http://www.outboundmusic.com
Your link to independent music!

 

[Michael Louis]

when a lens backfocuses things look great in the viewfinder yet when the mirror snaps back at the moment of truth the lens moves it's focus point back and leaves the photographer scratching thier head when reviewing what should have been in focus photos.

If there's not enough contrast, the AF shouldn't lock. It should
blink the green light, and refuse to fire a shot (in one-shot mode).

This would happen if there was not enough contrast in the pic or
the sensor was the size of the red square. We all know that is not
the case so can we not accept what it has done. It looks fairly
obvious to me.

Isn't the camera smart enough to recognize when there's not enough
contrast?

As above!

Apparently not. Even the 1D suffers from this . . . . apparently
not as frequently as the 10D, though.

I know not.

I agree that the tree stump would make a better AF target. But
it's plain stupid that the camera will mis-focus by such a large
amount and not know it. Of course, the extra-large AF sensor of
the 10D is largely to blame for this issue in this particular image.

Take the actual sensor size into acount and it has not mis focussed.

What I find difficult is that the taker of the photo could not see
that it was locking on to the wrong subject just by looking into
the view finder.

My 1D makes that shot for sure and probably my 10D get that shot
too. Maybe the lens is the problem. Try on diff. body to test the
lens.

--
http://www.outboundmusic.com
Your link to independent music!

--
http://www.pbase.com/markgillett

 

[DavidP #28649]

You're saying that the lens actually adjusts focus after the shutter has been snapped? Not in AI-Servo mode (where this can and does occur, by design).

I'd be curious to see how you're arriving at that particular conclusion. Would seem to be hard to demonstrate.

when a lens backfocuses things look great in the viewfinder yet
when the mirror snaps back at the moment of truth the lens moves
it's focus point back and leaves the photographer scratching thier
head when reviewing what should have been in focus photos.

--
http://www.outboundmusic.com
Your link to independent music!

 

[pixydust]

when a lens backfocuses things look great in the viewfinder yet
when the mirror snaps back at the moment of truth the lens moves
it's focus point back and leaves the photographer scratching thier
head when reviewing what should have been in focus photos.

What are you saying? Are you saying that when the focus is locked the lens got moved after the mirror is open to take picture? You're actually wittnessing this personally?

If there's not enough contrast, the AF shouldn't lock. It should
blink the green light, and refuse to fire a shot (in one-shot mode).

This would happen if there was not enough contrast in the pic or
the sensor was the size of the red square. We all know that is not
the case so can we not accept what it has done. It looks fairly
obvious to me.

Isn't the camera smart enough to recognize when there's not enough
contrast?

As above!

Apparently not. Even the 1D suffers from this . . . . apparently
not as frequently as the 10D, though.

I know not.

I agree that the tree stump would make a better AF target. But
it's plain stupid that the camera will mis-focus by such a large
amount and not know it. Of course, the extra-large AF sensor of
the 10D is largely to blame for this issue in this particular image.

Take the actual sensor size into acount and it has not mis focussed.

What I find difficult is that the taker of the photo could not see
that it was locking on to the wrong subject just by looking into
the view finder.

My 1D makes that shot for sure and probably my 10D get that shot
too. Maybe the lens is the problem. Try on diff. body to test the
lens.

--
http://www.outboundmusic.com
Your link to independent music!

--
http://www.pbase.com/markgillett

 

[Victor Engel]

Leaves and grass do not have the contrast that the tree edge has.

The tree edge is not in the focus region. The circle is NOT the focus region. The red rectangles are.

 

[Michael Louis]

but harder to demonstrate because you would have to see what I am seeing in the viewfinder and confirm it's focused on a subject yet when the photo is taken it's on something else.

This leads to certain variables which could make what I am saying a load of BS. Such as what I am seeing as being in focus is not as sharp as what the lens produces because I haven't paid enough attention to everything else in the viewfinder. Or, the DOF is so shallow that I misjudge what really should be in sharp focus as opposed to what I think should be due to miscalculations of the DOF charts in my head.

I'd be curious to see how you're arriving at that particular
conclusion. Would seem to be hard to demonstrate.

when a lens backfocuses things look great in the viewfinder yet
when the mirror snaps back at the moment of truth the lens moves
it's focus point back and leaves the photographer scratching thier
head when reviewing what should have been in focus photos.

--
http://www.outboundmusic.com
Your link to independent music!

 

[DavidP #28649]

Are you seeing the focus shift THROUGH the viewfinder? Are you using a tripod when seeing this? The image must have extremely shallow DOF to see this through the 10D viewfinder, I'd say. Near minimum focusing distance and very wide aperture.

If your comparison, though, is viewfinder vs. computer, I wouldn't come to the same conclusion that you are. I'd say that you have some sort of other problem in the camera/lens. Not that it couldn't be what you say . . but I wouldn't think of that as my first choice for what's causing the issue.

but harder to demonstrate because you would have to see what I am
seeing in the viewfinder and confirm it's focused on a subject yet
when the photo is taken it's on something else.

--
http://www.outboundmusic.com
Your link to independent music!

 

[KR2]

But, according to most, the focus region on the 10D is actually larger than the red rectangles. If this is true, than it most definitely could have chosen the tree trunk or the dirt/sawdust as they are definitely more contrasty than the saw blade.

Rgds
KR

Leaves and grass do not have the contrast that the tree edge has.

The tree edge is not in the focus region. The circle is NOT the
focus region. The red rectangles are.

 

[Mark Gillett]

The tree edge is not in the focus region. The circle is NOT the
focus region. The red rectangles are.

No they are not. The actual sensor size is about 80% bigger in the form of a cross. This makes the tree in the focus zone. Do a search and you will find the info somewhere. It has been discussed to death on this forum. Perhpas ask DavidP or Mishkin and they will point you to the material.

M

--
http://www.pbase.com/markgillett

 

[Mark Gillett]

Rgds
KR

Leaves and grass do not have the contrast that the tree edge has.

The tree edge is not in the focus region. The circle is NOT the
focus region. The red rectangles are.

--
http://www.pbase.com/markgillett

 

[Michael Louis]

of what I am saying.
http://photos.yahoo.com/[email protected]
Look in the Miskin syndrome folder.

The first photo is the original from the 10D and 100 f/2. Download and Look in the FUV and you'll see the focus points were the nose, between the eyes and the forehead. Everything looked good in the viewfinder so I snapped the shot.

Look at what the 10D did. It skipped over the nose, got the cheeks and then somehow magically glossed over the eyes and front forehead while getting the middle of the forehead.

God knows I was close enough to confirm that what I was seeing in the viewfinder should be accurate, and you can see that the lens chose something completly different.

How do you explain this phenomenon except that the moment the shot was taken the lens chose only to focus on what it wanted regardless of what I was seeing in the viewfinder.

when a lens backfocuses things look great in the viewfinder yet
when the mirror snaps back at the moment of truth the lens moves
it's focus point back and leaves the photographer scratching thier
head when reviewing what should have been in focus photos.

What are you saying? Are you saying that when the focus is locked
the lens got moved after the mirror is open to take picture? You're
actually wittnessing this personally?

If there's not enough contrast, the AF shouldn't lock. It should
blink the green light, and refuse to fire a shot (in one-shot mode).

This would happen if there was not enough contrast in the pic or
the sensor was the size of the red square. We all know that is not
the case so can we not accept what it has done. It looks fairly
obvious to me.

Isn't the camera smart enough to recognize when there's not enough
contrast?

As above!

Apparently not. Even the 1D suffers from this . . . . apparently
not as frequently as the 10D, though.

I know not.

I agree that the tree stump would make a better AF target. But
it's plain stupid that the camera will mis-focus by such a large
amount and not know it. Of course, the extra-large AF sensor of
the 10D is largely to blame for this issue in this particular image.

Take the actual sensor size into acount and it has not mis focussed.

What I find difficult is that the taker of the photo could not see
that it was locking on to the wrong subject just by looking into
the view finder.

My 1D makes that shot for sure and probably my 10D get that shot
too. Maybe the lens is the problem. Try on diff. body to test the
lens.

--
http://www.outboundmusic.com
Your link to independent music!

--
http://www.pbase.com/markgillett

 

[Mark Gillett]

I agree with you, David. It is all subjective until the camera is tested positive. This is my reckoning only and I still think its the case. There is a definite edge to focus on.

We just all like discussing it, really.

M

It could just as easily be that it found contrast somewhere else,
but misfocused.

With low contrast objects, these cameras CAN and DO achieve focus,
albeit inaccurately. This particular example can't show that . .
but for the same reason, it can't be shown that it was focusing on
the area that appears to be in focus.

But it has found enough contrast in the log directly below the
chain saw.

--
http://www.outboundmusic.com
Your link to independent music!

--
http://www.pbase.com/markgillett

 

[DavidP #28649]

It may be that the optical distance from mirror to viewfinder and from mirror to AF sensor is different than the optical distance from mirror to image sensor.

That would explain what you're experiencing.

Have you had that checked out yet?

of what I am saying.
http://photos.yahoo.com/[email protected]
Look in the Miskin syndrome folder.
The first photo is the original from the 10D and 100 f/2. Download
and Look in the FUV and you'll see the focus points were the nose,
between the eyes and the forehead. Everything looked good in the
viewfinder so I snapped the shot.
Look at what the 10D did. It skipped over the nose, got the cheeks
and then somehow magically glossed over the eyes and front forehead
while getting the middle of the forehead.
God knows I was close enough to confirm that what I was seeing in
the viewfinder should be accurate, and you can see that the lens
chose something completly different.
How do you explain this phenomenon except that the moment the shot
was taken the lens chose only to focus on what it wanted regardless
of what I was seeing in the viewfinder.

--
http://www.outboundmusic.com
Your link to independent music!

 

[Mark Gillett]

If there's not enough contrast, the AF shouldn't lock. It should
blink the green light, and refuse to fire a shot (in one-shot mode).

This would happen if there was not enough contrast in the pic or
the sensor was the size of the red square. We all know that is not
the case so can we not accept what it has done. It looks fairly
obvious to me.

Isn't the camera smart enough to recognize when there's not enough
contrast?

As above!

Apparently not. Even the 1D suffers from this . . . . apparently
not as frequently as the 10D, though.

I know not.

I agree that the tree stump would make a better AF target. But
it's plain stupid that the camera will mis-focus by such a large
amount and not know it. Of course, the extra-large AF sensor of
the 10D is largely to blame for this issue in this particular image.

Take the actual sensor size into acount and it has not mis focussed.

What I find difficult is that the taker of the photo could not see
that it was locking on to the wrong subject just by looking into
the view finder.

My 1D makes that shot for sure and probably my 10D get that shot
too. Maybe the lens is the problem. Try on diff. body to test the
lens.

--
http://www.outboundmusic.com
Your link to independent music!

--
http://www.pbase.com/markgillett

--
http://www.pbase.com/markgillett

 

[Mark Gillett]

maybe your little dioptric adjustment knob is incorrectly positioned? Have you adjusted this at all?

M

I'd be curious to see how you're arriving at that particular
conclusion. Would seem to be hard to demonstrate.

when a lens backfocuses things look great in the viewfinder yet
when the mirror snaps back at the moment of truth the lens moves
it's focus point back and leaves the photographer scratching thier
head when reviewing what should have been in focus photos.

--
http://www.outboundmusic.com
Your link to independent music!

--
http://www.pbase.com/markgillett

 

[DavidP #28649]

Hehe, ain't THAT the truth.

I don't know what your excuse is, but mine's that I'm a petroleum engineer, and we're always having to (try) to explain things that just don't make sense.

A recent example. Drilled a well the other day. The well was updip of a well that had produced gas (with some condensate). We took pressure data in the well when we logged it. The pressure data across the sand had a pressure gradient that was indicative of a gas reservoir (though with quite a bit of condesnate).

So, we concluded that this would be a gas well.

When it was completled, it was an oil well. Go figure.

The only explanation possible is that we're in a completely different sand lobe than the downdip well.

Things are not always what they appear.

We just all like discussing it, really.

--
http://www.outboundmusic.com
Your link to independent music!

 

[DavidP #28649]

I don't think that's it.

Have you EVER seen a dioptric that's out of whack make an out of focus image look focused? I haven't.

All it does it make things look more blurry.

The least blurry image still happens at the proper focus.

At least that's been my experience.

maybe your little dioptric adjustment knob is incorrectly
positioned? Have you adjusted this at all?

--
http://www.outboundmusic.com
Your link to independent music!

 

[Victor Engel]

You must look at the extended focus region. In this case, the subject is backfocused even if you consider the leftmost part of the focus region, which comes the closest to being in focus.



Your first example, where you focused at one zoom setting and then zoomed to the other for the snap is not a good example. Why? Because when zoomed wide, the focus region includes much more of the subject, including, presumably, a portion that is in focus.

The second example is illustrated here. It shows quite clearly and unambiguously a focus problem. Of course, this assumes you didn't focus on something else and then pan for the shot.



This is not a good example because of all the other stuff not in the focal plane. The camera could have legitimately chosen any of the twigs, etc. that are in the focus region.

 

[KR2]

It doesn't seem to happen the same way all the time. The first shot looks like it chose left of center (possibly for the more painted then chipped section). The first rock is totally out of focus, the second rock is focused on the more contrasty v cutout of the rock. However, the squirrel shot seems to me to be focused on the right of the squirell on the more contrasty small tree branch, which actually starts off slightly in front of the squirrel. This would only seem to support the focus area being larger than the red rectangle theory.

Rgds
KR

And I don't think they bode well from my problem...

All of these pics were center focus point selected and focused off
of without reframing with one exception which I will explain later.



Full Image: http://www.pbase.com/image/23667311/original

Focused on the center, but the further part of the cage to the left
is in focus. No more contrast there than there was were the focus
point was.

Two pics of a rock: The first was taken focused at 70mm then
zoomed in to 200mm to take picture. The second was focused and
taken at 200mm.



Full Image Rock 1: http://www.pbase.com/image/23667313



Full Image Rock 2: http://www.pbase.com/image/23667316/original

Notice on the second rock that the center, which has just as much
contrast as the top part (or farthest part) is blurry and the top
is sharp.

Lastly, the squirrel.



Full Image: http://www.pbase.com/image/23667318/original

The squirrel is slightly blurry, which takes up alot of the sensor,
and the small branch behind the squirrel is sharper, hardly hitting
the sensor.

So, am I crazy, or is this backfocusing?

VES

 

[Victor Engel]

The tree edge is not in the focus region. The circle is NOT the
focus region. The red rectangles are.

No they are not. The actual sensor size is about 80% bigger in the
form of a cross. This makes the tree in the focus zone. Do a
search and you will find the info somewhere. It has been discussed
to death on this forum. Perhpas ask DavidP or Mishkin and they
will point you to the material.

Before you suggest that someone do the research on the topic you suggest, you should first read the thread to which you're responding to see if it has already been done!!!

Read up to my first comment in this thread. I post the picture again here:



The red rectangles I was referring to are the red rectangles appearing in this picture, which are the actual focus areas that you alluded to, not the rectangles appearing in the viewfinder.