Hocus Focus Read This.....

[murphy]

This message is intended for all those who are experimenting and trying to solve problems with back focus and front focus problems.

I have been reading the threads and everyone seems to be using different objects to compare focus results.

You all will do yourself a big favor by using the following lens chart.

http://people.smu.edu/rmonagha/mf/usaf.pdf

Print it out and use this as a standard testing medium for all focus testing.

This will also allow other people to compare lens resolutions and quality by looking at the same targets for focus and sharpness.

Just my suggestion.
Murphy

 

[Rianeli]

Murphy,

I have been following your focus problems and testing process. I performed the cereal box test. 6” apart and 4” forward and 4” backwards. I used a smaller box then you. I tested five lens and all five turned out worse then yours. I was devastated ! Anyway, I was about to send all of my photos (each lens shot on all apertures) and a CD. Then I got to thinking want excuses could Canon come up with to say it wasn’t the camera it was me. I remembered making one change to my parameters to + sharpen as soon as I got my D60. I thought I should retest. This time I purchased the BIG cereal boxes and changed the camera to all default settings. You guess it. Almost all my shots came out centered focus. Just a three shots were slightly back focused on some extreme apertures setting. I don’t know if it was the cereal boxes (I suspect) or changing to default settings. I’m happy.

Just a thought

 

[DavidP #28649]

I'm very suspicious that the reason you suddenly are able to focus OK is that you increased the size of the boxes. You could've just as easily gone to a longer focal length, or moved the camera closer, too.

I don't suppose you've re-tested with the original setup (same distance, focal length, small boxes) ?

I thought I should retest. This time I purchased
the BIG cereal boxes and changed the camera to all default
settings. You guess it. Almost all my shots came out centered
focus. Just a three shots were slightly back focused on some
extreme apertures setting. I don’t know if it was the cereal boxes
(I suspect) or changing to default settings. I’m happy.

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

 

[DavidP #28649]

What I'd do with that chart is this:

Keep the focal length / aperture / distance the same.

Run a series of tests, using the center AF point, but placing that point on different parts of that chart.

I suspect you'll have better luck getting accurate AF when you're using the large bars/numbers under the AF sensor than you will when the smaller numbers/bars are under the sensor.

This message is intended for all those who are experimenting and
trying to solve problems with back focus and front focus problems.

I have been reading the threads and everyone seems to be using
different objects to compare focus results.

You all will do yourself a big favor by using the following lens
chart.

http://people.smu.edu/rmonagha/mf/usaf.pdf

Print it out and use this as a standard testing medium for all
focus testing.

This will also allow other people to compare lens resolutions and
quality by looking at the same targets for focus and sharpness.

Just my suggestion.
Murphy

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

 

[murphy]

What I'd do with that chart is this:

Keep the focal length / aperture / distance the same.

Run a series of tests, using the center AF point, but placing that
point on different parts of that chart.

I suspect you'll have better luck getting accurate AF when you're
using the large bars/numbers under the AF sensor than you will when
the smaller numbers/bars are under the sensor.

If I had the camera, I would do just that. Canon has it at the moment and the Service guy there confirmed my problem. However, I have failed to be able to produce a tack sharp image. I have tried every thing I can think of and nothing will turn out a sharp photo like I see posted in these forums. So I run a few tests with cereal boxes and lens charts and I get the same reslults. Are you trying to say that if I want to focus on an object I have to find some large vertical lines first? ) I know that this is not what you intended to suggest but do you see my point? Perhaps its me who is mistaken but shouldnt I just be able to point the camera, focus on something like a deer or a dog and take the picture?

I think I may have a difficult time getting the dear to stand still while I tape a lens chart to the front of him so I can focus on large numbers.

Back to serious... I will find out more when Canon sends my camera back to me. I sent it out on Monday (next day air) and they said they will have it back in my hands by Thursday so we shall see. ..

Murph

 

[DavidP #28649]

New Jersey, or Irvine?

Interesting that they "confirmed your problem". They just sent mine through the calibration, and returned it. I never heard a word from them. It sure didn't solve the problem.

No, you don't need large vertical lines. Horizontal might work better --- LOL.

If my theory is correct, you just have to have enough contrast/detail (and size is an important part of that) in your subject to get dead-on AF.

Do you have some examples? I don't know how bad an AF job you're talking about, or the size of the subject, lighting, etc.

I'll sure be interested to see if they can solve your problem, and how similar it is to the conditions that are causing my problems.

If I had the camera, I would do just that. Canon has it at the
moment and the Service guy there confirmed my problem. However, I
have failed to be able to produce a tack sharp image. I have tried
every thing I can think of and nothing will turn out a sharp photo
like I see posted in these forums. So I run a few tests with
cereal boxes and lens charts and I get the same reslults. Are you
trying to say that if I want to focus on an object I have to find
some large vertical lines first? ) I know that this is not
what you intended to suggest but do you see my point? Perhaps its
me who is mistaken but shouldnt I just be able to point the camera,
focus on something like a deer or a dog and take the picture?
I think I may have a difficult time getting the dear to stand still
while I tape a lens chart to the front of him so I can focus on
large numbers.

Back to serious... I will find out more when Canon sends my camera
back to me. I sent it out on Monday (next day air) and they said
they will have it back in my hands by Thursday so we shall see. ..

Murph

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

 

[murphy]

New Jersey, or Irvine?

New Jersey

Interesting that they "confirmed your problem". They just sent
mine through the calibration, and returned it. I never heard a
word from them. It sure didn't solve the problem.

This time I called them to confirm delivery and spoke to the supervisor again. His confirmation of my problem came from looking at the Lens Chart Test I posted on Pbase.

No, you don't need large vertical lines. Horizontal might work
better --- LOL.

Getting the animals to stand still while I hang the chart is still going to be hard to do.

If my theory is correct, you just have to have enough
contrast/detail (and size is an important part of that) in your
subject to get dead-on AF.

A wild animal, an automobile, a person is not enough?

Do you have some examples? I don't know how bad an AF job you're
talking about, or the size of the subject, lighting, etc.

http://www.pbase.com/image/2003521
http://www.pbase.com/image/1998326
http://www.pbase.com/image/2135659
http://www.pbase.com/image/2172606
http://www.pbase.com/image/2176234
http://www.pbase.com/image/2485583

I'll sure be interested to see if they can solve your problem, and
how similar it is to the conditions that are causing my problems.

When I get my camera back, I will be sure to take a bunch of test photos and post them for everyone to see. (In focus photos that is)

Murph

 

[DavidP #28649]

New Jersey

Irvine for me.

This time I called them to confirm delivery and spoke to the
supervisor again. His confirmation of my problem came from looking
at the Lens Chart Test I posted on Pbase.

Oh. Well, I included a print. So, I guess they "confirmed" the problem. Too bad they didn't TEST the camera (under similar conditions) to verify the fix.

Getting the animals to stand still while I hang the chart is still
going to be hard to do.

Who said photography was gonna be easy?

A wild animal, an automobile, a person is not enough?

Under normal circumstances, I'd say yes. But I think it depends on the lighting and the features (and size of features).

For instance, I've had better luck getting AF-lock on performers who have large wrinkles on their faces. Smoother faces are more problematic, and I see a lot more front-focusing then. Likewise, when a face is in shadows, the AF is more-likely to be off (even if it does achieve focus).

http://www.pbase.com/image/2003521
http://www.pbase.com/image/1998326
http://www.pbase.com/image/2135659
http://www.pbase.com/image/2172606
http://www.pbase.com/image/2176234
http://www.pbase.com/image/2485583

Aha! I shall review these! (after I'm done typing here)

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

 

[DavidP #28649]

http://www.pbase.com/image/2003521

What were you focusing on? I'd say the plane of focus is on the bird in flight. Looks like slight motion blur.

http://www.pbase.com/image/1998326

The turkey's the closest thing to in-focus. Motion blur in the right foot. Could be front-focused. Subject isn't super-high-contrast, to be sure. But I'd hope for better.

http://www.pbase.com/image/2135659

I can't really say. Motion blur? AI-Servo or not? Gray on blue isn't the most contrasty subject . . . but again, it's very typical of the type of contrast I have to deal with.

http://www.pbase.com/image/2172606

Similar results as mine. Did you try moving closer, to see if focus worked then? That caused mine to focus correctly, which is what prompted my theory about having enough detail/contrast

http://www.pbase.com/image/2176234

Ditto above

http://www.pbase.com/image/2485583

rear focus?

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

 

[murphy]

http://www.pbase.com/image/2003521

What were you focusing on? I'd say the plane of focus is on the
bird in flight. Looks like slight motion blur.

I focused on the bird in the water with "One Shot AF" then, while holding the shutter button down half way, I moved the frame up to recompose the shot (without refocusing) so I could get the trees in the background. Just then I saw another bird coming in for a landing and decided to take the shot without the trees. The focus was still on the bird on the ground.

Except for the pic of the commercial jet, all these shots were with tripod and IS=Off. (which I also tested, and IS turned on when using a tripod will always come out bad)

http://www.pbase.com/image/1998326

The turkey's the closest thing to in-focus. Motion blur in the
right foot. Could be front-focused. Subject isn't
super-high-contrast, to be sure. But I'd hope for better.

Ya. I wasnt sure about this one but it fit the profile because it is not in focus.

http://www.pbase.com/image/2135659

I can't really say. Motion blur? AI-Servo or not? Gray on blue
isn't the most contrasty subject . . . but again, it's very typical
of the type of contrast I have to deal with.

Not sure but as someone else told me, its a fast moving object.

http://www.pbase.com/image/2172606

Similar results as mine. Did you try moving closer, to see if
focus worked then? That caused mine to focus correctly, which is
what prompted my theory about having enough detail/contrast

No I did not try that. I figured a 400mm lens should be able to focus on a cereal box just across the room. Am I mistaken here?

I did, however, try this same test with the 28-70 2.8L and it focused perfectly. I made sure the boxes where the same size in the frame by adjusting the distance from the camera to the target.

http://www.pbase.com/image/2176234

Ditto above

I did this one just to make sure the center AF point had enough room to work. Thus, I moved the boxes apart some to make sure my lack of experience wasnt causing the problem.

http://www.pbase.com/image/2485583

rear focus?

Big time.. Look at the chart and find out which box can resolve and distinguish between the 3 lines the best. Its the box on the far Left which is about 4 -6 inches behind the box in the middle where the focus should be. No one can say Black on White is not enough contrast, but then again, im still learning at this.

Thank you for taking the time to look at these. I appreciate it very much as I am still learning. I will be doing more testing once my equipment comes back from Canon.

Murphy

The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

 

[DavidP #28649]

No I did not try that. I figured a 400mm lens should be able to
focus on a cereal box just across the room. Am I mistaken here?
I did, however, try this same test with the 28-70 2.8L and it
focused perfectly. I made sure the boxes where the same size in the
frame by adjusting the distance from the camera to the target.

Interesting. At the same size in the viewfinder? That sounds more like a lens problem, then. I've tested mine with several different lenses, and get the same results (front-focusing) at the subject size I've been shooting.

The relative size of the boxes in your viewfinder look very similar to what I've been shooting when I have problems. If you were to increase the subject size by moving closer, I'm gonna bet your problems wouldn't have shown up.

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

 

[DavidP #28649]

Good question . . . . let's try this thought experiment to try to understand the answer.

We'll start with the premise that it takes something with contrast for the AF mechanism to achieve focus.

Imagine a blank wall . . . I think we'd all agree that the AF would have a very difficult time focusing on that.

Now, start to add some contrast onto the wall. How? Let's start by adding some VERY SMALL black dots.

Can you imagine these dots being small enough that the AF mechanism can't achieve focus? And I mean so small that the AF just keeps hunting back and forth, and you never get a solid green AF light. I sure can.

I can also imagine them big enough so that the AF can achieve "perfect" focus each and every time.

Now, what happens in between those two extremes? Is there some size below which the AF hunts, and above which you get "perfect" focus every time? I don't think it works that way.

I think there's a range. Below ONE size, the AF will always hunt. Above ANOTHER size, the AF will always give "perfect" focus.

BETWEEN those two sizes, I can imagine that the contrast is good enough for the AF to think it has "perfect" AF, when in reality it's only getting "close".

That's what I think may be going on here.

If so, it should be very repeatable, with anybody's 1D or D30 or D60 or even film camera.

To test it, we simply need a few people to go out and test their cameras under similar conditions. So far, I've done it with my 1D and a friend's D30. And the results are identical.

TonyB's done it, with different results . . . but I suspect the results he showed weren't at the same subject magnification. IE, his "dots on the blank wall" were bigger than mine (as seen by the camera). Hopefully he'll get the time to test again this weekend, trying to duplicate the same conditions I had.

No I did not try that. I figured a 400mm lens should be able to
focus on a cereal box just across the room. Am I mistaken here?

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

 

[C.A.S.]

I am going to throw my 2 cents into this discussion by showing my examples of my back-focus problem. Check out this link...

http://www.onestarimaging.com/test/focus.html

As you can see, the manual focus came out tack sharp on the rock. The minute I switched to auto-focus, the focus point moved to about two to three feet behind the rock.

Funny thing is that in all three shots the image looked in focus through the viewfinder. I have a feeling that the D60 is shifting the focus when the shutter is released.

I am going to LA for the Fourth of July weekend and I will be dropping off my D60 in Irvine. I may also drop off my 400mm for them to check it but I do not think that it is the problem.

Carlos

 

[murphy]

If so, it should be very repeatable, with anybody's 1D or D30 or
D60 or even film camera.

To test it, we simply need a few people to go out and test their
cameras under similar conditions. So far, I've done it with my 1D
and a friend's D30. And the results are identical.

TonyB's done it, with different results . . . but I suspect the
results he showed weren't at the same subject magnification. IE,
his "dots on the blank wall" were bigger than mine (as seen by the
camera). Hopefully he'll get the time to test again this weekend,
trying to duplicate the same conditions I had.

I would still like to see someone take a D60 camera and set up those Resolution Charts to perform this test.

I think the resolution chart should be enough contrast for any camera to focus with.

My stuff is at Canon right now so no more testing for me at the moment.

Canon has given me 2 stories on the adjustment of my equipment. I am waiting to find out which one is true.

Murph

 

[murphy]

I am going to throw my 2 cents into this discussion by showing my
examples of my back-focus problem. Check out this link...

http://www.onestarimaging.com/test/focus.html

As you can see, the manual focus came out tack sharp on the rock.
The minute I switched to auto-focus, the focus point moved to about
two to three feet behind the rock.

Funny thing is that in all three shots the image looked in focus
through the viewfinder. I have a feeling that the D60 is shifting
the focus when the shutter is released.

I am going to LA for the Fourth of July weekend and I will be
dropping off my D60 in Irvine. I may also drop off my 400mm for
them to check it but I do not think that it is the problem.

Carlos

Carlos,

Print this chart out:
http://people.smu.edu/rmonagha/mf/usaf.pdf

Do this test:
http://www.pbase.com/image/2485583/large

Post your results please. A rock is a hard place to determine focus issues

Murph

 

[C.A.S.]

Carlos,

Print this chart out:
http://people.smu.edu/rmonagha/mf/usaf.pdf

Do this test:
http://www.pbase.com/image/2485583/large

Post your results please. A rock is a hard place to determine
focus issues

Murph

Hey Murphy,

I already did the test but the focusing problem is not very noticeable at the distance to make the chart that big. At less than 100 feet the 400 2.8 is WAY TOO SHARP to notice the small focus problem. I only notice the problem at beyound 100 feet or even further.

I will re-shoot the test and show you.

--
Carlos

http://www.onestarimaging.com

 

[DavidP #28649]

I would still like to see someone take a D60 camera and set up
those Resolution Charts to perform this test.

And MY tests.

I think the resolution chart should be enough contrast for any
camera to focus with.

One would think so. Depending exactly on WHERE your AF point was located on the chart. If on some of the smaller print, maybe not.

Canon has given me 2 stories on the adjustment of my equipment. I
am waiting to find out which one is true.

2 stories? What are they?

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

 

[Jason Hutchinson]

I think you're right on here David. Take the case of my solid grey cat. From far enough away, the cat has absolutely no contrast at all. From close up, the individual hairs actually provide enough contrast to focus. Of course, there is a "gray" region in the middle somewhere. I've always thought people don't take this into consideration enough when they say something has enough contrast.

A parafocal lens would help this situation out a bit as well.

Jason

We'll start with the premise that it takes something with contrast
for the AF mechanism to achieve focus.

Imagine a blank wall . . . I think we'd all agree that the AF would
have a very difficult time focusing on that.

Now, start to add some contrast onto the wall. How? Let's start
by adding some VERY SMALL black dots.

Can you imagine these dots being small enough that the AF mechanism
can't achieve focus? And I mean so small that the AF just keeps
hunting back and forth, and you never get a solid green AF light.
I sure can.

I can also imagine them big enough so that the AF can achieve
"perfect" focus each and every time.

Now, what happens in between those two extremes? Is there some
size below which the AF hunts, and above which you get "perfect"
focus every time? I don't think it works that way.

I think there's a range. Below ONE size, the AF will always hunt.
Above ANOTHER size, the AF will always give "perfect" focus.

BETWEEN those two sizes, I can imagine that the contrast is good
enough for the AF to think it has "perfect" AF, when in reality
it's only getting "close".

That's what I think may be going on here.

If so, it should be very repeatable, with anybody's 1D or D30 or
D60 or even film camera.

To test it, we simply need a few people to go out and test their
cameras under similar conditions. So far, I've done it with my 1D
and a friend's D30. And the results are identical.

TonyB's done it, with different results . . . but I suspect the
results he showed weren't at the same subject magnification. IE,
his "dots on the blank wall" were bigger than mine (as seen by the
camera). Hopefully he'll get the time to test again this weekend,
trying to duplicate the same conditions I had.

No I did not try that. I figured a 400mm lens should be able to
focus on a cereal box just across the room. Am I mistaken here?

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

 

[murphy]

I would still like to see someone take a D60 camera and set up
those Resolution Charts to perform this test.

And MY tests.

And your tests? You mean the Zip box ?

I think the resolution chart should be enough contrast for any
camera to focus with.

One would think so. Depending exactly on WHERE your AF point was
located on the chart. If on some of the smaller print, maybe not.

No.. I talked to the Canon guy about this and he didnt pause for even a second when he said it should focus effortlessly on that chart from any distance.

Canon has given me 2 stories on the adjustment of my equipment. I
am waiting to find out which one is true.

2 stories? What are they?

The stories are about Lens adjustment. Not sure where this issue stands. A service report I received from canon says "Focus Checked & Adjusted" and yet the service supervisor told me only the 28-70 2.8L has any internaly available adjustments. (Im still a little confused on this issue).

I dont want to get into apples and oranges here so I will wait before I comment any further. When my 100-400 comes home to me, I will know more about what is going on.

Murph

 

[C.A.S.]

I shot this test once before and it did not work since I shot it @f5.6...Damn 400mm f2.8 is so sharp at that setting that the shots were hard to read....so...(scroll to the bottom of the page)

http://www.onestarimaging.com/test/focus.html

Here are the new shots at f2.8. I don't think anyone would argue that the 400mm f2.8 L is very sharp even wide open. But it helps to shoot wide open to make the DOF very small.

After shooting these last five shots I can truly say that the problem is not with a focusing acquisition (sp?) but a focusing holding problem.

I can tell that the camera/lens focuses right on the spot where I want it to. The image in the viewfinder is just as sharp as the manual focused one. But somewhere in the time between the shutter being pressed and the photo being taken, the camera is moving the focusing back just a notch.

This is the fifth time I have taken test shots like these...although it's the first time using Murphy's chart...and I can tell you that there is definately a focusing problem in MY camera. I bet the majority of D60's DO NOT have this problem, but I BET there are a few out there that do.

--
Carlos

http://www.onestarimaging.com