Lens focus continued...

I want to thank everyone who replied. Savageduck suggested a yardstick
from Home Depot, and I found a crisply marked, flat, thin, aluminum
version that was just about the thickness of a wood saw. I just put a
45 degree cut in the side of a piece of wood, taped the focus chart to
the wood, and I was good to go. PAS also gave a link to the Dot Tune
method.

Regarding the Dot Tune method, even though it didn't quite work for me
(I have Pentax), it got me really close, and I would recommend it to
anyone. I believe it can save lots of time with the fine tuning.

I did find two issues. The first is just frustrating - one of the
lenses that needed no adjustments is also the one that I used in so
many of my OoF pictures. I need to dig a little deeper on that one.

But the main reason for this post is the second problem: I have a
70-200 F2.8 that is front focusing under all settings, and it is
outside the range of my fine tuning. But the real issue is that it is
also front focusing to the exact same degree when I use Live View, and
therefore contrast detection, as opposed to phase detection. I was
under the impression that using contrast detection *must* give you
correct focus. I am baffled. I don't see how it can be the body, since
other lenses do focus properly, and the ones that needed adjustment
focused properly with LV.

Any ideas? All of my results were very consistent - very repeatable.

On 1/11/2015 3:18 PM, Bill W wrote:
I want to thank everyone who replied. Savageduck suggested a yardstick
from Home Depot, and I found a crisply marked, flat, thin, aluminum
version that was just about the thickness of a wood saw. I just put a
45 degree cut in the side of a piece of wood, taped the focus chart to
the wood, and I was good to go. PAS also gave a link to the Dot Tune
method.

Regarding the Dot Tune method, even though it didn't quite work for me
(I have Pentax), it got me really close, and I would recommend it to
anyone. I believe it can save lots of time with the fine tuning.

I did find two issues. The first is just frustrating - one of the
lenses that needed no adjustments is also the one that I used in so
many of my OoF pictures. I need to dig a little deeper on that one.

But the main reason for this post is the second problem: I have a
70-200 F2.8 that is front focusing under all settings, and it is
outside the range of my fine tuning. But the real issue is that it is
also front focusing to the exact same degree when I use Live View, and
therefore contrast detection, as opposed to phase detection. I was
under the impression that using contrast detection *must* give you
correct focus. I am baffled. I don't see how it can be the body, since
other lenses do focus properly, and the ones that needed adjustment
focused properly with LV.

Any ideas? All of my results were very consistent - very repeatable.


Which 70-200 do you have, and which camera do you use it with?

The 70-200s I am familiar with have internal focusing. Even very
expensive external focusing lenses suffer from lens creep. Exactly what
are your focusing issues?
The reason I am asking is because some cameras have various methods of
focusing. With my Nikons I can use various focusing methods, nearest
object, 11 point, 51 point, etc. When my images are OOF it is usually
because I have used an incorrect method. The focus point can be
determined by viewing the image through Nikon Capture.
Some folks use release priority for focus tracking. I and others use
focus then release, so the shutter iwll not release unless the object is
in focus.
Here is an article that may help. Look up autofocus for your camera.

BTW Why do you use liveview for autofocus?
http://en.wikipedia.org/wiki/Autofocus


--
PeterN

On Sun, 11 Jan 2015 17:21:57 -0500, PeterN wrote:

On 1/11/2015 3:18 PM, Bill W wrote:
I want to thank everyone who replied. Savageduck suggested a yardstick
from Home Depot, and I found a crisply marked, flat, thin, aluminum
version that was just about the thickness of a wood saw. I just put a
45 degree cut in the side of a piece of wood, taped the focus chart to
the wood, and I was good to go. PAS also gave a link to the Dot Tune
method.

Regarding the Dot Tune method, even though it didn't quite work for me
(I have Pentax), it got me really close, and I would recommend it to
anyone. I believe it can save lots of time with the fine tuning.

I did find two issues. The first is just frustrating - one of the
lenses that needed no adjustments is also the one that I used in so
many of my OoF pictures. I need to dig a little deeper on that one.

But the main reason for this post is the second problem: I have a
70-200 F2.8 that is front focusing under all settings, and it is
outside the range of my fine tuning. But the real issue is that it is
also front focusing to the exact same degree when I use Live View, and
therefore contrast detection, as opposed to phase detection. I was
under the impression that using contrast detection *must* give you
correct focus. I am baffled. I don't see how it can be the body, since
other lenses do focus properly, and the ones that needed adjustment
focused properly with LV.

Any ideas? All of my results were very consistent - very repeatable.


Which 70-200 do you have, and which camera do you use it with?

The 70-200s I am familiar with have internal focusing. Even very
expensive external focusing lenses suffer from lens creep. Exactly what
are your focusing issues?
The reason I am asking is because some cameras have various methods of
focusing. With my Nikons I can use various focusing methods, nearest
object, 11 point, 51 point, etc. When my images are OOF it is usually
because I have used an incorrect method. The focus point can be
determined by viewing the image through Nikon Capture.
Some folks use release priority for focus tracking. I and others use
focus then release, so the shutter iwll not release unless the object is
in focus.
Here is an article that may help. Look up autofocus for your camera.

BTW Why do you use liveview for autofocus?
http://en.wikipedia.org/wiki/Autofocus

It's a Sigma on a Pentax K3. I was testing with good lighting, center
spot focusing. The lens had no trouble focusing - or at least thinking
it was focused, but it invariable front focused, always in exactly the
same place.

I don't use LV, it was simply for comparison purposes. It is part of
the Dot Tune method, and the reason is that it is supposed to always
focus correctly, just more slowly. And if I use MF, I will get focus
confirmation at the front focus position, but not the actual focus
position. Something is very wrong, and I'm waiting to see what Sigma
has to say.

On 1/11/2015 5:36 PM, Bill W wrote:
On Sun, 11 Jan 2015 17:21:57 -0500, PeterN wrote:

On 1/11/2015 3:18 PM, Bill W wrote:
I want to thank everyone who replied. Savageduck suggested a yardstick
from Home Depot, and I found a crisply marked, flat, thin, aluminum
version that was just about the thickness of a wood saw. I just put a
45 degree cut in the side of a piece of wood, taped the focus chart to
the wood, and I was good to go. PAS also gave a link to the Dot Tune
method.

Regarding the Dot Tune method, even though it didn't quite work for me
(I have Pentax), it got me really close, and I would recommend it to
anyone. I believe it can save lots of time with the fine tuning.

I did find two issues. The first is just frustrating - one of the
lenses that needed no adjustments is also the one that I used in so
many of my OoF pictures. I need to dig a little deeper on that one.

But the main reason for this post is the second problem: I have a
70-200 F2.8 that is front focusing under all settings, and it is
outside the range of my fine tuning. But the real issue is that it is
also front focusing to the exact same degree when I use Live View, and
therefore contrast detection, as opposed to phase detection. I was
under the impression that using contrast detection *must* give you
correct focus. I am baffled. I don't see how it can be the body, since
other lenses do focus properly, and the ones that needed adjustment
focused properly with LV.

Any ideas? All of my results were very consistent - very repeatable.


Which 70-200 do you have, and which camera do you use it with?

The 70-200s I am familiar with have internal focusing. Even very
expensive external focusing lenses suffer from lens creep. Exactly what
are your focusing issues?
The reason I am asking is because some cameras have various methods of
focusing. With my Nikons I can use various focusing methods, nearest
object, 11 point, 51 point, etc. When my images are OOF it is usually
because I have used an incorrect method. The focus point can be
determined by viewing the image through Nikon Capture.
Some folks use release priority for focus tracking. I and others use
focus then release, so the shutter iwll not release unless the object is
in focus.
Here is an article that may help. Look up autofocus for your camera.

BTW Why do you use liveview for autofocus?
http://en.wikipedia.org/wiki/Autofocus

It's a Sigma on a Pentax K3. I was testing with good lighting, center
spot focusing. The lens had no trouble focusing - or at least thinking
it was focused, but it invariable front focused, always in exactly the
same place.

I don't use LV, it was simply for comparison purposes. It is part of
the Dot Tune method, and the reason is that it is supposed to always
focus correctly, just more slowly. And if I use MF, I will get focus
confirmation at the front focus position, but not the actual focus
position. Something is very wrong, and I'm waiting to see what Sigma
has to say.


Now all is clear. Unfortunately Sigma has, IMHO, a reputation for poor
quality control on all but its higher end lenses, (Over $10,000.) I have
tried Sigma lenses at various times, and found them slow focusing and
not nearly as sharp as they should be. From what I hear though, Sigma
has been fair about dealing with defects. If PAS is listening he could
tell you more, as he uses Sigma. I want to be wrong, but Sigma may blame
your camera, and Pentax will blame Sigma. If you live within an hour or
two of Long Island, it might be worthwhile to go there with your camera.
Otherwise, I would try to sell the lens and get a different brand. One
of my friends is very happy with his Tamron 70-200. But he uses it on a
Canon.

After I wrote the above I did a quick Google search on "Pentax k-3
focus" and came up with a bunch of sites where there seems to be some
focus issues with Pentax K-3. I have not gone into any depth of reading,
but you might want to look at some of them. Particularly the Pentax
forums, and DP Review.
HTH





--
PeterN

On Sun, 11 Jan 2015 18:31:09 -0500, PeterN wrote:

On 1/11/2015 5:36 PM, Bill W wrote:
On Sun, 11 Jan 2015 17:21:57 -0500, PeterN wrote:

On 1/11/2015 3:18 PM, Bill W wrote:
I want to thank everyone who replied. Savageduck suggested a yardstick
from Home Depot, and I found a crisply marked, flat, thin, aluminum
version that was just about the thickness of a wood saw. I just put a
45 degree cut in the side of a piece of wood, taped the focus chart to
the wood, and I was good to go. PAS also gave a link to the Dot Tune
method.

Regarding the Dot Tune method, even though it didn't quite work for me
(I have Pentax), it got me really close, and I would recommend it to
anyone. I believe it can save lots of time with the fine tuning.

I did find two issues. The first is just frustrating - one of the
lenses that needed no adjustments is also the one that I used in so
many of my OoF pictures. I need to dig a little deeper on that one.

But the main reason for this post is the second problem: I have a
70-200 F2.8 that is front focusing under all settings, and it is
outside the range of my fine tuning. But the real issue is that it is
also front focusing to the exact same degree when I use Live View, and
therefore contrast detection, as opposed to phase detection. I was
under the impression that using contrast detection *must* give you
correct focus. I am baffled. I don't see how it can be the body, since
other lenses do focus properly, and the ones that needed adjustment
focused properly with LV.

Any ideas? All of my results were very consistent - very repeatable.


Which 70-200 do you have, and which camera do you use it with?

The 70-200s I am familiar with have internal focusing. Even very
expensive external focusing lenses suffer from lens creep. Exactly what
are your focusing issues?
The reason I am asking is because some cameras have various methods of
focusing. With my Nikons I can use various focusing methods, nearest
object, 11 point, 51 point, etc. When my images are OOF it is usually
because I have used an incorrect method. The focus point can be
determined by viewing the image through Nikon Capture.
Some folks use release priority for focus tracking. I and others use
focus then release, so the shutter iwll not release unless the object is
in focus.
Here is an article that may help. Look up autofocus for your camera.

BTW Why do you use liveview for autofocus?
http://en.wikipedia.org/wiki/Autofocus

It's a Sigma on a Pentax K3. I was testing with good lighting, center
spot focusing. The lens had no trouble focusing - or at least thinking
it was focused, but it invariable front focused, always in exactly the
same place.

I don't use LV, it was simply for comparison purposes. It is part of
the Dot Tune method, and the reason is that it is supposed to always
focus correctly, just more slowly. And if I use MF, I will get focus
confirmation at the front focus position, but not the actual focus
position. Something is very wrong, and I'm waiting to see what Sigma
has to say.


Now all is clear. Unfortunately Sigma has, IMHO, a reputation for poor
quality control on all but its higher end lenses, (Over $10,000.) I have
tried Sigma lenses at various times, and found them slow focusing and
not nearly as sharp as they should be. From what I hear though, Sigma
has been fair about dealing with defects. If PAS is listening he could
tell you more, as he uses Sigma. I want to be wrong, but Sigma may blame
your camera, and Pentax will blame Sigma. If you live within an hour or
two of Long Island, it might be worthwhile to go there with your camera.
Otherwise, I would try to sell the lens and get a different brand. One
of my friends is very happy with his Tamron 70-200. But he uses it on a
Canon.

After I wrote the above I did a quick Google search on "Pentax k-3
focus" and came up with a bunch of sites where there seems to be some
focus issues with Pentax K-3. I have not gone into any depth of reading,
but you might want to look at some of them. Particularly the Pentax
forums, and DP Review.
HTH

Yeah, I think I'll be doing a lot of research on this. The other
problem is that the lens makers, including Sigma, are not including
Pentax mounts on all of their new lenses. Pentax has been fading for
years, but I hold some hope that Ricoh can salvage the brand. I don't
want to start over.

"PeterN" wrote in message
...
On 1/11/2015 5:36 PM, Bill W wrote:
On Sun, 11 Jan 2015 17:21:57 -0500, PeterN wrote:

On 1/11/2015 3:18 PM, Bill W wrote:
I want to thank everyone who replied. Savageduck suggested a
yardstick
from Home Depot, and I found a crisply marked, flat, thin, aluminum
version that was just about the thickness of a wood saw. I just put
a
45 degree cut in the side of a piece of wood, taped the focus chart
to
the wood, and I was good to go. PAS also gave a link to the Dot
Tune
method.

Regarding the Dot Tune method, even though it didn't quite work for
me
(I have Pentax), it got me really close, and I would recommend it
to
anyone. I believe it can save lots of time with the fine tuning.

I did find two issues. The first is just frustrating - one of the
lenses that needed no adjustments is also the one that I used in so
many of my OoF pictures. I need to dig a little deeper on that one.

But the main reason for this post is the second problem: I have a
70-200 F2.8 that is front focusing under all settings, and it is
outside the range of my fine tuning. But the real issue is that it
is
also front focusing to the exact same degree when I use Live View,
and
therefore contrast detection, as opposed to phase detection. I was
under the impression that using contrast detection *must* give you
correct focus. I am baffled. I don't see how it can be the body,
since
other lenses do focus properly, and the ones that needed adjustment
focused properly with LV.

Any ideas? All of my results were very consistent - very
repeatable.


Which 70-200 do you have, and which camera do you use it with?

The 70-200s I am familiar with have internal focusing. Even very
expensive external focusing lenses suffer from lens creep. Exactly
what
are your focusing issues?
The reason I am asking is because some cameras have various methods
of
focusing. With my Nikons I can use various focusing methods, nearest
object, 11 point, 51 point, etc. When my images are OOF it is
usually
because I have used an incorrect method. The focus point can be
determined by viewing the image through Nikon Capture.
Some folks use release priority for focus tracking. I and others use
focus then release, so the shutter iwll not release unless the
object is
in focus.
Here is an article that may help. Look up autofocus for your camera.

BTW Why do you use liveview for autofocus?
http://en.wikipedia.org/wiki/Autofocus

It's a Sigma on a Pentax K3. I was testing with good lighting, center
spot focusing. The lens had no trouble focusing - or at least
thinking
it was focused, but it invariable front focused, always in exactly
the
same place.

I don't use LV, it was simply for comparison purposes. It is part of
the Dot Tune method, and the reason is that it is supposed to always
focus correctly, just more slowly. And if I use MF, I will get focus
confirmation at the front focus position, but not the actual focus
position. Something is very wrong, and I'm waiting to see what Sigma
has to say.


Now all is clear. Unfortunately Sigma has, IMHO, a reputation for poor
quality control on all but its higher end lenses, (Over $10,000.) I
have tried Sigma lenses at various times, and found them slow focusing
and not nearly as sharp as they should be. From what I hear though,
Sigma has been fair about dealing with defects. If PAS is listening he
could tell you more, as he uses Sigma. I want to be wrong, but Sigma
may blame your camera, and Pentax will blame Sigma. If you live within
an hour or two of Long Island, it might be worthwhile to go there with
your camera. Otherwise, I would try to sell the lens and get a
different brand. One of my friends is very happy with his Tamron
70-200. But he uses it on a Canon.

Sigma has a new QC procedure for all of their Global vision lenses (Art,
Contemporary, Sport). It is he most extensive QC procedure they've ever
had. The lenses are nice too, very well made and reviews are very
positive.

The latest Tamron 70-200mm VC lens is highly regarded and would likely
be at the top of my list for 3rd party versions of 70-200mm lenses. Had
it been available at the time I bought my Canon mount 70-200mm lens, I
would have bought it. But when I was shopping for one, the previous
version of the Tamron was the current one at the time and the AF is
slow, I didn't like it.

Sigma's service has been very good regarding calibrating lenses. I have
no personal experience of them blaming a camera for a problem but I'm
not saying it doesn't happen. A lens tech once told me that he liked to
calibrate lenses to the specific camera because be found slight
differences in some cameras in the mounting location of the sensor.
Very slight differences, but enough to cause a problem. When I've
needed a lens adjusted, they've done so without my camera and the
results have been good. The 70-200mm Sigma lens I use on my Canon DSLR
needed adjustment, it was front focusing slightly. My 70-200mm for my
Sigma DSLR needed no adjusting, wither by Sigma or with the
micro-adjustment feature of the camera.

The new Global Vision lenses have a wide array of micro adjustments that
can be done using he Sigma USB dock. For their 18-200mm lens, for
example, you can micro adjust the lens at four different focal lengths
and four different distances within each of those four focal lengths.

After I wrote the above I did a quick Google search on "Pentax k-3
focus" and came up with a bunch of sites where there seems to be some
focus issues with Pentax K-3. I have not gone into any depth of
reading, but you might want to look at some of them. Particularly the
Pentax forums, and DP Review.
HTH

It may be a problem with the camera rather than the lens. Since there
are reported problem with the K-3, I think it's best to have the lens
calibrated to the specific camera it is being used on. That can cause a
problem if the lens is used on another body should a user upgrade.

In article , PAS
wrote:

Now all is clear. Unfortunately Sigma has, IMHO, a reputation for poor
quality control on all but its higher end lenses, (Over $10,000.) I
have tried Sigma lenses at various times, and found them slow focusing
and not nearly as sharp as they should be. From what I hear though,
Sigma has been fair about dealing with defects. If PAS is listening he
could tell you more, as he uses Sigma. I want to be wrong, but Sigma
may blame your camera, and Pentax will blame Sigma. If you live within
an hour or two of Long Island, it might be worthwhile to go there with
your camera. Otherwise, I would try to sell the lens and get a
different brand. One of my friends is very happy with his Tamron
70-200. But he uses it on a Canon.

Sigma has a new QC procedure for all of their Global vision lenses (Art,
Contemporary, Sport). It is he most extensive QC procedure they've ever
had. The lenses are nice too, very well made and reviews are very
positive.

'most extensive qc procedure they've ever had' just means it's better
than the nonexistent system they had before. it's still bad and their
lenses are a crapshoot.

the main problem with sigma is that the company is run by sleazeballs
who lie about pretty much everything.

pawning off a 5 megapixel camera as a 39 mp or whatever this week's
number happens to be (it's been claimed as having 20, 39 and even 60
mp) is completely disgusting. if they are going to lie about that then
they will lie about anything, which they do.

however, i do give them credit for not using tape to hold lenses
together anymore. they really did do that, and not surprisingly, the
lenses tended to fall apart.