Dominic and Günter et al, SD14 + 30mm f1.4 EX DC HSM

Started Oct 9, 2006 | Discussions
Barry J Thompson Regular Member • Posts: 468
Dominic and Günter et al, SD14 + 30mm f1.4 EX DC HSM

Are you able to comment on the usability of this combination please?
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Gunter B Contributing Member • Posts: 951
Re: Dominic and Günter et al, SD14 + 30mm f1.4 EX DC HSM

Barry J Thompson wrote:

Are you able to comment on the usability of this combination please?

Hi Barry,

yes.

Works fine, AF-problems -as on the SD10- seem to be gone. CA-Problems in high-contrast situations remain of course.

Laurence Matson
Laurence Matson Forum Pro • Posts: 11,983
AF on SD14

The AF on the SD14 is more accurate and faster by a long shot. This will almost certainly benefit faster lenses, such as the 30. In addition, all newer lenses can be tuned to the camera (also to the SD10). At some point, we should get a list from Sigma for that.

Barry J Thompson wrote:

Are you able to comment on the usability of this combination please?
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Laurence

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Cecil Greek Senior Member • Posts: 1,133
Re: AF on SD14

How about for shooting action sports with the 120-300 EX?
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Tom Rowland Veteran Member • Posts: 5,891
Re: AF on SD14

Cecil Greek wrote:

How about for shooting action sports with the 120-300 EX?

Hi Cecil,

If you have a spare monent give me a call to talk about this.

Helge Hafting Contributing Member • Posts: 827
Re: AF on SD14

Laurence Matson wrote:

The AF on the SD14 is more accurate and faster by a long shot. This
will almost certainly benefit faster lenses, such as the 30. In
addition, all newer lenses can be tuned to the camera (also to the
SD10). At some point, we should get a list from Sigma for that.

How is a lens tuned to the camera? Is there a secret knob somewhere?

And what would such tuning do with the lens anyway? The focus sensor is in the camera, not the lens. So the camera always knows if the image is in focus or not - limited only by the precision of this focus sensor. Then the camera attempts using the lens motor to bring the image into better focus until it thinks it is "as good as it gets".

I cannot see any way a lens could be tuned to the camera. The camera is either correct, or wrong. If it is wrong, the focus sensor itself might need adjustment of course. The lens can probably be adjusted for what distances it reports, but that only improves EXIF data, it won't improve focusing.

Helge Hafting

J. Michael Veteran Member • Posts: 4,486
Re: AF on SD14

curious about the 120-300 focusing speed and accuracy with the SD14 also.

gepetto"at"gwi.net

thanks, Mike

Roland Karlsson Forum Pro • Posts: 29,164
Re: CA in high contrast?

Gunter B wrote:

Works fine, AF-problems -as on the SD10- seem to be gone.
CA-Problems in high-contrast situations remain of course.

Hi - when doing experiments with automatic CA removal I have found that SD10 pictures have this weird problem. CA in the bright parts only. Thats very hard to remove without doing desaturation.

CA from a lens is found all over the picture - bright or dark does not matter. There is no special CA in high contrast. Thats not how a lens works. If there is CA - then there is CA.

So - what is this CA in high-contrast situations?

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Sigma DP3 Merrill Sigma dp2 Quattro Sony RX100 III Pentax K-3 Pentax K-1 +14 more
JLK Veteran Member • Posts: 4,501
Re: AF on SD14

Helge Hafting wrote:

Laurence Matson wrote:

The AF on the SD14 is more accurate and faster by a long shot. This
will almost certainly benefit faster lenses, such as the 30. In
addition, all newer lenses can be tuned to the camera (also to the
SD10). At some point, we should get a list from Sigma for that.

How is a lens tuned to the camera? Is there a secret knob somewhere?

And what would such tuning do with the lens anyway? The focus
sensor is in the camera, not the lens. So the camera always knows
if the image is in focus or not - limited only by the precision of
this focus sensor. Then the camera attempts using the lens motor to
bring the image into better focus until it thinks it is "as good as
it gets".

I cannot see any way a lens could be tuned to the camera. The
camera is either correct, or wrong. If it is wrong, the focus
sensor itself might need adjustment of course. The lens can
probably be adjusted for what distances it reports, but that only
improves EXIF data, it won't improve focusing.

Helge Hafting

Not a secret knob. The AF drive motor can be tuned with a particular camera for optimum focussing. See the Canon fora for long discussions about folks sending their lenses back (and back again) to get this right.

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Jim

Halldor Eiriksson Senior Member • Posts: 1,989
Re: AF on SD14

JLK wrote:

Not a secret knob. The AF drive motor can be tuned with a
particular camera for optimum focussing. See the Canon fora for
long discussions about folks sending their lenses back (and back
again) to get this right.

But SIgma lenses with SA mount are meant for SD9/SD10. Aren't they fine tuned for them? Could I still benefit from a fine tune with my SD9?
Halldor
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Laurence Matson
Laurence Matson Forum Pro • Posts: 11,983
120-300 works very well

Fast and accurate

Mike Gerstner wrote:

curious about the 120-300 focusing speed and accuracy with the SD14
also.

gepetto"at"gwi.net

thanks, Mike

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Laurence

My idea of good company is the fellowship of clever, well-informed people, who have a great deal of conversation and liberality of ideas.

Jane Austen

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NarrBL Veteran Member • Posts: 6,137
Re: AF on SD14

Yes, I think it has to do with the fact that the AF method is not a closed-loop feedback system - in order to get best speed.

There's a measurement, then a one-time instruction sent to run the motor. To be sure it best ends up in the right spot, better to calibrate the lenses individually. If it can be done for different cameras, as also seems so for the Canons, maybe there's a lookup table in programmable memory, in the lens electronics.

JLK wrote:

Not a secret knob. The AF drive motor can be tuned with a
particular camera for optimum focussing. See the Canon fora for
long discussions about folks sending their lenses back (and back
again) to get this right.

J. Michael Veteran Member • Posts: 4,486
thank you (nt)........
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NarrBL Veteran Member • Posts: 6,137
Re: CA in high contrast?

Here's at least one discussion of a way to get rid of it, motivated by getting rid of the problem corner where jaggies once in a while appear:

http://forums.dpreview.com/forums/read.asp?forum=1027&message=19941865&q=gaussian&qf=m

Roland Karlsson wrote:

Gunter B wrote:

Works fine, AF-problems -as on the SD10- seem to be gone.
CA-Problems in high-contrast situations remain of course.

Hi - when doing experiments with automatic CA removal I have found
that SD10 pictures have this weird problem. CA in the bright parts
only. Thats very hard to remove without doing desaturation.

CA from a lens is found all over the picture - bright or dark does
not matter. There is no special CA in high contrast. Thats not how
a lens works. If there is CA - then there is CA.

So - what is this CA in high-contrast situations?

Paul Paris Les Images Senior Member • Posts: 1,015
Re: AF on SD14

In contrast to the reassuring words of Laurence "The AF on the SD 14 is more accurate and faster..."), Why than the restrictions: "certainly benefit faster lenses" and why than "all newer lenses can be tuned to the camera".
It seems the problems with the AF are not yet resolved.

According to laurence: "At some point (huh??, PP) we should get a list from Sigma for that" A list? with instructions to do it yourself calibrating? Or a list to not use some lenses?

I don't get this,

Paul

http://www.paulparislesimages.com

Erik Magnuson Forum Pro • Posts: 12,247
Re: AF on SD14

Paul Paris Les Images wrote:

In contrast to the reassuring words of Laurence "The AF on the SD
14 is more accurate and faster..."), Why than the restrictions:

Perhaps just because it's much better does not mean that it's perfect and there is room for improvement still (something that applies to all cameras.)

According to laurence: "At some point (huh??, PP) we should get a
list from Sigma for that" A list? with instructions to do it
yourself calibrating? Or a list to not use some lenses?

I doubt it would be a list of "do not use". More likely that some lenses may be able to better utilize the new capabilities of the SD14 AF system than others (e.g. older lenses from before the improvements were known/planned.) Some lenses might be able to be re-chipped or re-flashed to improve performance although this may be limited to only the high-performance lenses.

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Erik

Gunter B Contributing Member • Posts: 951
Re: CA in high contrast?

Roland Karlsson wrote:

Gunter B wrote:

Works fine, AF-problems -as on the SD10- seem to be gone.
CA-Problems in high-contrast situations remain of course.

Hi - when doing experiments with automatic CA removal I have found
that SD10 pictures have this weird problem. CA in the bright parts
only. Thats very hard to remove without doing desaturation.

CA from a lens is found all over the picture - bright or dark does
not matter. There is no special CA in high contrast. Thats not how
a lens works. If there is CA - then there is CA.

So - what is this CA in high-contrast situations?

Roland, I don´t know.

I just experienced that CA (or whatever it is) on the 30EX at dark edges in front of bright skies. There never was a sign of this in other parts of the images. And I dont have that with other lenses.
So, despite your description of what CA is, I cannot answer your question.

Paul Paris Les Images Senior Member • Posts: 1,015
Erik, ...

.. thanks for your clarification. It's a topical subject for me at the moment.

I'am struggeling - since several months- with a 10-20 mm lens. Sometimes it's only sharp in a small spot in the center and clearly unsharp at the edges (even at F8-F11). Very strange.

It was send to Sigma Benelux : "nothing wrong' , but this issue remains, have to send it back once again,

cheers, Paul

Just Looking Veteran Member • Posts: 5,740
bright skies, purple fringe, Rayleigh scattering

Gunter B wrote:

Roland Karlsson wrote:

Gunter B wrote:

Works fine, AF-problems -as on the SD10- seem to be gone.
CA-Problems in high-contrast situations remain of course.

Hi - when doing experiments with automatic CA removal I have found
that SD10 pictures have this weird problem. CA in the bright parts
only. Thats very hard to remove without doing desaturation.

CA from a lens is found all over the picture - bright or dark does
not matter. There is no special CA in high contrast. Thats not how
a lens works. If there is CA - then there is CA.

So - what is this CA in high-contrast situations?

Roland, I don´t know.
I just experienced that CA (or whatever it is) on the 30EX at dark
edges in front of bright skies. There never was a sign of this in
other parts of the images. And I dont have that with other lenses.
So, despite your description of what CA is, I cannot answer your
question.

It's very simple, really. Lens chromatic correction usually diverges rapidly from ideal at very short wavelengths, where usually there is not a lot of light energy. But in bright (blue or cloudy) skies, there's a dominance of short wavelengths due to Rayleigh scattering. So a contrast of a foreground object against a bright sky is where you see the sort of CA that is often referred to as purple fringe.

The fundamental trouble is that the infinite-dimensional spectrum has been reduced to 3D colorspace already by the time you get data off a sensor, so you no longer have all the info needed to do CA correction. You have to settle for a happy medium, or correct differently at different edges in the image. Or put a stronger UV-cut filter on the camera for such scenes.

j

Just Looking Veteran Member • Posts: 5,740
Re: AF on SD14

I sure hope they don't make a Canon-like AF system, where some kind of mutual calibration between lens and camera is needed to get it to not back-focus or front-focus. I'd rather have it slow than be a sloppy open-loop approach.

j

Helge Hafting wrote:

Laurence Matson wrote:

The AF on the SD14 is more accurate and faster by a long shot. This
will almost certainly benefit faster lenses, such as the 30. In
addition, all newer lenses can be tuned to the camera (also to the
SD10). At some point, we should get a list from Sigma for that.

How is a lens tuned to the camera? Is there a secret knob somewhere?

And what would such tuning do with the lens anyway? The focus
sensor is in the camera, not the lens. So the camera always knows
if the image is in focus or not - limited only by the precision of
this focus sensor. Then the camera attempts using the lens motor to
bring the image into better focus until it thinks it is "as good as
it gets".

I cannot see any way a lens could be tuned to the camera. The
camera is either correct, or wrong. If it is wrong, the focus
sensor itself might need adjustment of course. The lens can
probably be adjusted for what distances it reports, but that only
improves EXIF data, it won't improve focusing.

Helge Hafting

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