[AfterPentax Mark II]

I am confused; can you elaborate

AF fine tuning is meant to correct the way the camera understands the signal given by the AF sensor to K-30's processor, which with that information, focuses on the object by letting the focusmotor of lens or body run to achieve focus. With a manual lens there is not a motor involved and the instrument to focus is your eye. And as you wrote

the warranty on my eyes run out a while ago

perhaps there lies a problem. AF fine tuning does not influence the working of the AF sensor in the camera.

[January]

perhaps there lies a problem.

I can still see the green hexagon lighting up, thank you very much.

AF fine tuning does not influence the working of the AF sensor in the camera.

It most definitely appear to influence it, at least in K30. You can check it yourself; take a manual lens and a simple setup involving a ruler and a target, shoot a photograph with the green hexagon lit, change the AFFA setting, focus again, shoot another one. You will find that the focus is now at a different position. I have done it a hundred times with a half a dozen of different manual lenses. I attach fragment of two photographs taken with the same manual lens (M42, Pancolar 1.8/50). One photograph is without the AFFA correction, the other one with AFFA -10.

Alternatively, read this article. Quote:

This article addresses the specific case of focusing manually on Pentax digital cameras while using the optical viewfinder (OVF) and the camera’s focus indicator, commonly called the ‘Green Hexagon’. The paper describes a technique that employs the Auto Focus Fine Adjustment (AFFA) function and a positive, unambiguous Green Hexagon signal to achieve consistently accurate and precise focus.

[UncleVanya]

AF fine tuning is meant to correct the way the camera understands the signal given by the AF sensor to K-30's processor, which with that information, focuses on the object by letting the focus motor of lens or body run to achieve focus. With a manual lens there is not a motor involved and the instrument to focus is your eye. And as you wrote perhaps there lies a problem. AF fine tuning does not influence the working of the AF sensor in the camera.

This is not accurate. EDIT: Apologies. While this is true the earlier comment is what I meant to disagree with.

[vonBaloney]

It doesn't affect operation of *THE SENSOR*, i.e. nothing mechanical or electrical is changing. (With manual lenses, what could change?) It is simply a software parameter adjustment. It affects what the computer does with the sensor data. Of course the focus point moves, that's the whole reason for adjusting -- nobody is saying different.

[UncleVanya]

It doesn't affect operation of *THE SENSOR*, i.e. nothing mechanical or electrical is changing. (With manual lenses, what could change?) It is simply a software parameter adjustment. It affects what the computer does with the sensor data. Of course the focus point moves, that's the whole reason for adjusting -- nobody is saying different.

It changes how the PDAF data is used which impacts the focus confirmation including catch in focus.

[pschlute]

AF fine tuning does not influence the working of the AF sensor in the camera

. With a manual lens there is not a motor involved and the instrument to focus is your eye.

AF fine tuning changes two things:

1. Where an autofocus lens stops focussing having achieved accurate focus.

2. Where the autofocus confirmation, green hexagon + beep signals accurate focus has been achieved.

If you rely on the green hexagon/beep when focussing with a manual lens, and your AF-sensor registration distance is out of perfect alignment, then using the AF/FA menu to adjust for this will enable you to get a different and more accurate focus with a manual lens.

[vonBaloney]

It changes how the PDAF data is used which impacts the focus confirmation including catch in focus.

Yes, exactly. How the sensor data is used, not the operation of the sensor. What After Pentax Mark II said was precisely correct and accurate, and is the same thing you (and I) are saying.

[pschlute]

Yes, exactly. How the sensor data is used, not the operation of the sensor. What After Pentax Mark II said was precisely correct and accurate, and is the same thing you (and I) are saying.

Indeed. But remember that many readers of these forums are not seasoned photographers like yourself or "After Pentax Mark II". It would be very easy for someone with less knowlege to misinterpret what was said, and to believe that AF/FA can have no affect on focussing with a manual lens.

This is why "Uncle Vanya" and myself have endeavoured to clarify things.

[UncleVanya]

Yes, exactly. How the sensor data is used, not the operation of the sensor. What After Pentax Mark II said was precisely correct and accurate, and is the same thing you (and I) are saying.

I’m sorry I actually meant to quote a different post and I wasn’t paying attention. I have edited my quote to say that.

The fine tuning ONLY applies to AF lenses, it does not work with manual focusing lenses. The fine tuning for manual focusing lenses is done by your local optician, just like me.

And that is very easy to read as saying the af fine tuning has no effect on mf lenses. That’s simply not true. The mechanism used is described well in several posts. The key is: Af fine tuning changes how the camera determines focus by biasing what the camera considers focused - the way this happens is immaterial to the outcome - the point of focus is moved at which the camera indicates focus and this applies to mf and af lenses equally.

[photogem]

And that is very easy to read as saying the af fine tuning has no effect on mf lenses.
That’s simply not true. The mechanism used is described well in several posts.

Yes, and very well explained!
This was new to me and has to be explored.

The key is: Af fine tuning changes how the camera determines focus by biasing what the camera considers focused - the way this happens is immaterial to the outcome - the point of focus is moved at which the camera indicates focus and this applies to mf and af lenses equally.

Yes, but the way I understood it, it means that this single chose bias/value now "applies to all lenses", if I understood it correctly.
If I understood that correct: You cannot chose different data to different manual lenses.

If I am wrong, please correct me, I am more than happy to learn!

[pschlute]

Yes, but the way I understood it, it means that this single chose bias/value now "applies to all lenses", if I understood it correctly.
If I understood that correct: You cannot chose different data to different manual lenses.

Point 1.
If you use manual lenses and rely on the AF confirmation (green hexagon/beep), and you get front or back focus this means that the registration distance of the AF sensor is out of alignment. You can use the AF/FA menu item APPLY ALL setting to correct this, and indeed it will apply to all lenses (with the exception in point 2).

This is exactly as it should be. Manual lenses, unlike AF lenses, cannot FF or BF by themselves. If you correct for the registration distance alignment, then all manual lenses will focus correctly when relying on AF confirmation.

Point 2.
AF lenses can FF/BF by themselves. This is because some will over or under shoot the point where the camera tells it to stop. This is a separate issue to AF registration distance, although the two problems can exist together.

You can use the AF/FA menu item APPLY ONE to set an individual adjustment for up to 20 distinct autofocus lenses. The adjustment here will deal with both the lens FF/BF and registration distance issues.

Point 3.
Using the menu correctly.

As well as being able to set an adjustment in both the APPLY ALL and APPLY ONE menus, it is important you tell the camera which setting to use. If you exit the menu from OFF, then no adjustment will be applied. If you exit from APPLY ALL then the global adjustment will be used for all lenses, including ones you have set up individual adjustments.

If you exit the menu from APPLY ONE, then any lens that you have registered an individual adjustment for, the camera will use that adjustment. But if you then mount another lens like a manual lens, or a AF lens which has no adjustment recorded, the camera will default to the APPLY ALL setting.

[photogem]

Point 1.
If you use manual lenses and rely on the AF confirmation (green hexagon/beep), and you get front or back focus this means that the registration distance of the AF sensor is out of alignment.

This was the most important point, now I understand.
Thank you very much!

[UncleVanya]

Yes, but the way I understood it, it means that this single chose bias/value now "applies to all lenses", if I understood it correctly.
If I understood that correct: You cannot chose different data to different manual lenses.

If I am wrong, please correct me, I am more than happy to learn!

There are third party manual lenses that do communicate Exif data to the camera and a lens ID - those can use the individual adjustment option just like af lenses. There’s a limit of 20 lenses I think. If I recall it’s first in first out when the limit is reached. No error is generated if I recall correctly.

[photogem]

There are third party manual lenses that do communicate Exif data to the camera and a lens ID - those can use the individual adjustment option just like af lenses. There’s a limit of 20 lenses I think. If I recall it’s first in first out when the limit is reached. No error is generated if I recall correctly.

ok but those are A-lenses with contacts, yes?

[vonBaloney]

ok but those are A-lenses with contacts, yes?

Contacts would be necessary but sufficient -- older Pentax 'A' series lenses would not count. There needs to be a chip in there for id I think. I'm not sure what lenses would qualify -- possibly the offerings from Irix, maybe Samyang?