[m8o]

... this is in regards to my K-5 + 70-200mm f/2.8 HSM II ....

After a short honeymoon I soon came to realize that the critical focus region is noticeably in-front of the focus point. Using various subjects with surface detail at a 45-ish deg angle to me at distances near as well as well over MFD, I've went from -10 <-> +10 for the adjust all and adjust one settings taking many shots along the way. And at no time has any of it altered the in-focus region in relation to my focus point. ??? Am I the only one?

[kittykat46]

AF Fine Tune does work with the Sigma 17-70mm (screw drive), only it doesn't recognise it as a specific lens model, just "Sigma Lens". Pentax lens ID doesn't seem to work well with Sigma.

I don't have a Sigma HSM lens, so can't I comment on it
Have you tried adjusting AF with the lens on another Pentax with AF Fine Tune e.g. K-7 or K20D ?

[m8o]

I don't have the K-7 or K20D. Maybe I'll try and see if there's one @ a retailer I can try it on.

However you bring-up and interesting point. I was wondering if I should be seeing something specific to a lens. I see now, yes, I should. I don't even see "Sigma Lens" anywhere in the AF Fine Tune section.

[kent]

keep in mind, that sigma 70-200mm II has a focus shifting at close distance, which means, that you never know where is true focus .

[m8o]

keep in mind, that sigma 70-200mm II has a focus shifting at close distance, which means, that you never know where is true focus .

I see the same behavior with subjects 3 meters away, and an inability to adjust is the same. I am of like mind wondering if I know for sure what is getting focused on. Though I'm selecting a specific focus point, or using center-only, I'm going to switch to 5 point focusing later and re-try the subjects I was using last night.

[amvic]

I've found more or less an identical problem with a Sigma 17-70 HSM that was AF perfect on my K7 (see thread K5 and AF accuracy with Sigma 17-70mm HSM lens)

Adjusted to -10 my lens misses focus by less than at 0, but is still focusing at a point closer to what it should.

I've tried the Sigma lens on two K5 bodies and it performed identically; Pentax-branded lenses were perfect on both bodies.

Pentax may have made software changes that cause problems with Sigma HSM lenses. Or there's a less conspiratorial explanation. Whatever the reason, I'd love to find a solution.

[m8o]

Thanx for that. BTW, do you see lens as "Sigma Lens" in the AF Fine Adjustment section, or nothing at all?

[Winder]

My Sigma 50mm f/1.4 shows up as a Sigma 70-200 on the EXIF data. I am going to buy the Sigma 85mm so if I find one of them needs AF adjust I will probably sell the Sigma 50 and get the DA* 55mm. I'm not sure if different Sigma lenses register different or not.

[amvic]

Thanx for that. BTW, do you see lens as "Sigma Lens" in the AF Fine Adjustment section, or nothing at all?

I see nothing at all in the AF Fine Adjustment section beyond the adjustment bar and the option to apply the adjustment to one lens or all lenses.

[philbaum]

I see nothing at all in the AF Fine Adjustment section beyond the adjustment bar and the option to apply the adjustment to one lens or all lenses.

Just for the heck of it, why don't you try the all lenses option and see if that makes a difference to the Sigma's focus adjustment??? If that works, at the very least, you could make a change when you're going to be using that lens for awhile.

Let us know if you would. I've not had a problem making adjustments on my K20, but have never tried that with a Sigma.

[blende8]

I have only one Sigma and this is the Sigma 20/1.8.
It needed a focus correction on the K20 and when I got the K5 yesterday I found that exactly the same value is fitting on the K5.
So, it definitely works and it is consistent.

EDIT:
Oops, I have two Sigma lenses.
I also have the Sigma 180/3.5 Macro.
This does not need a correction.

[rudemood11]

Hi blende8,

So every time when you switch between your sigmas, do you need to go into the menu to change the AF fine tune values?

[RonHendriks1966]

It needed a focus correction on the K20 and when I got the K5 yesterday I found that exactly the same value is fitting on the K5.

I had the same experience for the adjusting of lenses that they all ended up with the same correction setting as in my K-7.:ugh:

[blende8]

So every time when you switch between your sigmas, do you need to go into the menu to change the AF fine tune values?

No.
The body recognizes the lens and sets the values accordingly.
I just checked again in the menu.
When I mount the Sigma 20, the correction -8 is set.
When I mount the Sigma 180, the value is zero.

[amvic]

Just for the heck of it, why don't you try the all lenses option and see if that makes a difference to the Sigma's focus adjustment??? If that works, at the very least, you could make a change when you're going to be using that lens for awhile.

Let us know if you would. I've not had a problem making adjustments on my K20, but have never tried that with a Sigma.

Tried it, neither all nor individual lens adjustment achieved sufficient correction to cure my Sigma 17-70 HSM's front focus problem.