[reytor]

I´m not sure if this has been brought up before but I´m using lenses like the 100mm WR macro for other stuff too and when AF makes full cycle every now and then it is really time consuming and noisy.
Would it be possible for Pentax to make focuslimiter in camera firmware so that when seleted in menu, the AF in these long throw lenses works only - lets say - from about (no need to be exact) 0,5m to infinity?

[Na Horuk]

The older FA 100mm macro has a focus limiter switch that does just what you want.
The idea of a digital focus limiter has been discussed before, but I don't think this is possible at the moment, as the camera doesn't really know where it is focusing. It just keeps going until it locks focus or gives up.
Maybe it could be done, but Im afraid it would need more than a firmware update.

That said, I use DFA 100mm WR and rarely use it in macro mode, so I would really like this feature! Just Focus range: All, Close, Far
It would be helpful

[RobA_Oz]

The idea of a digital focus limiter has been discussed before, but I don't think this is possible at the moment, as the camera doesn't really know where it is focusing. It just keeps going until it locks focus or gives up.
Maybe it could be done, but Im afraid it would need more than a firmware update.

If the AF system knows which way to drive the lens focus mechanism, then it doesn't need to know where the current focal point is. Presumably, it will continue providing a signal to drive focus in one direction or the other, until the sensors indicate that focus on the subject has been achieved. If that's the case, it may not be possible to provide this feature without a hardware component of the lens that provides position data. In theory, I suppose the AF system could drive the focus from one stop to the other, using a pulse count on the drive motor (which I assume is a stepper type) to determine those points, and then allow the user to select a band of movement at either end, but I don't know what else would be required to make this work satisfactorily.

[jddwoods]

I have the DFA 100 Macro WR and my way around this is simply to use quick shift just get close and let autofocus get the final focus. This shortens the time and screwdrive noise and most of the time eliminates the issue of the autofocus going from one end to the other.
It would be nice if there could be a software fix but somehow I think it is highly unlikely

[alpheios]

I also think that a software limiter is probably impossible to achieve.
The 100mm WR really is a great lens for almost everything. I actually use it mostly for landscape and portrait work and rarely for macro. My workaround for taming the autofocus is to use backbutton focusing and quickshift. If it starts hunting I just don’t let it do so. I take my finger off the AF button, prefocus manually and then push the AF button again to let it do fine focusing.

[Na Horuk]

The 100mm WR really is a great lens for almost everything. I actually use it mostly for landscape and portrait work and rarely for macro. My workaround for taming the autofocus is to use backbutton focusing and quickshift

Yes! This is what I do as well. I rarely have AF problems, because I learned how to use MF and AF combination, so I dont lose much time

[reytor]

Thanks, all for the info.
I also use quick shift to "fix" this problem but thought it could be really nice to have an "automatic" work around.
I don't know what type of motor runs the autofocus but if it is a stepper motor then it should be possible as indicated by Rob.
On the other hand; for each type of lens the focus throw (and end to end run time for each camera body) is a known fact (that may be effected by ambiente temperature and battery level) and that can be used as a limiter (drive to infinity and then permit only so much movement towards minimum distance).

For the future lenses a real time measurement system can be implemented, but that requires new protocol for lens data or at least new interpretation in firmware if there is available space in current data structure. Real distance is not requiered for this, just the fraction (or %) of full throw.