K3 refuses to store focus correction data for A lenses?

<p>Yesterday I put myself to work on the tedious but fundamental job of searching the best focus point for all my lenses on the K3 and I found some surprises.<br>

First, the Sima 10-20mm wanted quite different corrections at the two ends, i.e. +3 at 10mm et -10 at 20 (and possibly it needed more)<br>

Second, the camera refuses to store the -8 value for the manual focus 50mm f1.4 A and goes back to 0 every time (but the correction seems to be there at least just after I set it, the differences in focus point are sensible). <br>

Did anybody find similar issues? Any way around the problem for the MF lenses (I'll try with the 20mm f4 M as soon as I have time to see if the issue is common to all MF or just the 50.)</p>

Someone correct me if I am wrong, but the micro focus corrections are for autofocus lenses. The user determines focus

with MF lenses, so micro focus adjustment is irrelevant for that glass. And yes, for zooms there may be different optimal

values at different focal length in the range, thus one needs to compromise on an average value, or choose one that

favours a preferred or frequently used length.

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<p>Someone correct me if I am wrong, but the micro focus corrections are for autofocus lenses.</p>

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<p>They should work for focus confirmation as well and I expect that is what Maurizio was trying to adjust.<br>

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Personally, I would not rely on focus confirmation, because it is inaccurate when you're dealing with very thin DOF - I think that is mainly due to the large areas of the focus sensors, but there may be other factors involved.<br>

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The ease with which I can manually focus on mirrorless cameras is why I don't use DSLRs anymore. I recommend to all that are serious about manual focusing to give mirrorless cameras a try.</p>

<p>Several (most?) manual lenses do not send information about their ID to the camera. If the camera do not know what lens you have mounted it follow that it cannot store a specific focus adjustment for that lens. I am however not sure how new the lens must be in order for the camera to be able to know what lens you have mounted.</p>

<p>Best wishes<br>

Frode Langset<br>

(and excuse my English, it is not my native language)</p>

<p>Thanks to all<br>

yes, I was doing this for have higher precision in focus confirmation and this worked on all previous models I owned (K10, K20, K5). The difference is that there you set a manual lens as a common value applying to all, except if it knew the lens, in which case it applied a specific value you defined for that lens.<br>

Here it seems it does not have the possibility to store a value for manual lenses at all. Of course, if with previous cameras you put a correction for a lens and then used another, it might lead to gross errors, but having to set it every time is even more tedious, at least in the past you could note a value for each lens and dial it in when you changed lens, and then the value was applied to all shoots with that lens.<br>

I am not that interested in using manuals, I am gradually selling them, but the 50 f1.4 is still the best lens in terms of resolution I own, and sometimes it comes in handy. Provided it is in focus, that is...</p>

<p> </p>

<p>For the first issue: this is a problem for cameras of all makes as far as I know, the AF fine adjustment applies to all focal lengths. You can adjust it for your most used focal length or to the longer focal length (where DoF is shallower and focus errors will show up more -- assuming max. aperture is same).</p>

<p>For the second issue: did you set the "Apply One" value or "Apply All" value? For manual focus lenses, you should set the "Apply All" value -- unfortunately since MF lenses will not provide an ID to the camera body, one value will apply to all MF lenses.</p>

<p>For your AF lenses (that provide an ID to the camera body), the "Apply All" value will be ignored and "Apply One" value -- this can be set differently for lenses with different IDs -- will take effect.</p>

<ol>

<li>Only AF lenses (Pentax-F and newer) identify themselves uniquely to the camera. Camera knows nothing about adapted or Pentax-K or -M lenses, and very little about Pentax-A lenses (only min/max aperture, and doesn't know anything about zoom setting or whether max aperture changes during zoom). I'm not certain the degree that all third-party lenses identify themselves *uniquely* to the camera either. I've seen terms like "SIGMA LENS" in the EXIF, don't know whether each lens actually has a unique ID or not.</li>

<li><em><strong>I</strong> </em>am not certain whether the micro adjust settings have any bearing on the AF sensors themselves -- this value <em><strong>*may*</strong></em> be applied only when operating the AF motor in which case it would have no affect on manual focus. If you want to experiment with this, change adjust to maximum in one direction and see if you can even tell the difference.</li>

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<p>At any rate I don't this would be very effective anyway -- the focus confirmation in the viewfinder just doesn't seem exact enough that a generalized tweak one way or the other would help. If you really want that level of precision you should probably be focusing using magnified live view. I would give the same advice for AF lenses (it's my understanding that the AF micro-adjust has no effect on contrast-detect AF either).</p>

<p>Just to throw one more wrench into the works, there can be some degree of focus shift as the lens stops down. Phase-detect AF is normally executed with lens wide open. I don't expect the system to take any shift of this kind into account, and furthermore, you'd probably want to fix lens wide open when determining micro-adjust settings if you weren't already.</p>

 

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<p>this worked on all previous models I owned (K10, K20, K5)</p>

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<p>The K10D did not have any focus adjustment option. These settings were introduced in the K20D, I think (I skipped that model). Did you use some modified firmware perhaps?</p>

Seem to remember it was the first Pentax Dslr to have it, only it could memorize only a few lenses