The strangest things about these AF experiments are:
1. Front-focusing on LiveView, which (I thought) sought to maximize the
contrast of the image on the sensor, and thus should be IN FOCUS regardless of
the lens in use; and
2. The 16-45 front-focusing with LiveView, and back-focusing with viewfinder AF.
Thoughts?
Rick
On Mar 17, 2016, at 10:57 PM, Igor PDML-StR wrote:
>
> Larry,
>
> I do not know what is _typical_ for different Pentax cameras and lenses, but
> from the general point of view, I fully agree with what David wrote.
>
> Think about it this way: you have a set of deviation parameters
> for the camera C1= {c1, c2, c3,c4, c5... }, and then a set of "coupled"
> (sort of "reciprocal") deviations for the lens L1= {l1, l2, l3, l4, l5, ...}.
> The number you get for each lens is an average number that sort of minimizes
> the combined deviations {(c1,l1),(c2,l2), (c3,l3),...}.
> Since each of those individual parameters are essentially random,
> for a different set C2, the way you will need to minimize the combined
> deviations C2*L1 could be very different from that for C1*L1.
>
> So, in general, yes, for the best result, you want to calibrate each lens on
> each camera.
> However, I suspect that there will be some correlation. So,
> your first scenario of calibration will give (with some good probability)
> the result that on average [over all your lenses] is better than
> in case you haven't adjusted the calibration at all.
>
> Igor
>
>
> David Parsons wrote on Thu Mar 17 22:19:46 EDT 2016:
>
> The adjustments would only be similar if the two cameras were
> absolutely the same. Tolerances will be different from body to body
> and lens to lens, so you'd want to calibrate each lens to each body.
>
> On Thu, Mar 17, 2016 at 7:03 PM, Larry Colen wrote:
>
>> I have been thinking of posting a related question. When you determine the
>> per lens focus adjustment for a lens on one camera, does that number tend to
>> work on another camera, perhaps with a slight offset.
>>
>> For example if on camera 1 you have
>> lens A +5
>> lens B +2
>> lens C -1
>>
>> would you use the same numbers? Or if lens A works out to be +4, could you
>> assume that the corrections would be
>> lens A +4
>> lens B +1
>> lens C -2
>>
>> Or do they end up just being totally random?
>
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