[neal_grillot]

I shoot a lot in portrait (rather than landscape).
according to the e-book, the elongated AF points at the far left and right of the viewfinder are vertical linear sensors and detect the sharpest horizontal points only.
In portrait mode, does it stand to reason that these points would detect the sharpest Vertical point? ...
and are these AF points as accurate as the cross-hatch type?

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Last edited by neal_grillot; 05-14-2018 at 04:35 PM.

[enoeske]

I shoot a lot in portrait (rather than landscape).
according to the e-book. The elongated AF points at the far left and right of the viewfinder are vertical linear sensors and detect the sharpest horizontal points only.
In portrait mode, does it stand to reason that these points would detect the sharpest Vertical point? ...
and are these AF points as accurate as the cross-hatch type?

I don't believe they only detect the sharpest horizontal or vertical points. Only that the AF point its self is not a cross type point. Its less sensitive and less accurate than the other cross type AF points.

[neal_grillot]

I should add this is in reference to a K-1 Mark II

[enoeske]

I should add this is in reference to a K-1 Mark II

There is no different between a linear af point or cross type af point in the K-1 vs any other model camera.

This article explains the difference pretty well Canon DLC: Article: Canon Autofocus Series: What Is Cross-type AF?

[MarkJerling]

I shoot a lot in portrait (rather than landscape).
according to the e-book. The elongated AF points at the far left and right of the viewfinder are vertical linear sensors and detect the sharpest horizontal points only.
In portrait mode, does it stand to reason that these points would detect the sharpest Vertical point? ...
and are these AF points as accurate as the cross-hatch type?

Yes, and maybe.

Basically, a + sensor is good at obtaining focus on any linear textured object while a - sensor can only focus well on vertical or horizontal lined objects, depending on the orientation of the object and sensor. It goes without saying that, for irregular textured objects, this discussion hardly matters. The - sensor would be as good as the + sensor.

This is why, in the old days, when Pentax cameras like the SFX and SFXn only had one AF focus point, and the photographer tried to focus on a linear texture like a corrugated iron roof surface, or a weatherboard wall, then, in some cases, the camera more easily obtained focus if you turned the camera to vertical, obtained focus and then recomposed your image.

So, yes, if you're shooting objects / scenes with strong linear patterns, then, yes, altering the orientation of the camera will allow those - points to obtain focus more easily. In practice though, we're now spoilt for choice with modern cameras having multiple focus points and the need for such acrobatics has gone away!

Those - points are no less accurate than the + points - it's just that the + points are better at finding focus on a wider range of surfaces.

[neal_grillot]

Ok. So in portrait orientation, would you use the (-) or the furtherest upper (+) to best focus on the eye.. also speed matters as the subject could be moving

[MarkJerling]

Ok. So in portrait orientation, would you use the (-) or the furtherest upper (+) to best focus on the eye.. also speed matters as the subject could be moving

I can't find information specific to the K-1II, but for the K-1, the information I can find seems to suggest that the three central AF points may provide greatest accuracy when used with specific lenses.
See Features5 | PENTAX K-1 | RICOH IMAGING

Theoretically at least, any of the 33 AF points would be equally good at focussing on eyes. I would suggest that you experiment with the different AF modes and find one that suits your subject matter. What I'm saying is that, other than the three central points, any of the other 30 would be equally good, so, as to the choice between the two you suggest, I can't offer a suggestion as to which would be "better". Depending on the conditions you're shooting under, you may wish to make choices based upon that. Moving subject matter and all.

Which of these settings do you use?

Attached Images

 

[neal_grillot]

I can't find information specific to the K-1II, but for the K-1, the information I can find seems to suggest that the three central AF points may provide greatest accuracy when used with specific lenses.
See Features5 | PENTAX K-1 | RICOH IMAGING

Theoretically at least, any of the 33 AF points would be equally good at focussing on eyes. I would suggest that you experiment with the different AF modes and find one that suits your subject matter. What I'm saying is that, other than the three central points, any of the other 30 would be equally good, so, as to the choice between the two you suggest, I can't offer a suggestion as to which would be "better". Depending on the conditions you're shooting under, you may wish to make choices based upon that. Moving subject matter and all.

Which of these settings do you use?

Spot: focus and recompose. Select. Still experimenting with the area selections under Continuous.

[Adam]

I shoot a lot in portrait (rather than landscape).
according to the e-book, the elongated AF points at the far left and right of the viewfinder are vertical linear sensors and detect the sharpest horizontal points only.
In portrait mode, does it stand to reason that these points would detect the sharpest Vertical point? ...
and are these AF points as accurate as the cross-hatch type?

Yes, if you rotate the camera then the line sensor will be sensitive to lines at the new orientation.

[pentaxfall]

I think linear means AF compares X against its right-left neighbors only, where as cross-type compares against top-bottom-left-right neighbors. Visualizing it as grid makes it easy to understand.

[clackers]

I think linear means AF compares X against its right-left neighbors only, where as cross-type compares against top-bottom-left-right neighbors. Visualizing it as grid makes it easy to understand.

I don't think they ever compare against neighbours to achieve focus, Pentaxfall.

They compare one end of the 'focus point' pixels to the other.

Think of split focus or a rangefinder.

[beholder3]

I shoot a lot in portrait (rather than landscape).
according to the e-book, the elongated AF points at the far left and right of the viewfinder are vertical linear sensors and detect the sharpest horizontal points only.
In portrait mode, does it stand to reason that these points would detect the sharpest Vertical point? ...
and are these AF points as accurate as the cross-hatch type?

Yes, they are definitely vertical sensors. Vertical sensors can only detect a contrast edge if there is a vertical change to contrast, e.g. horizontal black and white stripes.
It would have issues with vertical stripes.

In theory "accuracy" of finding the correct focus plane should be the same. But that is hindered by such a sensor having only half the chance of finding the right and a good contrast edge to base measurments on.

Personal opinion: avoid normally, unless really needed.

Comment: Canon DualPixel AF and Sony on sensor detect AF does only have horizontal line sensors, not a single cross type.

[beholder3]

The text is only in German, but I think the following slides might help understand:



and