SEL20F28 impresses and puzzles at the same time

Started Apr 10, 2013 | Discussions thread
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blue_skies
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SEL20F28 impresses and puzzles at the same time
Apr 10, 2013

In the next post, I'll show some images, but first something that still stumps me.

I used a tripod, and remote to capture a series of images of different scenes.

Only the CV21 was focused manually, the others were E mounted and were focused using AF.

With the remote, each shot is re-focused. Remote shutter is different from a normal shoot, as that it complete refocuses before the shot - a normal shot will go from the pre-focus position.

Anyways, I see consistent differences with the E20 and the S19, in that the E20 front-focuses (more sharpness in foreground), and the S19 back-focuses (more sharpness in background). This happens in different scenes at different apertures. (I shot in JPG+RAW, but only looked at the JPG results).

Also, there was little wind at times, and this could perhaps also explain some of the weirdness, although, I used the Nex-7 and a Nex-6 for this, and both cameras show identical behavior. E.g. I have a shot where the E20 focuses very sharp at the left edge, but not at the foreground, whereas the S19 focuses sharp on the foreground, but not at the (very) left edge.

DOF does not explain this. Camera (tripod?) and possibly decentering perhaps, but for now, I am betting on in-camera lens corrections that may have a hand in this (straightening of lines), and are caused by the different optical formulas of both lenses.

Also, I am convinced that the center resolution in CDAF causes the two lenses to pick a slightly different focus point. The E20 seem sharper in the center, and picks a better focus point than the S19, given DOF in the shots I considered.

I have to go back and try some more differences (I have 2 S19, 1 E20, 2 E16, 2 ECU1 - as I am splitting the sets - one set will be a gift) when I have time to make some more comparisons.

Aside from this strange quirk, I find the E20 and S19 fairly comparable. The E20 does seem a tad softer at the corners, but it seems sharper in the center.

I wonder what RAW processing yields ...

  • Different lenses (E16, S19, E20, CV21, E24) f/2.8 images in next thread, down-sampled to 16Mp.

Quirks highlighted below:

Scene 2 - tripod setup

Scene 2 left edge - E20 on left, S19 on right

Scene 2 bottom right far corner - E20 on left, S19 on right

Scene 2 center - E20 on left, S19 on right.

Scene 1 - E20 on left, S19 on right - clearly visible that E20 front-focuses and S19 back-focuses

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Cheers,
Henry

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