SEL20F28 impresses and puzzles at the same time

Started Apr 10, 2013 | Discussions thread
OP blue_skies Forum Pro • Posts: 11,122
Re: Do NOT use AF in Lens Test. ReShoot with Peaking in MF. Fix that Focus

007peter wrote:

blue_skies wrote:

I 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.

Sound like wrongly focal point between each lens swap

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.

You should have DISABLE IN CAMERA CORRECTION to reduced outside factor (cpu/in camera software corner sharpening) that is ruining your test results

Let the chips fall where they may. Don't HIDE or MAKE EXCUSE for Sony.  Please show each lens "raw & uncorrected" image.  This is the only way we can compare a lens optics.

Otherwise, we never know if Sony is sharper due to in-camera-corner-sharping as part of its software corrections, or as your own result show, make it worst and produce mushy corners.

Either way, your test is ruin by enabling the in-camera-correction

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 cannot say which is lens is sharper because as you indicated, CDAF shoot different AF points after each lens swap.  The only valid way to compare lens is to MANUAL FOCUS with peaking.  This way, you take the "AF ERROR" out of the testing equation

I'll look forward to your re-shoot.  The current results are invalidated and I cannot form any conclusion when I doubt the test results itself.

Although I agree with you, I did this test to quantify the differences in my preferred workflow - which is AF with E-mount lenses, using JPG capture. I do use DMF a lot when snapping around, to make sure focus is critically adjusted, but with the Nex-6 I am more inclined to rely on AF in social settings than with the previous Nex cameras.

Also, with FL around 20mm, I did not expect AF to be critical - the DOF is already larger than that of longer FLs.

I am sure that there will be more comparisons - I did expect the S19 to be optically stronger than the E20, meaning that the E20 relies on software correction or lens profiles. Showing this in the RAW has no value to me - I would still compare the difference after post (meaning that I would need a E20 lens profile which not yet exist). To me the post-edit, or OOC JPG, are most meaningful.

This does bode for both the S19 and S30, they are two impressive lenses, and definitely a must have for sharpness.

But I plan to use the E20 in lieu of the E16 to make for a very compact Nex setup.

I am satisfied that the E20 yields acceptable images. I did not upload f/8 images, but I can already confirm that both the S19 and the E1650P beat the E20 in sharpness at the edges for sure.

The CV21 seems to be the sharpest overall, but it is in the center only, and this lens has the most field curvature, so it is a dichotomy, if edge-to-edge sharpness is desired, it is not a stellar lens. The odd thing is that the E20 seems to mimic some of the CV21's behavior: sharp center and soft corners/edges.

Performance wise, I would rank these lenses as follows:

  1. S19
  2. E1650 (at 20mm) (f/4)
  3. CV21 (f/4)
  4. E20
  5. E16

Size-wise, this list is of course inverted Both the CV21 and the E20 seem to suffer from field curvature. Neither are as bad as the E16, but the effect is more noticeable than on the E1650 or the S19, and it never really goes away.

At first, I thought that it was DOF related (2mm extra makes a difference), but the S19 remains sharp at said corners and edges.

I was hoping for a (much) closer gap between the S19 and the E20 (after corrections), but it is what it is. I guess the S19 will live on in the camera bag, yet I somehow expect the E20 to see more (social) action.

For landscape and architecture type of shots, I would definitely take the S19!

The lens that impresses me more and more is the E1650P - with the lens corrections applied it does rival the Sigmas for sharpness, both at 20 and at 30mm settings. (Note - I did not disable the OSS on the tripod, ah well.)

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