Absolutely stunning performance

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kenw
kenw Veteran Member • Posts: 5,512
Absolutely stunning performance
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This lens got mixed reviews on release and more than one reviewer did note their lens was "decentered" to some degree meaning one or more corners/edges were softer than the other side. This is of course depending on the degree a manufacturing defect and not something you want hear.

I recently purchased a 14-30 and so wanted to immediately test it for any decentering. One must have reasonable expectations here as a zoom will almost always show some, especially in the extreme corners, at some part of its zoom range.

The test I used is similar to that described on Jim Kasson's blog here:

https://blog.kasson.com/lens-screening-testing/

Basically it is to put a Siemens Star target at a good distance from the camera and shoot the target at the center and the corners.  In Kasson's case he makes it totally idiot proof by putting the camera so far away that the center and corners will all be within the DoF when you recompose to put the target in the corners.  This requires a very large target and often extreme distances from the target.  My test is similar except to keep the shooting distance reasonable for indoor work I calculate how much to change the target distance when moving from the center to the corners.  I do not refocus on the target after the distance change.  Thus I'm still testing for a flat field but don't have to be at outdoor distances to do this.  I just need to do a little math in a spreadsheet to get the distances correct for flat field testing.

I shot at 14mm, 20mm and 30mm.  I shot at F4 (wide open) and F11 (a typical aperture for landscape work).  I shot both 75% of the way to the corners and at the extreme corners.

Test was on a Z7 shooting RAW and processed in Adobe Lightroom.  No vignetting correction was applied.  In order to view the results similar to how I would shoot a landscape the "Detail" tab settings for "Sharpening" were set to my typical starting point which is Amount 50, Radius 0.8, Detail 80.

I'm pretty blown away by the results:

F4 Top row 14mm, middle 20mm, bottom 30mm.  Center and 75% towards each corner.

F11 Top row 14mm, middle 20mm, bottom 30mm.  Center and 75% towards each corner.

F4 Top row 14mm, middle 20mm, bottom 30mm.  Center and absolute extreme corners.

F11 Top row 14mm, middle 20mm, bottom 30mm.  Center and absolute extreme corners.

These are 100% crops from a 45MP sensor.  Note in the F4 shots the lens is resolving so well we are actually still seeing some Moire in the extreme corners.  At F11 the entire field including the extreme corners is essentially diffraction limited.

We can see the heavy vignetting at 14/4 which is not a surprise and reported elsewhere.

For the extreme corners the stars are not perfectly centered because it is extremely difficult to position precisely.  For the shots 75% to the corner I repositioned the crops slightly to center each star but for the extreme corners I wanted to keep the crops on the exact corner.

If you aren't familiar with how these kinds of tests should look check out the link above where Jim has a whole bunch of sample lens tests.

In my book this is pretty phenomenal performance.  The field appears to be nearly perfectly flat and this testing is far enough from the target (200 times the focal length) to likely represent infinity performance closely.

Perhaps I got extremely lucky with my "copy" of the lens.  Whatever the case my expectations were exceeded by a wide margin.  This is amazing good and consistent performance across the entire field.  I'm very happy with the lens!

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Ken W
See profile for equipment list

 kenw's gear list:kenw's gear list
Sony RX1 Panasonic Lumix DMC-G1 Panasonic Lumix DMC-GM1 Olympus E-M5 II Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS +34 more
Nikon Nikkor Z 14-30mm F4 S
Wideangle zoom lens • Nikon Z
Announced: Jan 8, 2019
kenw's score
5.0
Average community score
5.0
Nikon Z 14-30mm F4 Nikon Z7
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