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04-29-2016, 03:57 PM - 1 Like   #1
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Testing the D FA35/3.5

I've spent a couple of weeks getting acquainted with my new D FA35/3.5 on the 645Z.

My focusing, DOF, diffraction, and field curvature analysis for my copy were very favorable for this lens. I no longer have the A35 to compare, however, I find no fault in the DFA35 in performance.

I do not have sophisticated analysis equipment for visualizing the field curvature, but using an angled view of a grid pattern and rocking the focus with peaking on at wide open aperture, after awhile, revealed the in-focus field to me. At very near distances, the edges curve slightly forward of the center point/focus plane. This is a range I would never use with this lens. At a near-mid field focus point, it looks fairly straight. Then at far-mid focus distance, the curve shifts backward, such that the edges are in focus slightly behind the plane of focus. I find this quite acceptable for landscape work and it mimics my A45 almost exactly in this behavior.

The sweet spot for sharpness for every test (blindly scored), near to far focus distances, was always at f/5.6, dropping off beyond f/9 and unsharp by f/14. Obviously, if there are foreground objects nearer than 15 ft, I need to balance diffraction with DOF. I generally focus bracket for near foreground anyway, to maximize sharpness with a large DOF. I do this with the 25mm up through the 55mm

Contrast and micro-contrast appear to be very good, better than I remember from the A35, perhaps a result of modern coatings.

I did not have an opportunity to test flare and internal reflection, but should get out at sunrise one day this week to put it to the test.

In short, I am impressed with the DFA35 and find it an improvement from what was my favorite lens in the bag, the A35.

---------- Post added 04-29-2016 at 04:25 PM ----------

I wouldn't know how to share full rez DNG test images here, but if you want to see anything in particular, just pm me and I can maybe do a Dropbox for you.

Here is a processed final image(2 exposure composite with a 2 shot focus stack(near/far)), which represents my practical application of the lens:

Pilings At Twilight III
645Z & D FA35/3.5

04-29-2016, 05:51 PM - 1 Like   #2
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Awesome mate, makes me think my copy was possibly not too good. Damn.
05-01-2016, 06:21 PM   #3
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makes me think the copy variation is a bit shall we say sigma like, because mine is clearly sharpest at f/10 (but still very good before that)
05-01-2016, 07:30 PM   #4
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QuoteOriginally posted by gavincato Quote
makes me think the copy variation is a bit shall we say sigma like, because mine is clearly sharpest at f/10 (but still very good before that)
my center sharpness peaks at f/5.6
edge sharpness continues to improve to f/8-f/11 as DOF increases.

05-02-2016, 09:48 AM   #5
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Here's a close range test showing center vs. corner performance. I used a 60"(diag) LCD TV (approx 50" width depicted in images) to run a test chart, mainly to compare the edges and corners to the center.

Here is the chart itself:

DFA35mm @ f/5.6

Here are the f/5.6 crops comparing center to 4 corners:



You can see the corners are not quite in focus at f/5.6, but become sharp by f/8, seen here:



* illumination of the monitor screen was uneven causing the corners to be darker; no conclusions may be drawn beyond relative sharpness of center to corners (that is, no comparison of brightness, color and contrast is implied)
* i detected no visible astigmatism in the areas between center and edges.

Yesterday, I shot a series, focusing at ~10ft, for all apertures. I then examined the f/3.5 image at 100% and blindly applied black dots at the sharpest regions(by eye). Zooming out revealed a pattern which matches the same field curvature pattern I got in my focus peaking grid test.
Here are two examples, one at f/5.6:


and another at f/11 (showing infinity objects in focus):


*the grass area is not flat; it has some subtle mounding, which influences the test a little.
* intended focus point is a small white rubber eraser near the center of image
*for larger viewing, a section of the foreground was cropped out
05-02-2016, 12:58 PM - 1 Like   #6
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That is pretty much awesome as far as I can tell from the lowres reproduction of these pics in the forum. mine seems to be decentered a bit in one corner...
thanks so much Mike for posting this
cheers
Z
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