Autofocus questions (live view, viewfinder, etc)

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Brueghel
Brueghel Contributing Member • Posts: 688
Autofocus questions (live view, viewfinder, etc)

Not being always happy about the sharpness of my photos, I decided to follow photographylife’s quick test for autofocus issues (written by Nassim Mansurov). The equipment first tested is a D7100 with the 16-80 lens tested at max aperture F/3.3, focal length 35mm.

I am not going to post the results given the size of the RAW files but I discovered (by mistake) some strange things (I am uneducated in these matters):

The results with “Focal plane contrast AF” (live view) and “Phase detection AF, single servo AF-S” (view finder) were very close even at 200 % zoom. Hard to distinguish them… That was good news. Ooof my investment in the 16-80 was not a mistake….

But I had perplexing news too: By mistake I took my first shots with Continuous servo, i.e. “Phase detection AF, single servo AF-C”. At 100% the difference could be distinguished with the S version. It took some looking though…. But at 200% the difference is clear the S version has much better focus than the C version.

Wonder how this translates in regular pics. Probably hard to see on a print.

What I find puzzling is that not only is the C version not as good, but the black color is washed out.

Then I tried out the same with the 35mm 1.8. A much loved lens. The results were quite bad. The C version is not as sharp as the S version by far but there is a lot of color aberration (black turning to red…). Pretty sure the difference does show in a print version.

If I did not make a mistake then I can draw a few conclusions:

- If the subject is really still, use Live View!

- If the subject is not moving much, then make sure to use AF-S!

- The much decried 16-80mm DX lens does better at 35mm than its famous little fixed 35mm brother which should not be used with the AF-C setting

- I should study the settings more carefully. May be this will improve the technical quality of my pictures more than buying the (excellent) D7500

Am I discovering well known facts ? Am I making a mistake (or mistakes) somewhere ? Is this to be expected ?

 Brueghel's gear list:Brueghel's gear list
Nikon D7100 Nikon AF-S DX Nikkor 35mm F1.8G Nikon AF-S DX Micro-Nikkor 85mm f/3.5G ED VR Nikkor AF-S 300mm f/4E PF ED VR Nikon AF-S DX Nikkor 16-80mm F2.8-4E ED VR
Nikon AF-S DX Nikkor 16-80mm F2.8-4E ED VR Nikon D7100 Nikon D7500
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MOD Mako2011
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