16-35 f4: Mostly likely cause of soft Left & Right Edges?

Started 3 months ago | Questions thread
Doppler9000 Regular Member • Posts: 313
Re: 16-35 f4, in Infrared vs. Sony 10-18 f4 in visible light

nkistrup wrote:

Doppler9000 wrote:

Igor Sotelo wrote:

nkistrup wrote:

Agreed that wide lengths will suffer more from edge softness. But still think the Canon 16-35 should be doing better.

Took a photo w. the Canon @ f11, vs. f8 for the Sony (DoF should be the same); Canon shot at 16mm, Sony at 11mm, which should be close. Here are the results:

Sony 10-18 f4

Canon 16-35 f4

In both cases, cropped the lower right 1200x1200.

Canon is definitely softer. So back to my original question: Is the Canon lens a poor copy, or Does it suffer from softer edges in infrared?

Lenses for APS-C are smaller and less expensive to make and easier to make sharp at the edges.

The trade of using cropped sensors however, is lower high iso performance, and a stop less of subject isolation compared to FX.

Exactly. In addition, it is an entirely different lens, so the comparison provides no insight.

I think you will need to compare the lens to a known good copy of the same lens, and/or use the lens on a FF visible spectrum camera to gain insight into what is causing the issues you see.

Decided to reach out to Life Pixel, who sold me the converted A7iii body. Infrared is the culprit ==>

"... edges are soft for all wide angle and super wide angle lenses on any converted camera due to barrel distortion."

Conclusion: Another copy of the lens might be a little sharper. Fighting another quirk of infrared photography, so my options are:

  1. Search for a group of wide primes. So far, only the Irix 15mm has both the sharpness & is IR hot spot free.
  2. Scrap the idea of going wide in IR.
  3. Stop pixel peeping & live with it.

Thanks to both you & Igor for chiming in.

The issue might be both the camera and the lens, it still might be worthwhile checking the lens.

Here is a Flickr image, among others, from the 16-35mm 2.8 in IR.  This is on a GFX, which has a diagonal about 28% longer than a FF frame, so this might be a lens to look at.


I use the EF S 10-18mm which is pretty great in IR, on my 850nm converted Fuji X. I’m sure it would vignette on FF, but it might give you enough FOV. I haven’t peeped the corners, however.

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