Front Focussing of Sigma 24mm/1.8, Nikon 85mm/1.8 and Tamron 17-50mm/2.8

Surprise, Surprise! Got my Sigma 24mm back (remember the quick comparison with a Tamron 17-50 a few weeks ago). A professional photographer bought it and returned it a few weeks later, because of focussing issues. He suspected that it might suffer from Front Focussing. This is a problem with some third party lenses, where the autofocus focusses a point in front of the object and not exactly the object plane.  A short explanation and a quick test can be found at A more thorough test procedure is here. So I tested the Sigma and the two other lenses I own with the quick prodedure on my Nikon D80. This procedure also reveals tendencies of chromatic aberations in the defocus areas.

The Nikon 85mm/1.8 focusses perfectly fine, but shows strong vertical chromatic aberrations in the defocus areas: Green behind the focussing plane and magenta in front. The Tamron 17-50mm/2.8 focusses well, with – maybe – a slight tendency towards back focussing. There is nearly no chromatic aberration. The Sigma shows a clear front focussing affect and mild chromatic aberations.

Have a look at the test images:

Nikon Nikkor 85mm/1.8

Sigma 24mm/1.8 EX DG Macro

Tamron 17-50mm/2.8


No comments yet

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: