[Guest]

Hi Klaus & others,

 

Would it be possible to introduce a metric for field curvature in your tests, so that one can estimate how strong the effect actually is?

 

There is a concrete background to my question; I currently use the EF-S 15-85 on APS-C and the field curvature almost rules out this lens for scenery where there is relevant detail in the corners.

 

Now I am contemplating the EF 24-105 3.5-5.6 STM for a FF setup, but in your review I read about field curvature being "significant and noticeable". Now I am of course wondering how bad it really is. If it is as bad as my 15-85, I would definitely not buy such a lens.

 

Could you think of any way to express field curvature as a number, or quantify it otherwise?

 

If not, perhaps one could include sample pictures in future reviews that are taken with the following method: focus on a far-away subject with the center AF point; take a shot; then disable AF and recompose; take four more shots, recomposed, showing the focused subject in one of the four corners of the frames each time. This would also give an impression of the centering quality of that particular lens sample. While the centering may not be representative for other samples, this procedure would give a good impression of field curvature as well; something like the average over all 4 corners.

 

Then of course for a zoom, one would want these samples at different focal lengths, so it is getting a bit tedious. ;-)

 

But perhaps someone with better background in optics could think of a more scientific metric for curvature of field?

 

Thanks & best regards

 

Tom