[quote name='Rover' timestamp='1351008055' post='20688']
Yeah, I'm pretty sure this isn't a normal behavior... SLRGear review was pretty much in line with your findings and they specifically mentioned field curvature:
[url="http://slrgear.com/reviews/showproduct.php/product/80/cat/10"]http://slrgear.com/r...oduct/80/cat/10[/url]
Interestingly, their graph shows the lens sharpness to decrease slightly when going from f/5.6 to f/8, though it's nowhere near as wicked as what you've found.
[/quote]
This is normal.
I would be very surprised if slrgear performed tests on a flat plane rather than on the focus field. This would be naive testing (of defocused zones). Manufacturer MTFs are also provided based on the focus field.
Yeah, I'm pretty sure this isn't a normal behavior... SLRGear review was pretty much in line with your findings and they specifically mentioned field curvature:
[url="http://slrgear.com/reviews/showproduct.php/product/80/cat/10"]http://slrgear.com/r...oduct/80/cat/10[/url]
Interestingly, their graph shows the lens sharpness to decrease slightly when going from f/5.6 to f/8, though it's nowhere near as wicked as what you've found.
[/quote]
This is normal.
I would be very surprised if slrgear performed tests on a flat plane rather than on the focus field. This would be naive testing (of defocused zones). Manufacturer MTFs are also provided based on the focus field.