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next PZ lens test report: Canon EF 20mm f/2.8 USM - Printable Version

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next PZ lens test report: Canon EF 20mm f/2.8 USM - Klaus - 10-22-2012

An old lens and it shows:

[url="http://www.opticallimits.com/canon_eos_ff/775-canon20f28ff"]http://www.opticallimits.com/canon_eos_ff/775-canon20f28ff[/url]


next PZ lens test report: Canon EF 20mm f/2.8 USM - youpii - 10-22-2012

[quote name='Klaus' timestamp='1350937082' post='20682']

An old lens and it shows:

[url="http://www.opticallimits.com/canon_eos_ff/775-canon20f28ff"]http://www.opticallimits.com/canon_eos_ff/775-canon20f28ff[/url]

[/quote]



The field curvature of the Tokina 17/3.5 is the worst that I have encountered so far. I had to sell it because of that and it's a pity because it's a very fun lens to play with.


next PZ lens test report: Canon EF 20mm f/2.8 USM - Rover - 10-23-2012

[quote name='Klaus' timestamp='1350937082' post='20682']

An old lens and it shows:

[url="http://www.opticallimits.com/canon_eos_ff/775-canon20f28ff"]http://www.opticallimits.com/canon_eos_ff/775-canon20f28ff[/url]

[/quote]

The second resolution chart was the oddest one I've ever seen.



[quote name='youpii' timestamp='1350937977' post='20683']

The field curvature of the Tokina 17/3.5 is the worst that I have encountered so far. I had to sell it because of that and it's a pity because it's a very fun lens to play with.

[/quote]

Oddly enough, I wanted to buy this lens once, but didn't. Now I want to find one to try it out despite the lack of any need in it (since I have a 16-35 II).


next PZ lens test report: Canon EF 20mm f/2.8 USM - Klaus - 10-23-2012

[quote name='Rover' timestamp='1350976510' post='20685']

The second resolution chart was the oddest one I've ever seen.

[/quote]



That is the nature of field curvature. Interestingly it (the field curvature) gets worse the more you stop down thus resulting in this roller-coaster ride.






next PZ lens test report: Canon EF 20mm f/2.8 USM - Rover - 10-23-2012

[quote name='Klaus' timestamp='1350978227' post='20686']

That is the nature of field curvature. Interestingly it (the field curvature) gets worse the more you stop down thus resulting in this roller-coaster ride.

[/quote]

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:

http://slrgear.com/reviews/showproduct.php/product/80/cat/10

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.


next PZ lens test report: Canon EF 20mm f/2.8 USM - Klaus - 10-23-2012

[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.


next PZ lens test report: Canon EF 20mm f/2.8 USM - Rover - 10-25-2012

[quote name='Klaus' timestamp='1351019239' post='20689']

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.

[/quote]

"Normal" as in "expected and desirable for a lens". I can understand if it's normal for this particular model.



By the way, for the sake of completeness here's another review of this lens. The verdict is unsurprising.

http://slrlensreview.com/web/reviews/canon-lenses/canon-wide-angle/80-canon-ef-20mm-f28-usm-lens-review

By the way, I was bored today so I compared the results with those of the old Nikon 20/2.8 D, and it looked so much better in comparison (of course I didn't compare exact figures, just the resolution bar heights and general impressions), despite being an old design with mechanically dated implementation.