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 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.
http://flickr.com/ephankim
[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).
[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.
10-23-2012, 04:00 PM
(This post was last modified: 10-23-2012, 04:02 PM by Rover.)
[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.
10-23-2012, 07:07 PM
(This post was last modified: 10-23-2012, 07:09 PM by Klaus.)
[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.
10-25-2012, 06:07 PM
(This post was last modified: 10-25-2012, 06:10 PM by Rover.)
[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.
