p.1 #1 · FE 16-35mm f/4 ZA field curvature and aperture sweet spots
I while back, I tested my latest FE 16-35/4 ZA (which is a great copy) and wrote down some notes on field curvature, optimal apertures and focusing for it. I hope this may be of interest for owners of this lens.
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At 16mm: (best at f/5 or f/5.6)
f/4: Some field curvature (inwards). Great resolution across the field but not optimum.
At f/5 (sweet spot)
Edges and center look best when focused at the infinity mark.
Field curvature is masked by DOF and lens has sharp edges and center when focusing at the infinity mark.
At f/5.6
Very similar to f/5 with no real improvement towards the edges. Center still looks great.
f/8: More of the same but there is a slight loss of micro-contrast.
So best focusing at 16mm is at f/5.6 or f/8 at *infinity mark.
* This is how my 16-35/4 was calibrated (It may not be the same with your lens). My copy has perfect infinity focus using the camera distance scale. (turning the ring clock-wise until the infinity symbol first appears on screen)
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At 21mm: (best at f/5.6)
f/4: Higher field curvature than 16mm (inwards)
f/5.6: Edges and center look best when focused at the infinity mark.
Field curvature is somewhat masked by DOF and lens has sharp edges and center when focusing at the infinity mark. (edges and mid-field look weaker if focusing in the center)
f/8: Not much change from f/5.6 to f/8 except for a slight loss of center micro-contrast.
So best focusing at 21mm is at f/5.6 or f/8 at *infinity mark. (same as 16mm)
* turn the ring clock-wise until the infinity symbol first appears on screen.
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At 28mm: (best at f/6.3)
f/4: Higher field curvature than 21mm (inwards)
f/5.6: Edges and center look best when focused at the infinity mark.
Field curvature is somewhat masked by DOF and lens has sharp edges and center when focusing at the infinity mark. (edges and mid-field look weaker if focusing in the center)
f/8: extreme edges look slightly better for there is a slight loss of micro-contrast in center and mid-field. A compromise for best micro-contrast in center and better extreme edges is f/6.3.
So best focusing at 28mm is at f/6.3 or f/8 at *infinity mark.
* turn the ring clock-wise until the infinity symbol first appears on screen.
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At 35mm: (best at f/9)
f/4: Strongest field curvature. There is also a general contrast loss.
f/5.6: Does not completely mask field curvature. Contrast improves. Edges and center look best when focused at the infinity mark.
Field curvature is somewhat masked by DOF and lens has sharp edges and center when focusing at the infinity mark. (edges and mid-field look weaker if focusing in the center)
f/8: Best aperture for 35mm. Edges and Center regain contrast, field curvature is masked and there is strong corners, mid-field and center.
f/11: There is a slight improvement at the extreme edges in exchange for micro-contrast in the center and mid-field.
So best aperture at 35mm is at f/8 or f/9 (slight better corners) at *infinity mark.
* turn the ring clock-wise until the infinity symbol first appears on screen.
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NOTES:
Summary of best apertures as far as masked field curvature and optimum sharpness across the field:
p.1 #6 · FE 16-35mm f/4 ZA field curvature and aperture sweet spots
Interesting, I've always had the best results around the 18m mark for 35mm as far as edges go. I wonder if the tough E mount adapter being a little thicker causes it to hit the focus a little sooner?
I've noticed at 35mm the autofocus isn't all that reliable for infinity at least on my a7r, but the lens is pretty easy to manual focus so I do that most of the time
p.1 #7 · FE 16-35mm f/4 ZA field curvature and aperture sweet spots
trogdon wrote:
Interesting, I've always had the best results around the 18m mark for 35mm as far as edges go. I wonder if the tough E mount adapter being a little thicker causes it to hit the focus a little sooner?
I've noticed at 35mm the autofocus isn't all that reliable for infinity at least on my a7r, but the lens is pretty easy to manual focus so I do that most of the time
I removed the distance settings from my notes as this can be confusing. From my experience, each copy behaves differently and I have tried many 16-35/4 copies. What is surprising on my current 16-35/4 copy is how precise the 'digital' hard stop is which is not the case with other 'focus-by-wire' lenses I have.
p.1 #8 · FE 16-35mm f/4 ZA field curvature and aperture sweet spots
Fred Miranda wrote:
I removed the distance settings from my notes as this can be confusing. From my experience, each copy behaves differently and I have tried many 16-35/4 copies. What is surprising on my current 16-35/4 copy is how precise the 'digital' hard stop is which is not the case with other 'focus-by-wire' lenses I have.
After a previous conversation with Fred about the "digital hard stop" I've been doing tests; roughly speaking I'm finding my Batises and FE lenses to have remarkably accurate infinity stops *as long as you stop turning as soon as the infinity sign appears* as your focus from near to far.
Less roughly I've done enough comparisons of the FE 1.4/35 to be sure that focussing on infinity that way is *as or more accurate* than carefully focussing with magnified view. Don't know why I started on that lens, which I almost never use at infinity! Batis 18-25-85 to come....
p.1 #9 · FE 16-35mm f/4 ZA field curvature and aperture sweet spots
DavidBM wrote:
After a previous conversation with Fred about the "digital hard stop" I've been doing tests; roughly speaking I'm finding my Batises and FE lenses to have remarkably accurate infinity stops *as long as you stop turning as soon as the infinity sign appears* as your focus from near to far.
Less roughly I've done enough comparisons of the FE 1.4/35 to be sure that focussing on infinity that way is *as or more accurate* than carefully focussing with magnified view. Don't know why I started on that lens, which I almost never use at infinity! Batis 18-25-85 to come....
It works that way with my 16-35/4 and 55/1.8. However, I tested my Batis 85/1.8 and the "digital hard stop" was away off!...
p.1 #10 · FE 16-35mm f/4 ZA field curvature and aperture sweet spots
Fred Miranda wrote:
It works that way with my 16-35/4 and 55/1.8. However, I tested my Batis 85/1.8 and the "digital hard stop" was away off!...
Curses! It seems fine on the B25 and B18, though I need to look more closely....
I wonder if it's just the focal length magnifies the error, or is the error too gross for that?
EDIT
Hmm. I did a bit of testing with the B85; seems to be often OK but a bit erratic.
Sometimes as you focus you get 825metres and then infinity; if that happens it seems to be accurate.
At other times the last distance you get is 589metres, in that case when infinity comes it seems to be just short of infinity.
At first I thought it was just down to how slowly I rotated the dial; but I don't think that's it. At infinity distances the FBW on this lens doesn't seem great (I don't mind it at all at portrait distance, though I usually use AF there). Luckily I don't use the Batis at infinity much....that's a job for ZM
p.1 #11 · FE 16-35mm f/4 ZA field curvature and aperture sweet spots
I don't think it's magnification. It's more like variation. My Batis 85 was way off, just like some 16-35/4 copies I've tried.
It's nice when a lens is well calibrated for the digital hard stop. Lucky it's my 16-35 since I use it mainly for landscapes.
DavidBM wrote:
Curses! It seems fine on the B25 and B18, though I need to look more closely....
I wonder if it's just the focal length magnifies the error, or is the error too gross for that?
p.1 #12 · FE 16-35mm f/4 ZA field curvature and aperture sweet spots
Fred Miranda wrote:
I don't think it's magnification. It's more like variation. My Batis 85 was way off, just like some 16-35/4 copies I've tried.
It's nice when a lens is well calibrated for the digital hard stop. Lucky it's my 16-35 since I use it mainly for landscapes.
Just added this to the previous:
Hmm. I did a bit of testing with the B85; seems to be often OK but a bit erratic.
Sometimes as you focus you get 825metres and then infinity; if that happens it seems to be accurate.
At other times the last distance you get is 589metres, in that case when infinity comes it seems to be just short of infinity.
At first I thought it was just down to how slowly I rotated the dial; but I don't think that's it. At infinity distances the FBW on this lens doesn't seem great (I don't mind it at all at portrait distance, though I usually use AF there). Luckily I don't use the Batis at infinity much....that's a job for ZM
p.1 #14 · FE 16-35mm f/4 ZA field curvature and aperture sweet spots
DavidBM wrote:
Just added this to the previous:
Hmm. I did a bit of testing with the B85; seems to be often OK but a bit erratic.
Sometimes as you focus you get 825metres and then infinity; if that happens it seems to be accurate.
At other times the last distance you get is 589metres, in that case when infinity comes it seems to be just short of infinity.
At first I thought it was just down to how slowly I rotated the dial; but I don't think that's it. At infinity distances the FBW on this lens doesn't seem great (I don't mind it at all at portrait distance, though I usually use AF there). Luckily I don't use the Batis at infinity much....that's a job for ZM ...Show more →
These distance numbers seem a little aleatory and change depending on the lighting. Hopefully the digital distance will be improved with a newer body.
p.1 #15 · FE 16-35mm f/4 ZA field curvature and aperture sweet spots
Schlotkins wrote:
Still hoping the 16-35 gm is killer Fred lol
Perhaps the new 16-35GM won't be as big as many anticipate. The ultra-wide and wide field of view can take advantage of the short flange distance (something the 24-70GM could not)
p.1 #16 · FE 16-35mm f/4 ZA field curvature and aperture sweet spots
Just seeing this now. Great information from everyone. After the GM version comes out, I'm hoping the used F4's will be abundant and less expensive than they are now.
I'm planning on using the 16-35 F4 for Real Estate. Does anyone here have experience with this particular lens for Real Estate photography? If so, how well do you like it? Or would you recommend any other lenses over this one?
