http://www.lens-scape.com/article/zf21-2.jpg
Flare control is very good, way better than the CY21 and the Nikon 14-24. What u see is is a deliberate attempt to create the flare. The shape of the flare is very nice and I love it! Can be used it creatively. I don't detect any CA here.
Jman13 wrote:
How does the resolution compare to the C/Y 21? Also, any reason you didn't wait for the ZE?
I don't have the CY21 anymore. But it seems that the CY21 is a sharper lens.
The ZF suffers from curvature of field. U focus on an object in the center, then shift composition by placing the object in the corner, and u'll notice the focus is off.
Notice vignetting / dark edges / colour cast at the edges, even after stopping down to f4 or f5.6. I remember the CY only suffers from vignetting at f2.8 and all clears up once stopping down.
weekh wrote:
I don't have the CY21 anymore. But it seems that the CY21 is a sharper lens.
The ZF suffers from curvature of field. U focus on an object in the center, then shift composition by placing the object in the corner, and u'll notice the focus is off.
I'm not sure this analysis is correct. To start I would say that the C/Y21 also suffers from curvature of field -- it would be hard to find a wide-angle lens that doesn't. Certainly an in-depth, accurate head-to-head comparison between the C/Y21 and the ZF21 is in order. Until then, in the presence of superior MTF's for the newer ZF21 (predominately in the edges and corners), I'm inclined to believe that the ZF21 is indeed the sharper lens -- but they are are close.
I further think that your method of method of discovering curvature of field is flawed. Simply, the distance to the object in the corner of of image in the place of focus, is not the same distance from the camera as an item in the center of the image and place of focus. So, if you focus on the item in the center of an image and then move it to the corner it will necessarily be out of focus becuase it is no longer in the plane of focus (it is closer).
> I don't have the CY21 anymore. But it seems that the CY21 is a sharper lens.
A direct comparison (preferably of multiple copies of each model) would be needed
for a definitive statement.
> The ZF suffers from curvature of field. U focus on an object in the center, then shift
> composition by placing the object in the corner, and u'll notice the focus is off.
That is quite normal, since it is very difficult to maintain the same object distance
during the composition shift.
> Notice vignetting / dark edges / colour cast at the edges, even after stopping down to
> f4 or f5.6. I remember the CY only suffers from vignetting at f2.8 and all clears up once
> stopping down.
Again, there is need for a direct comparison. A noticeable change in vignetting is not
expected for two lenses of such a similar design. If anything, the lens sheets show
that the new design gives less vignetting.
Lotusm50 wrote:
I further think that your method of method of discovering curvature of field is flawed. Simply, the distance to the object in the corner of of image in the place of focus, is not the same distance from the camera as an item in the center of the image and place of focus. So, if you focus on the item in the center of an image and then move it to the corner it will necessarily be out of focus becuase it is no longer in the plane of focus (it is closer).
Of course, you are absolutely right, but for a lens this wide, I don't think it would make a difference. On the other hand, the field curvature effect can be very pronounced and much more obvious, and it can be experienced the way weekh did. I usually do differently, I focus manually at the frame center, then at the frame edge without moving the camera. Usually with my 16-35, when the center focus is at infinity, the extreme corner focus can be at just around 1-2 meters only. That's how pronounced it is.
weekh wrote:
The ZF suffers from curvature of field. U focus on an object in the center, then shift composition by placing the object in the corner, and u'll notice the focus is off.
I think this statement suggests more than there is as Lloyd Chambers only detected a very slight curvature of field in his extensive tests with this lens.
edwardkaraa wrote:
Of course, you are absolutely right, but for a lens this wide, I don't think it would make a difference.
That depends on the object distance.
On the other hand, the field curvature effect can be very pronounced and much more obvious, and it can be experienced the way weekh did. I usually do differently, I focus manually at the frame center, then at the frame edge without moving the camera. Usually with my 16-35, when the center focus is at infinity, the extreme corner focus can be at just around 1-2 meters only. That's how pronounced it is.
That is how pronounced it can be for a poor lens. Such a level of field curvature is
irreconcilable with the stellar MTF of the Distagon 21/2.8, which excludes easily
noticeable effects of any aberration except distortion.
Lotusm50 wrote:
I further think that your method of method of discovering curvature of field is flawed. Simply, the distance to the object in the corner of of image in the place of focus, is not the same distance from the camera as an item in the center of the image and place of focus. So, if you focus on the item in the center of an image and then move it to the corner it will necessarily be out of focus becuase it is no longer in the plane of focus (it is closer).
The object is a building at at infinity. I noted discrepancy is focus between center and corner after recomposing, down to f5.6. Sharpness ben be obtained after re-focus. I guess this should be called field curvature.
Comparison with the CY 21 are all based on my memory can checks with my shots taken previously. Just my personal opional. U really need both copies side by side for real comparison.
wiseguy010 wrote:
I think this statement suggests more than there is as Lloyd Chambers only detected a very slight curvature of field in his extensive tests with this lens.
Toothwalker wrote:
That is how pronounced it can be for a poor lens. Such a level of field curvature is
irreconcilable with the stellar MTF of the Distagon 21/2.8, which excludes easily
noticeable effects of any aberration except distortion.
Excuse me but calling the 16-35 a poor lens is a bit extreme as in my own findings it should at least be as good as the Nikon and the ZF 21 in the range of 16 to 28mm, and imo probably better than both. The only weak point is at 35mm. What I'm talking about is the very extreme corners which cover less than 1-2% of the entire image area. Have you ever used one or just making uneducated guesses?
, just curious).