Pics from ZF21

FM Forums \| Alternative Gear & Lenses \| Join Upload & Sell	Search Used
1 2 3 4 5 end

Archive 2009 · Pics from ZF21

edwardkaraa
Online
Dedicated FM
Upload & Sell: On

p.4 #1 · Pics from ZF21

Weekh,

You got it the other way around. When the center is in focus at infinity, the corners are focused beyond infinity. Imagine an arc which closest point to your camera is at the center and going further away from the camera the more you move to the image periphery. The distance scale on the lens is effectively measured at the center. In order to get the corners in focus, you have to focus closer.

To give you an example about the field curvature effects, if you take a picture of a person at 2 meters in the center of the image, the curvature will make objects which are further away in the background be in focus the more you move out of the center.

May 06, 2009 at 07:40 AM

edwardkaraa
Online
Dedicated FM
Upload & Sell: On

p.4 #2 · Pics from ZF21

To illustrate my point, I just took this photo with the ZA 16-35 at 16mm f/2.8. If you look carefully, you might discern the W shape of the field curvature instead of the simple arc shape of less corrected lenses. Now if you're shooting a landscape imagine that the infinity mark corresponds to the sharpest point in the center. In order to get the outer points in focus you have to focus closer than infinity. Note that curvature gets at its worst in the extreme corners, something which I couldn't show in the sample photo.

http://forum.getdpi.com/forum/showpost.php?p=97111&postcount=13

Just added these 2 to show extreme corners:

http://forum.getdpi.com/forum/showpost.php?p=97114&postcount=14

May 06, 2009 at 10:43 AM

snowboarder
Offline
Upload & Sell: On

p.4 #3 · Pics from ZF21

I don't understand - for years Zeiss 21mm has been the best thing around,
"OMG, look at the sharpness, OMG"
Now suddenly, out of the blue, the lines are not straight, the focus plane
is tilted... WTF?

May 07, 2009 at 06:07 PM

edwardkaraa
Online
Dedicated FM
Upload & Sell: On

p.4 #4 · Pics from ZF21

snowboarder wrote:
I don't understand - for years Zeiss 21mm has been the best thing around,
"OMG, look at the sharpness, OMG"
Now suddenly, out of the blue, the lines are not straight, the focus plane
is tilted... WTF?

Not talking about the 21 in particular, because I know it's an outstanding lens, but as you say for years, people used lenses on 6-12mp cameras and wondered about the sharpness. Now with 21-24mp cameras, we will start to hear a different story.

May 07, 2009 at 06:12 PM

Lotusm50
Offline
Dedicated FM
Upload & Sell: On

p.4 #5 · Pics from ZF21

edwardkaraa wrote:
snowboarder wrote:
I don't understand - for years Zeiss 21mm has been the best thing around,
"OMG, look at the sharpness, OMG"
Now suddenly, out of the blue, the lines are not straight, the focus plane
is tilted... WTF?

Not talking about the 21 in particular, because I know it's an outstanding lens, but as you say for years, people used lenses on 6-12mp cameras and wondered about the sharpness. Now with 21-24mp cameras, we will start to hear a different story.

Surely, not a "different" story, but perhaps a more detailed (and complete) one. If the CZ 21 was sharper on the 6-12mp camera, it will still be sharper on the 21-24 mp cameras. The relative ordering will not sudden switch. If anything, you might be now seeing the limits of the lens that were not visible on the lower resolution sensors. As for the lines not being straight, people have always commented on that. It's not a lens designed with architectural used in mind and Zeiss has indicated as much.

May 07, 2009 at 06:38 PM

jjlphoto
Offline
Dedicated FM
Upload & Sell: Off

p.4 #6 · Pics from ZF21

snowboarder wrote:
.....the lines are not straight, the focus plane is tilted...

I came from the old 4x5 school. Even a Schneider 55mm Super Angulon lenses exhibited a curved field of focus. Schneider states that the Super Angulon moniker is their designation for 'slightly retrofocus' design. I also had a Schneider 47mmXL Super Angulon, and there was indeed a bit of barrel distortion in that lens.

This curved field of focus is simply another byproduct of retrofocus lens design, along with linear (barrel, mustache, whatever) distortion. Unfortunately, the German school of lens design suffers from those two issues more so than other lens smiths.

May 07, 2009 at 07:07 PM

Lotusm50
Offline
Dedicated FM
Upload & Sell: On

p.4 #7 · Pics from ZF21

jjlphoto wrote:
I came from the old 4x5 school. Even a Schneider 55mm Super Angulon lenses exhibited a curved field of focus. Schneider states that the Super Angulon moniker is their designation for 'slightly retrofocus' design. I also had a Schneider 47mmXL Super Angulon, and there was indeed a bit of barrel distortion in that lens.

This curved field of focus is simply another byproduct of retrofocus lens design, along with linear (barrel, mustache, whatever) distortion. Unfortunately, the German school of lens design suffers from those two issues more so than other lens smiths.

I assume you mean to suggest that the "German School of lens design" might choose to emphasize other aspects of performance than field curvature and distortion in design trade-offs. Other schools of design might place greater emphasis on field curvature and distortion in their design decisions. Choose your lens based on the features that are important to you or your application.

Out of curiosity, what are the other schools of lens design you imply exist? Aren't all the possible others, essentially, copies of German design?

May 07, 2009 at 07:42 PM

pdmphoto
Offline
Dedicated FM
Upload & Sell: On

p.4 #8 · Pics from ZF21

It is well known that other companies like Olympus and Nikon have done thier own lens designs. What German design did Olympus copy to make that 18/3.5 OM lens? The same goes for the Nikon 20/4. Take a look at the history of that lens on the NIkon website.

May 07, 2009 at 10:27 PM

Lotusm50
Offline
Dedicated FM
Upload & Sell: On

p.4 #9 · Pics from ZF21

Now, I'm not talking about individual designs, but rather as was referred to, "design schools". Quite clearly, the model and "school" followed by Japanese lens designer/manufacturer was a German one. Is there now a "Japanese School"? That was essentially part of my question. If so, how is it distinct, and to what extent, from the German School they followed for so long, and when would we mark their design independence from their German origins?

May 07, 2009 at 11:02 PM

edwardkaraa
Online
Dedicated FM
Upload & Sell: On

p.4 #10 · Pics from ZF21

Hehehe, Obviously Nikon started as a copy of Leica and Canon as a copy of Contax, if I remember well (not that I was alive that time). What I find really funny is that Japanese would copy a lens design and "improve" it, which probably means for them make it get higher points on the testing charts, and produce flat life-less photos in real life. (I know this is a gross generalization as lotusm50 will soon point out

)

I wonder why some lens reviewers criticize Zeiss for insisting on introducing flawed "old-dated" designs that do not produce sharp corners on the testing charts, have some weird effects of LoCA, are not fully corrected for distortion, MF instead of AF... etc. As if Zeiss is not able to compute a design the same way Nikon or Canon does. What these "testers" either intentionally or not, ignore when bashing Zeiss lenses for the above, is that Zeiss is following a century long tradition of providing certain optical qualities to its glass. The other day I was reading a review of the ZF21 vs the 14-24 Nikon, and it was interesting to see that the Nikon generally produces equal or better results when examining the details at 100% but if you look at the photo as a whole, the Zeiss photo is so much more vibrant and appealing.

May 08, 2009 at 03:54 AM

pdmphoto
Offline
Dedicated FM
Upload & Sell: On

p.4 #11 · Pics from ZF21

Japanese companies clearly started by copying succesful designs, but they have(had) famous lens designers that think (thought) completely out of the German design box. In fact, those German manufacturers have surely learned a design or two from the Japanese by now. And what about other companies like Angenieux? Those French lens designers worked independently of the German companies, in the same time frame. I wouldn't be surprised if the Germans learned a few tricks from them.

New designs only come from design schools. Many Japanese designs are proof that other schools of thought now exist beyong the old German design. You are looking for a distinct line, but it has been a long and gradual process. A good example of the disparity today is the Nikon 14-24G.

Lotusm50 wrote:
Now, I'm not talking about individual designs, but rather as was referred to, "design schools". Quite clearly, the model and "school" followed by Japanese lens designer/manufacturer was a German one. Is there now a "Japanese School"? That was essentially part of my question. If so, how is it distinct, and to what extent, from the German School they followed for so long, and when would we mark their design independence from their German origins?

May 08, 2009 at 04:27 AM

wayne seltzer
Offline
Dedicated FM
Upload & Sell: On

p.4 #12 · Pics from ZF21

Edward,

Which review was this?
Diglloyd?
What did you like better about the zeiss? More contrast,color?

edwardkaraa wrote:
Hehehe, Obviously Nikon started as a copy of Leica and Canon as a copy of Contax, if I remember well (not that I was alive that time). What I find really funny is that Japanese would copy a lens design and "improve" it, which probably means for them make it get higher points on the testing charts, and produce flat life-less photos in real life. (I know this is a gross generalization as lotusm50 will soon point out

May 08, 2009 at 05:01 AM

erichard
Offline
Upload & Sell: On

p.4 #13 · Pics from ZF21

Dont' know if this was already discussed, but a definitive point on which the new lenses generally beat their predecessors is the fact that they are 9 blades vs. 5 or 6, and they are usually curved, vs. straight. You can see this in the flare and in the starburst pattern of the sun. The old 21 c/y has six points, and the new zf or ze has almost too many to count (18?). But it's the avoidance of the old pentagon or hexagon flare that I like. I suppose there is some retro flavor to the pentagon flare, but personally, been there, done that.

Same deal for the Nikon 14-24.

May 08, 2009 at 05:31 AM

trumpet_guy
Offline
Dedicated FM
Upload & Sell: Off

p.4 #14 · Pics from ZF21

This has been a very interesting discussion of Schools of Design in the science and
art of lens design.

This same thing (particular design approaches and trade-offs) shows up very
audibly in loudspeaker designs as well, as anyone with a serious interest in
audio systems can attest. The "Boston School," Canadian loudspeakers, British
(think B&W) loudspeakers, Japanese designs.

It's what makes different lens, speakers, yes even trumpets interesting to compare.

Carry on with the good discussion.

Tim

May 08, 2009 at 05:55 AM

brainiac
Offline
Dedicated FM
Account Locked

p.4 #15 · Pics from ZF21

Toothwalker 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.

Not really. When the lens is focussed closer, it will have less effective depth of field. Either way, using the centre to focus and then swinging the camera around to recompose will give you incorrect focus, even with a lens that has no field curvature at all. The wider the lens, the greater the angle of swing (recomposition), and therefore the greater the error. With wide angles, if you are interested in corner sharpness or off-centre subjects, focus recompose sucks. Smaller apertures hide the error, but it is still an error.

May 08, 2009 at 09:23 AM

Andi Dietrich
Offline
Dedicated FM
Account Locked

p.4 #16 · Pics from ZF21

brainiac wrote: Either way, using the centre to focus and then swinging the camera around to recompose will give you incorrect focus, even with a lens that has no field curvature at all. The wider the lens, the greater the angle of swing (recomposition), and therefore the greater the error. With wide angles, if you are interested in corner sharpness or off-centre subjects, focus recompose sucks. Smaller apertures hide the error, but it is still an error.

I dont quite agree, a lens with a strong curvature of field is more likely to give you correct focus distance with focus-recompose, Think about a fisheye.
On the other hand the same lens which is good at one thing will be poor in another situation, like Landscape/outdoor architecture where it would be nice to have a lens without any curvature of field.

May 08, 2009 at 09:52 AM

edwardkaraa
Online
Dedicated FM
Upload & Sell: On

p.4 #17 · Pics from ZF21

I have to disagree with that, Andi.

Focus-recompose induces a slight back focus with a perfect lens.

Since you need to front focus with a lens suffering from (or blessed with) field curvature, it makes things much worse.

Andi Dietrich wrote:
brainiac wrote: Either way, using the centre to focus and then swinging the camera around to recompose will give you incorrect focus, even with a lens that has no field curvature at all. The wider the lens, the greater the angle of swing (recomposition), and therefore the greater the error. With wide angles, if you are interested in corner sharpness or off-centre subjects, focus recompose sucks. Smaller apertures hide the error, but it is still an error.

I dont quite agree, a lens with a strong curvature of field is more likely to give you correct focus distance with focus-recompose, Think about a fisheye.
On the other hand the same lens which is good at one thing will be poor in another situation, like Landscape/outdoor architecture where it would be nice to have a lens without any curvature of field.

May 08, 2009 at 11:36 AM

edwardkaraa
Online
Dedicated FM
Upload & Sell: On

p.4 #18 · Pics from ZF21

brainiac wrote:
With wide angles, if you are interested in corner sharpness or off-centre subjects, focus recompose sucks. Smaller apertures hide the error, but it is still an error.

Totally agreed. Focus-recompose brings only trouble due to field curvature.

One has to compose first, then focus visually (or AF using a peripheral point but that is not always possible because AF points are too centered on FF bodies).

Focusing this way, it is not unusual to find that a peripheral object which is at 2 meters difference might require a focusing distance of 1.5 meters or less depending on the strength of the curvature and how far the object is from the center.

For snapshots and reportage, I try to focus-recompose with the closest AF point to the subject. Not perfect but fast.

For landscapes at infinity, it is best to focus visually at the corners and try to find a compromise with the centre focus (which should be at infinity) and cover the difference with a small f/stop.

May 08, 2009 at 11:49 AM

Toothwalker
Online
Upload & Sell: Off

p.4 #19 · Pics from ZF21

brainiac wrote:
Toothwalker 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.

Not really. When the lens is focussed closer, it will have less effective depth of field. Either way, using the centre to focus and then swinging the camera around to recompose will give you incorrect focus, even with a lens that has no field curvature at all. The wider the lens, the greater the angle of swing (recomposition), and therefore the greater the error. With wide angles, if you are interested in corner sharpness or off-centre subjects, focus recompose sucks. Smaller apertures hide the error, but it is still an error.

I don't say that focus recompose does not suck, I just say that the introduced error depends on the object distance. For a faraway scenery, there will be no error as everything is within the depth of field, before or after recomposition. At close(r) focus errors occur, hence the dependence on object distance.

May 08, 2009 at 05:00 PM

jjlphoto
Offline
Dedicated FM
Upload & Sell: Off

p.4 #20 · Pics from ZF21

There is an FM member that posted some Nikkor 14~24 shots here with Hubsand's adapter, I think he is in the UK. He had some rocks by the sea in the extreme foreground, with the sea in the horizon, and intense colored cloudy skies. He has the W/A focus procedure nailed.

May 08, 2009 at 05:25 PM

1 2 3 4 5 end
FM Forums \| Alternative Gear & Lenses \| Join Upload & Sell 1 2 3 4 5 end