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Author Topic: Another useless MF-D800 comparison ;)  (Read 9851 times)
jerome_m
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« Reply #60 on: October 23, 2013, 08:11:12 AM »
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the Nikon is soft through the entire image.

Not really. I has lower resolution than the Hasselblad and thus had to be enlarged to match. 50 versus 34 mpix. I could have done it the other way, of course, but then we lower the Hasselblad performance to that of the Nikon, which is just as unfair.
« Last Edit: October 23, 2013, 08:12:47 AM by jerome_m » Logged
ErikKaffehr
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« Reply #61 on: October 23, 2013, 08:19:08 AM »
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Hi,

Not what I see, but off axis performance doesn't seem reasonable to me.

Best regards
Erik


the Nikon is soft through the entire image.
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Dustbak
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« Reply #62 on: October 23, 2013, 08:39:20 AM »
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@jerome_m

Thanks for sharing this.
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peterv
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« Reply #63 on: October 23, 2013, 05:21:52 PM »
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+1, I found it very interesting. It confirmed my ideas about the differences between these systems.
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bjanes
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« Reply #64 on: October 24, 2013, 07:50:47 AM »
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This is likely correct, and it would be easy to test.  Focus manually on the corner(s).  Is the center then noticeably soft?  If field flatness is the problem, then a possible solution is focus stacking, as an alternative or addition to horizontal/vertical stitching.

Field curvature is one aberration that can cause blurred corners with a sharp central area, but many other aberrations can result in this defect. With field curvature, one can refocus to bring the edges in focus, but the central portions of the image will suffer. Refocusing will not work with other aberrations. With 3 dimensional subjects, field curvature is less problematic since edge detail at the focal plane will be reduced when focus is on central areas of the subject, but edge detail at another object distance will be sharp and the overall image may appear sharp.

With planar subjects (landscapes at infinity and copy work of paintings), a flat field is highly desirable. For general photography of 3D subjects, some curvature of field may be acceptable. The 35 mm f/1.4 lens is not the best choice for landscapes or copy work, but it can work well for general photography. The Nikon and Sigma 35 mm f/1.4 are excellent general purpose lenses.

Regards,

Bill

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BernardLanguillier
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« Reply #65 on: October 24, 2013, 07:08:26 PM »
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I am extrapolating this test and the whole collection of lens test I already did to a more generic assessment on all 24x36 wide-angle lenses, actually. I am not limiting myself to the D800. The problem we see with that 35mm lens is more general, you will not find a 35mm with this kind of homogeneity on 24x36 cameras.

No, I am not interested in landscape pictures with sharp corners and out of focus center. Let me suggest something else: since you rave about the Sigma 35mm, what about you getting your D800 out in a field and taking the same kind of photos to show us how that particular lens works for landscape? It is a very simple test and anybody can do it.

I'll be away on business for a couple of weeks and after going back to Japan, I live in an environment where there are few easily accessible flat horizons, but I'll give it a try some time in November.

As far as raving about the Sigma, don't get me wrong, my answer to perfect corner image quality is and will remain stitching.

Regarding the Nikkor, I am glad we agree that it is an excellent performer in the corners but suffers from field curvature. This is important information for general photography, but also for landscape because it tells us that there is a way to optimize the location of focus to improve the blend of sharpness accross the field on distant objects.

Typically, you will want to focus further away for such lenses (at infinity) and stop down a bit more to increase the DoF if perfect infinity focus is what you are looking for.

Cheers,
Bernard
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A few images online here!
jerome_m
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« Reply #66 on: October 25, 2013, 03:47:22 AM »
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There is no magic in bigger sensor, there is no magic in optics, just a very different marketing point.

The pictures have been taken with an HC 50-II. Can we find the equivalent lens for the D800 (or any other full frame camera)?

The HC 50-II:
-is 116mm long
-weights 975g
-is open at f/3.5
-uses 11 elements in its optical design
-costs 3555 without VAT

An equivalent lens for the D800 does not exist, but we can imagine one: we will suppose that we have a reducing machine which can make everything smaller in all dimensions. We make everything 40% smaller, so that we get a 35mm lens. What would that lens be? It would:
-be 82mm long
-weight 355g (the weight is divided by the cube of the distance, so 1.4^3)
-still be open at f/3.5 (aperture is dimensionless)
-still use 11 elements
-still cost 3555 (actually, maybe a bit less if we could benefit from economies of scale, but not less than, say, 2000-2500, because it is still a very complex design).

And there lies the difference. Actual lenses for the 35mm format are very different. You do not have an 11 elements f/3.5 in 35mm format at any price. Nobody would buy them. You have:
-either very fast lenses, so they are optimized for very different criterias
-or slower lenses, but they use relatively simple optical designs with 5-6 elements so are poorly corrected.
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ErikKaffehr
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« Reply #67 on: October 25, 2013, 04:08:53 AM »
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Hi,

I think that you may be spot on. I guess Zeiss is making some new lenses with excellent performance. Making medium aperture, high performance lenses may be a good idea. But, would anyone buy?

That Nikon 35/1.4 G seems quite good in Photozone's test but Photozone ignores field curvature in their tests. I would suggest that field curvature is a bad thing in landscape photography, mostly.

Best regards
Erik

There is no magic in bigger sensor, there is no magic in optics, just a very different marketing point.

The pictures have been taken with an HC 50-II. Can we find the equivalent lens for the D800 (or any other full frame camera)?

The HC 50-II:
-is 116mm long
-weights 975g
-is open at f/3.5
-uses 11 elements in its optical design
-costs 3555 without VAT

An equivalent lens for the D800 does not exist, but we can imagine one: we will suppose that we have a reducing machine which can make everything smaller in all dimensions. We make everything 40% smaller, so that we get a 35mm lens. What would that lens be? It would:
-be 82mm long
-weight 355g (the weight is divided by the cube of the distance, so 1.4^3)
-still be open at f/3.5 (aperture is dimensionless)
-still use 11 elements
-still cost 3555 (actually, maybe a bit less if we could benefit from economies of scale, but not less than, say, 2000-2500, because it is still a very complex design).

And there lies the difference. Actual lenses for the 35mm format are very different. You do not have an 11 elements f/3.5 in 35mm format at any price. Nobody would buy them. You have:
-either very fast lenses, so they are optimized for very different criterias
-or slower lenses, but they use relatively simple optical designs with 5-6 elements so are poorly corrected.
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jerome_m
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« Reply #68 on: October 25, 2013, 04:57:53 AM »
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That Nikon 35/1.4 G seems quite good in Photozone's test but Photozone ignores field curvature in their tests.

What they do, as in most tests where they give nice curves as a result, is test at a relative close distance because the resolution target is not that big. My resolution target is 2 Km wide. Testing at a shorter distance will give different results, because of the way these lenses are designed (e.g. internal focus).

Moreover, resolution figures are only loosely related to the visual impression of sharpness, photozone gives only 3 figures without specifying where they are exactly taken (and we see from my test that the resolution changes continuously across the frame), etc... Testing lenses is surprisingly complex.
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kers
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« Reply #69 on: October 25, 2013, 05:41:27 AM »
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....
And there lies the difference. Actual lenses for the 35mm format are very different. You do not have an 11 elements f/3.5 in 35mm format at any price. Nobody would buy them. You have:
-either very fast lenses, so they are optimized for very different criterias
-or slower lenses, but they use relatively simple optical designs with 5-6 elements so are poorly corrected....

In that respect it is very interesting to see a comparison with the new 58mm optics from both Nikon and Zeiss;
It is clear that these lenses are the first of a new, high standard, league of lenses trying to serve the people coming from medium format.
They both had a different approach to develop these lenses. Real world samples will tell an interesting story- i am sure.
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Pieter Kers
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ErikKaffehr
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« Reply #70 on: October 25, 2013, 06:15:23 AM »
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Hi,

50-100X the focal length is OK to test.

The problem with Photozone test is that they refocus the lens for center, border and corner. That means that field curvature is hidden. DPReview and DXO don't have that problem.

Photozone has documentation on which points they measure at.

I am pretty sure that Photozone data is good, but we need to be aware of what they measure.

The old Photodo tests were done at the Hasselblad factory.

Best regards
Erik

What they do, as in most tests where they give nice curves as a result, is test at a relative close distance because the resolution target is not that big. My resolution target is 2 Km wide. Testing at a shorter distance will give different results, because of the way these lenses are designed (e.g. internal focus).

Moreover, resolution figures are only loosely related to the visual impression of sharpness, photozone gives only 3 figures without specifying where they are exactly taken (and we see from my test that the resolution changes continuously across the frame), etc... Testing lenses is surprisingly complex.
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BartvanderWolf
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« Reply #71 on: October 25, 2013, 07:31:11 AM »
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Hi,

50-100X the focal length is OK to test.

Hi Erik,

That is will indeed often result in a distance for which the lens was optimized/designed anyway.

Quote
The problem with Photozone test is that they refocus the lens for center, border and corner. That means that field curvature is hidden. DPReview and DXO don't have that problem.

I don't see that as a problem (but rather as a benefit), unless one makes reproductions of a flat surfaced object, or focuses at the horizon instead of hyperfocal distance with an aperture that is not almost fully wide open. Most subjects are 3D and selectively focused (at an angle, or off center) or, when DOF needs to be maximized, one uses a (combination of) stopped down DOF and/or focus stacking.

In fact, I always recommend to test the corners individually, because a discrepancy between the maximum resolution of the four corners is usually an indication of decentering. That will prevent drawing conclusions on an issue with an isolated copy. Very useful when deciding to keep a new lens purchase or exchange it for a better copy, and when renting lenses.

Shooting a star target will give a quantifiable metric in cycles per millimetre. It's also very easy to make an objective comparison between camera platforms / sensor sizes that way. Good lens tests are not that difficult when using the right tools, although absolutely uncompromised focus accuracy may be a bit harder to achieve when searching for the absolute limits (which also requires solid/stable shooting conditions).

Cheers,
Bart
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