cputeq wrote:
MTF is part of the equation, but start throwing in field curvature in lenses and then the nature of the subject, and MTF might as well go out the window.

MTF is good for planar subjects and can get you in the ballpark of "sharpness" but is by no means the whole story.



Yep, that's why I threw in micro contrast. On planar subjects things like field curvature/bokeh rendering etc cannot be a factor.

Check Andens image, 100% planar. I dont know if it's 3D, but I believe it's an unusually "poppy" image of a flat subject.

SP12 suggests acutance which - checking wikipedia - looks an awful lot like PS filters USM or SM, i.e. (expressed simplified) gradually adds nonexisting light/dark edges to dark/light subject borders on a pixel-level.

This is - to my knowledge - not that far away from micro contrast, just applied in another scale. An increase in micro contrast increases the difference in adjacent areas light-/darkness.

The important difference is that whereas acutance artificially adds information to an image - micro contrast dont. Micro contrast strengthens what's already there. The latter is what I see many people associate with the optical behavior of e.g. Zeiss lenses.

For the record, Zeiss lenses do not "strengthen" anything, just interprets reality better according to the lords here in the alt group ;-)

It's a moveable feast and a work in progress, but my thinking on the (unfortunately important) subject is that there are two kinds of lens 3D:
(i) very high image centre macro and micro contrast and a rapid drop in these factors from around 12-15mm away from image centre, sometimes accompanied by field curvature in wider lenses (or other aberrations in others), where it is most likely to be found; and
(ii) flat, high parallel lines for 40 lpmm line pairs across the frame with at least very good macro contrast (5,10 lpmm lines).

The first, as seen often in Leica R lenses, provides the viewer with a wide gradient of lens performance across the frame and induces 3D.

The second, the Zeiss 'formula' but seen in Leica's finer tele/macro lenses, ensures a high impression of sharpness through constant lens performance across the frame with very high and even shaping (contour definition) of small objects (high spatial frequencies).

The Summicron R 50 MTF chart shows the first kind of '3D', almost all modern ZE/F Zeiss lenses and many CY lenses are of the second. Puts has this to say on the effect in the 50mm Summ R:

"Image quality falls off towards the corners, i.e. if the image quality
across the whole negative area is really crucial, one should
consider the Macro-Elmarit-R 60mm f/2.8." Indeed.

The much-vaunted 28/2.8 Elmarit-R suffers some mid aperture (f5.6) wobbles but is otherwise a fine performing lens at f8 as well as wide open if corner performance is not high on the agenda.

It is not helpful to include other extraneous factors for the OP's question, which asks about *lens* 3D - these include post processing (sharpening/midtone enhancement), sensor resolution and OOF. Otherwise all lenses would show 3D. [The *rate of OOF transition* is much more interesting to study in this context.] The same argument applies to choice of subject matter - leading lines, vignetting and other well-used photographic cliches.

It also helps if we exclude the interaction of colour handling as colour tonal separation is another critical factor in 3D perception, and depends on the contribution of sensor resolution, CFAs, etc. also.

When it comes to high spatial frequencies - near to the limit of what one can see in an image, *micro-contrast is resolution*. Think of the tiny thin grey lines in a resolution chart - the reason a 'high resolving' lens can see and show them and a lesser lens cannot is the ability to transfer ('modulate' in MTF terms) that separation of detail (as measured by contrast) in the object faithfully to the image.

If you cannot resolve the contrast, you cannot show it in the image - and no amount of sophisticated sharpening will recreate what a better lens provides, because at the limit there is no 'edge' to sharpen in a lesser resolving lens.

High micro-contrast images can easily appear unnatural due to the 'forced' small object rendition - the lens appears to see better than human vision, especially in even light. Almost too much texture...

Hmm, well, interesting post, but I disagree with several items. First of all, and this is a minor semantic quibble, the two types you list aren't lens 3D types, but rather characteristics of lenses which you propose can produce 3D images. Minor, but important.

Secondly, I disagree with your characterization of Leicas as falling off towards the corners, Modern Leicas are some of the most solid performers in this regard. If you want to restrict this characterization to older Leicas, then I would agree somewhat. I also disagree with Zeiss lenses having high sharpness across the frame. This depends very much on the specific lens, but even some of the top Zeiss ZF/ZE lenses have dramatic fall-off towards the corners. Saying that Leica lenses are about optical perfection, sometimes at the cost of some personality and rendering style, and Zeiss images are about the rendering style, sometimes at the cost of optical performance, is much closer to the truth.

I agree 100% that the discussion of 3D pop would need to include the topic of DoF falloff rate. I disagree that processing is not relevant, simply because the OP asked about lenses. Any discussion of 3D needs to include processing. Not all lenses can take the same processing, and so the final result comes from lens+processing appropriate for that lens. I also disagree that colour considerations are not important. The spatial/textural rendering of a lens depends very much on its ability to render subtle colour differences visible, and this is why so many Canon lenses have no 3D, among other things (such as missing micro-contrast).

Finally, perhaps you could post a 50 Cron shot with lots of 3D? I used to own this lens, and loved it to bits, but I don't recall seeing any 3D from it.

--

What I feel is direly missing from this discussion is a definition of 3D. All previous threads fell flat on their inability to have the participants agree what 3D is, in theory and in photos. Most people are merely referring to a sense of depth, usually foreground and background planes, when they say 3D. The vast majority even. I find that more is needed. But as long as we want to discuss something in detail, we need to agree on what we are discussing, no?

philip_pj wrote:
When it comes to high spatial frequencies - near to the limit of what one can see in an image, *micro-contrast is resolution*. Think of the tiny thin grey lines in a resolution chart - the reason a 'high resolving' lens can see and show them and a lesser lens cannot is the ability to transfer ('modulate' in MTF terms) that separation of detail (as measured by contrast) in the object faithfully to the image.

By now I'm no longer sure what the correct meaning of the term microcontrast is. I thought it was like this (for a full-frame lens):

30-40 lp/mm: resolution of finest detail
20 lp/mm: microcontrast or local contrast of image features bigger than the finest detail
10 lp/mm: macrocontrast or global contrast

Canon has a webpage with an explanation of their MTF charts saying basically what I have written above. I added some of my own interpretation of what microcontrast should mean, but I'm not entirely sure if my thinking is correct. AFAIK, acutance means edge contrast, which probably would fall into the category of 30lp/mm? I'd think lower lp/mm would indicate the contrast of features larger than just edges.

carstenw wrote:
Hmm, well, interesting post, but I disagree with several items. First of all, and this is a minor semantic quibble, the two types you list aren't lens 3D types, but rather characteristics of lenses which you propose can produce 3D images. Minor, but important.

Secondly, I disagree with your characterization of Leicas as falling off towards the corners, Modern Leicas are some of the most solid performers in this regard. If you want to restrict this characterization to older Leicas, then I would agree somewhat. I also disagree with Zeiss lenses having high sharpness across the frame. This depends very much on the specific lens, but even some of the top Zeiss ZF/ZE lenses have dramatic fall-off towards the corners. Saying that Leica lenses are about optical perfection, sometimes at the cost of some personality and rendering style, and Zeiss images are about the rendering style, sometimes at the cost of optical performance, is much closer to the truth.

I agree 100% that the discussion of 3D pop would need to include the topic of DoF falloff rate. I disagree that processing is not relevant, simply because the OP asked about lenses. Any discussion of 3D needs to include processing. Not all lenses can take the same processing, and so the final result comes from lens+processing appropriate for that lens. I also disagree that colour considerations are not important. The spatial/textural rendering of a lens depends very much on its ability to render subtle colour differences visible, and this is why so many Canon lenses have no 3D, among other things (such as missing micro-contrast).

Finally, perhaps you could post a 50 Cron shot with lots of 3D? I used to own this lens, and loved it to bits, but I don't recall seeing any 3D from it.

--

What I feel is direly missing from this discussion is a definition of 3D. All previous threads fell flat on their inability to have the participants agree what 3D is, in theory and in photos. Most people are merely referring to a sense of depth, usually foreground and background planes, when they say 3D. The vast majority even. I find that more is needed. But as long as we want to discuss something in detail, we need to agree on what we are discussing, no?

I agree with pretty much all of your points - and we all know how subjective the idea of "3D" rendering is - so here is a test shot from my v2 Summicron R showing what I find to exhibit some "3Dness". The only thing I did to this shot was to slightly push the black level up.

Interesting Tariq, I find these very flat. And you claim them to be 3D. We need a definition of 3D.

did anybod asked leica or zeiss how they do define 3D?
or has a link?
maybe interesting.

otherwise i will send them a mail and ask.

gruss
r

Anden wrote:
Interesting Tariq, I find these very flat. And you claim them to be 3D. We need a definition of 3D.

I think it's somewhat subjective myself. We can all state specific qualities that each of us think contribute to the illusion of 3D in a 2D image, but in the end, I doubt there will be a consensus on all points - and with all example images (as evidenced by your reaction to this shot of mine.)

rsrsrs wrote:
did anybod asked leica or zeiss how they do define 3D?


I have not heard of any scientific definition for it. Perhaps Zeiss has even refrained from precisely defining it in order to keep their magic design recipe a secret.

Because we're all human and see things slightly differently, plus we have opinions, I think it'll be near-impossible to nail down exactly what is 3-D, and even if that were possible, objectively defining which photo meets or doesn't meet these criteria would be extremely difficult, if not impossible.

I think one can only go on impressions of particular photos, etc. To be honest, some of the examples shown in this thread (and others) weren't impressive to me, while others have been great - others of course would disagree with me (hence, the existence of forums!)

... and that makes it interesting ...

AhamB wrote:
rsrsrs wrote:
did anybod asked leica or zeiss how they do define 3D?


I have not heard of any scientific definition for it.

Not true. It's been defined here:

http://photography-on-the.net/forum/showthread.php?t=1025674&highlight=devil

jffielde wrote:
AhamB wrote:
rsrsrs wrote:
did anybod asked leica or zeiss how they do define 3D?


I have not heard of any scientific definition for it.

Not true. It's been defined here:

http://photography-on-the.net/forum/showthread.php?t=1025674&highlight=devil

Very funny!

Anden wrote:
Interesting Tariq, I find these very flat. And you claim them to be 3D. We need a definition of 3D.

+1
The photo is like a painting to my eyes. I don't feel any 3D.

Are there any 3D qualities in this image? It's not a Zeiss.

Personally i don't see 3D in this pic wfrank, just like focus is in the closest subject i mean wheel, actually i see 3D better in the color photos, but it's just me.

wfrank wrote:
Are there any 3D qualities in this image? It's not a Zeiss.

I see depth and a remarkable amount of texture, but no real sense of shape or volume, so I don't personally see any 3D there. Do you?

Yeah, I guess I do. The isolation of the in-focus object is (in my mind) good and sharpness is excellent - even at the pixel level which of course is not visible in the web format. A fair amount of PP too, but only with the intention of keeping the lens'/original image characteristics into the small format presented here. But is it really 3D? Dont know, trying to find that out. Now I at least know the opinion of two respect-worthy posters... :-)

To take it one step further - thinking about the motif and the presumably juicy possibilities that steering wheel ought to possess when it comes to 3D. It really should be a fair object to "popize" - if my lens were to carry that capacity. Wouldnt it? Cant help thinking what gear would make it pop, if any. And if so, what would the difference be - compared to my humble fixed-4 attempt at 29mm.

Well, one question I can answer with absolute certainty: is it not 3D! It is a two-dimensional representation

Some of the oft-related clues are there, others not, but in the end it is a throw of the dice, and for me the necessary feeling about the shape and size and volume and feel and texture, and very importantly, the spatial relationship between foreground, middle and background, do not add up to something where I can squint a little and imagine that I am there. It looks like a (very good) photo of reality with very good texture, and two layers, foreground and background. I think I also miss the colour. I think colour is an important 3D clue, although I am not yet certain about that.

I should qualify this by saying that in all the time I have frequented this forum, I have seen maybe something like a dozen photos with convincing 3D. It is very hard to do, even for those who do it the best. I am not sure that I have made a single photo which has as strong 3D as brainiac's portrait, Martin's leather chair, or Luka's snail.

Yeah, I think that throws a lot of people off. I can understand the term "pop" but "3D" doesn't fit the description for me. I (and others?) just have too many other more appropriate associations for the term "3D". Oh well, what's in a term I guess... I suppose "3D" is better than calling it something else that doesn't fit either... like, "Goligafrigablop" or some shite. Still, I'll just go with "pop".