low_contrast VS high_contrast lenses

estudleon · Joined: 15 May 2008 Posts: 3754 Location: Argentina

Orio
I can take any image and say the same : When one lens is contrastier than other, the normal way is that the less contrastier win in the match of sharpness, because the picture with less contrast have - regularity - more details
And with this affirmation I want to say that the contrast always confuse the capacity of the lens to distinguish one line black and other line white, with the resolution power of this lens (to distinguish some pairs of lines per mm.). Both are differents concepts.
we "SEE" the contrastier image- with the darks black and brightness whites lines- as the sharper and isn't thrue. The sharpest image have the bigger quantity of pairs of lines par mm. be them plus or minus contrastier.
If we take two, or more, images of some lenses, the concept of improvement that is inherent to the contrastier lenses impede to us to "see" the less contrastier lens as the sharpest, but generaly it is.

Orio · Expire: 2012-12-04

Nesster · Expire: 2014-02-20

Maybe it's time to reload here.

Micro contrast works with lpm resolution. Think of a ruler - you need to be able to distinguish the ruler lines - the better defined the edges (resolution) the better off you are, but also, the more difference there is between the line and ground (micro contrast) the better off you are. Sure you can have more resolution, but with poor micro contrast you won't be able to see it clearly. And vice versa, without resolution you'll just get more dark fuzzy lines on a less white ground.

Then there's intermediate level of contrast - and here's where lens designs will differ. Now we have a whole row of rulers - and yes there will be differences in how distinctly the row is rendered by different lenses. It is at this level we usually register 'contrast'. A contrastier lens will seem sharper than a less contrasty one, because the objects at the level of perception are more distinct. This same contrastier lens may not actually resolve more than the less contrasty one. Also at this scale we'll register the lens with more ruler to ruler contrast as 'sharper' than another, which actually has less blur to each ruler.

(An example of this from personal experience: the Pentax SMC-A 28/2.8 on inspection resoves very well, but doesn't have the contrast, or 'concentrated tone' in color, that other lenses have. I think of it as plain spoken but accurate. The reputation of this fine lens suffers as a consequence.)

Finally, we have the full tonal latitude. I can produce an image with very wide tonal latitude, but with very little contrast of either of the above types. (Think of e.g. early Stieglitz or Julia Cameron) A histogram would show a wide, though perhaps not tall, pattern. What this says is the absolute contrast of an image, the difference between the darkest and lightest, doesn't necessarily translate into a sense of contrast.

So back to the original images - what SHOULD the absolute tonal range be for the scene? Is it the sensor/software that keeps the histogram from both edges? Is it the lens? Is it the total difference in luminance in the scene?

Rob Leslie · Joined: 20 Mar 2007 Posts: 1103 Location: UK Swindon

I think these two links will explain most of it.

Understanding Lens Contrast
http://luminous-landscape.com/tutorials/understanding-series/lens-contrast.shtml

Understanding Sharpness
http://luminous-landscape.com/tutorials/sharpness.shtml

Nesster Explanation is very good pretty well spot on.

It would be interesting to get back to the samples (Original post) and the idea that default settings can show us so much?

Orio · Expire: 2012-12-04

Rob Leslie · Joined: 20 Mar 2007 Posts: 1103 Location: UK Swindon

Orio · Expire: 2012-12-04

Nesster · Expire: 2014-02-20

How does the advice to expose to the right (ie bias towards bright) square with all this? Does it have to do with perceptual limitations in discerning dark contrast - or limitations in the medium itself?

Orio · Expire: 2012-12-04

poilu · Expire: 2019-08-29

Orio · Expire: 2012-12-04

Another plus point for the lenses with optimal contrast (vs. lenses with lower contrast): most reflex cameras offer a contrast control, both in-camera before recording, and off-camera in the RAW converter.
When shooting RAW, it is easy -before or after the fact- to lower the contrast of an image taken with an optimally contrasted lens, and mimick the result that a low contrast lens would obtain.
So there is no reason to choose a lower contrast lens for the sake of that.

Orio · Expire: 2012-12-04

F16SUNSHINE · Expire: 2011-11-18

This last comparison really shows the "Zeiss formula" at work. I agree it work for me also. Maybe it is a bit of a harsh way to take Portraits of bank notes though aye? Laughing

Nesster · Expire: 2014-02-20

LMAO! this is a fun and informative thread!

I thought of a way to illustrate the two types of contrast, in photoshop.
Take a reasonable photo, with decent focus exposure etc.
Use the sharpen filter in two different ways: we know the sharpen filter doesn't add detail, if anything it may remove some, and it works by accentuating border contrast.

Experiment 1: at a radius of .2 or .3, and 150% or so - % not critical. This simulates to the eye what micro contrast/resolution might do.

Experiment 2: use a radius of 24-26 or thereabouts, and maybe 15-17% sharpening. This simulates intermediate size object contrast.

Back to flare or glare resistance - I think the Zeiss first of all resists the flare that reduces effective contrast - especially the second kind. And the Zeiss formuls probably favors this as well (though probably not to the same extent as Leica and Zuiko have).

I wonder if doing 2 to the jup9 image makes it more Zeiss like in rendition? (I'll try that myself when I get home)

poilu · Expire: 2019-08-29

Orio · Expire: 2012-12-04

estudleon · Joined: 15 May 2008 Posts: 3754 Location: Argentina

The lens resolving power is a thing by itself. And the resolving power determine the sharpness of the lens. Till 1930, securely before, zeiss and leica have this affirmation as certain. It's evident that the concepts of today's technology are going more deeply to the images science.
Sharpness, as a complex concept, have adepts and opponents.
And to distinguish between sharpness and contrast is one cuestion that was and will be a serious item that a lot of lens makers considerated to give to determinate lens a personal character (nikon, leica, canon, schneider, don't think that the theme haven't sense, no?)
All this considerations are in the camp of the theory.
Of course that the image of the zeiss match the jupiter. Give me the Zeiss not the jupiter, but in the purity of concepts, and for the reasons just expounded, The sharpness (in resoltion power's terms) of the zeiss don't appear evident to me.
Perhaps for somebody this theoretician cuestion don't have sense, but perhaps other persons like this, nobody have the knowlegde of the world's preferences, no?

estudleon · Joined: 15 May 2008 Posts: 3754 Location: Argentina

[quote="Rob Leslie"][quote="estudleon"]Rob Leslie
Sorry I don't understand?
Is this an answer to my point about different exposures and RAW conversion?
I see no indication of blown highlights or lost shadow detail in the displayed histograms or the images?[/quote]

Rob leslie
I wanted to do a simple and comical commentary about to "play the game", please take it like it is. Thanks.
You don't see the raw and histograma cuestions, because I wrote about lenses. Why? Because I study them from 1965 and from this moment I had have @ 4000 or 4500 lenses. Of course I didn't probe all of them, but a good cuantity.
I write this for you becase I wan't that who have 50 lenses beleave that I don't answer your questions. May be all of us have to learn, no Rob?

Rob Leslie · Joined: 20 Mar 2007 Posts: 1103 Location: UK Swindon

I believe somebody else has already written that some lenses use contrast to give the 'Perception' of resolution.
Such lenses are sharp but have poor resolving power. They are optimised to be sharp around 25/30 lpm and they won't resolve much more. Some people like such lenses which IMO shows that the 'Perception' works (for some)
IMO Contrast and resolution can be separated to some degree.
One can have a lens with plenty of contrast and little resolution but not a high resolution lens with very poor contrast.
Of course the traditional method of measuring pairs of BW lines isn't that good for digital or for the real world. Unless you spend your time photographing black and white lines! It was perfect for film as film is a binary recording method so sometimes the idea or usual method of measuring resolution sometimes falls short of the reality, in other words the some low contrast lenses will show a surprising amount of resolution when not faced by a high contrast test chart!
Perhaps this is why we all enjoy trying new lenses and have favourite ones which are not generally considered to be classics?
For example one of mine is the early Tamron Ad1 f2.8/3.5 35-80, the one before the SP Ad 2 model.

estudleon
My apoligies as you say we all have to learn.
I have not studied lenses since 1965.
I choose to study photography. Optics was only part of it.
65 was about when I bought my Pentax SL.
1966 was when I started Art College.
Now is the time I'm still wondering how to do it right!!
As you say we have to learn and after 40 years I still haven't a clue.
I do know if you are using lenses on a camera you should consider the effect the camera and its recording medium has on them!

estudleon · Joined: 15 May 2008 Posts: 3754 Location: Argentina

Rob
Thanks. I agree in totum with this. When you say "Of course the traditional method of measuring pairs of BW lines isn't that good for digital or for the real world." It's true.
But this method, across the years, somebody (like me) have it stuck at the skin.
In the real word, for me, the picture satisfaced my aesthetics request or not (the art and the mediums was one of the questions of the70's). No more. But in the theory....... Regards.

Orio · Expire: 2012-12-04

Rob Leslie · Joined: 20 Mar 2007 Posts: 1103 Location: UK Swindon

Hi Orio. I think we agree !!!

You missed the bit
'In other words the some low contrast lenses will show a surprising amount of resolution when not faced by a high contrast test chart'

Or to put it another way low contrast lenses can have good resolution but often fail the old black and white line test.

I am also not too adverse to a bit of controlled flare. Re the old Tam lens I mentioned. one of the things I love about it is the way it will give predictable nice flare (Almost a glow) when used wide open. It is one of my favourite glam lenses.
The complete opposite is true of the Tamron SP f2.8 35-80 lens. This often gives uncontrollable flare or a flare haze which ruins its normal fantastic performance. This lens is an example for picking the right lens for the circumstances. It is great in low contrast light but a dead loss and a big risk in bright open high contrast conditions