Jump to content

Lens Contrast


Susie

Recommended Posts

Advertisement (gone after registration)

Hi Guys,

 

Today I got my 111f and Summar lens back after having them overhauled at CRR at Luton, and what a lovely job Peter did: cla, new light seals and a new beam splitter for the rangefinder.

 

One comment he made when we chatted on the 'phone, was that the Summar was in exceptional condition :), despite not being coated: it has picked up its own blooming over the last 75 years. All it needed was a chemical clean of the glass.

 

This got me thinking about the oft-quoted 'fault' of low contrast of old lenses, and a possible reason for it. When the lens was new (1938), film speeds were generally much lower than now, Low speed films usually have higher contrast than faster ones, so could the low contrast of the lenses have been beneficial in taming the high contrast of the film? With the use of higher speed, lower contrast films now, the benefit of the lens is now observed as a fault.

 

What do you think?

 

Susie

Link to post
Share on other sites

Basically, you are right in my opinion : 75 years ago photography was ALL ANOTHER ERA, and is difficult for us to imagine how concepts like "contrast" "sharpness" not to speak of "color rendition" were considered at those times, and so more in the context of 35mm photography... at those times an INCREDIBLY LITTLE format for a negative : to obtain a DECENT image, apt to be enlarged to formats like 9x12 or 13x18 was considered a good result : if it was , too, WELL FOCUSED, then it was considered an almost stunning achievement : and the Summar, worth noting, was made FROM THE START with RF coupling, meaning that its usage was adressed to RF coupled Leicas (though the unrangefinder Leica Standards were good sellers... but typically equipped with to the Elmar 50, much less "risky" with its 3,5 max aperture)

 

And high contrast films were the best media to put in evidence the ability of Leica to fine focus the subject... photographers did know well that to have an image really RICH in graytones (which, roughly speaking, needs a low contrast film and a high contrast lens, with proper processing) there was only one way : big negatives/plates on Large Format cameras, on tripod etc... Leica did open a whole new way of photographing, and some tech detail on its lenses (for instance, the low contrast of the Summar) were absolutely MINOR compared to the capability to use a small camera, at f2, and, thanks to this, to catch good images (well focused and with minimal motion blur) of subjects quickly taken on the streets, even moving ones... a way of working simply impossible with the classic Large Format set.

Link to post
Share on other sites

The two arch rivals in 1930/40 were Zeiss and Leica. ONe built highish contrast lenses, the other went for resolution. I forget which was what.

 

As technology advanced, they have come to the conclusion you can not have resolution without contrast otherwise the fine details merge.

 

There was no way to build a high contrast lens at the time. The only control was the number of air/glass interfaces which contributed to flare and low contrast. Then came coating and single coating gave a big boost. Multi coating a bit more , Leica still tries to minimize the number of elements perhaps more so for cost, weight, & size.

 

As late as the 1960`s, Leica and Zeiss to some degree are higher contrast and had way more color saturation than Japanese lenses. There was a definite difference that could be seen a mile away. But the Japanese have different color tastes and they were made that way on purpose. Films were targeted to different world areas also.

 

But no they did not build low contrast lenses to match high contrast film.

Link to post
Share on other sites

It was, of course, the improved contrast given by old lenses' bloom that gave rise to the idea of coating. I will now start a controversy for the forum's physicists.

The received wisdom is that coating reduces contrast by interference. That is the coating is 0.25 of the wavelength of the light thick. Then the ray reflected from the glass surface bcomes half a wavelength out of phase with the incoming light wave and cancels itself out. This always jars with me. If true, then only one colour of light can cancel itself out in this way.

A less prominent theory proposes that the intensity of the reflected light is proportional to the difference in the refractive indices of the two media through which the light is travelling. The refractive index of air can be taken as 1 for all practical purposes. Hence diamond (refractive index 2.42) reflects a greater proportion of light from its surface than a beer bottle (think Newcastle Brown) whose refractive index is ~1.5. Early coatings were made of magnesium fluoride whose refractive index of ~1.38 was about halfway between that of air and the optical glass of the time (refractive index ~1.65). Thus it eased the passage of light through the interface by breaking the transition into two steps.

Multicoating does the same thing for the high refractive index cerium glass (refractive index ~1.9) used in the front element of the f/1.0 Noctilux if the layers of coating have their refractive indices stepped.

Let battle commence!

Link to post
Share on other sites

  • 4 weeks later...

Hello Everybody,

 

Except:

 

Generally speaking Multi-Coating, often seen as a green color cast, is generally more beneficial for lenses made with Low Index glass or lenses having elements with steep curves.

 

Single Coating, generally purple or brown in color, is more often used for lenses made with High Index glass or for lenses made with gentle curves.

 

When Pentax began using & advertising Multi-Coating in the 1970's Leitz said they had been using "Staggered Coating" ,which is using the specific number of layers best suited for an individual lens element's individual surface, for a considerable period of time prior to Pentax's announcement.

 

Keep in mind: Lens coatings can contain a number of inert layers, spacing layers, etc just like the layers that make up a piece of (especially color) film.

 

Leitz also reminded people that they were one of the early inventors of Multi-Coating. Prior to Pentax's announcement.

 

As they were also one of the early inventors of Auto Focus: Correphot.

 

Best Regards,

 

Michael

Link to post
Share on other sites

...This got me thinking about the oft-quoted 'fault' of low contrast of old lenses, and a possible reason for it. When the lens was new (1938), film speeds were generally much lower than now, Low speed films usually have higher contrast than faster ones, so could the low contrast of the lenses have been beneficial in taming the high contrast of the film? With the use of higher speed, lower contrast films now, the benefit of the lens is now observed as a fault.

 

...

 

I don't know if you really can compare film material from the 30s with film as we know it today. My impression is that even low speeds films from the past had lower contrast than faster films today.

 

And I also don't think that they designed lenses deliberately against contrast. It's the mere rules of optics which led to the "muddy" look of old lenses: film had low speeds but they wanted to use an ordinary camera which was not fixed on a tripod (i.e. the Leica and all its followers) at low light. Therefore they looked for lenses with larger openings f/2 (Summar), 1.9 (7.3cm Hektor), f/1.5 (Xenon, Sonnar etc.). But they had to use more and more lens-elements to achieve this - and more lens elements have more borders from air to glass which cause reflections and dramatic loss of contrast. Only coating and new glass sorts got the lens design out of this trap.

 

On the other hand you are right that low contrast lenses become more interesting when too much contrast causes problems. While black and white film is extremely tolerant to high contrast (slide film much less so) it's the digital sensor where too much contrast becomes "dangerous": burned out highlights are the real set back if you compare film to digital photography.

 

If you try out an old lens with low contrast and a modern high-contrasty asph. lens, there are situations where you may be surprised. With sharp lights and deep shadows the modern lens may easily lead to burned out highlights. When you compare the histogram of the same subject taken by an old lens with much less contrast, it looks much narrower and will seldom reach the border of burning out highlights or drowning shadows - but it also looks muddy.

 

Now post-procession comes in: with the old lenses file you can increase contrast dramatically without acieviung artefacts etc. Those "boring" files seem to be much more flexible in post processing than the tack-sharp files from an aspherical lens.

 

If you look into the threads with "old glass" on different digital M-bodies you find many examples where contrast is no problem for old lenses - I think this is a result of successful post-processing. Of course these lenses have other issues which cannot be solved by software, but "old glass" could gain a lot of attractivity when it is cleverly used with digital photography.

  • Like 2
Link to post
Share on other sites

It is a nice idea that low contrast lenses tamed the high contrast films.

 

The only problem with the theory comes during the following decades with the development of faster films with higher contrast and the parrallel development of faster lenses with higher contrast. The contrast war was on, and Leica have never stopped.

 

We have a situation today where the rendering an image in high micro contrast is considered 'normal', and far higher and sharper than you would see in real life. Lenses with high micro contrast together with the 'Clarity' slider in Adobe Camera Raw are both used to boost an image. So it is a relief when I put a 5cm Elmar on my M9 and render the file with low micro contrast, something more in tune with normal human vision. There is a lot to be said in favour of using low contrast lenses today because you can always increase it digitally, but it is far less easy to decrease it.

 

Steve

  • Like 6
Link to post
Share on other sites

  • 3 weeks later...

My experience with "old" Leitz lenses, not only with the M8/M9 but with b&w films such as the late lamented Kodak Technical Pan or present Spur films as well as Kodachrome, tells me that for my taste, some types of scenery will only look as I subjectively remember if I use the older lenses such as the 1st version of the 35mm Summicron, the collapsible 50mm Summicron or the second version of that lens etc.

As an example I usually mention the Yangste Gorges, where haze produces pastel like scenes of mountain ranges fading away into the distance. With the modern lenses the picture is less pastel like and more contrasty, which the original scene was not according to my eyes and, as I said, my subjective memory.

That means that I chose lenses according to what I want the picture to look like, very much depending on the subject and the lighting, the mood and so forth.

Teddy

  • Like 2
Link to post
Share on other sites

Hello Teddy,

 

Interesting observation.

 

I would agree that photographing in daylight with a 1st version 35mmm Summicron using Kodachrome 64 gives a more accurate record of what is there than doing the same with some other lenses using the same film. Especially at F4, 5.6 & 8.

 

I have also found that if you then photograph a portion of that same scene again using a 135mm F4 Tele-Elmar, also with Kodachrome 64, that the quality of the image captured is even better. That image has even more brilliance, depth & permutations of shades of difference. And really deep blacks. Just like when you were there.

 

Best Regards,

 

Michael

Link to post
Share on other sites

Thanks for the comment.

Presently, I am wondering what the performance of my favorite Mandler lenses may be like on the new M.

I have a new M on order but am not decided on the purchase until the firmware is more or less final and I have tried some of my "old" lenses on the new camera. Apart from the possibility to use my R lenses, the most important facet for me is the rendering of the old lenses. High ISO without noise is secondary to me, as I usually photograph non-moving subjects and use either large openings or a monopod (where possible).

Teddy

Link to post
Share on other sites

Thanks for the comment.

Presently, I am wondering what the performance of my favorite Mandler lenses may be like on the new M.

I have a new M on order but am not decided on the purchase until the firmware is more or less final and I have tried some of my "old" lenses on the new camera. Apart from the possibility to use my R lenses, the most important facet for me is the rendering of the old lenses. High ISO without noise is secondary to me, as I usually photograph non-moving subjects and use either large openings or a monopod (where possible).

Teddy

Hi Teddy,

Modestly I made some tests you can check in ther :

http://www.l-camera-forum.com/leica-forum/leica-m9-forum/276893-m240-old-lenses.html

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...