On Lens Quality...a question for the optical Gurus

[Michael Graves]

It has been pointed out in numerous threads that some lenses give a different "quality" than others. Some measurements of quality can be measured and explained in mathematical terms. Resolution can be measured in lines per millimeter. Image circle is easily determinted. However, it's clear to me that some qualities cannot be quantified.

As an example I present my 203 Ektar and my 210 Fujinon. Both are extremetly sharp and both have excellent contrast. Tet the same image shot with both lenses is not identical when printed. The Fujinon is almost clinical in its reproduction, and the Ektar is buttery smooth in tonality. I've always attributed some of this to flare, since the Ektar is much more afflicted by it than the Fuji. But the other day I was shooting with overcast skies and using my compendium lens shade. I tried the same experiment with an image of a dam with icicles hanging from it and with banks of finely textured snow. I won't bother posting the images, because the JPEGS are indistinguishable. However, in silver prints on Oriental paper, the differences I described above are apparent. The Ektar digs into the shadows better, while the Fuji separates the ice textures. Is that simply flare or is there another phenomenon at work here?

Or should I speak to my pharmicist about the strength of my prescriptions?

[Jim Noel]

I like and use old lenses because of this difficult to measure or define quality. I only own one essentially "Modern" lens because I do no like the "Cut & Paste" quality of the which is due to their sharp cut-off.

I believe the "body" or "fullness" or "roundness" exhibited by the older lenses is due to a slight to moderate internal flair.I have tried experiments similar to yours with the same results. The uncoated, or single coated lenses have some almost unmeasurable internal flair which is evident even with a very good lens shade. There was an article in the 1939 magazine, "The Encyclopedia of Photography" entitled "Invisible Glass" which did a very good job of describing this almost undetectable internal flair.

[Peter K]

Every lens has it's own personality and multicoating is not always an improvement. And some flare can help to get better shadow details.

But why not discuss this with your pharmicist?

[Ash]

Of all the barrel lenses I've used, I quite like the 'character' they have, versus the clinical reproduction of my Fujinon 150/5,6. Then again, if I take photo's that need quality, I go for the Fuji. If I want a smooth or creamy or flarey or less than perfect reproduction, I'll use an older lens.

[Keith Clementson]

Without seeing your prescriptions, I can't offer an intelligent opinion, which has never stopped me from offering my opinion before.

If you are seeing more detail in the shadows, then you could have a difference in aperature sizes for the same f stop settings. But if the shadows are a higher value without any more detail, then your flare theory is likely correct. If stinging fish fly out of the shadows and attack your pack camel, then your prescription drug theory is most likely the culprit.

[Keith Clementson]

Also, an inaccurate shutter (my guess - the Ektar) would open up your shadows.

[Glenn Thoreson]

I like to use old lenses for a number of reasons, not the least of which is cost. I bought quite a number of superb oldies a number of years ago when it seemed that nobody wanted them. Eurynars for 20 bucks, for example. I have a 203 Ektar and it's really a good lens. The print is indeed where the differences will show up. If I find one lens has a distinct character that I like, that's the one I'll use. I don't question why. It might take away the magic.

[Robert A. Zeichner]

http://web.mac.com/razeichner/iWeb/RAZP%20large%20pix/Shade%20pg%201.html

In the above article you will see two identically exposed and processed negatives that differ only in the type of shade used. In the example on the left, a barn door shade was carefully adjusted to exclude as much non image-forming light from entering the 165mm single coated Angulon used to make the picture. The difference is not only easy to see, but easily measured with a densitometer. It's anything but subtle. the difference with uncoated optics would be even more dramatic.

[Dan Fromm]

Robert, if you didn't use the same shutter with both lenses your results are suspect.

I make this point because in all of the trials (acceptance tests, if you will) I've run with LF lenses on Ektachrome in a Nikon (FG, N8008S on aperture priority auto exposure) very few lenses showed the kind if differences you folks are talking about. I have had a few lenses shoot blue when the subject was temporarily in shadow, but the effect has always disappeared on retest.

The lusable lens that stood out for flare was a 210/9 Konica Hexanon GRII, and that effect is reproducible. The others that stood out were essentially unusable. Of interest, my uncoated 1940 203/7.7 Kodak Anastigmat was just fine.

Cheers,

Dan

[Robert A. Zeichner]

Robert, if you didn't use the same shutter with both lenses your results are suspect..............

Cheers,

Dan

The same shutter was used for both negatives. The exposures were made within a minute of each other under unchanging lighting conditions. I made the first exposure with the barn door shade, removed the shade and replaced it with a round rubber shade and then made the second exposure. Aperture, focus, film processing was identical. Scanning of the two negatives was done simultaneously. The differences you see are due purely to the shade used. I've been able to repeat these kinds of results with other lenses time and again.

[Michael Graves]

Essentially then, we're looking for some way of quantifying flare then, if we want an accurate comparison of two lenses in this regard. Can that be done?

[Brian Ellis]

http://web.mac.com/razeichner/iWeb/RAZP%20large%20pix/Shade%20pg%201.html

In the above article you will see two identically exposed and processed negatives that differ only in the type of shade used. In the example on the left, a barn door shade was carefully adjusted to exclude as much non image-forming light from entering the 165mm single coated Angulon used to make the picture. The difference is not only easy to see, but easily measured with a densitometer. It's anything but subtle. the difference with uncoated optics would be even more dramatic.

I've always suspected that those little round metal filters Nikon, Canon, et al sell at exorbitant prices for their 35mm and digital lenses, as well as the generic rubber ones, are next to useless. In fact they may be worse than useless in that they can create a false sense of security. Thanks for posting a comparison that proves it. The next interesting comparison would be your barn door vs using your hand to shade the lens. I think the results would be similar to what you've posted.

[Jim Jones]

Essentially then, we're looking for some way of quantifying flare then, if we want an accurate comparison of two lenses in this regard. Can that be done?

If a standard subject contains a pure black area and is photographed at a standard exposure, relative flare can be measured with a densitometer. Black paint may not be black enough. A light trap with a glossy black interior that reflects an unilluminated black surface has beenused for this.

[john borrelli]

I am not a lens expert but I think FWIW the differences go beyond flair. I believe at some point in the mid 1970's to early 1980's the designs of lenses and lens coatings became based more on computer analysis. At this point lens designers chose a couple of parameters they thought were most important and designed their lenses around maximizing those few parameters for example one company may have emphasized controlling lens flare and maximizing contrast. Characteristics that were important to the photo magazine lens tests of that time. Lens designers prior to this, I believe just tried to produce a lens that was capable of making the best overall image. These older designs may not generally be as contrasty but may have other appealing qualities, (nice shadow detail, more pleasing bokeh) that the modern computer aided designs deemphasized.

[Robert A. Zeichner]

I've always suspected that those little round metal filters Nikon, Canon, et al sell at exorbitant prices for their 35mm and digital lenses, as well as the generic rubber ones, are next to useless. In fact they may be worse than useless in that they can create a false sense of security. Thanks for posting a comparison that proves it. The next interesting comparison would be your barn door vs using your hand to shade the lens. I think the results would be similar to what you've posted.

Simple round shades do tend to instill a false sense of security, but in their defense and for the user of a hand held camera, they do have some limited effectiveness and are better than none at all. In comparing even those types of shades, I have found a wide range of attention to design detail. Take for example, the treatment of the inside of the shade. Have you ever noticed how some have concentric ridges? These are knife edge baffles and are quite effective in preventing rays of light that are nearly parallel with the lens axis from being reflected back into the lens. The modern shades that have a "petal" design are actually quite good in that from the point of view of the image projected onto the film, they cut in quite close to the frame without vignetting. On LF equipment though, the problem is more daunting. Take as an example a 240 mm lens with an image circle of 320 mm used on a 4x5 camera. The image circle of the lens is more than twice what is needed for 4x5. If you are focused on something much nearer than infinity, that image circle has just grown some. When the dark slide is withdrawn, there is no way you could see what your hand, your hat, your dark slide or any other object you have to hold in front of the lens is doing with respect to shading unwanted non-image forming light. And even if you could predict this, it would only take care of light from one direction as would one of those French flags on an adjustable arm. In a shooting situation where you might have highly reflective sand or snow in the foreground in addition to bright skylight, at best, you would only be reducing the amount of non-image forming light by a small amount. With lenses that have ample coverage for movements and especially when the film format is approaching panoramic in aspect ratio, far more of the lens' rear projected light never reaches the film than does. And we haven't even touched on the business of bellows flare, which btw, with my barn door shade is a non-issue. I'm convinced beyond doubt, that proper shading will reduce flare from the lens and eliminate bellows flare resulting in better local contrast and as a result of that, the appearance of a sharper image.

[venchka]

I am not a lens expert but I think FWIW the differences go beyond flair. I believe at some point in the mid 1970's to early 1980's the designs of lenses and lens coatings became based more on computer analysis. At this point lens designers chose a couple of parameters they thought were most important and designed their lenses around maximizing those few parameters for example one company may have emphasized controlling lens flare and maximizing contrast. Characteristics that were important to the photo magazine lens tests of that time. Lens designers prior to this, I believe just tried to produce a lens that was capable of making the best overall image. These older designs may not generally be as contrasty but may have other appealing qualities, (nice shadow detail, more pleasing bokeh) that the modern computer aided designs deemphasized.

What I remember reading: The MTF chart became the standard for testing lenses. The MTF chart rewards contrast over resolution. Degigners reacted accordingly. All of this seems to happened in the same time frame that you mention.

I still use and like my lenses desinged in the 1950s & 1960s. Lots of resolution without too much contrast. Natural versus "clinical" images.

EDIT:
ps: Someday I'll stumble across a late production 203mm Ektar and pounce all over it.

[David Vickery]

Flare reduces contrast only, and has no other affect on the image. So when you use a good quality lens hood on both lenses then you may allow other characteristics of the lenses to become more visibly apparent. I would expect that the "buttery smooth in tonality" quality of the Ektar is due to residual lens aberrations like coma, etc. that where corrected for in the newer Plasmat or unsymmetrical double gauss Fuji.
I am not sure what the Fuji is but would guess that it has at least six elements and if it only has single coating then under conditions of high flare I can easily imagine that the Ektar, having only four elements, could handle flare better, especially if it is one of the later Luminized examples, even though it is an Dialyte, (two air spaced symmetrical or near symmetrical doublets).

So I think the answer to your question is that the difference that you notice between the two lenses is not due to flare but to the slight lens aberrations that exist in the Ektar. Which were corrected for in the Plasmats and other newer lens designs, which took advantage of the advanced engineering and computer aided design and resulted in sharper, crispier lenses, but not necessarily "better" lenses for Black and White Photography.

I think that Ektar is one of the best lenses ever made and wish that Kodak had made more than just one version of it--an 8x10 version would have been nice. Mine is older and is labeled Anastigmat instead of Ektar.

[David Vickery]

Also, Robert's point about higher local contrast due to less flare is an important part of your answer. While the Ektar is a very sharp lens I wouldn't expect it to be as sharp or have as much resolution as the Fuji. For 5x7 black and white photography, I would rather have the Ektar than the Fuji.

[Steve Hamley]

Folks,

Bob Salomon (HP Marketing, Linhof, etc) has said that the best shade is a compendium just short of vignetting the image circle. I think the conversation here tends to confirm that. ??

Cheers,

Steve

[Robert A. Zeichner]

Folks,

Bob Salomon (HP Marketing, Linhof, etc) has said that the best shade is a compendium just short of vignetting the image circle. I think the conversation here tends to confirm that. ??

Cheers,

Steve

I'm not completely certain of what this means. "Just short of vignetting the image circle"? The image circle as I understand it, is the maximum, evenly illuminated circle of light projected reward and measured at the film plane when focused at infinity. If it's still visible as a circle, the shade has done absolutely nothing to exclude non-image forming light. Could you have meant that a compendium just short of vignetting the image striking the film would be the best shade? In this case, the projection would be close to a rectangle of just slightly larger dimension than the film.

Take a look at the attached image. This is a 14" Commercial Ektar that has been shaded with the barn door shade. It has been adjusted so as not to vignette the image on the film. Notice how much of the front element it obscures? That's because it's preventing all the excess portions of the scene (that aren't part of the composed image) and the related portions of the projected image circle from coming into play. The exclusion of what's coming into the lens reduces lens flare. The attendant reduction of what's projected rearward eliminates bellows flare. That amounts to over half the light that strikes an unshaded lens of this type!

As far as resolution and contrast are concerned, I have seen comparisons of pictures made with lenses of high resolution and so-so contrast with ones made with lenses of modest resolution and excellent contrast and guess what? It is possible to make a sharper looking picture with the latter. This is what MTF is all about. Ideally you would want good bandwidth (high frequency response) aka resolution as well as good depth of modulation (dynamic range) aka contrast to achieve good apparent sharpness. The reduction of flare helps to improve the dynamic range and this is why it is possible to achieve what appears to be a sharper picture.

[Bjorn Nilsson]

In this discussion I'm all with Robert. My primary LF camera is a Sinar F2 (unless when I'm at home and/or shooting 5X7", where I use a P back end, making it a Sinar C). IMO, the trick is to adjust the compendium so that it is just shy of clipping the edges of the image formed at working aperture. This is easy to check if your ground glass has the corners clipped so that you can check the shape of the aperture through the corner. If it's still round you are safe. A more practical (read quick and dirty) approach is to be aware of how to properly use a compendium and then try to set the compendium to at least 80-90% length of the bellows draw. Learning how to do this is probably something for a cold rainy Sunday with nothing else to do. I mean it could be worse, i.e. you could have your mind set to test film and developer combos, which is a lot of fun. ;)
Sinar have some expensive toys to achieve this, see: Sinar.ch shades (http://www.sinar.ch/site/index__gast-e-1978-50-2113.html) but most of these items are available as used gear at a more humane price level.

//Björn