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plaubel
1-Feb-2016, 02:47
Let me share some informations I have learned out of the book "the Praxis of Weichzeichnung" from Michael Neumüller.
Some formulas, descriptions - but no illustrations; I don't want to hurt any copyrights...
So if you need this informations, you have to buy the book, or to look at Wiki and so on.

My idea is to bring some informations, day after day, and after all we may discuss point to point.
This may give a good overview in understanding and using soft focus lenses.
Please give me one or two weeks at all.
_________________________________

The basic of a Weichzeichner is a simple meniscus, a positive lens, a konkav/convex formed lens.
This simple lens has a lot of optical mistakes, which are not corrected.
The most important "mistakes" for the Weichzeichnung are chromatic and sphaerical abberations.

Chromatic abberations:
they result in different focus planes of each of the colours of the daylight spectrum, like red, blue, yellow,green.
Remember an optical prisma braking the wavelengths of our light.
So each colour has her own focus point onto the screen, too.

Our eyes will see yellow, and red, more bright than blue or magenta, so we will focus on the screen to the yellow and red focus points.

This means, focusing to the yellow focus point, the blue one is not sharp focused. The first reason for giving a soft focus picture; you can't bring each colour to one focus point.

Depending on the type (ortho/pan/orthopanchromatic) and the sensibilisation of the film, this also gives a focus shift, because the film may see blue better than yellow.
Your eye says yes, it's sharp, and the film may say, no, it isn't.
Focused eyes are sharp on the screen, but the ear is sharp in the picture then. The nose?? Think yourself :-)

As a solution, you can shorten the bellows extension ( focusing more to the blue point),
1/50 of the focal length from your lens. Focused to infinity.
Focusing to near objects, you have to shorten the bellows 1/40 of the focal length.
The given formula is :

(bellows extension x bellows extension) : ( 50 x focal length ).
This will give the needed correction of the bellows.

Using a yellow filter instead the mathematics is easier; that's the reason why some early soft focus lenses came with an installed yellow filter.

- the longer the focal length, the bigger the focus shift
- the bigger the bellows extensions, the bigger the need for correction

Reading this, please don't think of me as a master of Weichzeichnung, I am just a student and want to share some informations!

Thanks,
Ritchie

Tin Can
1-Feb-2016, 03:32
Very interesting. So perhaps I am not so blind. My 405 mm SF lens could require a 10mm focus correction. Which is quite significant.

plaubel
1-Feb-2016, 04:41
My idea is to bring some informations, day after day, and after all we may discuss point to point.

Thanks,
Ritchie

:-)

jp
1-Feb-2016, 05:08
Randy, the Kodak portrait lenses do require a focus shift!

cowanw
1-Feb-2016, 06:41
Kodak claims the portrait lens is colour corrected, to be used with colour film.
jp, are you sure?

djdister
1-Feb-2016, 07:35
Kodak's brochure for the 305mm Portrait lens on the CameraEccentric website describes two different focusing compensation methods, "Catchlight focusing" and "Front focusing" - so yeah, a shift is necessary.

Peter De Smidt
1-Feb-2016, 07:43
While using a filter would help with focus shift, it would lessen softness but also the extended depth-of-field given by the color of light focusing on different points, right?

jp
1-Feb-2016, 08:47
Kodak claims the portrait lens is colour corrected, to be used with colour film.
jp, are you sure?

I believe it is color corrected, but still needs a focus shift. The spherical aberration is tuned such that depth of field is not 1/3 in front focused, but roughly zero DOF in front of the focused point. For portraits with my 305, I focus on the tip of the nose. I'd imagine 405 is even more fussy.

Soft focus lenses have increased depth of field, whether from color or spherical aberration.

cowanw
1-Feb-2016, 10:20
yes this is my experience as well.
I thought we were talking about the shift of film sensitization to blue light as opposed to the eye's GG viewing

I wrote this in 2010

One thing that becomes apparent with these lenses is that wysiwyg on the GG is not really true.
I have found it very helpful to use a sharp specular light source such as a maglight with the top screwed off, with the older style of bulb, not LED
http://www.maglite.com/productline.asp for the non North Americans.
Using this I find a real difference in the nature of the depth of field in front of and behind the subject (light filament)
The Universal Heliar, Kodak Portrait , Verito, Imagon and Veritar all maintain the central core of the filament when the bellows are focussed closer. Focussing towards Infinity the filament changes to a diffuse circle with a dark core. This suggests that these lenses are best focussed on the nose to use the depth of field to extend back to the catch light of the eyes. This is the opposite of what John says so I set up two mag lights for and aft to test this. And this confirms the focus on the front light the a core of specular light in the distant light is maintained. When the focus is on the distant light the core of the front filament is lost to darkness.
The Kodak portrait lens manual on Camera eccentric agrees with this, describing racking the bellows out to focus "the tip of the nose to bring the face into the depth of field". It is a bit confusing about the depth of field being behind the lens focus but it is clear the bellows is racked out to the nose so the face is in the depth of field. "The lack of depth of field is in front of the focused plane." (not behind)
I think if you check out pages 3 and 4 of Camera eccentric
http://www.cameraeccentric.com/html/info/kodak_1.html
You will see this.

The Graf Variable is the opposite of this with the central core of the image being maintained as the bellows is shortened or as focus is shifted to infinity.
The instructions on camera eccentric page 6
http://www.cameraeccentric.com/html/info/graf_1.html
warn against too much bellows extension, which coincides with my observations of it being the opposite of the others.

The Cooke RVP flares as the focus is move to infinity and looses the central core of the filament as the bellows are lengthened, the same as the Graf but with worse flare.

The Cooke soft and the Velostigmat soft favour neither front or rear depth of field.
As to focus shift, it is true that my choice of best focus is different at different f stops but I still wonder if the above different depth of field effects have more to do with this than focus shift. Actual Photos of rulers are in order.
As In all things I may be totally out to lunch

Summarizing, the Graf and Cooke RVP favour focussing on the ears.
The Universal Heliar, Kodak Portrait , Verito, Imagon and Veritar favour focussing on the nose.
Cooke soft and the Velostigmat soft favour focussing on the eyes

Louis Pacilla
1-Feb-2016, 10:34
I believe it is color corrected, but still needs a focus shift. The spherical aberration is tuned such that depth of field is not 1/3 in front focused, but roughly zero DOF in front of the focused point. For portraits with my 305, I focus on the tip of the nose. I'd imagine 405 is even more fussy.

Soft focus lenses have increased depth of field, whether from color or spherical aberration.

Not Exactly the same as focus shift but more a result of having an Achromatic pair behind iris/shutter and this is pretty much true to some extent w/ all Diffused focus lenses set up the same way. Some where not corrected for 'color' and worked on chromatic aberrations and they had 'true' focus shift and what you see was not what you got and the diffusion differs from one type of film to the next and not observable to the eye on ground glass.

W/ focus shift what you see on the ground glass is NOT what will show up in final negative because of shift. W/ the Kodak Portrait what you see on the ground glass should be what you WILL see in the negative. The fact that the image forming behind the point of sharp focus is a result of the pair behind the iris. NOT FOCUS SHIFT.

plaubel
2-Feb-2016, 04:45
After discussing the quality of Kodak lenses, I wish to continue with Weichzeichnung.

The chrom. abberations are contraproductive against Weichzeichnung, because they avoid a sharp picture, which is necessary for a Weichzeichnerpicture.. They look more like an unsharp focused pic.
So, not having much chro. abb. is better for a good WZ picture.

More important for the Weichzeichnung are the sphaeric abberations.
Such a Meniscus lens isn't flat, but it has a concav-convex form and the center is more thick then the rest of the lens.
Again, this results in different focus points, because the rays of the transiting light don't focus on one plane; the center rays go straight to the lens, and wider, but the outer (edge?) rays get a knick depending on the form of the lens - the focus points are not so wide as the center rays.
Because of my language problems, an illustration may help to understand.
If somebody could bring in illustrations of sp. and chrom. abberations, this would be nice.

The sphaeric abberations give the real Weichzeichnung, combined with chrom. abb. or not.

You can focus sharp with the center rays ( we all hope that), but the edge rays will overlay the whole picture with different unsharp pictures. This makes it hard to find a perfect focus.
But this also gives the smooth picture, a lower contrast, and a special deepness in the pic. And, of course, a higher depth of field, undependent of the aperture.

This kind of unsharpness is a totally other one than the unsharpness of the chrom. abberations. It ist unsharp sharp, diffus sharp, or something like this. But somehow sharp.

Using the aperture, you can cut off the outer rays, the center rays will stay, and the picture becomes really sharp.
That's one reason, why older lenses sometimes start at f/11, not at f/4 or f/5,6, when a Weichzeichnung wasn't demanded..

A good light ( p.e. bright sunshine) is very important to bring in some glow, and in my experience, I can better control the Weichzeichnung with the light ( and with stretching the bellows ) then with aperture.
Giving less light as said by the light meter will be a good idea, too, because of the diffusing , the stray light.
A soft focus makes the shadows more bright, too.

On page 18 of the named book, there is given an example for a selfmade soft focus lens.

200 to 300 mm seem to be very useful for 9x12 cm ( 4x5"); you can grab a "Monokel" - this is a half of a pair of glasses. One lens of the glasses. Or other meniscus lenses..
Neumüller named a "Zeiss Punktalglas", but I don't know, if the still excist thisadays.

For installing an aperture, he gives the formula:

install the aperture 1/8 or 1/10 of the focal length, in front of the lens.
This will avoid vignettes.
I remember that he says not to use a normal aperture like if you install the lens in a shutter with aperturte blades.
I am sure, I will find the reason, which I forgot, in the next pages.

Before starting to explain how to use a soft focus lens, Neumüller speaks in some few words about some interesting lenses like a Periskop, a Wessely lens, the famous Nicola Perscheid, the Thambar, the Kühn Achromat, the Universal Heliar - and the Imagon.
Nothing special, just an overview.
Other important, or not so important informations like how to compare diopter with focal length, how to find the aperture of a given focal length and so on are described in this book, too.

Some words to the pictures in the book:
They are not as smooth as the fantastic pictures in this forum.
While reading some real old stuff, I have seen, that historically the german photographers didn't favourite this smooth american style, often described as "to smooth ( like sugar), to dreamish" and so on.
They preferred a subtile Weichzeichnung. I don't know the reason, but I am sure, there has been a reason for them.
This said 100 years ago, Neumüller says the same around 1940,1950, and in listening to some professional phoptographers from today, I can hear the same.
So I believe, this is a kind of old school, and I am lucky to see this dreamish pictures, too :-)
Continueing next with page 36, I will speak about using a Weichzeichner, like Neumüller has done.

Ritchie

Dan Fromm
2-Feb-2016, 07:49
The chrom. abberations are contraproductive against Weichzeichnung, because they avoid a sharp picture, which is necessary for a Weichzeichnerpicture.. They look more like an unsharp focused pic.
So, not having much chro. abb. is better for a good WZ picture.

Neumüller is mistaken.

Berthiot and Boyer both produced soft focus lenses that used chromatic aberration to get the effect. Color (85, 150, 210, 360 f/4 and 750/5) and Opale (a broad range of focal lengths from 50 - 500 mm, all f/4.5) respectively. Both are anachromatic tessar types.

And then there are Puyo-Pulligny anachromatic soft focus lenses. Read about them at http://cnum.cnam.fr/CGI/redire.cgi?8KE464

And of course the highly-valued Pinkham & Smith Semi-achromatic lenses.

For a good overview of soft focus lenses with a discussion of the uses of chromatic aberration, see http://research-repository.st-andrews.ac.uk/handle/10023/505

What, I ask you, has become of the famous teutonic thoroughness?

mdarnton
2-Feb-2016, 08:46
I am suspecting that early on with blue sensitive films the chromatic component of SF was moot, and mainly an impediment to focusing visually. When panchromatic and color films took over, isn't this added problem of seeing the chromatic issues exactly why Wollensak regrouped, discontinued the Verito and replaced it with the Veritar?

After all, how could chromatic behavior been a consideration with film that didn't see that? So much for French fussiness. :-)

plaubel
2-Feb-2016, 08:50
What, I ask you, has become of the famous teutonic thoroughness?

Dan, by using the last quantum of the loosen teutonic thoroughness I have to answer, that Neumüller did not speak about chromatically corrected lenses like Achromates and Anachromates.
At this time, he spoke/ I speak about not corrected, simple meniscus lenses.
Saying "contraproductive against Weichzeichnung" here means the not corrected abberations and may be a bit too global.

The achromat is a lens of a plus and a minus lens, and then further developed to the Achromat, if I don't fail.
Not completely correcting ( but of course correcting, so I believe ) the chrom. abberations may result in a Weichzeichner, too; without owning even one of the described lenses, I will believe your experience.

In reading the whole book we can see, that some chrom.abb. are not so bad, and Neumüller speaks about the differences of soft focus lenses depending on their ratio of chrom. and sph. abberations.

Maybe you will agree, that for a first understanding of the SF theme the sph. abb. are more important than the chrom.ones; if Neumüller or myself are totally wrong, you have to clear this, of course.

Ritchie.

Jim Galli
2-Feb-2016, 09:30
I did not read through everything so forgive me if I'm stepping on toes. Any Achromatic doublet has solved chromatic aberration. That's almost everything. Pinkham got part of his softness WITH chromatic aberration, thus Semi Achromatic in the name. The later Visual Quality series didn't use chromatic aberration any more.

OP; Such a Meniscus lens isn't flat, but it has a concav-convex form and the center is more thick then the rest of the lens.

The ONLY lens I've ever seen that uses this is the Struss. Non achromatic. It is a single meniscus with this type of shape. Highlights have lots of coma.

plaubel
2-Feb-2016, 10:09
Maybe extracting some, but not all informations out of this book is not a perfect solution.
Neumüller described the possibility of using glasses (Monokel, Meniscus) for building a SF lens.

Any Achromatic doublet has solved chromatic aberration.

That's the reason why they call A-chromat, but I'm not sure..

""The ONLY lens I've ever seen that uses this is the Struss.""

I'm sure that some cheap and early german cameras have used meniscus lenses.

5 minutes ago, I immediately grabbed the early Weltax of my father, remembering a Meniscus; I looked at the meniscus lens - but then I have read "Achromat", and right, it's a meniscuslike looking doubled lens..

mdarnton
2-Feb-2016, 10:12
Jim, it's not an old, traditional lens, but now we have the Reinhold-Wollaston if you don't want to recognize the original as a SF, so "ONLY" doesn't fit.

Jim Galli
2-Feb-2016, 10:49
Jim, it's not an old, traditional lens, but now we have the Reinhold-Wollaston if you don't want to recognize the original as a SF, so "ONLY" doesn't fit.

Reinhold's lenses are doublets. I think he just buys them from Edmunds Scientific.

Yes, any dollar store magnifying glass will produce images and some are lovely.

Dan Fromm
2-Feb-2016, 11:51
Dan, by using the last quantum of the loosen teutonic thoroughness I have to answer, that Neumüller did not speak about chromatically corrected lenses like Achromates and Anachromates.
At this time, he spoke/ I speak about not corrected, simple meniscus lenses.
Saying "contraproductive against Weichzeichnung" here means the not corrected abberations and may be a bit too global.

Thanks for the clarification. Anacromats are not acromats, i.e., have chromatic aberration. The terminology is a little difficult.

mdarnton
2-Feb-2016, 13:09
Reinhold's lenses are doublets. I think he just buys them from Edmunds Scientific.

Yes, any dollar store magnifying glass will produce images and some are lovely.

We should ask him but I believe they are sold as single meniscus elements, and I believe I know the source, but won't spill the beans.
http://re-inventedphotoequip.com/Lenses.html
I have two of them and they're definitely not very thick, nor would that be true to what he claims to be doing, which is to replicate the original.

Mark Sawyer
2-Feb-2016, 13:36
The Wollaston is by definition a single meniscus.

A meniscus is by definition a concave-convex lens. A doublet meniscus is also known as a French Landscape Lens, while a plano-convex doublet is known as an English Landscape Lens.

Jim's quite right about doublets being corrected for chromatic aberration; that's the whole reason behind going to the trouble of making a doublet. Some of the better diopter lenses are doublets, like the Nikon 5T and 6T.

In b/w, the chromatic aberrations show very little, and in a conventional soft lens they're overwhelmed by spherical aberration. But in color, you'd get noticeable color fringing.

There were a few soft lenses that achieved their effect primarily by chromatic aberration, such as the Boyer Opale or the Puyo-Pulligny Objectif d'Artiste.

Spherical aberration is the culprit behind focus shift. It's best to focus soft lenses at the taking aperture.

russyoung
2-Feb-2016, 16:25
Heinrich Kühn's Technik der Lichtbildnerei (Halle Saale: Wilhelm Knapp, 1921 ) almost a hundred years later remains IMHO the great German treatise on soft focus although only a portion of the book is about that topic. Kühn's practical knowledge combined with his technical expertise allowed him to address the relevant issues in a clear, concise manner. Read it.

Dan Fromm, thanks for citing my dissertation. Some consolation to know that eight years on, it still has some worth. I am slowly working on revising and updating it for publication, no end in sight, however.

Russ Young

Dan Fromm
2-Feb-2016, 17:15
Russ, your dissertation isn't bad at all and is a useful source of information and insight. I hope you're pleased with it.