US2925338A - Photographic masking using the callier effect - Google Patents

Description

Un -e SW PemQ Serial-No. 556,036 4 Claims. (Cl. 96-6) This 'inventiori relates to photography and to a method of producingmasked photographic images. F

More particularly, it relates 'to the. use of the -Callier effect in the preparation of corrected: color Separations.

; In the practice of color photography,it is; frequently:

necessary to make prints from color film originals? In making prints, a loss of color saturation occurs; dueyin large measure, to the imperfect. absorption' andftrans Other objects will be-readily apparent from the followinstance, the one vdescribed in US. Patent 2,635,959.; provides only a compromise gradient thatdoes not comp'ensate for the differences betweenthe unequalspurious blueand red densities' in the; magenta layer when used in the;usual described manner.

=It is an object of this invention'to provide a process of masking in-which a single silver mask 'is used toy correct completelyrtwog unequal spurious densities in a-g subtractive dye image-which absorbsto a difierent ex-;

it is supposed to transtent the two .1 primaries which ing description; v

I have found that these objects can be accomplished by utilizing the. Callier efliect to alter and controlthe effective gradient'or printing gamma of a: silver mask.

Bythis means, a single silver mask can providejthe f tvvoj-gradients, required to satisfy optimum masking: con-,

ditions. I

1909 :and' is"discussed-thoroughly inmany photographic V f texts including ,Mees TheTheoryof .the Photographic mission characteristics of the dyes available for use in' color films. F or example,'tlie greenrecord is commonly composed of a magenta dye and should modulatejand absorb only green light." However, available magenta; dye images which are formed the available color processes have considerable undesired blue and red density and will undesirablymodula'te and absorb blue andflredlight to that extenh This same difiiculty also exists with respect to the cyan dye images because" the cyan dyes formed absorbsome'of the blue and green light whic'h they are supported' to transmit completely.

Theavaflable yellow dye images are*generally-closer to ideal and are frequently althou'gh' not always, ac-

cept-able in "regard to color absorption characteri'sticsy These defects in'color absorption are remedied by a "mask-ing procedure which consist's essentially of making an inver'se' record of the original dye image processedto a coiitrast suitable" for cancellation of the undesirable d ensit E This inverse recordis used combined in registration fwith theoriginal'image to effect the desired cancellation.

Processj" ,revisededition; 1954, :pages 816 821, and-Neb-j 'lettes Photography; Its .Materials andP-rocesses. 5th edition (1952); pages*25025 1. Stated in essence, Callier zfound ythat specular light yields'maximum density) --andcontrast from a silver -image,'and the addition of diftusionin'to thealightrwillreduce the etfective density. and contrast; The-ratio of specular to difluse density, .is called theifQ factor. This etfect'is based on the-light Y 'sca'tteringability ofythe silver'ima'ge. By a suitable selec- I tiori of. a film material' for-a mask which exhibits a rela- I tively :high, Q'tactor; a Ivariety; of effective gradients 1 canibevefiected from a single mask by controlling .the 2 In gendegree of difiusionof the printing-light source.

Xeral,the efie'c-t becomeS-Qmore pronounced and'gtheQ maskitselfl It has also been proposed to-use a 'vecto-- -45.

qui'red for the diiiei ent spectrum" bands. In this solution tothe'problem, the mask image is composed offa d'ye image to provide the required differential-of contrast versus Wavelength. The'use offdye images for correction suffers from the disadvantagesofrequiring special processing andcontrol methodsl" Even under optimum;

conditions, the very natureof tlie' dyes and of the dye images" formed renders the color"'1r iasks less .precis'e than silver masks.

Silver images for masking have thefprac-tical advantage of simplicity because the commonly available proc-' essingsmethods provide the needed accuracyofgradient control. Unfortunately, these-silver masks'are nottcolor selective and; in most instances, several masks" must.

be used sinceyfor example, the'un'desired blue and red densities of "a typical magenta dye are .notcq'ual, usually havingLabout'twice as.much=-undes'ired blue density as record'--mus't-be used for correcting the? undesired blue density when printing the blue separatiomor record.:

Anotherl silvermask processed to a lower contrastjthan the-blue mask must be usediwhenprinting the red sepa-= ra-tionwor record. J

2v It 'lias:also';b'een'proposed to. useintegral silver masks factor increases with anincreasein grain'size and density of-th'e silver. image."

butdoesnot'aflect the: effective printing gamma ofthe graph ora silver iodide'image for the formation of the mask and to control the .amount' of correction by. ad-

justingjthe orientation of thepolarizing filter. These, methods require'not 'only additional equipment and opera'tions and are limitedjto thej use of special materials? but,also.introduceadditional sources of error into the reproduction-method, andlack the simplicity connected with the use ofa' simple vsilver "mask.

5 The essential requirements -to utilize my'method of masking are as follows.

.factorimage so'that its contrast will not be" affected to any appreciable degree. Thisrequirement is readily met by most color images because the dyes have inherently a veryhl'ow'Q factor. The masking image must have a high Q factor as provided by a silver image of larger.

v grain size so that various degrees of diffusion or colliimage contrasts.

In. the productionof matio n of -the light willproduce. relatively effective mask -film of the integral three-layer type is used for the original':photography'. From this, direct prints can belmade V wh'enevepno special efiectsarelrequired But, in order; tof-include. special efiects, to providezadditional master: e at ve an r o hetr asqn uc f -a din rdama "to the original, a duplicate negative is prepared using a;

inewhich'za-wcorrecting silver image 1s lncorporated in I the color film. 0f necessity; thisi-type' of, mask; for, 1

Patented Feb. 15; 1960 The Ca-llier elfect,-.or::Q factor, has, been known since motionpictures, the -f o1l owing' q I process sequence is commonly used. color negative set of separation positives. From these separation positives, a duplicate negative is made which is then used to make the final prints. This duplicate negative, be-

cause 'of the process-and printing steps, can include special effects. Inasmuch as the dyesof the original negative display undesired absorption, masking is used in printing the separation positives." Ordinarily, two different masks must be used for the'correction of the green record because the blue and red absorptions of the magenta layer are of different magnitudes. In accordance with my invention, the Q factor of the mask is controlled in printing the separation positives, and permits the use of a single mask to correct for the unequal blue and red spurious densities of the color negative magenta image. Similarly,'unequal green and blue spurious densities of the cyan dye may be cancelled by the use of a single mask.

The following example will'serveto specifically describe the invention as applied to a multilayer color negative film containing color formers. This example should not, however, be construed as limiting or restricting the present invention, but should be considered 'as merely illustrative.

A multilayer color negative camera film containing color formers is prepared according to the methods described in US. Patents 2,179,228,"2,179,239, 2,186,849 and 2,220,187, and consists of an integral tripack emulsion coated on the usual clear cellulose acetate or nitrate film base. Each of the silver halide emulsions is sensitized to one of the primary colors of light, namely, blue, green, and red, and contains a color former fast to diffusion capable of coupling with the oxidation products of an aromatic amino developer to form dyestufi images complementary in color to the sensitivity of the layers. The top layer is blue sensitive and contains p-stearylamino benzoylacetamino-S-terephthalic acid as a yellow color former. A filter layer, yellow in color and blue absorbing, lies under the top layer. Below this filter layer, lies a green sensitive emulsion layer containing 1-(4'-phenoxy- 3'-sulfophenyl)-3-stearyl-5-pyrazolone as the magenta color former. The lowest emulsion layer is red sensitive and contains a mixture of l-hydroxy-Z-naphthoyl-N- octadecylamide-4-sulfonic acid and l-hydroxy-2-naphthoyl-2-N-methyloctadecylamino-5'-sulfoanilide as a cyan color former.

The film was exposed in a camera to an original scene and color developed for 15 minutes in-a color developer of the following composition:

Sodium hexametaphosphate gms 1 Sodium sul-fite ms 3 N-ethyl-N-(fl-hydroxyethyl)amino aniline gms 7 Sodium carbonate (monohydrate) gms 75 Sodium sulfate (anhydrous) gms 30 Potassium bromide gms" 2 Thallium nitrate, solution ml 5 Potassium iodide mgs 3 Water to make 1 liter.

The developed film was shortstopped for 3 minutes in a bath of the following composition:

Sodium acetate gms 20 Acetic acid re Water to make 1 liter.

The shortstopped film was hardened for 5 minutes in a.

3% aqueous solution of potassium chrome alum.

After washing for 5 minutes in running water, the film was treated in a bleach bath of the following composition:

Water to make 1 liter.

The developed material was washed for 5 minutes and then fixed for 3 minutes in a solution of the following composition:

Hypo gms 200 Water to make 1 liter.

After fixing, the film was washed for 10 minutes in running water and allowed to dry.

A slow speed, fine grain panchromatic film of the type ordinarily used for duplicating black and white negatives was used as the light sensitive material for the preparation of the mask. It was exposed in a contact step printer fithrough the color negative with green light. provided by a 3200 K. lamp in combination with a Wratten #61 and a Wratten #15 filter to-provide a positive record of the magenta layer. The exposed film was developed to a gamma of .32 (as measured by the Ansco Sweet Densitomet'er, Model 12).in a developer having the. following Water to make 1 liter.

The developing time is 3 minutes at 68 F. The separation positives are made in an optical printer.

The original negative andthe raw stock (a fine grain,-

panchromatic black and white film of the positive duplicating motion picture type) are placed emulsion to 6111111? sion side in contact as a bipack in the camera head side.

The mask is used in the projector head side, emulsion This orientation is used side toward the light source. to facilitate registration because it permits mask image 1 size and position adjustments. a

The green separation is exposed with green' light.

through the combination of a Wratten #61 and a Wratten #15 filter without the use of a mask. The green separation is developed for a period of 4 minutes in the;

above blackv and white developer to a gamma of 0.67.

The blue separation is exposed in registry with the mask through a Wratten #47 combined with an Ansco UV 16P ultraviolet filter. The normally highly collimated light source is used to provide specular light with maximum efiective density of the silver image in the mask. The effective gamma of the mask is .43. The blue separation is developed to a gamma of 1.77 which is obtained after 17 minutes of development.

The red separation is exposed in registry with the maskv Twowith ditfuse'light through a Wratten #29 filter. plates of ground glass were placed in the beam of the light source to produce the desired diffusion. Measured in diffused light, the mask had an effective gamma of .21. The red separation is processed to a gamma of 1.07 by developing the exposed film for 9 minutes in the above black and white developer.

A balanced set of masked and color corrected separations was obtained which was printed in the conventional manner onto a color negative multilayer film available as Ansco Color Duplicating Negative Type 846 to prepare a duplicate negative. This duplicating film is similar to the camera color negative film except for the use of emulsions of slower speed which is characteristic of duplicating materials.

It will be evident from the foregoing description that, in my masking method, the effective image contrast of the mask depends upon the relative degree or ratio of diffusion or collimation of the printer light; and to a lesser degree, upon the particle size, a factor as expressed by the shape and distribution characteristics of the developed silver in the mask. For maximum utilization of the effect,

a high Q factor is desired. V

My masking method can also be used to improve the results obtained with an integral silver mask such as the one described in Harsh and Friedmans US. Patent 2,635,959. In this method, a mask is formed after oolor development in the magenta layer utilizing the residual halides which are developed to a silver mask image. Whenprinting from such an integral silver mask color negative, the silver mask will exhibit a Q factor much higher than the dye image. The exposurewith red light is carried out with diffusion to produce a relatively lower efiective mask contrast while the exposure with blue light is carried out with specular light to produce a higher eifective contrast. The green light exposure may be printed with either diffuse or specular light since the mask does not have a color corrective action upon the green record magenta dye, but provides only a contrast reduction. However, the mask has both a color corrective and contrast reducing effect upon the cyan and yellow dye images. Proper compensation for the loss of contrast is accomplished by increasing the layer contrasts of the negative, the positive or both. In this manner, only the dual color correction effect of the mask is retained without any loss of contrast.

While I have herein disclosed the preferred embodiments of my invention, I do not desire to limit myself solely to the foregoing illustrative example, since it will be readily apparent to those skilled in the art that the foregoing procedural steps may be varied and other similar steps and processing solutions employed without departing from the spirit and scope thereof. For example, a positive record of the cyan image can be used to correct for unequal spurious absorptions of the blue and green primaries by the cyan layer. In this case, the red record is printed with red light without the use of a mask While both the green and blue records are printed in registration with the silver mask using specular light for the primary requiring a higher effective mask-contrast and using diffuse light for the other primary requiring a lower effective mask contrast.

Instead of color formers fast to diffusion, there may be used a multicolor film in which each element bears a color yielding layer comprising a hydrophilic, film-forming synthetic polymer containing a plurality of hydroxyl groups and having a plurality of color components and, in addition, containing light sensitive silver salts as described in US. Patents 2,397,864, 2,397,865, 2,397,866 and 2,397,867. Accordingly, therefore, only such limitations should be imposed as are indicated in the following claims.

I claim:

1. The method of making color corrected color separation positives from a multilayer subtractive color negative containing in the magenta layer, a magenta dye image having, in addition to the green absorption density, an undesired absorption density for blue and an undesired absorption density for red, the undesired density of blue being greater than the undesired density of red, which includes the steps of preparing a positive colorcorrection silver masking image which is a positiverecord 0f, the magenta image, placing the silver mask in registry with said multicolor negative and printing the masked negative onto a black and whitefilm while changing the effective printing gamma of the silver mask by using a collimated blue light for the printing of the blue separation, and a difius'ed red printing light for the printing of the red separation, the degree ofdiffusion of said red printing light being such as to equalize the effective printing gamma of the silver correction mask with the gamma of the undesired absorption density for red.

2. The method of preparing color corrected color separation positives from a multilayer subtractive negative containing in the several layers, yellow, magenta and .posing a lightsensitive silver halide film with green light through the negative and developing the exposed film to a silver positive, placing the mask thus obtained in registry with the multicolor negative and printing the blue separation with specular blue light, and printing the red separation with diffused red light, the degree of diffusion of said red printing light being such as to equalize the effective printing gamma of the silver correction mask with the gamma of the undesired density of red.

3. The method of making color corrected color separation positives from a multilayer subtractive color negative containing in the cyan layer, a cyan dye image having, in addition to the red absorption density, an undesired absorption density for blue and an undesired absorption density for green, the undesired density of blue being greater than the undesired density of green,

which includes the steps of preparing a positive color' correction silver masking image which is a positive record of the cyan image, placing the silver mask in registry with said multicolor negative and'printing the masked negative onto a black and white film while changing the effective printing gamma of the silver mask by using a collimated blue light for the printing of the blue separation, and a djfius edfgreen printing light for the printing of the green separation, the degree of diffusion of said green printing light being such as to equalize, the effective printing gamma of 111615111161 correction mask with the gamma of the undesired absorption density for green.

4. The method of preparing color corrected color separation positives from a multilayer, subtractivenegative containing in the several layers, yellow, magenta and cyan part images in which the yellow part image does not require correction, in which the cyan part image absorbs, in addition to red, also lower and undesired densities of blue and green, the undesired density of blue being greater than the undesired absorption of green and in which the magenta image absorbs, in addition to green, also the primaries red and blue, which includes the steps of preparing a positive color correction silver mask by exposing a light sensitive silver halide film with red light through the negative and developing the exposed film to a silver positive, placing the mask thus obtained in regis try with the multicolor negative and printing the blue separation withspecular blue light, and printing the green separation with diffused green light, the degree of diffusion of said green printing light being such as to equalize the effective printing gamma of the silver correction mask with the gamma of the undesired density of green.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Mees: The Theory of the Photographic Process, revised edition, Macmillan Co., N.Y., (Copy in Scientific Library.)

1954, page 818.

Claims (1)

1. THE METHOD OF MAKING COLOR CORRECTED COLOR SEPARATION POSITIVES FROM A MULTILAYER SUBTRACTIVE COLOR NEGATIVE CONTAINING IN THE MAGENTA LAYER, A MAGENTA DYE IMAGE HAVING, IN ADDITION TO THE GREEN ABSORPTION DENSITY, AN UNDESIRED ABSORPTION DENSITY FOR BLUE AND AN UNDESIRED ABSORPTION DENSITY FOR RED, THE UNDESIRED DENSITY OF BLUE BEING GREATER THAN THE UNDESIRED DENSITY OF RED, WHICH INCLUDES THE STEPS OF PREPARING A POSITIVE COLOR CORRECTION SILVER MASKING IMAGE WHICH IS A POSITIVE RECORD OF THE MAGENTA IMAGE, PLACING THE SILVER MASK IN REGISTRY WITH SAID MULTICOLOR NEGATIVE AND PRINTING THE MASKED NEGATIVE ONTO A BLACK AND WHITE FILM WHILE CHANGING THE EFFECTIVE PRINTING GAMMA OF THE SILVER MASK BY USING A COLLIMATED BLUE LIGHT FOR THE PRINTING OF THE BLUE SEPARATION, AND A DIFFUSED RED PRINTING LIGHT FOR THE PRINTING OF THE RED SEPARATION, THE DEGREE OF DIFFUSION OF SAID RED PRINTING LIGHT BEING SUCH AS TO EQUALIZE THE EFFECTIVE PRINTING GAMMA OF THE SILVER CORRECTION MASK WITH THE GAMMA OF THE UNDESIRED ABSORPTION DENSITY FOR RED.