Abstract:
Low silver black-and-white photographic silver halide elements, such as radiographic films, can be processed quickly using black-and-white developing and fixing compositions having reduced photoprocessing activity. The entire process is fairly rapid and effective despite the lowered concentrations of photographic developing and fixing agents.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to photography and in particular to improved processing of black-and-white photographic elements. More particularly, it relates to a method of processing low silver black-and-white films using suitable development and fixing steps, and to a processing kit useful therein. 
     BACKGROUND OF THE INVENTION 
     Roentgen discovered X-radiation by the inadvertent exposure of a silver halide photographic element. In 1913, Eastman Kodak Company introduced its first product specifically intended to be exposed by X-radiation (X-rays). Silver halide radiographic films account for the overwhelming majority of medical diagnostic images. It was recognized almost immediately that the high energy ionizing X-rays are potentially harmful, and ways were sought to avoid high levels of patient exposure. Radiographic films provide viewable silver images upon imagewise exposure followed by rapid access processing. 
     One approach, still in wide-spread use is to coat the silver halide emulsions useful in radiographic films on both sides of the film support. Thus, the number of X-rays that can be absorbed and used for imaging are doubled, providing higher sensitivity. Dual-coated radiographic films are sold by Eastman Kodak Company under the trademark DUPLITIZED films. Films that rely entirely on X-radiation absorption for image capture are referred to in the art as &#34;direct&#34; radiographic elements, while those that rely on intensifying screen light emission are referred to as &#34;indirect&#34; radiographic elements. 
     There are other applications for direct radiographic films, such as in various industrial applications where X-rays are captured in imaging, but intensifying screens cannot be used for some reason (such as for pipeline and turbine blade welds). 
     It is the prevailing practice to process radiographic films using black-and-white development, fixing, washing and drying. Films processed in this manner are then ready for image viewing. 
     Photographic black-and-white developing compositions containing a silver halide black-and-white developing agent are well known in the photographic art for reducing silver halide grains containing a latent image to yield a developed photographic image. Many useful developing agents are known in the art, with hydroquinone and similar dihydroxybenzene compounds and ascorbic acid (and derivatives) being some of the most common. Such compositions generally contain other components such as sulfites, buffers, antifoggants, halides and hardeners. 
     Fixing compositions for radiographic films are also well known and include one or more fixing agents, of which thiosulfates are most common. Such compositions generally include sulfites as antioxidants. 
     U.S. Pat. No. 5,800,976 (Dickerson et al) describes radiographic elements having lower silver coverage and including certain covering power enhancing compounds within the silver halide emulsions. Such elements are generally processed in conventional developing compositions that include hydroquinone or other dihydroxybenzene compounds. 
     There is a need however to have less costly processing compositions that have less reactive components, particularly when elements having lowered silver are processed. In addition, the industry needs a processing method that can provide acceptable black-and-white images in a short time. 
     SUMMARY OF THE INVENTION 
     The noted problems are overcome with a method for providing a black-and-white image comprising: 
     A) developing an imagewise exposed black-and-white photographic silver halide element using a black-and-white developing composition that has a pH of from about 9 to about 12 and comprises: 
     from about 25 to about 200 mmol/l of a dihydroxybenzene black-and-white developing agent, 
     from about 100 to about 600 mmol/l of sulfite ions, and 
     from about 2 to about 12 mmol/l of an auxiliary co-developing agent, and 
     B) fixing the developed black-and-white photographic silver halide element with a fixing composition that has a pH of from about 4 to about 6 and comprises from about 40 to about 120 mmol/l of sulfite ions, and from about 250 to about 950 mmol/l of a photographic fixing agent other than a sulfite, 
     the method being carried out for at least 60 seconds, 
     wherein prior to step A, the black-and-white photographic silver halide element comprises a support having disposed on each side thereof, a silver halide emulsion unit that comprises silver halide grains and a gelatino-vehicle, the silver halide grains comprising at least 95 mol % bromide based on total silver, at least 50% of the silver halide grain projected area being provided by tabular grains having an average aspect ratio greater than 8, a thickness no greater than 0.10 μm, and an average grain diameter of from about 1.5 to about 3 μm, 
     the coverage of silver in each silver halide emulsion unit being no more than 11 mg/dm 2 , and the coverage of the gelatino-vehicle in each silver halide emulsion unit being no more than 11 mg/dm 2 . 
     This invention also provides a processing kit comprising: 
     a) a black-and-white developing composition that has a pH of from about 9 to about 12 and comprises: 
     from about 25 to about 200 mmol/l of a black-and-white dihydroxybenzene developing agent, 
     from about 100 to about 600 mmol/l of sulfite ions, and 
     from about 2 to about 12 mmol/l of an auxiliary co-developing agent, 
     b) a fixing composition that has a pH of from about 4 to about 6 and comprises from about 40 to about 120 mmol/l of sulfite ions and from about 250 to about 950 mmol/l of a photographic fixing agent other than a sulfite, and 
     c) a black-and-white photographic silver halide element comprising a support having disposed on each side thereof, a silver halide emulsion unit that comprises silver halide grains and a gelatino-vehicle, the silver halide grains comprising at least 95 mol % bromide based on total silver, at least 50% of the silver halide grain projected area being provided by tabular grains having an average aspect ratio greater than 8, a thickness no greater than 0.10 μm, and an average grain diameter of from about 1.5 to about 3 μm, 
     the coverage of silver in each silver halide emulsion unit being no more than 11 mg/dm 2 , and the coverage of the gelatino-vehicle in each silver halide emulsion unit being no more than 11 mg/dm 2 . 
     The present invention provides a means for effectively and efficiently processing low silver black-and-white photographic silver halide elements using lower cost black-and-white developing and fixing compositions. These compositions include reduced amounts of photographic processing reagents. 
     Processing can be accomplished in a relatively rapid fashion because of the combination of the low silver element and specific processing compositions. The element has lower silver and binder coverage than normal, allowing for the processing compositions to diffuse quickly into the element, cause desired chemical reactions, and remove unwanted silver with less photographic reagents than normal. This is particularly true for fixing wherein the lower silver level also allows for faster reaction between photographic fixing agents and the silver. As processing times increase, further dilution of the compositions is possible. Thus, the advantage can be realized with faster processing times or processing with more dilute compositions. The developing and fixing compositions can also be formulated as one-part powders that readily dissolve and provide other advantages. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is useful for providing a black-and-white image in a photographic silver halide element, and preferably a low silver halide radiographic film. Other types of elements that can be processed using the present invention include, but are not limited to, aerial films, black-and-white motion picture films, duplicating and copy films, and amateur and professional continuous tone black-and-white films that have lower silver halide coverage. The general composition of such materials is well known in the art but specific features that render them particularly adaptable to the present invention are described below in more detail. 
     The black-and-white developing composition of this invention contains one or more black-and-white dihydroxybenzene developing agents, including hydroquinone and derivatives thereof that would be readily apparent to those skilled in the art (see for example, U.S. Pat. No. 4,269,929 of Nothnagle and U.S. Pat. No. 5,457,011 of Lehr et al). Hydroquinone is the preferred black-and-white developing agent. Mixtures of these developing agents can be used if desired. 
     The black-and-white developing composition also includes one or more auxiliary co-developing agents that are also well known (for example, Mason, Photographic Processing Chemistry, Focal Press, London, 1975). Any auxiliary developing agent can be used, but the 3-pyrazolidone developing agents are preferred (also known as &#34;phenidone&#34; type developing agents). Such compounds are described, for example, in U.S. Pat. No. 5,236,816 (noted above). The most commonly used compounds of this class are 1-phenyl-3-pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazolidone, 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone, 5-phenyl-3-pyrazolidone, 1-p-aminophenyl-4,4-dimethyl-3-pyrazolidone, 1-p-tolyl-4,4-dimethyl-3-pyrazolidone, 1-p-tolyl-4-hydroxymethyl-4-methyl-3-pyrazolidone, and 1-phenyl-4,4-dihydroxymethyl-3-pyrazolidone. Other useful auxiliary co-developing agents comprise one or more solubilizing groups, such as sulfo, carboxy or hydroxy groups attached to aliphatic chains or aromatic rings, and preferably attached to the hydroxymethyl unction of a pyrazolidone, as described for example, in U.S. Pat. No. 5,837,434 (Roussihie et al). A most preferred auxiliary co-developing agent is 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone. 
     Less preferred auxiliary co-developing agents include aminophenols such as p-aminophenol, o-aminophenol, N-methylaminophenol, 2,4-diaminophenol hydrochloride, N-(4-hydroxyphenyl)glycine, p-benzylaminophenol hydrochloride, 2,4-diamino-6-methylphenol, 2,4-diaminoresorcinol and N-(β-hydroxyethyl)-p-aminophenol. 
     A mixture of different types of auxiliary developing agents can also be used if desired. 
     An organic antifoggant is preferably present in the black-and-white developing composition, either singly or in admixture. Such compounds control the gross fog appearance in the processed elements. Suitable antifoggants include, but are not limited to, benzimidazoles, benzotriazoles, mercaptotetrazoles, indazoles and mercaptothiadiazoles. Representative antifoggants include 5-nitroindazole, 5-p-nitrobenzoylaminoimidazole, 1-methyl-5-nitroindazole, 6-nitroindazole, 3-methyl-5-nitroindazole, 5-nitrobenzimidazole, 2-isopropyl-5-nitrobenzimidazole, 5-nitrobenzotriazole, sodium 4-(2-mercapto-1,3,4-thiadiazol-2-yl-thio)butanesulfonate, 5-amino-1,3,4-thiadiazol-2-thiol, 5-methylbenzotriazole, benzotriazole and 1-phenyl-5-mercaptotetrazole. Benzotriazole is most preferred. 
     The developing composition also includes one or more preservatives or antioxidants. Various conventional black-and-white preservatives can be used including sulfites. A &#34;sulfite&#34; preservative is used herein to mean any sulfur compound that is capable of forming or providing sulfite ions in aqueous alkaline solution. Examples include, but are not limited to, alkali metal sulfites, alkali metal bisulfites, alkali metal metabisulfites, amine sulfur dioxide complexes, sulfurous acid and carbonyl-bisulfite adducts. Mixtures of these materials can also be used. 
     Examples of preferred sulfites include sodium sulfite, potassium sulfite, lithium sulfite, sodium bisulfite, potassium bisulfite, sodium metabisulfite, potassium metabisulfite, and lithium metabisulfite. The carbonyl-bisulfite adducts that are useful include alkali metal or amine bisulfite adducts of aldehydes and bisulfite adducts of ketones. Examples of these compounds include sodium formaldehyde bisulfite, sodium acetaldehyde bisulfite, succinaldehyde bis-sodium bisulfite, sodium acetone bisulfite, β-methyl glutaraldehyde bis-sodium bisulfite, sodium butanone bisulfite, and 2,4-pentandione bis-sodium bisulfite. 
     Various known buffers, such as borates, carbonates and phosphates, can be included in the composition to maintain the desired pH. The pH can be adjusted with a suitable base (such as a hydroxide) or acid. The pH of the developing/fixing composition is generally from about 9 to about 12, and more preferably from about 10 to about 11. 
     It is also optional that the black-and-white developing composition contain one or more sequestering agents that typically function to form stable complexes with free metal ions (such as silver ions) in solution, in conventional amounts. Many useful sequestering agents are known in the art, but particularly useful classes of compounds include, but are not limited to, multimeric carboxylic acids as described in U.S. Pat. No. 5,389,502 (Fitterman et al), aminopolycarboxylic acids, polyphosphate ligands, ketocarboxylic acids, and alkanolamines. Representative sequestering agents include ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, 1,3-propylenediaminetetraacetic acid, 1,3-diamino-2-propanoltetraacetic acid, ethylenediaminodisuccinic acid and ethylenediaminomonosuccinic acid. 
     The black-and-white developing composition can contain other additives including various development restrainers, development accelerators, swelling control agents and stabilizing agents, each in conventional amounts. Examples of such optional components are described in U.S. Pat. No. 5,236,816 (noted above), U.S. Pat. No. 5,474,879 (Fitterman et al), Japanese Kokai 7-56286 and EP-A-0 585 792. 
     In the second step of the method of this invention, a fixing composition containing a photographic fixing agent is used to remove silver. While sulfite ions are present and sometimes acts as a fixing agent, the primary photographic fixing agents used in the fixing composition are not sulfites. Rather, the useful photographic fixing agents are chosen from thiosulfates (including sodium thiosulfate, ammonium thiosulfate, potassium thiosulfate and others readily known in the art), cysteine (and similar thiol containing compounds), mercapto-substituted compounds (such as those described by Haist, Modern Photographic Processing, John Wiley &amp; Sons, N.Y., 1979), thiocyanates (such as sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate and others readily known in the art), amines and halides. Mixtures of one or more of these classes of fixing agents can be used if desired. Thiosulfates and thiocyanates are preferred. In some embodiments, a mixture of a thiocyanate (such as sodium thiocyanate) and a thiosulfate (such as sodium thiosulfate) is used. In such mixtures, the molar ratio of a thiosulfate to a thiocyanate is from about 1:1 to about 1:10, and preferably from about 1:1 to about 1:2. 
     The fixing composition can also include various addenda commonly employed therein, such as buffers, fixing accelerators, sequestering agents, swelling control agents, and stabilizing agents, each in conventional amounts. In its aqueous form, the fixing composition generally has a pH of at least 4, preferably at least 4.5, and generally less than 6, and preferably less than 5.5. 
     The essential (and some optional) components described above are present in the aqueous developing and fixing compositions in the general and preferred amounts listed in Table I, all minimum and maximum amounts being approximate (that is, &#34;about&#34;). If formulated in dry form, the developing compositions would have the essential components in amounts readily apparent to one skilled in the art suitable to provide the desired liquid concentrations. 
     
                       TABLE I______________________________________        General Amount                   Preferred Amount______________________________________Developing CompositionDihydroxybenzene developing          25 to 200 mmol/l                       30 to 90 mmol/lagentAuxiliary co-developing agent          2 to 12 mmol/l                       2.5 to 7.5 mmol/lSulfite ions   100 to 600 mmol/l                       160 to 460 mmol/lBromide ions   10 to 50 mmol/l                       15 to 45 mmol/lBuffer, e.g. carbonate          100 to 500 mmol/l                       100 to 300 mmol/lTetraborate    0 to 20 mmol/l                       6.2 to 17.2 mmol/lFixing CompositionFixing agent other than          250 to 950 mmol/l                       300 to 750 mmol/lsulfiteSulfite ions   40 to 120 mmol/l                       50 to 100 mmol/lBuffer, e.g. acetate          80 to 250 mmol/l                       120 to 180 mmol/lTetraborate    2.5 to 7 mmol/l                       3 to 5 mmol/lAluminum sulfate          20 to 70 mmol/l                       20 to 50 mmol/l______________________________________ 
    
     The black-and-white developing and fixing compositions useful in the practice of this invention are prepared by dissolving or dispersing the components in water and adjusting the pH to the desired value. The compositions can also be provided in concentrated form, and diluted to working strength just before use or during use. The components of the compositions can also be provided in a kit of two or more parts to be combined and diluted with water to the desired strength and placed in the processing equipment. The compositions can be used as their own replenishers, or another similar solutions can be used as the replenishers. 
     Processing can be carried out in any suitable processor or processing container for a given type of photographic element. For example, for radiographic films, the method can be carried out using one or more containers or vessels for carrying out both stages of development and fixing. 
     In most instances, the processed element is a film sheet, but it can also be a continuous element. Each element is bathed in the processing compositions for a suitable period of time in each stage. 
     Development and fixing are preferably, but not essentially, followed by a suitable washing step to remove silver salts dissolved by fixing and excess fixing agents, and to reduce swelling in the element. The wash solution can be water, but preferably the wash solution is acidic, and more preferably, the pH is 7 or less, and preferably from about 4.5 to about 7, as provided by a suitable chemical acid or buffer. 
     After washing, the processed elements may be dried for suitable times and temperatures, but in some instances the black-and-white images may be viewed in a wet condition. 
     Processing times and conditions for the invention are listed in the following Table II with the minimum and maximum values being approximate (that is, &#34;about&#34;). The total time for the method of this invention is generally at least 60, and preferably at least 90 seconds, and generally less than 180 and preferably less than 150 seconds. 
     
                       TABLE II______________________________________PROCESSING STEP          TEMPERATURE (° C.)                         TIME (sec)______________________________________Development    15-30          30-60Fixing         15-30          30-60Washing        15-30          30-60______________________________________ 
    
     The black-and-white photographic silver halide elements processed using the present invention are generally composed of a conventional flexible, transparent film support (polyester, cellulose acetate or polycarbonate) that has applied to each side one or more photographic silver halide emulsion layers. For radiographic films, it is conventional to use blue-tinted support materials to contribute to the blue-black image tone sought in fully processed films. Polyethylene terephthalate and polyethylene naphthalate are preferred film supports. 
     In general, such elements, emulsions, and layer compositions are described in many publications, including Research Disclosure, publication 36544, September 1994. Research Disclosure is a publication of Kenneth Mason Publications, Ltd., Dudley House, 12 North Street, Emsworth, Hampshire PO10 7DQ England. 
     The emulsion layers contain a light-sensitive high silver bromide relied upon for image formation. To facilitate rapid access processing the grains preferably contain less than 2 mol % (mole percent) iodide, based on total silver. The silver halide grains are predominantly silver bromide in content. Thus, the grains can be composed of silver bromide, silver iodobromide, silver chlorobromide, silver iodochlorobromide, silver chloroiodobromide or silver iodochlorobromide as long as bromide is present in an amount of at least 95 mol % (preferably at least 98 mol %) based on total silver content. 
     In addition to the advantages obtained by composition selection described above it is specifically contemplated to employ silver halide grains that exhibit a coefficient of variation (COV) of grain ECD of less than 20% and, preferably, less than 10%. It is preferred to employ a grain population that is as highly monodisperse as can be conveniently realized. 
     In addition, at least 50% (and preferably at least 70%) of the silver halide grain projected area is provided by tabular grains having an average aspect ratio greater than 8, and preferably greater than 12. The average thickness of the grains is generally at least 0.06 and no more than 0.10 μm, and preferably at least 0.07 and no more than 0.09 μm. The average grain diameter is from about 1.5 to about 3 μm, and preferably from about 1.8 to about 2.4 μm. 
     Tabular grain emulsions that satisfy high bromide grain requirements and gelatino-vehicle requirements, except that the gelatino-vehicle is fully forehardened, are described in greater detail in the following patents, the disclosures of which are here incorporated by reference: 
     Dickerson U.S. Pat. No. 4,414,310, 
     Abbott et al U.S. Pat. No. 4,425,425, 
     Abbott et al U.S. Pat. No. 4,425,426, 
     Kofron et al U.S. Pat. No. 4,439,520, 
     Wilgus et al U.S. Pat. No. 4,434,226, 
     Maskasky U.S. Pat. No. 4,435,501, 
     Maskasky U.S. Pat. No. 4,713,320, 
     Dickerson et al U.S. Pat. No. 4,803,150, 
     Dickerson et al U.S. Pat. No. 4,900,355, 
     Dickerson et al U.S. Pat. No. 4,994,355, 
     Dickerson et al U.S. Pat. No. 4,997,750, 
     Bunch et al U.S. Pat. No. 5,021,327, 
     Tsaur et al U.S. Pat. No. 5,147,771, 
     Tsaur et al U.S. Pat. No. 5,147,772, 
     Tsaur et al U.S. Pat. No. 5,147,773, 
     Tsaur et al U.S. Pat. No. 5,171,659, 
     Dickerson et al U.S. Pat. No. 5,252,442, 
     Dickerson U.S. Pat. No. 5,391,469, 
     Dickerson et al U.S. Pat. No. 5,399,470, 
     Maskasky U.S. Pat. No. 5,411,853, 
     Maskasky U.S. Pat. No. 5,418,125, 
     Daubendiek et al U.S. Pat. No. 5,494,789, 
     Olm et al U.S. Pat. No. 5,503,970, 
     Wen et al U.S. Pat. No. 5,536,632, 
     King et al U.S. Pat. No. 5,518,872, 
     Fenton et al U.S. Pat. No. 5,567,580, 
     Daubendiek et al U.S. Pat. No. 5,573,902, 
     Dickerson U.S. Pat. No. 5,576,156, 
     Daubendiek et al U.S. Pat. No. 5,576,168, 
     Olm et al U.S. Pat. No. 5,576,171, and 
     Deaton et al U.S. Pat. No. 5,582,965. The patents to Abbott et al, Fenton et al, Dickerson and Dickerson et al are cited and incorporated by reference to show conventional element features in addition to the gelatino-vehicle, high bromide tabular grain emulsions and other critical features of the present invention. 
     Film contrast can be raised by the incorporation of one or more contrast enhancing dopants. Rhodium, cadmium, lead and bismuth are all well known to increase contrast by restraining toe development. The toxicity of cadmium has precluded its continued use. Rhodium is most commonly employed to increase contrast and is specifically preferred. Contrast enhancing concentrations are known to range from as low 10 -9  mole/Ag mole. Rhodium concentrations up to 5×10 -3  mole/Ag mole are specifically contemplated. A specifically preferred rhodium doping level is from 1×10 -6  to 1×10 -4  mole/Ag mole. 
     A variety of other dopants are known, individually and in combination, to improve contrast as well as other common properties, such as speed and reciprocity characteristics. Dopants capable providing &#34;shallow electron trapping&#34; sites, commonly referred to as SET dopants, are specifically contemplated. SET dopants are described in Research Disclosure, Vol. 367, Nov. 1994, Item 36736. Iridium dopants are very commonly employed to decrease reciprocity failure. A summary of conventional dopants to improve speed, reciprocity and other imaging characteristics is provided by Research Disclosure, Item 36544, cited above, Section I. Emulsion grains and their preparation, sub-section D. Grain modifying conditions and adjustments, paragraphs (3), (4) and (5). 
     Low COV emulsions can be selected from among those prepared by conventional batch double jet precipitation techniques. A general summary of silver halide emulsions and their preparation is provided by Research Disclosure, Item 36544, cited above, Section I. Emulsion grains and their preparation. After precipitation and before chemical sensitization the emulsions can be washed by any convenient conventional technique using techniques disclosed by Research Disclosure, Item 36544, cited above, Section III. Emulsion washing. 
     The emulsions can be chemically sensitized by any convenient conventional technique as illustrated by Research Disclosure, Item 36544, Section IV. Chemical sensitization. Sulfur and gold sensitizations are specifically contemplated. 
     Both silver bromide and silver iodide have significant native sensitivity within the blue portion of the visible spectrum. Hence, when the emulsion grains contain high (&gt;50 mol %, based on total silver) bromide concentrations, spectral sensitization of the grains is not essential, though still preferred. It is specifically contemplated that one or more spectral sensitizing dyes will be absorbed to the surfaces of the grains to impart or increase their light-sensitivity. Ideally the maximum absorption of the spectral sensitizing dye is matched (e.g., within±10 nm) to the principal emission band or bands of the fluorescent intensifying screen. In practice any spectral sensitizing dye can be employed which, as coated, exhibits a half peak absorption bandwidth that overlaps the principal spectral region(s) of emission by a fluorescent intensifying screen intended to be used with the first radiographic film. 
     A wide variety of conventional spectral sensitizing dyes are known having absorption maxima extending throughout the near ultraviolet (300 to 400 nm), visible (400 to 700 nm) and near infrared (700 to 1000 nm) regions of the spectrum. Specific illustrations of conventional spectral sensitizing dyes is provided by Research Disclosure, Item 18431, Section X. Spectral Sensitization, and Item 36544, Section V. Spectral sensitization and desensitization, A. Sensitizing dyes. 
     Instability which increases minimum density in negative-type emulsion coatings (i.e., fog) can be protected against by incorporation of stabilizers, antifoggants, antikinking agents, latent-image stabilizers and similar addenda in the emulsion and contiguous layers prior to coating. Such addenda are illustrated by Research Disclosure, Item 36544, Section VII. Antifoggants and stabilizers, and Item 18431, Section II. Emulsion Stabilizers, Antifoggants and Antikinking Agents. 
     It is also preferred that the silver halide emulsions include one or more covering power enhancing compounds adsorbed to surfaces of the silver halide grains. A number of such materials are known in the art, but preferred covering power enhancing compounds contain at least one divalent sulfur atom that can take the form of a --S-- or ═S moiety. Such compounds include, but are not limited to, 5-mercapotetrazoles, dithioxotriazoles, mercapto-substituted tetraazaindenes, and others described in U.S. Pat. No. 5,800,976 (noted above) that is incorporated herein by reference for the teaching of the sulfur-containing covering power enhancing compounds. Such compounds are generally present at concentrations of at least 20 mg/silver mole, and preferably of at least 30 mg/silver mole. The concentration can generally be as much as 2000 mg/silver mole and preferably as much as 700 mg/silver mole. 
     It is still again preferred that the silver halide emulsion on each side of the support includes dextran or polyacrylamide as water-soluble polymers that can also enhance covering power. These polymers are generally present in an amount of at least 0.1:1 weight ratio to the gelatino-vehicle (described below), and preferably in an amount of from about 0.3:1 to about 0.5:1 weight ratio to the gelatino-vehicle. The dextran or polyacrylamide can be present in an amount of up to 5 mg/dm 2 , and preferably at from about 2 to about a 4 mg/dm 2 . The amount of covering power enhancing compounds on the two sides of the support can be the same or different. 
     The silver halide emulsion and other layers forming the imaging units on opposite sides of the support of the radiographic element contain conventional hydrophilic colloid vehicles (peptizers and binders) that are typically gelatin or a gelatin derivative (identified herein as &#34;gelatino-vehicles&#34;). Conventional gelatino-vehicles and related layer features are disclosed in Research Disclosure, Item 36544, Section II. Vehicles, vehicle extenders, vehicle-like addenda and vehicle related addenda. The emulsions themselves can contain peptizers of the type set out in Section II noted above, paragraph A. Gelatin and hydrophilic colloid peptizers. The hydrophilic colloid peptizers are also useful as binders and hence are commonly present in much higher concentrations than required to perform the peptizing function alone. The gelatino-vehicle extends also to materials that are not themselves useful as peptizers. The preferred gelatino-vehicles include alkali-treated gelatin, acid-treated gelatin or gelatin derivatives (such as acetylated gelatin and phthalated gelatin). 
     To allow maximum density requirements to be satisfied with minimal silver coating coverage it is necessary to limit the forehardening of the gelatino-vehicle. Whereas it has become the typical practice to fully foreharden radiographic elements containing tabular grain emulsions, the radiographic elements of this invention are only partially forehardened. Thus, the amount of hardener in each silver halide emulsion unit is generally at least 0.1% and less than 0.8%, and preferably at least 0.3% and less than 0.6%, based on the total dry weight of the gelatino-vehicle. 
     Conventional hardeners can be used for this purpose, including formaldehyde and free dialdehydes such as succinaldehyde and glutaraldehyde, blocked dialdehydes, α-diketones, active esters, sulfonate esters, active halogen compounds, s-triazines and diazines, epoxides, aziridines, active olefins having two or more active bonds, blocked active olefins, carbodiimides, isoxazolium salts unsubstituted in the 3-position, esters of 2-alkoxy-N-carboxydihydro-quinoline, N-carbamoyl pyridinium salts, carbamoyl oxypyridinium salts, bis(imoniomethyl) ether salts, particularly bis(amidino) ether salts, surface-applied carboxyl-activating hardeners in combination with complex-forming salts, carbamoylonium, carbamoyl pyridinium and carbamoyl oxypyridinium salts in combination with certain aldehyde scavengers, dication ethers, hydroxylamine esters of imidic acid salts and chloroformamidinium salts, hardeners of mixed function such as halogen-substituted aldehyde acids (e.g., mucochloric and mucobromic acids), onium-substituted acroleins, vinyl sulfones containing other hardening functional groups, polymeric hardeners such as dialdehyde starches, and copoly(acrolein-methacrylic acid). 
     In each silver halide emulsion unit in the radiographic element, the level of silver is generally at least 8 and no more than 11 mg/dm 2 , and preferably at least 9 and no more than 10 mg/dm 2 . In addition, the coverage of gelatino-vehicle is generally at least 6 and no more than 11 mg/dm 2 , and preferably at least 7.5 and no more than 9.5 mg/dm 2 . The amounts of silver and gelatino-vehicle on the two sides of the support can be the same or different. 
     The radiographic elements generally include a surface overcoat on each side of the support that are typically provided for physical protection of the emulsion layers. In addition to vehicle features discussed above the overcoats can contain various addenda to modify the physical properties of the overcoats. Such addenda are illustrated by Research Disclosure, Item 36544, Section IX. Coating physical property modifying addenda, A. Coating aids, B. Plasticizers and lubricants, C. Antistats, and D. Matting agents. Interlayers that are typically thin hydrophilic colloid layers can be used to provide a separation between the emulsion layers and the surface overcoats. It is quite common to locate some emulsion compatible types of surface overcoat addenda, such as anti-matte particles, in the interlayers. 
     Advantageously, the processing method of this invention can be carried out using a processing kit that includes the processing compositions and elements described herein. Minimally, the processing kit would include the black-and-white developing composition, the fixing composition, and the black-and-white photographic silver halide element (one or more samples thereof). The kit can also include instructions for use, a washing solution, fluid or composition metering devices, or any other conventional components of a photographic processing kit. All of the components can be suitably packaged in dry or liquid form in glass or plastic bottles, fluid-impermeable packets or vials. 
    
    
     The following example is provided for illustrative purposes, and is not to be considered limiting in any manner. 
     MATERIALS AND METHODS FOR EXAMPLES 
     A radiographic film (Element A) within the scope of the present invention was prepared having the following layer arrangement and composition on each side of a poly(ethylene terephthalate) support: 
     
         ______________________________________                Coverage (mg/dm.sup.2)______________________________________Overcoat FormulationGelatin vehicle        3.4Methyl methacrylate matte beads                  0.14Carboxymethyl casein   0.57Colloidal silica       0.57Polyacrylamide         0.57Chrome alum            0.025Resorcinol             0.058Whale oil lubricant    0.15Interlayer FormulationGelatin vehicle        3.4AgI Lippmann emulsion (0.08 μm)                  0.11Carboxymethyl casein   0.57Colloidal silica       0.57Polyacrylamide         0.57Chrome alum            0.025Resorcinol             0.058Nitron                 0.044Emulsion FormulationT-grain emulsion (AgBr 2.0 × 0.07 μm)                  10.6Gelatin                7.54-hydroxy-6-methyl-1,3,3a,7-tetraazaindene                  2.1 g/Ag mole4-hydroxy-6-methyl-2-methylmercapto-1,3,3a,7-                  400 mg/Ag moletetraazaindene2-mercapto-1,3-benzothiazole                  30 mg/Ag molePotassium nitrate      1.8Ammonium hexachloropalladate                  0.0022Maleic acid hydrazide  0.0087Sorbitol               0.53Glycerin               0.57Potassium bromide      0.14Resorcinol             0.44Dextran P              2.5Polyacrylamide         2.69Carboxymethyl casein   1.61Bisvinylsulfonylmethlyether                  0.4% based on                  total gelatin in                  all layers______________________________________ 
    
     A Control radiographic element (Element B) was also evaluated using the compositions and methods of this invention. This element is commercially available as KODAK T-MAT G radiographic film. 
     The black-and white developing and fixing compositions of the following Table III were used in the Example. The pH values were adjusted in the compositions by addition of various acids, bases or buffers. 
     
                                           TABLE III__________________________________________________________________________     Developing           Developing                 Developing                       Developing                              Developing                                    Fixing                                          Fixing                                               Fixing                                                    Fixing     Comp. I           Comp. II                 Comp. III                       Comp. IV                              Comp. V                                    Comp. I                                          Comp. II                                               Comp.                                                    Comp. IVCOMPONENT (mmol/l)           (mmol/l)                 (mmol/l)                       (mmol/l)                              (mmol/l)                                    (mmol/l)                                          (mmol/l)                                               (mmol/l)                                                    (mmol/l)__________________________________________________________________________Hydroquinone     91    68.2  45.5  31.8   182   0     0    0    0ELON      0     0     0     0      11.6  0     0    0    04-Hydroxymethyl-     7.3   5.3   3.9   2.4    0     0     0    0    04-methyl-1-phenyl-3-pyrazolidoneSodium sulfite     571   428   285   200    714   120   90   59   42Potassium 42    32    21    15     42    0     0    0    0bromideSodium carbonate     302   226   151   106    500   0     0    0    0Sodium    25    18    12    8.5    0     9.5   7.1  4.7  3.3tetraborateSodium hydroxide     125   95    62.5  45     75    0     0    0    0Sodium    0     0     0     0      0     950   711  475  332thiosulfateAmmonium  0     0     0     0      0     66    50   33   23aluminum sulfateCitric acid     0     0     0     0      0     15.6  12   7.8  5.7Sodium acetate     0     0     0     0      0     245   183  123  86pH        10-11 10-11 10-11 10-11  10-11 4.5-5.5                                          4.5-5.5                                               4.5-5.5                                                    4.5-5.5__________________________________________________________________________ 
    
     EXAMPLE 
     This example was used to determine the performance of various black-and white developer and fixing compositions in the practice the invention. 
     Samples of the radiographic elements A and B described above were exposed to 500 Lux fluorescent lighting for 60 seconds, then processed using the various black-and-white developing and fixing compositions at room temperature as shown in TABLE IV below. The various sensitometric results [fog, speed, contrast, lower scale contrast (LDC) and upper density point (UDP)] have conventional meanings, were measured using conventional procedures, and are also shown in TABLE IV. 
     
                                           TABLE IV__________________________________________________________________________    Developing     Developing           Fixing                 Fixing timeElement    Composition     time (sec)           Composition                 (sec) Fog                          Speed                              Contrast                                  &#34;LSC&#34;                                      &#34;UDP&#34;__________________________________________________________________________A   I     60    I     60    0.21                          440 2.26                                  2.10                                      2.69A   III   60    III   60    0.22                          430 1.34                                  1.96                                      2.34A   IV    60    IV    60    0.20                          424 1.80                                  1.98                                      2.38A   IV    30    IV    30    0.2l                          410 1.48                                  1.89                                      2.31B   I     60    I     60    0.27                          427 3.12                                  2.19                                      3.62B   III   60    III   60    0.25                          419 2.57                                  2.08                                      3.24B   IV    60    IV    60    0.20                          424 2.47                                  2.12                                      2.89B   I     30    IV    30    0.52                          369 --  1.18                                      1.96__________________________________________________________________________ 
    
     These results show that in general the weaker the processing chemistries and the shorter the processing times, Element A exhibited lower fog (better fixing) and higher speeds. The contrast and upper density were lower for Element A because its silver coverage was lower. Some of the density contributing to higher Dmax and contrast in Element B may be a result of incomplete fixing. 
     The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.