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Photography Theory and Practice

Focussing Of The Image
Focussing Of The Image And The Position Of The Subject On The Plate 307. Focussing. In All Cameras Fitted With A Ground Glass Screen, The Focussing Is Done, As Far As Possible, By Visual Examination. The Image Formed By The Lens On The Ground Is Examined Under A Black Cloth, ...

Gaslight Papers For Black
Gaslight Papers For Black Tones 571. Suitable Light For Working. One Of The Factors Which Have Tended Most To Popularize The Use Of These Papers Among Amateur Photo Graphers Is The Fact That They May Be Worked In Safety Without A Dark-room.' Any Domestic Room May He Used Simply By ...

Gelatine
Gelatine 68x. General. The Process Of Making Prints In Greasy Inks On Bichromated Gelatine (called Also The Oil Process)i Introduced In 1904 By G. E. H. Rawlins, As A Method For Use In Pic Torial Photography, Is, In Fact, Only A Variation Of Methods Used Since A. Poitevin (1855) In ...

Gelatine And
Gelatine And C0ll0dias P.o. P. 529. Print-out Silver Emulsions. Print-out Emulsions Are Made On The Commercial Scale By The Precipitation In Gelatine (gelatine P.o.p.' Abney, 1882) Or In Collodion (collodion Papers, G. Wharton-simpson, 1865) Of Silver Chloride (or Sometimes Bromide Or Phosphate Of Silver), Together With Citrate, Tartrate, Or Oxalate ...

General Notes 368
General Notes 368. Preliminaries. Before Beginning The De Velopment Of A Negative It Is Necessary To See That All Solutions And Utensils Are At Hand. The Tanks Or Dishes Should Be So Arranged That The Negative Being Developed May Be Transferred From One To Another In Their Proper They Should ...

General Principles Of Radiography
General Principles Of Radiography 924. X-ray Generators. X-rays (w. C. Röntgen, 1895) Are Comparable With Rays Of Light, But Have Wavelengths Shorter Than Those Of The Extreme Ultra-violet, And Are Produced By A Very Different Process. An X-ray Generator, Reduced To Its Simplest Form, Consists Of A Thin Bulb Of ...

General Properties Of Optical
General Properties Of Optical Systems : Aberrations 40. Lenses. Lenses Are Masses Of Glass, Bounded, By Successive Moulding, Grinding And Polishing Operations, By Two Spherical' Surfaces, Or A Spherical And A Plane Surface. According As The Beam Of Light Emerging From A Lens Held Up To The Sun Has A ...

Geometrical Considerations Deformation
Geometrical Considerations ; Deform Ation Of The Reconstructed Object 819. Corresponding Points -variations Of Their Separation. The Pairs Of Points Appearing One In Each Image Of A Stereoscopic Pair And Corresponding With A Single Point In The Object Are Termed Homologous (corresponding) Points. Consider (fig. 207) Two Photographs T And ...

Hand Cameras 162
Hand Cameras 162. General Notes. Owing To The Great Variety Of Hand Cameras, A Detailed Description Of Them Would Demand More Space Than Is Warranted By The Interest Of Such An Account, Which Would To A Large Extent Be A Repetition Of The Catalogues Of Makers And Dealers. We Shall ...

Handling Of Sensitive Materials
Handling Of Sensitive Materials Loading And Unloading Of Dark Slides ; Repacking 280. Storage Of Sensitive Materials. Sensitive Materials Should Be Stored In A Dry Place Of Moderate Temperature, Where They Cannot Be Reached By Any Gases And Emanations From Volatile Products. They Should Especially Be Protected From Hydrogen Sulphide ...

Inorganic Developers 345
Inorganic Developers 345. Mineral Salts As Developers. Iii Addition To Ferrous Oxalate (which Is The Only One Of These Various Developers Which Has Come Into Effective Practical Use) And Various Other Ferrous Salts (fluoride, Citrate, Etc.), The Following Have Been Suggested For Use As Developers : Clipro Oxalate Of Ammonia ...

Intensification 445
Intensification 445. Choice At Method Of Intensification. The Method Which, Unfortunately, Is Generally Em Ployed (bleaching The Image In Mercuric Chloride And Blackening With Ammonia) Has Contributed Not A Little To The Discredit Of Intensification ; It Destroys The Details Of The Shadows And Blocks Up The High-lights ; In ...

Intensifying Fixing
Fixing, Intensifying, And Reducing Development Prints And Transparencies 581. Fixing Developed Images. The Action And Chemistry Of Fixing Are The Same As In The Case Of Negatives (§§ 400 And 401). Most Fre Quently Acid Fixing Baths Will Be Used, And In Warm Weather The Fixing Solutions Containing Alum Already ...

Its Variations 666
Its Variations 666. Gum-bichromate. Invented In 1858 By Pouncy, At A Time When The Only Working Methods In Favour Were Those Yielding Abso Lutely Sharp Pictures Of A Structure Imperceptible To The Eye, The Gum-bichromate Process Fell Into Oblivion Until Rouille-ladeveze (1894), Then R. Demachy, A. 11askell, C. Puyo, And ...

Lantern Screens 800
Lantern Screens 800. General Notes. Types And Efficiency Of Screens. Pictures May Be Projected On An Opaque Screen, The Lantern Being On The Same Side Of The Screen As The Spectators (projection By Reflection), Or On A Translucent Screen, The Lantern Being On One Side Of The Screen And The ...

Light Filters Lens Accessories Supplementary
Lens Accessories Supplementary Lenses, Light-filters, Prisms And Mirrors, Polarizers, Lens Hoods, Sky Shades 118. Supplementary Lenses (magnifiers).' Cameras With Fixed Focus Will Produce A Sharply Defined Image Of The Object Only If It Is At A Sufficient Distance From The Camera, The Picture Being Necessarily On A Small Scale. It ...

Light And Colour
Light And Colour X. White Light. When A Beam Of Daylight, Which We Call White Light, In Spite Of The Fact That Its Quality Is Continually Changing,' Is Decomposed, E.g. By Passing It Through A Glass Prism Which Separates It Into The Constituent Elements Of The Incident Light, The Colours ...

Lighting Of The Subject
Lighting Of The Subject ; Daylight ; Artificial Light 287. Daylight. Daylight Is Not Only Of A Very Variable Intensity, According To The Geographical Position, The Season, Time Of Day, And The Atmospheric Conditions, But Its Composition Also Varies Over Very Wide Limits, Although It Is Always Conventionally Called " ...

Limits Of Luminosity In
Limits Of Luminosity In Photographic Subjects 15. Range Between Extreme Luminosities In Some Common Cases. There Is A General Ten Dency To Exaggerate Very Considerably The Ratio Of The Extreme Luminosities Of The Various Sub Jects Which Are Photographed. Measurements Which Have Been Carried Out, Either Indirectly By Means Of ...

Manipulation Of Print Out Papers
Manipulation Of Print-out Papers 2 532. The Printing-room. The Loading Of The Printing Frames, The Control Of The Exposure, And The Unloading Of The Frames Should Be Done In A Room Lighted With Yellow Light Or In Any Place Where The Illumination Is Weak. On The Commercial Scale, One Side ...

Mounting Finishing And Working Up
Finishing And Working-up Prints ; Trimming, Mounting, Retouching And Colouring 702. General. Trimming Must Obviously Re Move The Edges Of The Print, Which Are Often Defective, Owing To Gelatine Having Separated, Finger Marks, Etc. It Gives The Print A Neat Appearance, And Should Also Remove Unnecessary Portions Which Are Without ...

Nominal Outside
Nominal Outside Dimensions Continental Europe (fig_ 195) 85 X 100 Mm.(3.35 X 3-95 Ins. Great Britain (fig. X96) 31 X 31 In. (82-5.x 82-5 Min.) United States (fig. 3} X 4 In. (82-5- X 'or Ma.) In Principle, The Two Rectangular Sizes Must Always Be Used As Shown In The ...