j Photographic Lenses, Shutters, Prisms. $ attach & $mb optical Co. The Cummins Photo Stock Co. 106 N. Charles Street, BALTIHORE, MD. Bausch & Lomb Optical Co., MANUFACTURERS OF PHOTOGRAPHIC LENSES, SHUTTERS, PRISMS, ETC. BRANCH OFFICE AND WAREROOMS 130 Fulton Street, NEW YORK CITY P. O. Box 432. FACTORY AND MAIN OFFICE: 515-543 North St. Paul Street, ROCHESTER, N. Y. P. O. Drawer 1033. SEVENTH EDITION. June, 1894. E. R. ANDREWS, PUBLISHER, I AQUEDUCT STREET, ROCHESTER, N. Y. PREFACE. With this issue we HAVE MADE AND SOLD 33,000 LENSES. This enormous increase in the demand of our lenses by professional and amateur photographers requires no words to show their general and increasing popularity. We shall continue in the future, as we have in the past, to make our work the synonym of the highest quality and absolute regularity, and utilize every opportunity to make improvements. We introduce herewith TWO NEW SERIES OF PORTRAIT LENSES, which possess unusual merit and to which we call the special attention of profes- sional photographers. We have also received the computations and material for A NEW SERIES OF ZEISS-ANASTIGMAT LENSES, which will be particularly interesting to the amateur and view photographer. At the same time a very material REDUCTION IN PRICES OF THE ZEISS-ANASTIGMATS will take effect. We are particularly pleased to make this announcement, since, with all the advantages which these lenses possess^ many who have appreciated and been desirous of possessing one or the other, have been deterred from doing so by the comparatively high prices. We have made strenuous efforts to change this condition, believing that their great popularity will be considerably enhanced. We call particular attention to their various advantages in the pages devoted to them. We introduce herewith a new series of IMPROVED IRIS DIAPHRAGMS, which are now attached to all of our lenses excepting Velox Series at NO ADVANCE IN PRICE, except the Rapid Universal and A. G. Clark, in which, however, it is very slight. We also introduce herewith our new TELE-PHOTO LENSES, which we commend for practicability and moderate prices. We also offer our STEREOSCOPIC SHUTTER, which has proven very satisfactory in its work, and which, now that stereoscopic photography is becoming more popular, will be welcomed as an effective aid. Any of our lenses will be cheerfully sent to responsible parties for exam- ination and comparison. Bausch & Lomb Optical Co. June, 1894. 4 BAUSCH & LOMB OPTICAL COMPANY, THE goods enumerated in this Catalogue can be obtained from any of the Photographic Stock Dealers in this country and in Canada. In cases where there is any difficulty in so obtaining, we will be pleased to supply direct at Catalogue Prices. They may also be obtained in foreign countries from the follow- ing prominent firms, who are our representatives for their respective countries. CHARLES, REYNOLDS & CO , London, England. N. FELLHEIMER, - Stuttgart, Germany. CARL ZEISS, - Jena, Germany. CLEMENT & . GILMER, Paris, France. KARL FRITSCH, Vienna, Austria. L. VAN NECK & CO., Antwerp, Belgium. F. KORISTKA, Milano, Italy. 0. DIRADOUR, .... Constantinople, Turkey. J. LEWELLYN &. CO., Shanghai, China. COCKING & CO., Yokohama, Japan. HOLLISTER DRUG CO., LIMITED, Honolulu, Hawaian 1st. JULIO LABADIE, Suc'rs y Cia, Mexico City, Mexico. CURTIS BROTHERS, Dublin, Ireland. We also issue a very complete List of Microscopes, Objectives, and Accessories, which we will be pleased to forward to any person interested in Microscopy. ROCHESTER, N. Y., AND NEW YORK CITY. 5 SELECTION OF LENSES. To select a lens, suitable for certain purposes, is a matter of considerable difficulty, even for a person adept in photography, and we are sure that a few words from us, which will aid in making proper selections, will not be found amiss. There are such a variety of claims made for different lenses, that we are not surprised to receive so many inquiries as to the various conditions involved. While results in photography depend to a great extent upon personal skill and experience, the basis of all good work is always the lens. The camera may be more or less crude, and its adjuncts as well, but that part of it which gives the photographic image, the lens, should be of as high grade as possible, so as to give a correct representation of what it is desired to retain in the form of a picture. From lack of a true understanding of the subject, many persons endeavor to economize by purchasing a cheap and in many cases a useless lens, unmindful of the fact that instead of acquiring what will always be a source of pleasure, they are burdening themselves with what will be a continual cause of annoyance and dissatisfaction. The outcome is, that such lenses are almost always discarded and become a loss, while others of known reliability are pur- chased. In other cases lenses are purchased wholly unsuited to the purpose t© which they are put, with usually the same result. Achromatism is the first condition in a good objective. It is that quality which brings the chemical rays, or those which produce the photographic image, in exact coincidence with visual rays, or those which make the image apparent to the eye on the ground glass. A slight deviation from perfect achromatism will produce the photographic image either in front or behind the plate and will therefore cause indistinctness. This may sometimes be partially corrected by the use of small stops, but when it exists it is always a serious fault. Angle of View depends upon the proportion of focal length to the size of plate and is expressed by the angle formed by the extreme rays forming the image. Lenses of the rectilinear type have an angular aperture varying from 40 0 to 70 0 . Those giving an angle of from 85 0 to no° are termed Wide Angle. Owing to the large apertures of the lenses in the ordinary types of these latter, and their inability to combine the rays on the edges of the plate, it is usually necessary to use them with small stops to obtain good results. This involves another quality. 6 BAUSCH & LOMB OPTICAL COMPANY, Speed or Rapidity. — It represents the quality of forming a correct image within a given time, and depends upon the proportion of working aperture to length of focus. In addition it depends upon the quality of the lens in design and mechanical execution, and is the principal feature in determining the quality of a lens from an optical standpoint, providing its other qualities are of corresponding perfection. At this day, when instantaneous photography is so generally practiced, it is of the greatest importance, not only as a quality in itself, but of the ability of the lens to give with it a sharp, clearly defined picture. While the rapidity of a lens depends to some extent upon its angle, the aperture through which the light passes, or the size of the stop, determines it. The speed decreases propor- tionately with the decrease in the size of stop. In this regard the recommen- dation of the English society is now generally followed, by which each succeeding smaller stop requires double the exposure of the preceding. By this system the stops are designated, 8, 16, 32, etc., but their relative value to focal length is also used. The f-8 is one-eight of the equivalent focal length and really expresses the value of the speed. From this it will be seen that the focal length is as great a factor as the aperture. Depth of Focus is another important quality and represents the degree of sharpness with which objects lying at different distances in front of the camera are shown at the same time on the plate. It depends upon the focal length, angle of view and working aperture, and increases with the decrease of these three factors. As can easily be determined by experiment, an object close to the camera will be found to have a longer posterior focus than one at a distance and no lens can ever be constructed, which with full aperture will bring the two in one plane, so that the advertised claims, which are made for a large number of lenses, of great speed with great depth of focus may be put down as false. The extent to which a lens possesses speed and depth of focus is variable, however, and depends upon the skill of the optician, but it may be added that under the same conditions, the depth increases with the decrease in focus, as there is less variation between the different planes at the back for the different distances at the front of the lens. For this reason it is, that only short focus lenses can have approximately a " Universal focus." If plates could be constructed of such sensitiveness as to admit the use of small apertures, depth of focus would be the result to a much higher degree, but this attainment depends upon the chemist and not the optician. A lens may be made to have approximately a universa lfocus for a 3^ x inch plate, and even 4x5 inch plate, but here it ceases. Flatness is the quality of defining an object equally well upon the entire surface of the plate, but can never be wholly accomplished because in the nature of things there is a certain amount of curvature. It depends upon the angle, aperture and focus, but after these conditions entirely upon the skill of the ROCHESTER, N. Y., AND NEW YORK CITY. 7 optician, and in this respect probably the greatest difference is apparent in lenses coming from the hands of different manufacturers. With many lenses it is found necessary to use one intended for a certain plate on one or two sizes smaller to obtain satisfactory results. Definition is the capacity to concentrate the rays to one point so as to give a sharp, clearly denned image. It is of the greatest importance, as it shows principally the amount of care which has been devoted to the lens during its construction. Any lens not having this property in the highest degree may be put down at once as of inferior quality. The fault is overcome, only partially however, by reducing the aperture, but this is of course, at the sacrifice of speed. When due to non-achromatism it may be determined by observing whether the visual image is sharp, and chemical image or photograph indistinct, although in this case great care should be observed that the ground glass and plate are in exact coincidence, which very often is not the case. When due to faulty construction or workmanship, it can easily be determined by observing the image on the ground glass. The image should be an exact representation of the real object in detail and should be determined by the aid of a magnifier or focusing glass. Testing lenses is a matter of no small importance, and should be done with the greatest care and regard to the points mentioned above. As speed, depth and flatness are varying qualities in different lenses, we emphatically recommend that they be not judged in a lens by themselves, but in comparison with another lens of about the same proportion, preferably with one of known excellence. A person well experienced in photography may be able to form a correct judgment, but one who is not, cannot do so with security. Care should be taken that comparisons be made under the same conditions as to light, size of stop and time of exposure, and if indefinite, should be repeated. TEST-CHART. The above is a reduced fac-simile of our Test Chart (16 x 48 inches) which we send with each one of our lenses. We appreciate the value of the ability of the purchaser of a lens to convince himself of its perfection, and put the means in his hands of making comparisons with lenses of different makers. s BAUSCH & LOMB OPTICAL COMPANY, UNIVERSAL PORTRAIT LENSES. Series A. (Cut i size No. 3.) QUICK WORKING LENSES FOR GENERAL PORTRAIT WORK. Although these lenses have been in use in the hands of some of our best known photographers for the purpose of testing their particular qualities, they are herewith introduced for the first time to the general public. The general commendations of their high qualities convince us that after these become more generally known they will be the means of making these the leading lenses with professional photographers. They are quick working and have an unusual delicacy of definition, freedom from distortion, and even illumination. They are at least equal to the lenses of the best 'European makers intended for the same work, and are very materially lower in price than any of these. The No. 3 of this series is recommended as the most useful lens for cabinet and whole-plate work in the studio. They are Supplied only with our Improved Iris Diaphragm. No. Size. » Diameter of Lenses. Back Focus. Price. Telegraphic Code. 1 4x5 2f in. 6i in. $ 65.00 Uberty. 2 5x8 8* " 90.00 Udal. 3 6£x 8£ H " Hi " 135.00 Udaler. 4 8 x 10 4 " 13* " 190.00 Udder. ROCHESTER, N. Y., AND NEW YORK CITY. 9 EXTRA RAPID UNIVERSAL LENSES. Series D. F-6. Cut full size No. 00. FOR HEADS, GROUPS, FIGURES AND OUTDOOR WORK OF GREAT SPEED. The larger lenses of this series will be welcomed as portrait lenses par excellence, having unusually delicate definition with uniform illumination, good depth and speed in all ordinarily lighted studios. It is rare that a lens which is designed to do good portrait work is suited for good landscape work as well, but these qualities are combined to an unusual degree in these lenses. The lower numbers are designed for very quick hand camera work, giving even illumination and possessing perfect definition. The mountings are compara- tively short, which overcomes to a considerable extent the inherent astigmatism in lenses of similar construction. These lenses may be had with or without hood, but will be supplied with hood unless otherwise ordered. By unscrewing the front combination the back only may be used, giving about twice the focus with about one half the speed. These lenses have an angle of 70 degrees. They are Supplied only with our Improved Iris Diaphragm. Brass Aluminum No. Size. Diameter of Lenses. Equivalent Focus. Back Focus. Mounting. Telegraphic Code. Price. Price. 0 3±x 4i 1 in. 4f in. 31f in. $ 24.00 $ 27.00 Ukase. 00 4x5 n " 6f " 5 7 - :: 28.00 32.00 Ulaus. 1 5x8 i+ " 8 " 36.00 40.00 Ulcer. 2 6£x 8* if " » A " 8i " 46.00 50.00 Ulema. 3 8 xlO 2i " iii - m " 58.00 64.00 Ulnim. 4 10 x 12 H " 14i " 12 T V " 75.00 82.00 Ulnage. 5 1Z. xl5 3 A " m M I5i « 100.00 108.00 Umbel. 6 16 x20 34 " 22£ " m " 130.00 139.00 Umber. Telegraphic code refers to lenses in brass mounting ; if desired in aluminum it should be so stated. 1 o BAUSCH & LOMB OPTICAL COMPANY, RAPID UNIVERSAL LENSES. F. 8. Cut full size No. 5. FOR INSTANTANEOUS OUTDOOR WORK, GROUPS AND STANDING FIGURES. These lenses have enjoyed an unusual popularity since their first introduction. They are of the rectilinear, symmetrical type and have a construction peculiarly their own. The glass is specially manufactured of unusual hardness and brilliancy, involving specially favorable curves. While these lenses do not have the speed of the Extra Rapid Series, they give excellent results in a well lighted studio on groups, figures and large heads having great depth and covering capacity. For outdoor work they have an unusual crispness of definition with full opening and great covering capacity and depth. The speed is ample for all ordinary instantaneous work without sunlight. While it may be used on archi- tectural subjects and interiors, a wide angle lens is recommended for this purpose. The back combination may be used with good results on twice the size of plate with about one-half the speed. These lenses vary in angle from 70 degrees in the smaller to 60 degrees in the larger sizes. Our new test chart (copyrighted) accompanies each lens. They are Supplied only with our Improved Iris Diaphragm. Waterhouse stops in place of Iris at the same prices. Brass Aluminum No. Large Stop Covers. Diameter of Image Circle. Diameter of Lenses. Back Focus. Equivalent Focus. Mounting. Telegraphic Code. Price. Price. 4i 8 in. i in. 4f in. 5i in. $ 18.00 $ 21.00 Ucubis. 5 4x5 9i " 5f " 6f " 22.00 25.00 Umbria. 8 5x8 11 " 1-f " 7f " 81 " 26.00 30.00 Unca. 8i . 6^x 8£ 13* " If " 10f " llf " 35.00 39.00 Unelli. 10 8 xlO 16f " a << 12* " 13| V 48.00 52.00 Upis. 12 10 x 12 20 " 2i " 15 " 17 " 60.00 66.00 Uraca. 15 12 x 15 21* " 2f ■« 18 " 20i " 75.00 82.00 Uxantis. 18 16 xl8 27i " 3i " 22± " 24f " 95.00 108.00 Utica. 22 20 x22 36 " 4* " 28 " 31f " 125.00 139.00 Uzita. Telegraphic code refers to lenses in brass mounting ; if desired in aluminum it should be so stated. ROCHESTER, N. Y., AND NEW YORK CITY. ALVAN G. CLARK LENSES. F. 8. Cut full size No. 5. FOR INSTANTANEOUS OUTDOOR WORKGROUPS, STANDING FIGURES, INTERIORS AND ARCHITECTURE. These lenses are the invention of Alvan G. Clark, the celebrated manufac- turer of telescopes, and are of a construction dissimilar from anything hereto- fore followed, and are as striking in their results as Mr. Clark's success in the telescope objectives has been. They may be used: In all work to which the Rapid Rectilinear type may be adapted, when they give an angle of about 55 degrees with stop f 8, on size of plate as listed. As wide angle objectives, giving an aperture of about 90 degrees with stop f 45, on larger sizes of plates up to the stated limit of image circle. They are quite free from marginal distortion and magnified perspective, so common to lenses of this class. The lenses are uncemented, each lens of the combination being mounted for itself, and are therefore free from danger of gradual decrease in speed, so common in many lenses owing to the chemical change in the cement. The crown glass is on the outside, and therefore less liable to become scratched. They possess less astigmatism than any known lenses of the symmetrical type. The back combination may be used on larger plates at one-half the speed. These lenses are fully covered by patent. Our new test chart (copyrighted) accompanies each lens. They are Supplied only with our Improved Iris Diaphragm. Waterhouse stops in place of Iris at the same prices. No. Size of Plate working with Stop F. 8. Diameter of Image Circle. Diameter of Lenses. Back Focus. Equivalent Focus. Brass j Aluminum Mounting. Price. Price. Telegraphic Code. 4i 8i in. f in. 4f in. 5i in. 6i " $ 20.00 $ 23.00 Abel. 5 4x5 13 " i " 5f " 24.00 27.00 Abner. 8 5x8 16 " H " 7£ " 8i " 30.00 34.00 Achan. 8i 6£x 8£ 21* " H " iH " 38.00 42.00 Adam. 10 8 xlO 24f " if « i2 T y< m " 50.00 54.00 Agate. 12 10 xl2 33 " n - 15 " 16 " 64.00 70.00 Alema. 15 12 xl5 38 " 2% " 18 " 19i " 82.00 89.00 Amasa. 18 1(5 x 18 47 " 3 " 22 " 23 x y< 105.00 113.00 Arab. 22 20 x22 64 " H " 28 " 30 " 145.00 155.00 Arbah. Telegraphic code refers to lenses in brass mounting ; if desired in aluminum it should be so stated. I 2 BAUSCH & LOME OPTICAL COMPANY, UNIVERSAL WIDE ANGLE LENSES F. 16. Cut full size No. 8j-. In these lenses we have sought to combine high efficiency with moderate prices and the results show that this has been accomplished to an unusual degree. The angular aperture is about 100°. With these wide angles they have rare covering capacity and equality of illumination. Further than this the largest stop gives a speed which will allow of their use in flash light exposures and instantaneous in out-door work under favorable conditions of light. We quote their capacity in a different manner than is usually the case. While the angular aperture of the lenses is about 100°, we quote them working with largest stop, and in another column with small stops, in each case giving the angular aperture which the lenses have on specified plates. If a careful comparison is made with other lists it will be found that they are misleading in so far, that while the angular aperture of lenses is given, they fail, and in some cases very considerably, from giving these angles on the plates for which they are quoted. Sizes up to and including 8 x 10 are fitted with revolving diaphragm, larger sizes with our improved Iris diaphragm. Our new test chart (copyrighted) accompanies each lens. No. Size of Plate covered with Stop f. 16. Angle 8o°. Size of Plate covered with Stop /. 64. Angle 95 0 . Diameter of Image. Circle. Diameter of Lenses. Back Focus. Equivalent Focus. Price. Telegraphic Code. 5 4x5 5x8 8f in. £■ in. 3i in. 3* in. $16.00 Wade. 8 5x8 6£x 8£ 13 " * " U " 5*' «• 20.00 Wait. 8* 6ix 8£ 8 xlO 15 " i " .50 Opening of Largest Stop. i in. If " Telegraphic Code. Dalphon. Danites. Dara. Darius. To graduate disk to correspond with stop accompanying lens, extra, $ .50. Finger release attachment to shutters, f to T 8 ¥ size, extra, $1.00. (f way at no additional charge.) Telegraphic code refers to shutters in brass mounting ; if desired in aluminum it should be so stated. * Indicates shutter being fitted to back of lens; cannot otherwise be adapted on account of combi- nation of lenses being too close together. SIZE OF SHUTTER OVER ALL IN HEIGHTH AND WIDTH. Size of Opening, | 1£ If If inches. 2f x 4 3£ x 4£ 3f x 5i 4i x 5£ 26 BAUSCH & LOMB OPTICAL COMPANY, » B. & L. STEREOSCOPIC SHUTTER. Cut % actual size. At this time when stereoscopic photography is becoming more popular and where a suitable shutter for almost all work in photography has become a neces- sity, a good stereoscopic shutter properly constructed, offering advantages not possessed by others, is important. In designing this we have as much as possible, applied the desirable features of our Diaphragm Shutter, which, with the balance of the construction makes this unquestionably the best shutter now before the public. The centers of opening are 3^- inch apart. The action of the leaves is abso- lutely synchronous, thus giving the same amount of exposure through both lenses. Revolving diaphragms are provided for stops. The speed regulator of our Diaphragm Shutter is applied, thus giving all variations in speed from t -J-q to 3 seconds. Release may be made by bulb or finger. We make these shutters in two forms. A. Unless otherwise ordered, this is always sent. In this form the openings are made diamond shape, starting from a small square opening, which is the nearest approach to the diaphragm shutter and gives similar effects. B. The blades open with a horizontal parallel opening over the entire diameter, having a slight wedge form at full opening. This form gives more exposure for the same amount of time and is preferable where it is desired to make very quick exposures. In applying the shutter it is screwed directly on the front board of camera. In attaching lenses we can assume no responsibility in accurately fitting unless lenses are in our possession. Opening. Rapid Universal. A. G. Clark. Velox Rectilinear. Zeiss-Anastigmat. Price. Series II. Series \\a. Series III. Series Ilia. Brass. Alumi- num. £ in. No. 5 No. 5 No. 1 No. 2 No. 2 & 3 No. 2 & 3 No. 2 & 3 $18.00 $22.00 ROCHESTER, N. Y., AND NEW YORK CITY. 27 IRIS DIAPHRAGM. After a series of experiments we have devised a new construction which offers manifest advantages over the forms hitherto used. While the desirability of iris diaphragms have been fully appreciated many have been deterred from using them or have discarded them on account of poor workmanship and consequent liability to get out of order, lack of compactness in mounting, and then because the intertwining leaves being made of metal and chemically blackened, have lost their black from friction and created internal reflections which are fatal to good results. In those of our construction the leaves are made of hard rubber, with mat surfaces which will always remain black and furthermore add no weight to the mounting. When applied to our lenses, there is no projecting ring except in a few of the larger sizes, but the entire iris diaphragm is contained within the tube. Having constructed special machinery, all work is done with the greatest accuracy, effecting a circular opening and a change in size is produced with the utmost delicacy. On some of our lenses we have made no advance in price for replacing these diaphragms over the ordinary loose stops, while, where it has been necessary, the extra charge is slight. We will apply these diaphragms to other lenses than our own; but on account of the differences in sizes of tubes it will be necessary to make the mounting of the diaphragm project beyond the diameter of adapters to which the lens mounts will be fitted. The opening is varied by a milled edge, whereas in the other form it is done by a small lever with pointer. Prices include Iris Diaphragm and the necessary adapters for receiving the lens mounts. No. Diameter of Opening. Price. Telegraphic Code. 1 2 3 4 5 6 7 8 9 $4.50 5.00 6.00 6.00 7.00 7.00 8.00 8.00 10.00 Ibex. Ibid. Ibis. Ichor. Icon. Idea. Idem. Idest. Idiom 28 BAUSCH & LOME OPTICAL COMPANY, PRISMS. These Prisms are intended to be used in all classes of photo-mechanical pro- cesses. They invert the image and make stripping of the film unnecessary. The glass is specially made for us, of the highest possible excellence, the surfaces are as accurately ground and polished as the surfaces of a first-class lens, so as to give an absolutely true reflection of the image. The hypothenuse is carefully silvered. These prisms are in lacquered brass mountings and arranged to fit the hood of lens. In estimating the size of prism which is required for a particular lens, a size should be selected which is at least equal to the diameter of the hood. A size which is larger than this is preferable, but under no condition should a smaller one be selected, as in the work in which these prisms are required, it is of great importance to utilize all the possible light which the lens can transmit. Fitted to Fitted to Fitted to Fitted to Fitted to Fitted to Price when Full Rapid Univ. Zeiss-An- Zeiss-An- Zeiss-An- Zeiss- An- Zeiss-An- Price. fitted to Aperture. and Alvan G. astigmat, astigmat. astigmat, astigmat, Series IV. astigmat, other Series II. a. Series III. Ser. Ula. Series V. Lenses. Clark Lenses. H in. No. 4J Nos. 1 & 2 Nos. 1 & 2 Nos. 1 & 2 Nos. 1 & 2 Nos. 1 & 2 $ 28.00 $ 30.00 2 " No. 5 No. 3 No. 3 Nos. 3 & 4 No. 3 No. 3 36.00 38.00 2* " No. 8 No. 4 No. 4 Nos. 5&6 Nos. 4 & 5 Nos. 4 & 5 45.00 47.00 2f » No. 8i No. 5 No. 5 No. 7 No. 6 Nos. 6 & 7 53.00 55.00 3 " No. 10 No. 6 No. 6 No. 8 No. 7 No. 8 65.00 67.00 3i " No. 12 No. 7 No. 7 No. 9 No. 8 No, 9 78.00 80.00 4 " No. 15 No. 8 No. 10 No. 10 90.00 93.00 4£ « No. 18 No. 8 No. 11 No. 9 No. 11 140.00 145.00 5* " No. 22 No. 9 No. 12 No. 10 No. 12 180.00 185.00 ROCHESTER, N. Y., AND NEW YORK CITY. 29 CONDENSING LENSES. These lenses we make of the very highest grade and of strong curvature so as to give the greatest concentration of light. They should not be confounded with plano-convex lenses of weak curvature and therefore of insufficient concen- trating capacity. Price, Price, In Brass Mounting. Telegraphic Code. No. Diameter. Focus. Unmounted. H U in. 2 in. $ 1.50 each. % 4.50 per pair. Obal. 2* " 2f " 1.75 " 5.00 " Oboth. 3 3 " 3i " 2.00 " 6.00 " Ochill. 3£ 4i " 2.25 y\ 7.00 " Ocina. 4 4 " 5 " 2.50 V 8.00 " Oded. 4£ 4i " 5* " 3.00 " 10.00 " Olamus. 5 5 " 6* k ' 3.75 " 11.50 Oman. 6 6 " 7i " 6.00 2.50 Rechab. 252 Metal Frame, Black Enameled Handle; " 2 " .80 Rehum. 253 2i " .90 Resen. 254 H " 1.00 Rezia. 255 2f » 1.25 Rhoda. 256 " ■ "3 " 1.50 Ribai. 257 Si " 1.75 Rufus. 258 3£ " 2.00 Ruma. 259 3f " 2.25 Runen. 260 4 " 2.50 Ruoti. 261 3.25 Ruti. 262 5 " 4.00 Ruvo. 263 5i " 5.00 Rys. 264 6 " 6.00 Ryssen. ROCHESTER, N. Y., AND NEW YORK CITY. 31 FLANGES, LEATHER CAPS, AND CASES. BRASS FLANGES. No. 1 2 3 Jf 5 6 7. 8 9 Diam. Price, ! H $-.50 2 -.75 2£ 3 3£ 4 5 1.00 1.25 1.50 1.75 2.00 H 2.50 6 3.00 inches, each. No. 1 2 ALUMINUM FLANGES. 3 4 5 6 7 8 9 Diam. Price, ! H 11.00 2 1.25 2| 3 3| 4 5 1.50 2.00 2.50 3.00 3.50 H 4.00 6 4.50 inches, each. MOROCCO LEATHER CAPS, For Universal, Clark, and Zeiss Lenses. No. 1 2 3 4 5 6 7 8 9 10 11 12 Diam. H If H 2 T V> 2A, H « 3 t V, 3 t V, 4 t V, 4 t V, 5* inches. Price, $.60 -.60 -.65 -.70 -.70 -.75 -.80 -.90 1.00 1.10 1.20 1.25 each. MOROCCO LEATHER DIAPHRAGM CASES, For Universal, Clarlc, and Zeiss Lenses. No. 1 2 3 4 5 6 7 8 9 10 11 12 Size ifxli, l^xlf, lfWi l x \x2 4 V, Hx2i, lfx2i, l T fx2f , 2 T \x3 T V, 2Jx3A, 3x4£, 3 x \x4| ( 4x5^ in. $-.75 -.75 -.80 -.85 -.85 -.90 -.95 1.00 1.15 1.30 1.50 1.75 ea. LEATHER CAPS For Yelox Lenses. No. 1 2 3 4 5 6 7 8 9 10 Diam. If, H, 2 T V, % 5 2f, 3, 3^, 3 T %, 5f inches. Price, $-.40 -.45 -.50 -.55 -.60 -.65 -.70 -.80 -.90 1.00 each. LEATHER DIAPHRAGM CASES For Velox Lenses. No. 12 3 4 5 6 7 8 Size, l T Vxlf, lix2i, lfx2J, 2 T Vx2 T f, 2^x3^, 2fx3f, 3 T \x4|, 4x5^ inches. Price, $-.60 -.65 -.70 -.80 -.90 1.00 1.25 1.50 each. WATERHOUSE STOPS (Exclusive of Leather Case). Size, 4x5, 5x8, 6|x8|, 8x10, 10x12, 11x14, 12x15 14x17 16x20 20x24 Per set, $-.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3- BAUSCH & LOMB OPTICAL COMPANY. Table for Finding the Minimum Length of Studio for a Given Lens. (From the American Amqteur Photographer.) DISTANCES IN INCHES FROM OBJECT TO LENS. Equivalent Focus of Lens. 3 in. high. 4 in. high. 5 in. high. 6 in high. 8 in. high. io in. high. i2 in. high. 16 in high. 20 in high. 24 in high. 30 in high. 36 in high. 48 in high. . 54 in . high. 60 in high. high. 3 inches 75 57 4 " 100 76 61* 52 5 " 125 95 77 65 50 6 . 150 1 1 A 114 92f to 60 A ft 1 49 i 8 " 200 152 1231 104 80 65 T % 56 10 " 250 190 154 130 100 82 70 55 12 " 300 228 184* 156 120 98 1 84 66 551 16 " 400 304 246f 208 161 1311 112 88 72f 64 54* 48 20 " 500 380 308 260 200 164 140 110 90| 80 68 60 50 46* 24 " 600 456 369f 312 240 196f 168 132 HOf 96 81* 72 60 56 521 48 30 " 750 540 462 390 300 246 210 165 1361 120 102 90 75 70 65 60 36 " 900 684 554| 463 360 3071 252 198 165f 144 122* 108 90 84 791 72 48 " 1200 912 7391 624 480 3931 336 264 2201 192 1631 144 120 112 105* 96 60 " 1500 1080 1024 780 600 492 420 330 2721 240 204 180 150 140 132 120 72 " 1800 1368 1108f 936 720 614 1 504 396 3211 288 2441 216 180 168 158* 144 DISTANCES IN INCHES FROM LENS TO GROUND-GLASS. Equivalent Focus of Lens. 3 in- high. 4 in. high. 5 in. high. 6 in. high. 8 in. high. 10 in. high. 12 in. high. 16 in. high. 20 in. high. 24 in. high. 30 in. high. 36 in. high. 48 in. high. 54 in. high. 60 in. high. 72 in. high. 3 inches 31 4 " 41 4f *18 41 5 " K 5 5t 5 f 5ff BA 5| 6 " 2* 6£ 6fV 61 6* 71 8 " 81 8f 8* 8* n 91 10 " 10A 10 1 10** 10 f Hi 1H 12* 12 " 12 i 12 1 12* 13 131 13* 14 14* 151 16 " 16* 16 | in 17* m 18 1 18* 19* 201 211 22* 24 20 " 20 f 21i 21 T 7 8 21* 22f 221 231 24* 26* 281 30 33* 35 24 " 25 251 25 f 26 26* 26* 28 291 30* 32 34 36 40 42 44 48 30 " 31 i 31* 32 T V 321 33* 34? 35 36* 381 40 42^ 45 50 521 55 60 36 " 37 i 38 381 39 39* 40 42 44 46 48 51 54 60 63 66 72 48 " 50 50* 511 52 531 54 * 56 58* 611 64 68 72 80 84 88 96 60 " 62 i 631 641 65 66* 681 70 731 77* 80 85 90 100 105 110 120 72 " 75 76 77 78 791 80 84 88 92 96 102 108 120 126 132 144 Suppose the lens used is 24 in. equiv. focus, and you wish to make a full-length portrait of a man six feet high, in which the image will be six inches high. Look at the left-hand column for lens focus, and in the top line for size of image. At the intersection of these columns we find 312 inches = 26 feet, to be the distance the person must stand from the lens. In the next table, using the same lens and size of image as before, at the intersection of the columns we find twenty-six inches, which repre- sents the distance of the ground glass from lens center. And in the same way any lens and size of image may be computed for. Table of View Angles. DIVIDE THE BASE OF THE PLATE BY THE EQUIVALENT FOCUS OF THE LENS, If the The If the The If the The If the The If the The If the The quotient angle quotient angle is quotient angle quotient angle quotient angle is quotient angle is is is is is is is is is is Deg. Deg. Deg-. 42 1.041 Deg. 1.36 Deg. Deg. .282 16 .517 29 .768 55 68 1.7 81 .3 17 .536 30 .788 43 1.063 56 1.375 69 1.739 82 .317 18 .555 31 .808 44 1.086 57 1.4 1° 1.769 83 .335 19 .573 32 .828 45 1.108 58 1.427 1.8 84 .353 20 .592 33 .849 46 1.132 59 1.45 72 1.833 85 .37 .389 21 .611 34 .87 47 1.155 60 1.48 73 1.865 86 22 .631 35 .89 48 1.178 61 1.5 74 .898 87 .407 23 .65 36 .911 49 1.2 62 1.53 75 1.931 88 .425 24 .67 37 .933 50 1.225 63 1.56 76 1.965 89 .443 25 .689 38 .954 51 1.25 64 1.59 77 2. 90 .462 26 .708 39 .975 52 1.274 65 1.62 78 .48 27 .728 40 1. 53 1.3 66 1.649 79 .5 28 .748 41 1.02 54 1.32 67 1.678 80 This table has been calculated by Dr. Woodman for the use of those who wish to know the precise angle of view included by any particular lens on a given size of plate. Its mode of use will be easily seen by inspection. WORKS OF BAUSCH & LOMB OPTICAL CO. ROCHESTER N. Y. FRONT VIEW — FACING NORTH ST. PAUL ST WORKS OF BAUSCH & LOMB OPTICAL CO., ROCHESTER, N. Y. REAR VIEW — ON THE BANK OF THE GENESEE RIVER.