= NOTES ON OPTICAL PRINTER TECHNIQUE Magnification 1 Fadea in Original 14 Blowup.& Reduotion 2 Chart C: Neutral Déneity and Blowup Sharpness 2 Equivalent Shutter Printer Lenses 3 Angle 15 Optical Zoom 3 Image Superposition 16 Lene Aperture 3 Gamma # Bipack 16 Focusing 4 Incidentally 16 Focusing Aperture 4 Exposure Compensation 18 Focusing Precision 4 Special Originals 18 Focusing Target 4 Texturing 18 Depth of Field 4 Multi-Exposure 19 Bolex Priam 4 Multi-Pack 19 Bolex Groundglass 4 Natural Superposition 19 Defecus 4 Flashing 19 X-Y Adjustment 4 Contrast Adjustment 19 Exact 13:1 5 Color Image Superposition 20 Ainframe 5 Weighted Double Exposures 20 Franelines 6 Dissolves 21 Emulsion Position T Effects Dissolves 2} Time 8 Fades from Negative 21 Fancy Freeze 8 Color Exposure 22 Fancy Slow 8 Testing 22 Diffusers 8 CC Pack Reduction 25 UV Filter 9 High Contrast Printa 25 IR Filter 9 Hicon Exposure 26 Green Filter 3 Contrast Building Steps 26 Filter Location 9 Hicon Speckle 26 Exposure 9 Tone Isolation 27 Exposure Adjusters 9 Logie of Mask Combination 27 Specifying Exposure 11 Image Spread and Bloom 27 Film Speed 11 Mask and Countermask 28 Right Exposure 1 Reversal/Negative Fitting 28 Generations 2 Feathered Maska 29 Bellows Formula 13 Image Marriage 2g Fades 13 Mask Blacknesé 30 Log Fade 14 Hicona from Color Originals 30 Bolex Variable Shutter 14 Hicon Processing 30 Linear Fade 14 Optical Printed Release Prints 31 Other Fades 14 Ritual and Art 31 i on | revisec . NOTES ON OPTICAL PRINTER TECHNIQUE DENNIS COUZIN March 1983 An optical printer 18 a device for photographing the frames of one film sco as to make another filn. e 2 - . , I Cc It consists essentially of @ camera (C) connected by a bellows (B) to a lens (L) aimed at a film in a gate (G) illuminated from behind by a lamp (I). The camera and gate each have motorized intermittant filin movements so that any frame of the "original" film can be conveniently photographed onto any frame of the "print" filo. The camera can be an ordinary cine camera, less its lens, and the gate can be an ordinary cine projector, less its lens. Ideally they have identical syatemsa of film registration, aa if one Were the lens’ image of the other. The lens can be any bellows mountable lens. Ideally it ie specially corrected for the amall and nearly equal sizes of this object and image. The camera and the lens can elide independently to and fro the film gate. Thie adjustea the magnification and the focus of the photography. MAGNIFICATION If the lens is (nominally) midway between the films when one is focused on the other, then the magnification is 1. At M=1 (also called 1:1} the whole of the original frame 1s photographed at a size which fllis the whole of the print frame. i ) oY ? If the lens 18 moved closer to the gate, then the camera must be moved back, farther from the gate, _ to keep the one film focused on the other. Then the Copyright (1983 by Dennie Couzin r 2 magnification is greater than 1. At M>1 a part of the original frame is photographed at a size which fille the whole of the print frame. If, starting from the 1:1! setup, the lene is moved farther from the gate, then the camera must also be moved back, farther from the gate, to keep the one film focused on the other. Then the magnification is loser than 1. At M<1! the whole of the original frame is photographed at a size wohich does not fill the whole of the print frame. The remainder of the print frane 46 filled with a photograph of the gate as it surrounds the original frame (ideslly perfectly black). 6 y For each position of the lens there is exactly one correct (focused) position for the camera. But for each position of the camera (except the 13:1 position) there are two correct positions for the lens. One gives M>1, the other M<}. BLOWUP & REDUCTION The printer gate may hold Smm film and the printer camera 16mm, or vice versa. With ap M=2 setup an Sum original frame 18 photographed onto a whole 1énm frame. With an M=¢t setup a whole !6um original frame is photographed onto an Smm frame. Conversion between any two film gauges 4s possible thia way, provided the frames have the sane proportions, as Sum, super San, 16mm, and some 55ma do. BLOWUP SHARPNESS A 16mm picture of a flea can be just as sharp ae @ 16mm picture of an elephant. Fut & \é6an picture of an Smm picture cannot be expected to be as sharp as a t6mn picture of a 16mm picture. Pictures differ . from thinge in having very limited detail. The 16as blawup, even if it preserven all the pictorial detail of the mm original, spreads it out, so the blowup ie less sharp absolutely than the original. , 3 Under extreme magnification -- a microscope objec eould be the printer lene -- pictorial detail i: diffuse and the underlying natural thing, the enulsion, is all that could be photographed sharply. But the grains are too small to be sharply imaged with light. Here even the natural thing haa been photographically exhausted, an 8mm original blown up to 16mm and projected will appear sharper than the sane 8mm original optically printed onto Smm and projected. If the blowup optics are good thie is even true when the 1:1 printing is by contact. Likewise for 16mm to 35mm. (This ie all due to the print film being in effect twice as sharp and half as grainy in a bigger frame.) PRINTER LENSES A lens well-corrected for M-1 is less well-corrected for M=? (or M=t). A lene Wwell-corrected for M=2 is leas wall-corrected for M=4 (or M=%). Etc. (Floating elementea improve this.) A lens well-corrected for M=1 for a larger format is lees than ideal for M-1 for a smaller format. With such specialization (and expense) in optical printer optics what ie the hope for the $50 SOmm enlarger lens, optimized for M=.1 and much too large a format? Wot bac, provided the sharpest aperture ie found and heeded and focusing technique is eine. Aleo, for Mé! ano asyunetrical lens should be mounted the right way, which is usually with its smaller glass facing the smaller image. A very sharp cheap printer lens is the Canon Macrophoto 35mm £/2.8. OPTICAL ZOOM Optical printers do not use soom lenses, although they could. An optical printer toom is made by moving the camera and lene each frame, so as to vary magnification while holding focus. It is a dolly shot! A dolly abot is equivalent to a toom for a flat subject. Geometrically this zoom oan be identical to a zoom had it been made in the original photography. It can also be deviant, by tracking not to the center of the frame. Pictorially the zoom gets grainy, showing that it was not made in the original photography. Rather than focua at each frame, camera am lene positions can be precharted for, say, every 10th frame, and the other positions interpolated or computed. On the J-E, counting the turns of the lead screw ie a means of repeatable positioning. A follo¥-focus sechanian is @ boon to optical Z£oons. The rate and course of s00ming is a factor of style, as it is in original cinematography. LESS APERTURE” For picture taking the printer lens should be at whichever aperture gives the sharpest pictures. This 4e found in teste. If a lens must be atopped down past f/8 to reach optimum it is a terrible printer lene. F 4 FOCUSING Printer focusing procedure is different at different magnifi At 1:1 the camera, not the lens, 4e moved for focusing,’ Gulp) at magnifications greater than about 1.4 18 it better to nove the lens for focusing. Near the t:1 setup lens motion has no focusing effect. With the camera fixed in its 1:1 position lens motion: adjusts magnification between about M=.96 and M=1.04 (at f/5.6). FOCUSING APERTURE With all but the best optical printer lenses either (1) foous at the taking aperture or (2) foous at a larger aperture and then shift focus by a pre-established distance before taking. This "fudge-factor" is found in film teate. FOCUSING PRECISION Especially when focusing stopped dowm, focus many times (perhaps 20) and set an average position. FOCUSING TARGET Use whatever target ie found eablest to focus on. One caution: the fudge-factor is target dependent. Very fine resolution targete may require different fudge factora than coarser targete do. DEPTH OF FIELD at indicated f/5.6 there is already more than enough depth of field for a4 bipack, at 1:1. dAleo it ig unnecessary to refocus when adding the second film. Likewlee when a single film ie reversed’ emulsion to base. At larger apertures and at larger magnifications depth of field is lese. BOLEX PRISM It isn't a worry. There len't a distinetion between RX lenees and non-RX lenses for most any lens which will be used on a bellows for optical printing. BOLEX GROUNDGLASS Only for the best optical printer lenses, which will be used at apertures larger than f/4, does the Bolex groundglass need to be reset from its everyday position. DEFOCUS To throw an image out of focua without changing ite size, if printing at i:1, move the camera 4 distance and the lens ¢ this dietance, in the same direction. X-Y ADJUSTMENT Besides its to and fro movement the lene haa lateral movements. These adjust the position of the original frame's image on the print frame. For example, if the lens is raised a bit... 5 At 1:1 moving the lens up a distance d raises the viewed field by twice 4d. Likewise for down, right, and left. At M>1 lateral adjustment effects a scan of the original frame. This is not geometrically equivalent to a pan, bad it been made in the original photography, On simple optical printers the only lateral ad Justment is of the lens (rather than the heavier camera or gate). Thie is Geometrically adequate. But the J-K adjustments are even too flimsy for a lens. It helps, after they are set, to gently tap the lens, ac it finds a stable position, and then to readjust if necessary, etc., etc. EXACT 1:1 The lateral movements of the lens, the to-fro movements of the lens and camera, and a tilting of the camera (if necessary) allow the optical printer to be set for exact 1:1 reproduction. Then the printed image is the same aize and in the same position as the original image. If the printer lacks a tilt adjustment the oamera may be shinmed. AIMFRAME A Special frame is made to guide the exact 1:1 setup. To make an "aimframe" use the optical printer camera (though not necessarily with the optical printer lens) to photograph a target which is epecially drawn to contain detaila exactly’ coinciding, as seen through the camera eyepiece, with details permanently on the groundglass. The photograph made while the coincidence is seen is the ainfrane. Every groundglass has some permanent detaile, even if only ite flaws. The field edge is a poor choice of detail if the mask is thick or if the eyepiece is aberrated at the edge. Two points of detail are enough for a well~aligned printer, three pointe for a suspect one. A reticle made on high resolution film may be attached to the groundglass to add details. Small patterns of concentric circles and other patterns which self-moiré are ideal. also the ainframe can be a negative of the fine-patterned reticle. For exact 1:1! setup, the aimframe film is registered in the printer gate and the printer camera and lens adjusted to achieve that same coincidence of details, as seen through the eyepiece. Focusing must be completed before the final adjustment to the aimframe. It is convenient to incorporate a focusing target in the aimframe. The aimframe has validity only for the camera in which it was made. It does not depend on the accuracy of the camera'a reflex viewing eystem, only the stability of the eysten. Whenever there is doubt about the validity of the aimfrane, such as after a camera repair or because of wear to the filn, the old aimframe can be registered in the printer gate, aimed on, .and photographed to make a newly valid aimframe. For rotoscoping with primitive contrapLions, an aimframe may be projected and drawn. This drawing is later used to aim the camera (whose aimframe it was) when photographing the rotoscoped drawings. Fo 6 The 1:1 accuracy of optical printing with aimframe setups ie limited by 1. the precision in the making and then in the use of the aimnfraze, 2. the precision in the film registration mechanians of camera and gate, 3. only if the two mechanieme are different, the precision in the film dimensions (perforation and alitting). Btep contact printing, Buch 48 by bipacking in the optical printer eamera, if & convenient method for making exact 1:1 reproductions. It must give exposures which are exact 1:1, but there 18 then sone shrinkage in processing. Optical printing with the ainfrane methoc compensates for processing shrinkage. Shrinkage errore are too apall to matter with simple printers. GAMEFRAME A atrip of identical frames, shot in the optical printer camera, is cut in two and registered in both the printer gate (upright, eanulgion away from lene) and the camera gate (ae it was shot). The coincidence of detaile of image and sameframe is viewed throug an opening in the rear of a special pressure plate. ™~.90 (3 stops) 12.6 23 1A 30 ~.95 11.2 20.2 15 26 ™ 4,00: - 10 18 13 24 ee ™1.05 8.91 16 12 21 ad 1.10: - 7.94 14.2 19 19 | 1.15 7.08 12.7 2 17 | . ™“1.20.-(4 stops) 6,31 11.4 3 15 1.25 5.62 10.1 7 13 ~. ™1.30° 5.01 9 7 12 13s 4,47 B 2 11 “1. 40 3.98 7.2 G 9 ™ 1,45. *~ 3.55 6.4 5 3 5 1.50 (5 stops) 3.15 5.7 4 7 . ~~ 2:00 16 IMAGE SUPERPOSITION In an overall combination of two images, the two can infuse each other as lightness or as darkness, or they can be slapped onto each other. There are three basic types of image superposition, named according to how they are made. Pictures A & B combined by... (1) Double exposure from positives. The print film is eared twice, once from A's positive, once from B's positive. (2) Double exposure fron mepetizes: The print film Ts expose wice, once from A 8 negative, once from B's negative. (3) Bipack. Two films, either A's and B's positives, Or é6lee A's and B's negatives, are inserted together in the printer gate. The print film 4s exposed once, from this pair. The print film is unspecified. It is in the final positive print that the three types of combination are compared, and they look very different. For B&W the differences can be described by how tones combine. With (t}, lightness dominates. Where one tone combines with another tone the result is nearly the lighter of the two tones. With (2), darkness dominates. The result ia nearly the darker of the two tones. ———=> With (3), there is contrastification which complicates the tone combination. If a bipack is examined ray (unprinted) wherever both images are clear the bipaer 4a clear. Wherever either image is black the bipack 4s at least that black. Wherever both images are black the bipack is doubly black. The bipack, whiob appears dark, has a tonal range doubling that of the single images. The bipack is wprintable in toto. To abstract a pioture from the unprintable bipack printing exposure is typically increased 1-4 atops. With 4 stops increase, where clear and black eoincide printe as a dark grey would—not 4 clear domination of either lightness or darkness. With 2 stops increase there is darkness domination. GaMMa ¢ BIPACK If the bipack is printed onto gamma $ material, to reduce the contrast to normal, it is a true tonal blender, without dowinance, of the two images. As the graphs below show, the gamma # bipack ia the mean between the type (1) ~ and type (2) double exposures. INCIDENTALLY A type (3) of a type (1) and a type (2) le just a type (3) again. r. a a 17 Four idealized graphs summarize the three basic types of superposition and the gamma # bipack. Example: 4 has density .75 and B has denaity 1.75 in one place. From the first graph, the double exposure from positives has density about 1.0 in that place. as Pous exfosup am Foss as BiPACK. (10 Come as Me de is ib fo] je ia cy - e 5 = io LS ts a: Sg = he Lf wt as Ly Ltt L Pi 5 A ‘a 2 2 APPA L elie = i wat ae Le ‘ly \ WX | Fo x7 14 ie to as 85 e 2 4 20 oe For a double exposure it doesn’t matter which exposure is first, or what time separates the two. In some multi-head optical printers, using 4 bean-splitter, the two exposures are simultaneous. Kither way, the two filma can be independently adjusted for exposure, filtered, etc. For a bipack it doesn't matter which film ie in front. Also the two may be optically instead of mechanically bipacked. In some multi-head optical printers the films are in separate ~gates, ones projection becoming the other's illumination. Ir a simple printer one film may be in the gate and the other in the camera, in front of the print film. Any Way, the two films ehare one exposure adjustment and filtration. 18 When filmwe will be physically bipacked they should firet be wiped with a lubricating film cleaner. This ie good practice for all optical printing when delicate originals receive heavy handling. EXPOSURE COMPENSATION For superpositions from random pictorial originale: For double exposures, the typical exposure adjustment is one stop of decrease from normal, during each exposure. With this adjustment a double exposure of picture A with picture A ie the Bame as a single normal exposure of A. For bipacks there ie no recipe. Expoaure adjustment ie extremely dependent on whioh tones coincide with which. The adjustment is an increase from normal. In ignorance of the originals (why?) and ignorance of the intentions (why?) guess 2% stops increase. No exposure adjustment can make a bipack of picture A with picture A the same as picture A printed the same. But a gamma $ bipack of picture A with picture A is the same a6 picture . SPECIAL ORIGINALS For superpositions not from random pictorial originals tones might not combine at all. One image might fall on the other's black, or clear, and exposure compensation 48 different, perhaps unnecessary. With special, rigged, originale superposition is not image combination in the earlier sense but image apportionment -- implantings and supplantings. The rulee of tone combination etill apply, but trivially, and a eimpler logic prevails. Double exposing from positives, where one image is ——_>> black the other image appears, unaffected by the doubie exposure, Where one image is very light it appears, hardly affected by the double exposure. Double exposing from negatives, where one image (the picture, not the film) ie clear the other image appears, unaffected by the double exposure. Bipacking, where one image is any even tone, the other image appears, unaffected exoept for brightness. The clear parts of one film are windowa for the other film. But it is possible, with enough extra exposure, to force one image through the blackened window of the other The most extreme cases of rigged originals involve high contrast masks, Gisoussed below. TEXTURING In~a bipack, an image.of a plain white eurface, showing just = ite texture, imparte this texture to the other image. 19 MULTI-EXPOBURE Triple, quadruple, etc. multiple exposures are made similarly to double exposures. If there would be 5 exposurea from the same or nearly the same original, then each should receive 1/5 normal exposure. From Chart C, 1/5 of full shutter equals ND.70 compensation. eat lizely the originals are special, and the compensation ess, MULTI-PAck Tripacks, quadripacks, etc. are unmanageable in simple optical printers. For suob effects intermediate prints must be made. For example, to quadripack A,B,0,D make printed bipacks of A with B and C with Dand bipack these two printe. The order of the originals doesn't matter. NATURAL SUPERPOSITION Of the three types only (1), the double exposure from positives, corresponds to possible camera origina: 4n original double exposure made from two real scenes la practically the same as a printer double exposure made from positive images of the acenes. Type (2), the double exposure from negatives, ia an artifact of the "log linear" response of negative films. Type (3), the bipack, is an artifact of the transparency of film images, at least one of then. Type (1) 16 nature's super. Preasing one eyeball produces such superpositions. FLASHING Double exposing an image with no image -- sere light -- lightens (or with colored light and color print filma, colors) the blacks and darker tones while having little effect on middle tones and even lese on lights. It is8 not a true method of contrast reduction. Sepia toning can be simulated by both color flashing and color filtering when printing B&W original onto color reversal print filr A healthy yellow, magenta, or cyan flash when printing onto color reversal film yields, respectively, the yellow, magenta, or cyan ~ image, as if this dye layer were prised from the original film. There ie no photographic method for unflashing a flashed image. There is image addition (double exposure} and image pultipliocation (Dipack) and even image division (bipack of positive with negative), but no image subtraction. CONTRAST ADJUSTMENT Gammas add or subtract in a bipack, so bipacking can adjust contrast. A bipack (printed gamma 1 or Viewed raw) of an original with its duplicate is like a double contrast original.