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Contenuti / Contents

Finding and Keeping the Time / Trovando e Mantenendo il Tempo

Holograms of Real and Virtual Point Trajectories

Ologrammi del Reale e Traitettorie del Punto Virtuale (estratto)

Sad Young Man on a Train / Uomo Giovane e Triste su un Treno

A Study of the Persistence of Vision

Uno Studio Sulla Persistenza Della Visione (estratto)

A Photograph of Duchamp Using a Hinged Mirror

The Truth Is Out There

La Verità Stà La Fuori

Fotografia di Duchamp usando uno specchio movibile

Maker, Above Below and Between

A List of Blending Modes

Elenco dei metodi di fusione

An Event Over the Skies of France / Un Evento sui Cieli della Francia

Credits / Crediti

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Presented as the Problem

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CHAPTER 2

HOL OGR A MS OF R E A L A NDV IR T UA L P OIN T T R A JE C T OR IE S

2.1 Introduction

In relativity, the orbit of a point event through space-time is called its world line. The world line itself is timeless, because it contains time as one of its dimensions. Over a period of years, we have been fascinated by the prospect of recording world lines of moving points of light holographically. Of course, these will have their three-dimensional (3D) spatial (the 3D trajectory) pattern and be timeless. There will be no way to give a direction of time and all we know is what events (3D positions) are the time neighbors of others.

Does this multidecade effort shed light on relativity or make it easier to understand? Prob-ably not. Holography can help us understand relativity, but that work is due to Abramson, not us. Surprisingly, our efforts have caused us to understand holography better. In this work we discuss holographic recording of moving points and compare the results with various aspects of other ways of recording a line in 3D space, such as recording an actual luminous line, sequential recording of points, and computer generation of lines.

2.2 Early Work

Our interest began with our efforts to generate 3D holographic images of synthetic scenes. Why not draw the scene with a moving point source using holography with a fixed reference beam to record the 3d object? Figure 2.1 shows the geometry. We moved the point continu-

ously parallel to the recording plate. Our results were wonderful, both theoretically and experi- mentally.

Theoretically, we showed that the coherently time averaging an Airy pattern (the far-field complex wave front of a point source) leads to a sin x/x pattern (the far-field complex wave front that would have been produced had the whole line been present at once). This seemed quite profound at the time. The coherent integration obliterated the time dimension. It may still be profound. We know that physics based on in-stants and infinitesimal points fails profoundly at the quantum level. It lacks the coherent integration into the whole. Experimentally, we found that the image of a clean bright line was produced. Without that success, we would not have persisted through the dark decades of disappointments and partial successes that followed.

Physicists progress by jumping to unwarranted generalizations and then examining the results. This is not so much a method as a predisposi- tion. The obvious thing to do after the first suc-cess was to move to more complex space-time patterns. We expected, naively it now appears, no problem in recording arbitrarily complex scenes in this way. Instead, we encountered two major problems. One problem we understood almost immediately and later were able to work around to some extent. The other problem we did not even understand, although we im-mediately invented a way to work around it. We address those two problems below.

2.2.1 Brightness Problem

As we all should have known, there is a commu-nication-theoretic limitation on the information

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content of the image and how much informa-tion we actually see depends on the encryption method. All of the great holographers (e.g., Gabor, Leith, and Denisyuk) knew that.

Figure 2.1 Schematics of the optical configura-tion. S is a point source and H is the hologram.

We did too, but it is easy to forget. The informa-tion storage density (that is bits per square centimeters for thin holograms and bits per cubic centimeters for thick holograms) is very material dependent. Resolution and noise are the primary determinants. If we use all of that capacity coherently to record a single point, the image may have tremendous signal-to-noise ratio (SNR). On the other hand, if we record and reconstruct N distinct, equally bright points, then each can have at most 1/N of the available light and 1/N of the single-point SNR. We emphasized the words “at most.” Only if each point comes from a hologram with unit contrast can we achieve the 1/N brightness condition. This would be the case if we recorded the hologram of N coherent points simultane-ously. However, in the case as was done in our first holograms, we are talking about recording the N points sequentially. Thus we have holo-grams from N essentially independent points full overlapping and then each will use only 1/N of the shared dynamic range. The bright-ness and SNR of each point can be at most 1/N of the values achievable for a single point. So, whichever way we choose to record the N

points, the brighness and SNR cannot be better than 1/N that of a single point and, usually, it will be much lower.

Returning to our special interest here of a continuously moving point, one should ask the question: How big is N? That is a question we did not even begin to answer in the middle period of this multidecade effort.

We now know that the above discussion is over-simplified and that there are ways, depending on the recording material and recording condi-tion, to improve the situation. In fact, at a quite early stage we did conceive of and demonstrate a way to improve the brightness and SNR. We simply moved the points close to the record-ing medium. Because of the limited angular divergence of the point source, the area on the recording medium illuminated at any instant was small. Thus there was no need for a refer-ence beam where there was no object beam, so we could block that part of the reference beam. Using a complicated optomechanical system, we scanned a point in 3d space near the record-ing plate and tracked it with the corresponding part of the reference beam. All of the time, most of the recording material received light only near the image of the reference point. The rest of the recording medium was shielded and, therefore, not degraded. thus no point suffered the full 1/N penalty, and very bright images were obtained.

2.2.2 Longitudinal Motion Problem

Initially, we did not call the problem by this name. All we observed was that when we moved the point in a 3D orbit (rather than in the 2D plane, parallel to the recording medium), we did not get very good images. In fact, the images

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were terrible. We did not know why, but we did find a satisfactory experimental way to fix the problem. We chopped (binary time modulated) both beams. For reasons we did not understand at the time, this allowed us to record beautiful 3D images.

This review of the history of a small part of holography allows us to introduce the current state of the art. We now know what the longi-tudinal motion problem was and why chopping “cured” it. We will show below that all parts of the Airy pattern are “blurred out” during any substantial longitudinal motion. Chopping reduced the blurring effects by recording just a very short light segment for each chopping cycle. A general mathematical analysis of the phenomena involved in holographic recording of moving sources follows below. The general consequences will then be represented with some demonstrative examples of special inter-esting cases.

CAPITOLO 2

OL OGR A MMI DEL R E A L E E T R A IE T T OR IE DEL PUN T O V IR T UA L E

2.1 Introduzione

Nella relatività, l’orbita di un punto attraverso il tempo e lo spazio è chiamata linea del mondo. La linea del mondo è senza tempo perchè lo contiene come una delle sue dimensioni. Sono anni che siamo affascinati dalla prospettiva di registrare le linee del mondo dei punti di luce in movimento, olograficamente. Naturalmente, questi avranno il loro schema tri-dimensionale (3D) spaziale (traiettoria 3D) e saranno senza tempo. Non ci sarà modo di dare una traiettoria del tempo e tutto quello che sappiamo è che gli eventi (posizioni 3D) sono i vicini del tempo di altri.

Questo sforzo illumina sulla relatività o la rende più semplice da capire ? Probabilmente no. L’olografia ci può aiutare a capire la relativ-ità ma questo lavoro appartiene a Abramson, non a noi. Sorprendentemente, i nostri sforzi ci hanno portato a meglio capire la relatività. In questo lavoro abbiamo discusso registrazioni olografiche di punti in movimento e comparato i risultati con vari aspetti di altri modi di regis-trare una linea nello spazio 3D, come registrare una linea di luce, registrare sequenze di punti e linee generate dal computer.

2.2 Lavori Precedenti

Il nostro interesse nasce con gli sforzi di gener-are immagini olografiche di scene sintetiche in 3D. Perchè non disegnare la scena con un punto di luce usando l’olografia con un raggio di ref-erenza fissato per registrare un oggetto in 3D ?

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Teoricamente, abbiamo mostrato che medi-ando coerentemente il tempo, uno schema Airy (il campo lontano complesso dell onda frontale di un punto fonte) porta a una sin x\x (il campo lontano complesso dell onda frontale di un punto fonte che sarebbe stato prodotto aveva l’intera linea formanta in una volta). Questo sembrava ben profondo a quel tempo. L’integrazione coerente obliterava la dimensione del tempo. Potrebbe essere ancora profondo. Sappiamo che fisica basata su istanti e punti infinitesimali fallisce profondamente ai livelli dei quanti. Manca l’integrazione coerente nell’intero. Sperimentalmente, abbiamo trovato che l’immagine di una linea pulita e luminosa è stata prodotta. Senza quel successo non avremmo persitito attraverso i decenni bui della delusione e il successo parziale che ha seguito.

Il progresso dei fisici salta su una non giustifi-cata generalizzazione e esaminando i risultati in seguito. Questo non è tanto un metodo quando una predisposizione. La cosa ovvia da fare dopo un primo successo era muovere schemi spazio temporali più complessi. Ci aspettavamo, adesso sembra incoscentemente, nessun problema nel registrare arbitrariamente scene complesse in questa maniera. Invece incontrammo due grandi problemi. Il primo lo capimmo quasi immediatamente e in seguito eravamo in grado di lavorare su alcune esten-sioni. L’altro problema non lo avevamo capito anche se avevamo immediatamente inventato una maniera per lavorarci intorno. Trattiamo questi due problemi di seguito.

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SAD YOUNG MAN ON A TRAINUOMO GIOVANE E TRISTE SU UN TRENO

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it should be noted that in this material there is no further formation of rods. The coarse-ly granular precipitate is well marked in the second and third divisions, but no rods are formed. It is evident that my conclusion from a study of the material described is that the basophilic bodies found are not in the nature of chromidia, but are the result of indi-rect nuclear activity. As to the applicability of these results to cases in which basophilic inclusions occur normally, it is impossible to say more than that such cases should be con-sidered in the light of the evidence here given. The explanation offered for the formation of the basophilic extra nuclear bodies described is intended to be suggestive rather than conclusive. It brings together facts which have not hitherto been associated. A more detailed paper with illustrations is forthcoming. Beckwith, Cora J., The Genesis of the plasma-structure in the egg of Hydractinia echinata. J. Morph., 25,

1914.

Chambers, Robert. Microdissection Studies I. Amer. J. Physiol., 43, 1917; and Microdissection Studies II,

Exper. Zool., 23, 1917.

Dantchakoff, Vera. Studies in cell division and cell differentiation I, J. Morph., 27, 1916.

Gatenby. J. Brouté. The Cytoplasmic Inclusions of the Germ Cells. Part V, Quar. Jour. Mic. Sci., 63, 1919.

Schaxel, Julius, Das Zusammenwirken der ZelIbestandteile bei Eireifung. Furchung, und ersten Organ-

bilung der Echinodermen. Arch. Micr. Anat. 76, 1911; Plasmastructuren, Chondriosomen und Chromidien. Anat.

Anz., 39, 1911.

Wilson. E B., Archoplasm, Centrosome, and Chromatin in the Sea-Urchin Egg, J. Morph., II, 1895.

A S T U DY O F T H E P E R S I S T E N C E O F V I S I O N By Arthur C. Hardy

Department of Physics, Massachusetts Institute of Technology. Communicated by Edwin II, Wilson, February 20. 1920

Introduction.—It was observed by Allen,1 while investigating the effect of the color of the light on the persistence of vision, that there seemed to be portions of the retina where the persistence of the retinal impression was less than on the fovea. That is, when no flickering of the color under observation was perceptible in the center of the retina, a slight movement of the eye in any direction which allowed the light to fall upon the periph-eral portions of the retina was sufficient to destroy the apparent continuity of the light. Allen attempted to measure the persistence for regions on the temperal side of the retina at 10 and 20 degrees from the axis of the eye but found that the results were “too uncer-tain to be of any use.” The writer has measured the persistence of vision for several colors within the cone whose semi-vertical angle is nearly 40 degrees. More than one hundred points on the retina within this area were observed for each color used. From these data, it is possible to construct a map of the retina showing the persistence of vision for each portion.

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Results of this sort should be of interest, not only to the illumination engineer, but to the physiologist and the psychologist as well. If the number of observers were large to insure that the results represent the average eye, it would be possible to construct a map of the retina with “contour lines” to show equal values of the persistence of vision. This was done by the author using the values obtained for his own eyes. The general shape of the lines was found to coincide more or less with the shape of the color fields given by Ab-ney.2 The extent of the color fields is, of course, dependent upon the intensity of the light. It was not possible to show that the area of the retina covered in this investigation was greater than the color field for the blue for the intensity used. As the color field for the blue is larger in area than for any other color, it seems natural to suppose that the persistence of vision should depend only upon the intensity of the light on portions of the retina outside this area and should be independent of the wave-length. Description of apparatus.—The persistence of vision was measured by observ-ing the minimum speed at which a sectored disk could be driven without destroying the apparent continuity of the light. The source of light was a concentrated filament incandes-cent lamp operated at constant voltage. A lens system was used to bring the rays to focus on the sectored disk. When the position of the disk is such that the rays do not strike it, they diverge until they strike a ground-glass screen about 6 centimeters square. An iris diaphragm placed just in front of it makes the size of the illuminated area on the ground-glass adjustable without altering the brightness. The sectored disk, the necessary electric motor to drive it, the incandescent lamp and the lens system are all placed in a light tight box. The eye was then placed 1 meter in front of the ground-glass and a chin rest was pro-vided to insure steady conditions of the retina while making the observations. Needless to say, the investigation was carried on in total darkness. A small electric lamp operated on the storage battery current and carefully shielded was used to read the instruments when necessary. The time for the recovery of the retina after this stimulus was less than the time required to place the apparatus in adjustment for the next reading. The speed of the disk was measured by means of a small magneto and a volt-meter calibrated to read the speed directly in revolutions per minute. The persistence of vision was first determined for the fovea by causing the disk to rotate at sufficient speed so that no flicker was apparent and then slowly to lose velocity until the first flicker was observed. On the average, it was found possible to determine the critical speed so that subsequent readings would not differ by more than 2 percent. Observations were also made with the speed of the disk increasing and the average was taken as the persistence measure. A set of filters made by the Wratten and Wainwright Company was used one at a time when it was desired to use light of a particular color. These filters were found to be very nearly monochromatic. The use of spectrum colors would be more accurate but the intensity of the light cannot be adjusted within as wide limits. To determine the persistence of vision for off center portions of the retina, a small radiolight sight was used. This was mounted on a slider attached to a long rod and so constructed as to revolve about the center of the diaphragm. In this way it was possible to

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place the sight in any desired position with respect to the center of the diaphragm. Shallow grooves were placed at intervals along the rod so that it was possible to read the position of the slider in the dark. In the experimental work, readings were taken about every 3 degrees from the center and along directions which made angles with the horizontal of 45, 90, 135, ISO, 225, 270 and 315 degrees. The manipulation was the same as before except that the attention was directed toward the radiolight sight and the persistence of vision measured with the light from the ground-glass screen falling on some other portion of the retina. It was, of course, necessary to cover one eye during all of the experimental work. Experimental results.—Before results could be obtained which were consistent with themselves, it was found necessary to take several precautions. For example, time was given for the eye to become accustomed to the darkness. Results were obtained which showed that 5 minutes in total darkness was sufficient. It was also found that any motion of the body, however slight, would cause the interest to flag. For this reason, the motor controls had to be adjusted so that the motor would change its speed slowly as it was im-possible to operate a rheostat by hand. One hand was held on a key which was pressed at the instant that the flicker was seen to appear or disappear and the critical speed noted. The size of the diaphragm which seemed to give the best results was a circle of diameter 5.84 mm. The persistence of vision is dependent upon the size of the retinal area stimulated and also the scintillation of the light from a small aperture caused more or less uncertainty.3 The above aperture was chosen as being the smallest that it was practicable to use. With the diaphragm placed at a distance of 1 meter from the eye, the angle sub-tended by the diaphragm at the eye is 3-30°. As has already been said, the persistence of vision was determined for several colors and in each case the persistence was measured for about one hundred points on the retina lying inside a circle which is the base of a cone whose semivertical angle is 38.7°. No attempt will be made to give the results in full. They represent the persistence of an impression on the retina of the eye of the author. The eye is known to be normal for color perception but has a moderate amount of astigmatism which should not affect the persis-tence of vision. A few results will be given to show the nature of the inferences which have be drawn from the investigation. For red light (6776 A°) the persistence of vision in the fovea was 0.0209 second. The persistence for points lying at equal distances from the fovea was found to be very nearly the same. That is, if lines are drawn showing equal values of the persistence of vi-sion, they appear to approximate circles with the fovea at the center. The deviation from the circle is enough to make them resemble the limits of the color fields for the retina. The circles are in every case flattened so that the major axis of the resulting ellipse is horizon-tal. The persistence is less for the fovea than for any other part of the retina, and there is a steady increase in the persistence nearly proportional to the distance from the fovea. The maximum value observed occurs on the nasal side of the retina at about 88° from the fovea. The persistence is slightly greater on the nasal side than on the temporal. The maximum value is 0.109 second.

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For the yellow-green (3310 A°) very similar results were obtained. The persis-tence of vision for the fovea is 0.0179 second and is less than any other portion of the reti-na. The lines of equal values of the persistence are ellipses with the major axes horizontal. The persistence is still slightly greater on the nasal side. The maximum value is observed to occur for the same region as for the red light but the maximum in this case is 0.0339 second showing that the persistence is more nearly constant over the whole retina. For the blue-violet (4631 A°) the persistence of the fovea is 0.0346 second. There is little change in the persistence for different portions of the retina. The region which gave a maximum value for the red and the yellow-green, now gives a value of 0.0339 sec-ond or slightly less than the fovea. The maximum occurs about 7° from the fovea on the nasal side and is 0.0401 second. The minimum of 0.0305 second occurs on the temporal side at an angle of 35° from the fovea. The change between the maximum and minimum amounts only to the difference between 1/25 second and 1/35 second. For the blue-violet light used, the persistence is very nearly constant over the whole retina. It will be noticed that these values for the persistence are smaller than those which are sometimes quoted. The values given here represent the time required for the im-pression on the retina to fade sufficiently to be noticed when compared to a fresh stimulus. They do not represent the time for the total extinction of the retinal image. The above results were obtained at the laboratories of the Department of Phys-ics at the University of California.

1 Physic. Rev., 28, 1909 (48). 2 Sir William Abncy, Researches in Color Vision, p. 190, et. seq. 3 See Almey, loc. cit., p. 181.

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U N O S T U D I O S U L L A P E R S I S T E N Z A D E L L A V I S I O N EDi Arthur C. Hardy

Dipartimento di Fisica, Massachusetts Institute of Technology. Comunicato by Edwin II, Wilson, 20 Feb-braio 1920; (estratto)

Per la luce rossa (6776 A°) la persistenza della visione nella fovea era 0,0209 sec. Fu scoperto che la persistenza per i punti disposti a distanze uguali dalla fovea era quasi la stessa. Se linee sono tracciate mostrando valori uguali della persistenza della vi-sione, sembrano approssimare cerchi con la fovea al centro. La deviazione dal cerchio è sufficiente per farli assomigliare ai limiti del colore dei campi per la retina. I cerchi sono schiacciati in tutti i casi così che l’asse maggiore della risultante ellisse è orizzontale. La persistenza è minore sulla fovea che in ogni altra parte della retina e si nota un costante aumento quasi proporzionale alla distanza dalla stessa. Il valore massimo osservato è vi-cino al lato nasale della retina a circa 88° dalla fovea. La persistenza e leggermente mag-giore sul lato nasale che su quello della temperal. Il valore massio è 0.109 secondi. Per la luce giallo-verde (3310 A°) sono stati ottenuti risultati molti simili. La persistenza della luce nella fovea è 0,0179 secondi ed è inferiore che in ogni altra porzione della retina. Le linee di valori uguali della persistenza sono ellissi con l’asse maggiore oriz-zontale. La persistenza è ancora leggermente più alta sul lato nasale. Il valore massimo accade per la stessa regione della luce rossa ma in questo caso il massimo è 0,0339 secondi mostrando che la persistenza è più costante su tutta la retina. Per il blu-viola (4631 A°) la persistenza nella fovea è (0,0346 secondi) C’è un pic-colo cambio nella persistenza per porzioni differenti della retina. La regione che ha dato un valore massimo per il rosso e giallo-verde adesso dà un valore di 0,0339 secondi o poco meno della fovea. Il massimo si registra circa a 7° dalla fovea sul lato nasale ed è 0,0401 secondi. Il minimo 0,0305 secondi, si mostra sul lato temporale ad un angolo di 35° dalla fovea. Il cambio trà il massimo e il minimo ammonta solo alla differenza trà 1\25 secondi e 1\35 secondi. Per la luce blu-viola usata la persistenza è molto vicina alla costanza su tutta la retina. Sarà notificato che questi valori per la persistenza sono minori di quelli che a volte sono quotati. I valori quì dati rappresentano il tempo richiesto per l’impressione sulla retina di sfumare sufficientemente forti per essere registrate quando comparate ad uno stimolo fresco. I risultati di sopra sono stati ottenuti nei laboratori del Dipartimento di Fisica dell’ Università della California

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LA VERITÀ STÀ LA FUORI

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83. Fotografia di Duchamp usando uno specchio movibile, 1917.

Il piacere di Duchamp per le nuove maniere popolari e oggetti tecnologici si estende naturalmente alla fotografia, di cui ha esplorato le varie dimensioni durante tutta la vita. Quì, il ripetuto ‘uomo di fronte allo specchio’ sembra essere prodotto senza il fotografo, una specie di autoritratto automatico che lascia la domanda dell’ autorietà irrisolta. Gli amici di Duchamp, Francis Picabia e Henri-Pierre Rochè avevano scattoto fotografie simili, probabilmente nella stessa occasione: 10 otobre 1917 al Broadway Photo Shop di New York.

Se richiamiamo il commento di Duchamp a Pierre Cabanne riguardo le altre funzioni che la pittura aveva ricoperto in passato: ‘religiosa, filosofica, morale’, in quale dimensione ha inteso Duchamp il Grande Vetro per avere una visione concettuale che poteva riformare la funzione dell arte ? O, per dirlo in altre parole, che funzione hanno nel Grande Vetro le diverse referenze alla religione, mitologia e letteratura ? Abbiamo visto come scienza e prospettiva come modi di descrivere il ‘reale’ avevano una ruolo nella genesi della sua immagineria. Cosa diciamo di sistemi di credenze o miti di tipo differente ?

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MAKER, BETWEEN ABOVE AND BELOW

Two or three points of departure Where edge blank eddies The texure of receivability By Vectors may saturate Pieces of layered approximations received

The surfacing of a parallel drift, generating a sense of out and in

Angular spin, the depth-maker of a surface Distance of time, pre-hole Tunneling volumes of degrees, as if broken tubes Within but between the numbers being counted

The setting of a broken rail The enormous movability of a sucking passage (omnidirectional) Random, partial shrinking

Appearance of some profile junctures, some linear burps, many

16. Review and Self-Criticism.94.

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Volumes exchanged, a speed of shifting

Place for construction of a core of flexibility only

Diffuse receding which parallels and contours waiting texture

The unique range of elasticities of impressionable stretching, not yet texture

The regulating of reflection, deflection, inflection Coalescence of sound joints, guides Realization of mounting and push of duration (instant group) Both senders and receivers, configurational coverings on all and any scale Pull of breath To keep the end in sight As always the necessity of out of the blue, “to” and “from” A sudden drop into a scale of action

The call of continuity

16. Review and Self-Criticism. 95.

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A LIST OF BLENDING MODES

NormalEdits or paints each pixel to make it the result color. This is the default mode. (Normal mode is called Threshold when you’re working with a bitmapped or indexed-color image.)

DissolveEdits or paints each pixel to make it the result color. However, the result color is a random replacement of the pixels with the base color or the blend color, depending on the opacity at any pixel location.

DarkenLooks at the color information in each channel and selects the base or blend color—whichever is darker—as the result color. Pixels lighter than the blend color are replaced, and pixels darker than the blend color do not change.

MultiplyLooks at the color information in each channel and multiplies the base color by the blend color. The result color is always a darker color. Mul-tiplying any color with black produces black. Multiplying any color with white leaves the color unchanged. When you’re painting with a color other than black or white, successive strokes with a painting tool produce progres-sively darker colors. The effect is similar to drawing on the image with multiple marking pens.

Color BurnLooks at the color information in each channel and darkens the base color to reflect the blend color by increasing the contrast. Blending with white produces no change.

Linear BurnLooks at the color information in each channel and darkens the base color to reflect the blend color by decreasing the brightness. Blending with white produces no change.

LightenLooks at the color information in each channel and selects the base or blend color—whichever is lighter—as the result color. Pixels darker than the blend color are replaced, and pixels lighter than the blend color do not change.

ScreenLooks at each channel’s color information and multiplies the inverse of the blend and base colors. The result color is always a lighter color. Screening with black leaves the color un-changed. Screening with white produces white. The effect is similar to projecting multiple photographic slides on top of each other.

Color DodgeLooks at the color information in each channel and brightens the base color to reflect the blend color by decreasing the contrast. Blending with black produces no change.

OverlayMultiplies or screens the colors, depending on the base color. Patterns or colors overlay the existing pixels while preserving the highlights and shadows of the base color. The base color is not replaced, but mixed with the blend color to reflect the lightness or darkness of the original color.

Soft LightDarkens or lightens the colors, depending on the blend color. The effect is similar to shining a diffused spotlight on the image. If the blend

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color (light source) is lighter than 50% gray, the image is lightened as if it were dodged. If the blend color is darker than 50% gray, the image is darkened as if it were burned in. Painting with pure black or white produces a distinctly darker or lighter area, but does not result in pure black or white.

Linear Dodge (Add)Looks at the color information in each channel and brightens the base color to reflect the blend color by increasing the brightness. Blending with black produces no change.

Hard LightMultiplies or screens the colors, depending on the blend color. The effect is similar to shining a harsh spotlight on the image. If the blend color (light source) is lighter than 50% gray, the image is lightened, as if it were screened. This is useful for adding highlights to an image. If the blend color is darker than 50% gray, the image is darkened, as if it were multiplied. This is useful for adding shadows to an image. Paint-ing with pure black or white results in pure black or white.

Vivid LightBurns or dodges the colors by increasing or decreasing the contrast, depending on the blend color. If the blend color (light source) is lighter than 50% gray, the image is lightened by decreasing the contrast. If the blend color is darker than 50% gray, the image is darkened by increasing the contrast.

Linear LightBurns or dodges the colors by decreasing or increasing the brightness, depending on the blend color. If the blend color (light source) is lighter than 50% gray, the image is lightened by

increasing the brightness. If the blend color is darker than 50% gray, the image is darkened by decreasing the brightness.

Pin LightReplaces the colors, depending on the blend color. If the blend color (light source) is lighter than 50% gray, pixels darker than the blend color are replaced, and pixels lighter than the blend color do not change. If the blend color is darker than 50% gray, pixels lighter than the blend color are replaced, and pixels darker than the blend color do not change. This is useful for adding special effects to an image.

Hard MixAdds the red, green and blue channel values of the blend color to the RGB values of the base color. If the resulting sum for a channel is 255 or greater, it receives a value of 255; if less than 255, a value of 0. Therefore, all blended pixels have red, green, and blue channel values of ei-ther 0 or 255. This changes all pixels to primary colors: red, green, blue, cyan, yellow, magenta, white, or black.

DifferenceLooks at the color information in each channel and subtracts either the blend color from the base color or the base color from the blend color, depending on which has the greater brightness value. Blending with white inverts the base color values; blending with black produces no change.

ExclusionCreates an effect similar to but lower in con-trast than the Difference mode. Blending with white inverts the base color values. Blending with black produces no change.

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HueCreates a result color with the luminance and saturation of the base color and the hue of the blend color.

SaturationCreates a result color with the luminance and hue of the base color and the saturation of the blend color. Painting with this mode in an area with no (0) saturation (gray) causes no change.

ColorCreates a result color with the luminance of the base color and the hue and saturation of the blend color. This preserves the gray levels in the image and is useful for coloring monochrome images and for tinting color images.

LuminosityCreates a result color with the hue and satura-tion of the base color and the luminance of the blend color. This mode creates the inverse effect of Color mode.

Lighter ColorCompares the total of all channel values for the blend and base color and displays the higher value color. Lighter Color does not produce a third color, which can result from the Lighten blend, because it chooses the highest channel values from both the base and blend color to create the result color.

Darker ColorCompares the total of all channel values for the blend and base color and displays the lower value color. Darker Color does not produce a third color, which can result from the Darken blend, because it chooses the lowest channel values from both the base and the blend color to create the result color.

ELENCO DEI METODI DI FUSIONE

NormaleModifica o colora ciascun pixel per trasfor-marlo nel colore risultante. Questo è il metodo predefinito. Il metodo normale si chiama Soglia quando si lavora con un’immagine bitmap o in scala di colore.

DissolviModifica o colora ciascun pixel per trasformar-lo nel colore risultante. Il colore risultante, tut-tavia, viene creato sostituendo in modo casuale i pixel con il colore di base o quello applicato, secondo l’opacità in ogni posizione dei pixel.

ScurisciEsamina le informazioni cromatiche in ciascun canale e seleziona il colore di base o il colore applicato, il più scuro dei due, come colore risultante. I pixel più chiari del colore ap-plicato vengono sostituiti, quelli più scuri non cambiano.

MoltiplicaEsamina le informazioni cromatiche in ciascun canale e moltiplica il colore di base per quello applicato. Il colore risultante è sempre più scuro. La moltiplicazione di un colore con nero produce nero; la moltiplicazione di un colore con bianco non cambia il colore. Se state appli-cando un colore diverso dal nero o dal bianco, i tratti sovrapposti creati con uno strumento di pittura producono colori gradualmente più scuri. L’effetto è simile a quello ottenuto diseg-nando sull’immagine con più evidenziatori.

Colore bruciaEsamina le informazioni cromatiche in ciascun canale e scurisce il colore di base per riflettere quello applicato aumentando il contrasto. L’uso

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del colore bianco non produce alcun cambia-mento.

Brucia lineareEsamina le informazioni cromatiche in ciascun canale e scurisce il colore di base per riflettere quello applicato diminuendo la luminosità. L’uso del colore bianco non produce alcun cambiamento.

SchiarisciEsamina il colore in ciascun canale e seleziona il colore di base o il colore applicato, il più chiaro dei due, come colore risultante. I pixel più scuri del colore applicato vengono sostituiti e quelli più chiari non cambiano.

ScoloraEsamina le informazioni cromatiche in ciascun canale e moltiplica l’inverso del colore applicato e del colore di base. Il colore risultante è sempre più chiaro. Scolorando con il nero, il colore resta invariato. Scolorando con il bianco, si ottiene il bianco. L’effetto è simile a quello otte-nuto proiettando più diapositive l’una sull’altra.

Colore schermaEsamina le informazioni cromatiche in ciascun canale e schiarisce il colore di base per riflettere il colore applicato diminuendo il contrasto. La fusione con nero non produce alcun cambia-mento.

Scherma lineare (Aggiungi)Esamina le informazioni cromatiche in ciascun canale e schiarisce il colore di base per riflettere il colore applicato aumentando la luminosità. La fusione con nero non produce alcun cam-biamento.

SovrapponiMoltiplica o scolora i colori, a seconda del colore di base. I pattern o i colori si sovrappon-gono ai pixel esistenti mantenendo le luci e le ombre del colore di base. Il colore di base non viene sostituito ma viene miscelato con il colore applicato per riflettere la luminosità o l’oscurità del colore originale.

Luce soffusaScurisce o schiarisce i colori, a seconda del colore applicato. L’effetto è simile a quello ot-tenuto illuminando l’immagine con un faretto a luce diffusa. Se il colore applicato (sorgente luminosa) è più chiaro del grigio al 50%, l’immagine viene schiarita, come se venisse schermata; se è più scuro del grigio al 50%, l’immagine viene scurita, come se venisse bru-ciata. L’uso del nero o del bianco puro produce un’area chiaramente più scura o più chiara, ma non produce il nero o il bianco puro.

Luce intensaMoltiplica o scolora i colori, a seconda del colore applicato. L’effetto è simile a quello ot-tenuto illuminando l’immagine con un faretto intenso. Se il colore applicato (sorgente lumi-nosa) è più chiaro del grigio al 50%, l’immagine viene schiarita come se fosse scolorata. Ciò è utile per aggiungere zone di luce all’immagine. Se il colore applicato è più scuro del grigio al 50%, l’immagine viene scurita come se fosse moltiplicata. Ciò è utile per aggiungere le ombre all’immagine. L’uso del nero o del bianco puro produce il nero o il bianco puro.

Luce vividaBrucia o scherma i colori aumentando o diminuendo il contrasto, a seconda del colore applicato. Se il colore applicato (sorgente lumi-nosa) è più chiaro del grigio al 50%, l’immagine

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viene schiarita diminuendo il contrasto; se è più scuro del grigio al 50%, l’immagine viene scurita aumentando il contrasto.

Luce lineareBrucia o scherma i colori diminuendo o aumentando la luminosità, a seconda del colore applicato. Se il colore applicato (sorgente lumi-nosa) è più chiaro del grigio al 50%, l’immagine viene schiarita aumentando la luminosità; se è più scuro del grigio al 50%, l’immagine viene scurita diminuendo la luminosità.

Luce puntiformeSostituisce i colori, a seconda del colore appli-cato. Se il colore applicato (sorgente luminosa) è più chiaro del grigio al 50%, i pixel più scuri rispetto al colore applicato vengono sostituiti mentre quelli più chiari restano inalterati. Se il colore applicato è più scuro del grigio al 50%, i pixel più chiari rispetto al colore applicato ven-gono sostituiti mentre quelli più scuri restano inalterati. Questa opzione è utile per aggiun-gere effetti speciali a un’immagine.

Miscela duraAggiunge i valori dei canali rosso, verde e blu del colore di fusione ai valori RGB del colore base. Se la somma risultante per un canale è maggiore o uguale a 255, il valore ricevuto è 255; se è minore di 255, il valore è 0. Pertanto tutti i pixel fusi hanno valori dei canali rosso, verde e blu pari a 0 o 255. Tutti i pixel vengono quindi trasformati nei rispettivi colori primari: rosso, verde, blu, cyan, giallo, magenta, bianco o nero.

DifferenzaEsamina le informazioni cromatiche in ciascun canale e sottrae il colore applicato da quello di base oppure il colore di base da quello ap-plicato, a seconda di quale dei due ha il valore

di luminosità maggiore. La fusione con bianco inverte i valori del colore di base; la fusione con nero non produce alcun cambiamento.

EsclusioneCrea un effetto simile al metodo Differenza ma con un contrasto minore. La fusione con il bianco inverte i valori del colore di base; La fusione con nero non produce alcun cambia-mento.

TonalitàCrea un colore risultante con la luminanza e la saturazione del colore di base e la tonalità del colore applicato.

SaturazioneCrea un colore risultante con la luminosità e la tonalità del colore di base e la saturazione del colore applicato. Applicando questo metodo a un’area con saturazione pari a zero (grigia), non viene prodotto alcun cambiamento.

ColoreCrea un colore risultante con la luminosità del colore di base e la tonalità e la saturazione del colore applicato. In questo modo vengono mantenuti i livelli di grigio nell’immagine; ciò risulta utile per la colorazione di immagini monocromatiche e per tingere immagini a colori.

LuminositàCrea un colore risultante con la tonalità e la saturazione del colore di base e la luminosità del colore applicato. Questo metodo crea un effetto opposto a quello del metodo Colore.

Colore più chiaroConfronta il totale di tutti i valori dei canali per il colore di fusione e di base, e visualizza il

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colore con valore più alto. Colore più chiaro non genera un terzo colore, che può essere ottenuto tramite la fusione Schiarisci, ma crea il colore risultante scegliendo i valori dei canali più alti dal colore base e dal colore di fusione.

Colore più scuroConfronta il totale di tutti i valori dei canali per il colore di fusione e di base, e visualizza il col-ore con valore più basso. Colore più scuro non genera un terzo colore, che può essere ottenuto tramite la fusione Scurisci, ma crea il colore risultante scegliendo i valori dei canali più bassi dal colore base e dal colore di fusione.

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Finding and Keeping the Time / Trovando e Mantenendo il Tempo - National Institute of Standards and Technology - 1977

Holograms of Real and Virtual Point Trajectories / Ologrammi del Reale e Traitettorie del Punto Virtuale - Three-dimensional

Holographic Imaging - Chung J. Kuo & Meng Hua Tsai - 2002

Sad Young Man on a Train / Uomo Giovane e Triste su un Treno - Marcel Duchamp - 1911-12

A Study of the Persistence of Vision / Uno Studio Sulla Persistenza Della Visione - Proceedings of the National Academy of Sci-

ences of the United States of America - A. C. Hardy - Communicated by Edwin B. Wilson - 1920

A Photograph of Duchamp Using a Hinged Mirror / Fotografia di Duchamp Usando uno Specchio Movibile - 1917

Maker, Above Below and Between - The Mechanism of Meaning . Arakawa & Gins - 1978

A List of Blending Modes / Elenco Dei Met Odi di Fusione - Adobe Photoshop CS3 User Guide - Adobe Systems Incorporated - 2007

An Event Over the Skies of France / Un Evento sui Cieli della Francia - Rouen, France - March 1954

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Pubblicato da Project Gentili in occasione del mostra

Published by Project Gentili on the occasion of the exhibition

Presented as the Problem, Damon Zucconi, 2009

Some Rights Reserved, 2009, Project Gentili

ISSN 1973-2163

www.damonzucconi.com

mail@damonzucconi.com

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