- Part 1 - Part 2 - Part 3 - Part 4 - Part 5 - Part 6 -
22. Chapter XXII. WHAT IS WRONG WITH THE MAXIMUM DENSITY AND HOW IS IT DEFINED?
In 2005, the lunar images were re-scanned at high resolution (1800 dpi) and posted on the Internet “for all mankind”. Most of the frames were aligned with a graphic editor for brightness and contrast, but nevertheless, you can find unprocessed scanned originals on Flicker. And here's the weird thing: in all these frames, the black space turned green.
This is especially striking if there is a black edging nearby (Fig. XXII-1).
Figure XXII-1. Black space looks dark green.
And this is not a single shot, this is a rule. This is a trend that seems inexplicable at first glance. Deep black space appears dark green in almost all color images (Figure XXII-2).
Figure XXII-2. Black space looks dark green in almost all frames.
We are very far from assuming that Kodak has supplied defective slide film to NASA for several years. On the contrary, we are confident that the Kodak film was well balanced in both layer sensitivity and contrast. And even such an option that the slide processing mode was violated, we also do not consider. We are sure that the processing mode was impeccable, strictly regulated, namely E-6, and that the temperature of the developer was maintained with an accuracy of ± 0.15 ° by the automatic temperature control of the solution (thermostats), and the chemical composition of the solutions was monitored by experienced chemists. And on this issue - on the issue of film processing - they did not deviate from the standard recommendations of the Kodak company. Therefore, we believe that the lack of a dense black tone in the images has nothing to do with the processing of the photographic film.
Promotional video:
So maybe the color change in the shadows happened during the scanning stage? Perhaps the range of densities, from the lightest to the darkest that the scanner can “illuminate”, is much larger than the range of image densities on the slide, and therefore, due to the large latitude of the scanner, the slide turned out to be low-contrast and not black in the shadows?
To give an unambiguous answer about the effect of scanning, it is necessary to clarify two questions: what is the range of densities usually on a slide and what is the maximum range of densities that the scanner can “penetrate”?
Since we are talking about a range of densities, we need a device to measure the density. Such a device is called a densitometer, from the English word “density” - “density”. A unit (1 Bel) is taken to be such an opacity that reduces the amount of transmitted light by 10 times, or, in other words, allows 10% of the light to pass through. Density 2 reduces light by 100 times, allowing only 1% of the light to pass through, and density 3 - attenuates the luminous flux by a factor of a thousand, and, accordingly, allows only 0.1% of the light to pass through (Figure XXII-3).
Figure XXII-3. The relationship between density and amount of transmitted light.
In other words, density is the decimal logarithm of the amount of light attenuation. 102 = 100, 103 = 1000, respectively, if any part of the film attenuates the light 100 times, then lg100 = 2, and the densitometer will show the value D = 2. Decimal lg1000 = 3, then the densitometer will show a value of 3 in the area where the light is attenuated a thousand times. If the area is light gray and reduces the light by 2 times (transmits 50% of the light), then the densitometer in this place will show a density of 0.3, since lg2 = 0.3. And if you bought a 4x gray filter for photography (it lets 25% of the light through) - Fig. XXII-4, then its density will be 0.6, since lg4 = 0.6.
Figure XXII-4. 4x gray filter with a density of 0.6.
It is quite easy to visualize a unit of density. So, sunglasses with polarizing filters most often have a density of about unity. The glasses that we had at our disposal had a density D = 1.01 - Fig. XXII-5, i.e. weakened the light exactly 10 times.
Figure XXII-5. Measurement of the density of the light filter of sunglasses on a densitometer.
When measuring the density of the filter, the light from the bottom of the incandescent lamp passes through a calibrated hole with a diameter of 1 to 3 mm, surrounded by a black background (Fig. XXII-6), is weakened due to the installed light filter (or other density) and then enters the top of the photocell (photoresistance).
Figure XXII-6. Measurement through a calibrated hole 1 mm in diameter. Due to the yellowish incandescent lamp, the gray glasses of the glasses appear brown in the light.
We measured the density of the other two sunglasses. Some of them turned out to be slightly lighter than glasses with polarizing filters, had a density D = 0.78, i.e. weakened the light by 100.78 = 5.6 times. And dark sunglasses with a mirrored coating (D = 1.57) attenuated the light by a factor of 101.57 = 37 (Fig. XXII-7).
Figure XXII-7. Dark (mirrored) and light-colored sunglasses.
Then we measured the density of dark areas on the positives. The interframe space on the color film positive (Fig. XXII-8) had a density of more than 3 B (D = 3.04 - Fig. XXII-9), which meant a weakening of light by 1000 times.
Figure XXII-8. The darkest place in a film print is the space between frames.
Figure XXII-9. Measurement of the darkest part of the film.
The darkest place in the frame on the slide film that we had at our disposal (black scarf - see Fig. XXII-10) turned out to be with a density of D = 2.6.
Figure XXII-10. Slide 6x6 cm.
We can say that for our vision, those areas that have a density higher than 2.5, in the transmission, unambiguously seem to be already black, be it a certain place in a film copy or some particular light filter.
On the Internet, you can find the characteristic curves of reversible Ektachrom-E100G film - how the film reacts to different amounts of light. The amount of light is the exposure, expressed in lux seconds, and plotted on a horizontal scale as a logarithmic value. The maximum density, which is achieved on this photographic film in dark areas, on a vertical scale is 3.4 B (Fig. XXII-11).
Figure XXII-11. Characteristic curves of reversible photographic film Ektachrom E100G. Top left - the maximum density (Density) of black.
It is possible that such a high maximum density on a slide, 3.4 B, may have unexposed parts of the frame, where no light falls at all during shooting.
However, in those slides that we had, the most black places turned out to be with density values from 2.6 to 3.0 B.
So, speaking about the darkest place on a slide, we can say that the maximum density value is usually in the range from 2, 6 to 3.0 B, and the maximum possible density achieved on a slide can be up to 3.4 B.
Now let's try to understand what range of densities the scanner “shines through”.
There is such an interesting work called “Scanning negatives. The view of a photographer.”, By Vasily Gladky.
fotavoka.org/docs/113
The author analyzes the dynamic range of densities that can be transmitted by the Epson perfection 1650 photo scanner. As a test object, he uses a sensitogram on black and white photographic film with a maximum density Dtest = 2.6 B. The sensitograms usually look like this - Fig. XXII-12.
Figure XXII-12. Typical sensitogram on 35 mm black and white film. The rectangular notches on the left indicate the field number (top to bottom: 5th, 10th, 15th, 20th).
At high densities (and this is almost half of the sensitogram), the eye no longer notice the difference, and the camera does not see this difference (in photo XXII-12, more than half of the fields are equally black). But the densitometer shows that from field to field the densities increase to the densest upper (first) field.
The most interesting thing in the work done is that the author comes to a paradoxical conclusion for himself: despite the fact that the maximum value of the printed densities Dmax = 3.4 is mentioned in the passport data of the scanner, the scanner no longer distinguishes the density after the value D = 2.35. The horizontal scale (Figure XXII-13) shows the density values of the test, from 0 to 2.6, and the vertical scale shows the scanner's response. The red area on the graph shows the scanner has not responded to the increase in density after the value of 2.35.
Figure XXII-13. Dependence of the density that the scanner gives out (vertical scale) on the density of the test sensitogram (horizontal scale).
Densities higher than this value (2.35) turn out to be "impenetrable", they turn out to be equally black even when the "lamp brightness increase" mode is turned on.
The author's conclusion is that "the scanner is blind to the density 2.4, it perceives any density above this value as black." - Figure XXII-14:
Figure XXII-14. Conclusions about the transmitted range of scanner densities from the work “Scanning negatives. A photographer's view”.
Moreover, the author also considers unreliable information that a special film "Nikon Coolscan 4000 scanner is able to reproduce the range of optical densities 4.2".
Figure XXII-15. Special film scanner Nikon Coolscan 4000.
Although we did not test this scanner for photographic films, but tested scanners for cinema, we also believe that the Nikon Coolscan 4000 scanner (Fig. XXII-15) is not capable of penetrating densities higher than 4. To be honest, we even doubt that that the scanner can "see" a density of 3.6.
By scanning a sensitogram with a wide range of densities (up to Dmax = 3.95 B) - Fig. XXII-16.
Figure XXII-16. Sensitogram on positive film with a wide range of densities.
We tested a cine scanner available at the Institute of Cinematography (VGIK) - Fig. XXII-17, it occupies an isolated part of the room.
Figure XXII-17. Cinema scanner at VGIK.
The maximum density that the scanner saw was D = 1.8 (Figure XXII-18).
Figure XXII-18. Sensitogram after scanning (left), option on the right - removed chromaticity.
There are Imacon scanners, the technical characteristics of which indicate a dynamic density range of up to 4.8 B and even 4.9 (Fig. XXII-19), but in our opinion, this is nothing more than a marketing ploy that has no real meaning.
Figure XXII-19. Imacon scanners.
It is possible that there are drum scanners that can actually "illuminate" a density of 3.6. It is quite possible that such scanners, which cost more than $ 10,000, include a Crossfield scanner (Fig. XXII-20).
Figure XXII-20. Drum scanner Crossfield.
What do we get if the scanner actually illuminates a density of 3.6? Let's take the exact data of the maximum blackening of reversible films from Kodak advertising brochures.
Here are the technical characteristics of the slide films Ektahrom 100 and Ektahrom 200 (Fig. XXII-21).
Figure XXII-21. Advertising brochures for Kodak Ektahrom reversible films.
Among the many characteristics of the reversible photographic film (Fig. XXII-22) we find a picture with characteristic curves (Fig. XXII-23).
Figure XXII-22. Technical characteristics of reversible photographic film, data from Kodak.
Figure XXII-23. Characteristic curves of reversible photographic film Ektachrom.
What do we see in high densities? This is the upper left corner of Figure XXII-23. We see that the three curves have diverged. As we know from film prints, areas where the density exceeds 2.5 are visually perceived as “black”. Here all three curves rise above 3.0 density.
But when measuring the area with maximum blackness behind the blue filter, the densitometer gives a value of approximately 3.8 (i.e., the attenuation of blue rays occurs 6300 times), behind the green filter - a density of 3.6 (weakening of green rays by 4 thousand times), and when measured behind the red filter, the lowest density is found, D = 3.2 (red rays are attenuated 1600 times). Red rays pass through the maximum blackness, weakening least of all, which means that they will paint the "blackness" in the transmission in a reddish tint. In other words, “blackness” should be black and red, i.e. dark brown. On real Ektachrom films, the deepest blacks should appear brown.
But on the other hand, we see that the maximum density of the "blackest area" on the slide (3.2-3.8) corresponds to the limit of the most expensive scanners. It follows from this that no matter what settings we use when scanning, the maximum blackness of space on the slide should be transmitted by the extreme blackness on the scanner. Black space in NASA scans should turn out completely black if the lens is not exposed to the sun.
If the dynamic range of the scanner was greater than the range (from Dmin to Dmax) of slide densities, then we would observe open space with a black-brown tint on slide images. But in the scanned moon images posted on Flicker, we see an excess of green. The maximum shadow densities in the image posted on NASA's website are not like the shadows of Ektachrom film, and these densities are significantly lower than typical slide densities in shadows. NASA images don't look like scanned slides at all. So what was NASA scanning then? Our answer is simple - a completely different film was scanned, and it is definitely not reversible.
Chapter XXIII. SCANNING NEGATIVES
When in scanned images, "deep shadows" are not black? Apparently, only in those cases when a material with a small density range is scanned. A typical case is scanning negatives. Negative photographic films are always made low-contrast, and the range of densities that take part in the construction of the image is actually quite small. So, on negative photographic film it is easy to obtain densities of 1.7 and higher (Fig. XXII-24, left, the density of the veil is taken as “zero”). But when printing onto photographic paper, negative image densities above 1.24 are no longer worked through (Figure XXII-24, right). And low densities of the negative (0.02-0.08) merge in the positive with blackness. The range of working densities of the negative involved in the construction of the image is very small, usually ΔD = 1.1-1.2.
Figure XXIII-1. Photo frame (negative 6x6 cm) with sensitogram (left), printed on photographic paper (right).
The exposed tip of negative film may have a density of about D = 3. For the negative, it’s bulletproof blackness. Even frames close to the density D = 2 are already considered a marriage (top frames in Figure XXIII-2).
Figure XXIII-2. Very dark frames on the negative are considered a marriage, and the optimal negatives are those where there are no high densities (for example, the frame at the bottom right).
And the optimal are negatives in which the densities of the brightest objects (for example, a white sheet of paper) do not go beyond the value D = 1.1-1.2 above the veil (above the minimum density, above Dmin) - Fig. XXIII-3.
Figure XXIII-3. In optimal negatives, the density of the white sheet of paper is 1.10-1.20 over the veil.
It so happened historically that a low-contrast negative is printed on high-contrast photo paper. The range of working densities of the negative (i.e. the range of densities that are printed in the positive) is quite small, ΔD = 1.2. These are the densities that are actually involved in the construction of the image. Above this value, non-printable, non-working densities begin. Add to this value the density of the veil along with the colored base, approximately 0.18-0.25 (this is called the minimum density - the density of the non-exposed area, but that has passed the entire processing process). In total, when scanning a negative, we need densities no higher than 1.45 (1.20 + 0.25), since then the area of non-working densities begins. And the range of the scanner's capabilities is much larger - at least ΔD = 1.8. In this mode, the largest density range from black to white is processed. Therefore, if the negative is scanned without additional software processing, then it will turn out to be low-contrast, gray.
Pay attention to the above figure XXII-13, where a white horizontal stripe marks the density range of optimal black-and-white negatives, compared to the slide it is quite small.
It is possible to digitize a negative not only with a scanner, now it can be done with any digital camera. After reshooting, the negative ("Photo-65", Svema) looks low-contrast, there are no high densities in it (Fig. XXIII-4).
Figure XXIII-4. Negatives 6x6 cm ("Photo-65", Svema) were retaken with a digital camera.
If you do only one operation in a graphics editor - inversion, then the negative will turn into a positive, but the positive will also look low-contrast: the white areas will be light gray, and there will be no “blackness” in the shadows (Fig. XXIII-5).
Figure XXIII-5. The negative taken by the camera is inverted by the graphic editor.
When we digitize the negative with a scanner and then invert it, the resulting image looks low-contrast, this is the so-called “unprocessed” image, “unprocessed” (Figure XXIII-6, left). In such an image it is necessary to change the “black” level and “white” level - only then the image becomes acceptable (Fig. XXIII-6, right).
Figure XXIII-6. Negative after scanning and inversion without “processing, unprocessed” (left). The same frame, processed using the "white level" and "black level" functions (right).
If you set the "NEGATIVE" mode during scanning, the result of negative printing on contrasting photo paper will be simulated - additional computer processing of the negative image will be activated, which will lead to the fact that the scanned image will first be inverted into positive, and then become more contrasting.
NASA's Lyndon Johnson Space Center scanned high-resolution films from the Apollo series of lunar missions and uploaded them in raw form to Flickr:
This is how, for example, on Flicker the raw image AS12-49-7278 looks like (Figure XXIII-7, left):
Figure XXIII-7. Image from the Apollo 12 mission: on the left - raw (taken from Flicker), on the right - processed (taken from the NASA website).
We can see that deep black space (in the left image) does not look black enough, and the whole image appears to be a little grayish, with low contrast. And on the right in Figure XXIII-7 is how this image is usually published on the Internet, this is how it looks on the NASA website:
After processing in a graphic editor using "levels", the lunar images change in contrast in about the same way as the frames we made on the "Photo-65" film, Svema (see Fig. XXIII-6).
According to NASA, the astronauts used Panatomic-X fine-grained 80 ASA negative fine-grained photographic film for black-and-white photography - Figure XXIII-7.
Figure XXIII-8. Black and white negative film Panatomik-X.
This film is airbrushed, i.e. it is intended for aerial photography - an aircraft photographing the earth's surface from an altitude of approximately 3 km (10,000 feet). Since the shooting of the earth's surface for cartography or for other purposes is carried out on a sunny day in the absence of clouds (the illumination on the earth is about 50,000 lux), then high-sensitivity film is not required. Usually, photographic film with a sensitivity of 40-80 units is used. To obtain such a light sensitivity, emulsions with fine grain are used, therefore the name of the film contains the phrase “fine grain” (fine grain). Fine grain allows for high detail resolution. Shooting is performed at a very fast shutter speed: 1/500 s with an aperture of 5.6 is recommended. Fast shutter speeds avoid image blurand fine grain provides high resolution.
There is one parameter that distinguishes conventional film from airbrushed film. Anyone who photographed the earth's surface through the window of a flying plane noticed that the haze of the air markedly reduces the contrast. In addition, objects located on the ground are themselves of low contrast (Figure XXIII-9).
Figure XXIII-9. A typical view of the earth's surface from a flying plane.
In order to improve the difference between low-contrast objects, aerial film is made obviously more contrasting. If ordinary photographic films have a contrast ratio of 0.65-0.90 (which is defined as the tangent of the slope of the characteristic curve), then Panatomik is about 2 times more contrast. Judging by the characteristic curves, its contrast ratio is about 1.5 (Figure XXIII-10). This gives a very high contrast.
Figure XXIII-10. Characteristic curves of the Panatomik film at different times of development. Development time in the processor is estimated by the speed of the tape along the path (in feet per minute, fpm).
The choice of such a film for lunar expeditions seems somewhat strange to us. There is no air haze on the moon; in the bright sun, the white spacesuits look dazzlingly bright, and the shadows are not highlighted by anything. (In terrestrial conditions, shadow areas on a sunny day are illuminated by the light of the sky and clouds.) The contrast on the lunar object is very high. Why use a contrasting film for such objects, make an already contrasting image more contrasting?
Considering the scanned black and white images laid out on Flicker, and noting the good elaboration of details not only in the highlights (the illuminated side of the white spacesuit), but also in the shadows, we fully admit the idea that a completely different - usual negative photographic film - not Panatomik aerial film. (But this is just a guess so far.)
All original film material from the Apollo missions is stored in the film archive (building 8) of the Johnson Space Center. Due to the importance of preserving these films, the original film is not allowed to leave the building.
The film is stored in a freezer in special sealed jars at -18 ° C (0 ° F). This temperature is recommended by Kodak for long-term storage.
To scan or make copies, do the following: A sealed film can (Figure XXIII-11).
Figure XXIII-11. The film is stored in a sealed jar.
It is transferred from the freezer to the refrigerator (with a temperature of about + 13 ° С) where it stands for 24 hours, then for another 24 hours the jar with the film remains at room temperature, and only then is it removed and scanned (Fig. XXIII-12).
Fig. XXIII-12. Scanning transparent originals (photographic films).
Scanning is performed with a Leica DSW700 scanner (Fig. XXIII-13).
Figure XXIII-13. The Leica DSW700 scanner that scanned the moon photographic films.
The estimated cost of such a scanner is about $ 25,000.
After scanning, the film is returned to the freezer in its original packaging container (jar).
And now, returning to color images, let's ask a question: so maybe the black space on the lunar images turned out to be not black, but green due to the fact that in fact NASA scanned not a slide, but a negative? Indeed, only in this case it becomes clear why unprocessed scanned images look low-contrast and do not have the maximum density in the shadows.
Maybe there was no color reversible film, but there was an ordinary negative-positive process, and the shooting was carried out on ordinary negative film? This is what we have to figure out now.
24. CHAPTER XXIV. WHAT WILL HAPPEN IF I INVERTED THE MOON IMAGE?
Let's check how plausible the version is that NASA, under the guise of slides, actually scanned the negatives, and then, on a computer in a graphic editor, the scanned images were inverted into positive.
If we take a lunar frame that has not been processed by "levels" and invert it (ie, turn it into a negative), we will see that the dark green space (Fig. XXIII-1) will turn into a light pink fill of the entire frame (Fig. XXIII- 2).
Figure XXIII-1. A still from the Apollo 12 mission.
Figure XXIII-2. Frame from Apollo 12 mission inverted (turned into negative).
Some will probably think that this pink hue appeared by accident when setting up the scan, and it was not in reality, and we know for sure that this pink color was present in the image initially. And we can state this unequivocally, since this "pink tone" is nothing more than a colored color-forming component, which for simplicity is called a mask.
Everyone knows that color negative film has a bright yellow color, but not everyone knows that this color belongs to a special mask located in the two lower layers, because of this, color negative film is called masked. The color of the mask is not necessarily yellow-orange, it can be pink-red. The yellow-orange mask is used in negative films, and to obtain duplicate negatives (countertypes), films with a pink-red mask are made (Fig. XXIII-3).
Figure XXIII-3. Color masked films: negative (left) and countertype (right).
Negative films have a high sensitivity - from 50 to 500 ISO units and are intended for shooting on location or in a pavilion. But no one uses countertype films for filming, they have a very low sensitivity, 100-200 times less than the sensitivity of negative films, and they work with them in laboratories, on copiers. These tapes are used to make duplicates.
A few words about the appearance of the mask. Once upon a time, in the 40-50s of the twentieth century, color films were unmasked, both negative and positive - Fig. XXIII-4.
Figure XXIII-4. Color unmasked films Agfa, negative and positive.
Fuji produced unmasked negative photographic films until the end of the 1980s. XX century, and "Svema" stopped producing unmasked photographic film DC-4 (Fig. XXIII-5) only by the year 2000.
Figure XXIII-5. Color negative unmasked film DS-4 * Svema *.
To improve the color rendering, the Kodak company in the late 40s of the XX century came up with a method for masking dyes. Negative film, like positive and reversal, contains three dyes in three different layers - yellow, magenta, and cyan. From the point of view of spectral transmission of light, yellow dye is considered the best, but magenta and cyan absorb a lot of light in those areas where, from the point of view of "ideal" dyes, they should not absorb. Therefore, harmful absorptions of magenta and cyan dyes are fixed by using internal color masks. Since the yellow dye is located in the upper layer and it is almost "perfect", it is not touched, and accordingly the two lower dyes are masked. The orange color of the negative film mask is formed by two masks: pink in the lower layer and yellow in the middle layer - Fig. XXIII-6.
Figure XXIII-6. The orange negatives mask actually consists of two masks - pink and yellow.
Those wishing to understand the principle of masking can read two articles: "About masking magenta dye" and "About masking cyan dye" in the book "How to understand film strips", pp. 31-40.
And, as you understand, masking is not used in films intended for direct viewing (positive, slide films), but only in those materials that are involved in the intermediate stages of obtaining the final image (negative and counter-type films). Contrasting tapes are called “intermediate”, or in English “Intermediate” (inter - intermediate, media - means).
Figure: XXIII-7. Contemporary film Intermedia, Kodak 5254.
Technical documentation for Intermedia, Kodak website.
If you thought that Intermediate films were some kind of exotic films of special narrow application (as, for example, there are films for recording tracks of nuclear particles), then this is not so. For decades, Intermedia films have been released in the millions of kilometers, and without these films, no film could be released.
Why is there a need for counterfeit films?
Imagine a typical situation - a new film is released, and this film will be shown on the same day and not only in several cinemas, but in many cities at once. If this is a blockbuster and it is broadcast in Russia, then depending on the number of cinemas, it may take from 800 to 1100 copies of this film. The film is replicated at copy factories by the contact method - by pressing the negative to the positive on a round drum and shining through it at the point of contact. On the edge of the drum there are teeth for transporting the film, and in the middle there is a slit for exposure equal to the width of the image and not overexposed perforations (Figure XXIII-8).
Figure XXIII-8. Image drum on copier with light slit.
To obtain a film copy, the negative is run through a copier. In simple terms, the negative video is rewound from one side of the apparatus to the other, and passing by the light slit, the image from the negative is reprinted onto positive film. The sound track from the phonogram roller, which is located nearby on the copying machine, is also imprinted on the same positive film strip (Fig. XXIII-9).
Figure XXIII-9. The scheme of printing a film copy on a copier: on a roll of positive film, which is charged from above, printing is carried out from two films - from the negative of the image and from the negative of sound (phono).
After one film print has been printed, the exposed positive roll is sent to the developing machine, and the copier is filled with a new roll of positive film (Figure XXIII-10).
Figure XXIII-10. Cinema copier.
Since after printing the negative roll was at the end, it (like the phonogram roll) is rewound to the beginning. A roll of negative image is constantly rewound back and forth while mass printing is in progress, which can take several days. It is easy to guess how the negative will look after thousands of runs. It will be scratched all over.
Now imagine that some Hollywood blockbuster is shown in several countries at once. And what is required is not a thousand copies, but several tens of thousands of film copies. Not a single negative can withstand such a circulation. Besides, who will allow you to give the negative of a blockbuster for destruction? The original negative is carefully guarded. Duplicates are made from it (a duplicate of a negative is called a countertype, a duplicate of a positive is called lavender), and these duplicate copies are sold to different countries for subsequent replication in their own country.
Many years of efforts by film design engineers have been aimed at making such a countertype film so that the image printed from it does not differ visually from the image printed from the original negative.
It is quite possible, not only theoretically, but also practically, any film that goes on the cinema screen, to be reshomed with a film camera on negative film, and we will get a duplicate of the film. But the quality will noticeably deteriorate. The fact is that ordinary negative film is not very suitable for countertyping purposes, primarily due to graininess. All negative films are highly sensitive. The higher the light sensitivity of the film, the larger the grain on it. And if you make a duplicate of the negative on the same negative film, the grain will noticeably increase. Such a frame will be knocked out by the "boiling" of grain from the general row of frames. Unlike negative ones, countertype films have a very low photosensitivity (no more than 1.5 ISO units) and, accordingly, very fine grain.
Negative films are not suitable for countertyping for one more reason - they are sensitive to all visible rays of the spectrum, they would have to be worked with in complete darkness, placing them on a copier by touch, and not being able to control the printing process. But countertype films have a small dip in the sensitivity in the region of 570-580 nm, between the green and red sensitivity zones. Visually, 580 nm is a color close to the emission of yellow sodium lamps, so the copy department, where they work with positive and counter-typed materials, is illuminated with a non-actinic warm yellow light.
I was about to give a graph of the spectral sensitivity of the countertype film from Kodak Avenue to show this failure, but I saw that this graph on the official Kodak website contains errors. Apparently, the designer who drew the graphics did his work using the copy-paste method, not paying attention to the fact that different types of films can be very different from each other. Thus, an insensitive countertype film turned out to have a photosensitivity of more than 1000 units in the blue layer - the sensitivity curve of the blue layer rises above 3 logarithmic units on the vertical scale. Three logarithmic units, this is 103 = 1000 (see Figure XXIII-11).
Figure XXIII-11. Spectral sensitivity graph of the Intermediate from the Kodak official website.
We had to correct the vertical scale of the graph, the scale of the logarithms of photosensitivity. To the left of the revised logarithmic scale, we have added the conversion of logarithmic values to arithmetic values. Now the graph (Figure XXIII-12) has made real sense: the sensitivity of the blue layer of the countertype film is just above 2 ISO units, and the sensitivity at 580 nm (the lowest point in the visible range from 400 to 680 nm) is -2, 3 log units, which corresponds to the sensitivity of 0.005 ISO units.
Fig. XXIII-12. Spectral sensitivity graph of Intermediate film with a corrected vertical scale. The light yellow line indicates the area (580 nm) with the minimum sensitivity.
The eye has a very high sensitivity to yellow rays, the maximum sensitivity of the eye, as is known from any reference book on lighting technology, falls on 550-560 nm. And in the countertype film there is a drop in sensitivity with a minimum around 580 nm. Therefore, the copier working with countertype films is well oriented in the copier department, illuminated by a narrow-zone yellow light, and the film is not exposed to light.
Due to their very low light sensitivity and correctly selected contrast, Intermediate films have become simply irreplaceable in countertyping processes.
The Kodak company usually arranged the presentation of new films in the Cinema Houses of different countries. When it came to counterfeit films, Kodak demonstrated the following video: the screen was split in half by a vertical line, and one half of the image was printed from the original negative, and the other half from a duplicate. And the audience was asked to determine where the original is and where the copy is. And viewers could not always determine exactly where which image was.
But not only for the replication of films, countertype tape was used. Most of the combined filming was based on countertype films. Take at least the simplest thing - captions on the image. In almost all films, we see opening credits (title of the film, leading actors) on a moving background, in the image. But these credits weren't filmed on the day the cast was filmed. The decision to put titles on this very image and of exactly this duration was made already at the final stage of editing. In order for the credits to appear in the right place of the film, a duplicate was made from the original negative by the method of countertiping and, until it was developed, the credits were imprinted into this duplicate by means of the second exposure. Titles, as a rule, were filmed by another cine camera with a single frame mode on a setup called a multistand.
Here is one of the options for a cartoon machine (Figure XXIII-13):
jarwhite.livejournal.com/34776.html
Figure XXIII-13. Cartoon machine.
A sheet of contrasting photographic film with titles: white letters on a black background was fixed on the desktop. The sheet itself was slightly larger than A4 format. (Fig. XXIII-14).
Fig. XXIII-14 Captions made on photographic film.
From below, the title page was illuminated by a lamp and shot frame by frame by a movie camera looking at the text from top to bottom (Fig. XXIII-15).
Figure XXIII-15. The cartoon camera looks straight down.
So that the ceiling is not reflected in a sheet of film placed horizontally on the table, the ceiling is painted black.
The traditional method was considered when the credits were filmed with one device, and the image (an actor's scene or landscape) and actions with it (exiting from blackout, freezing, going into blackout) were obtained using a different installation - a time-lapse projector and a time-lapse movie camera. That is, the final frame was obtained due to two exposures taken by different devices.
Continued: Part 8
Author: Leonid Konovalov