Printing Color Motion Pictures

Transcription

1 Printing Color Motion Pictures The short answer is: lower printer lights lighten the color and make it more apparent. Higher printer lights darken the color and make it less apparent. As one prints down a color, that color is reduced. Printing down means using higher printer lights. Printing up means using lower printer lights. In printing color motion picture film, there is not a luminance control other than the three color printer lights which control both color and density. When printing down one color, one necessarily makes its complimentary color more apparent. When printing up one color that color becomes more apparent and its compliment becomes less apparent. A dense negative requires higher printer lights. High printer lights are an indication of a dense (also referred to as well exposed) negative. This is not an evaluation of the image, but rather the image density as it relates to the amount of information recorded. If your intention is a dark scene with few highlights, the overall density will be quite low, yet the image rendered will match your intended result. Motion picture printers have three lights, each of which works on a scale from 0 to 50 points. Printing up makes the image brighter, and increases the chrominance of the color light affected to a point. Increased lightening will start to wash out the color and reveal a low chrominance image. In other words, when looking at a printer report whose numbers read: Copyright 1997 & revised 2005 Christopher Chomyn page 86

2 If one were to print up the red, the image would become more red, while at the same time becoming brighter. If one were to print down the red, the image would become more cyan at the same time becoming darker. If one wanted to increase the red color cast, by printing up the red, while maintaining the overall density (brightness) of the image, then the red would be printed up, while the green and blue lights would be printed down After talking with several motion picture labs, it seems that the rule of thumb is that a change of 8 points of light represents a change of one stop thereby either halving or doubling the brightness of the scene. *At FotoKem, their printers are trimmed so that 6 points represents a one stop change. Keep in mind that when one shifts the color away from red, it moves toward cyan, away from green is toward magenta and away from blue is toward yellow. It is also necessary to remember that we are talking about color negative film, which has a red sensitive emulsion layer that presents as cyan, a green sensitive layer which presents as magenta and a blue sensitive layer which presents as yellow. The positive image that is rendered on the print is a negative, of the negative. This means that if something is blue in the actual location where filming occurs (the sky, for example) it will be rendered on the negative as yellow. The more yellow light (lower numbered blue printing light) that is pushed through the negative will result in more blue on the print (a negative of the negative). Less yellow light (higher numbered blue printing light) will result in less blue on the print. Also, lower lights will result in a brighter image, and higher lights will darken the image by increasing the exposure of the print from the negative. Positive Negative Notice how the light areas within the positive image are rendered dark in the negative indicating a high negative density due to high exposure, and the darker areas within the positive are rendered as light in the negative indicating a low negative density due to minimal exposure. When you compare the positive image above to its negative counterpart, you can see how each of the colors in the positive are represented by their complimentary color in the negative. See the Copyright 1997 & revised 2005 Christopher Chomyn page 87

3 man s pink skin is cyan in the negative, the blue-green water has a yellow-pink color cast, the green line along the boom is magenta in the negative, the white cockpit is black and gray in the negative, the blue cushion is orange in the negative, etc. Higher and lower printing lights are in direct relationship to the lights that are established in the first answer print. If a scene prints with lights: A higher blue light would be any light with a number from (printing down would render the print darker) and a lower blue light would be range from 0-27 (printing up would lighten the print). It bears repeating, when adjusting lights to affect the overall color of a scene, remember that you are also affecting the image density, so to maintain density you will want to compensate by adjusting the other lights as described earlier in this paper. Typical color negative films have between 11 and 17 separate layers comprised of photo sensitive silver halides bonded to dye couplers for each range of the electromagnetic spectrum for which they are designed to record, as well as layers of color filters between each color sensitive layer which prevent wavelengths from affecting the exposure on layers of the emulsion which are not designed to record those wavelengths. This illustration represents an over simplified look the emulsion layers of color film. Cyan filter to block red wavelengths and allow green and blue light to pass green sensitive layer red sensitive layer Magenta filter to block green wavelengths and allow blue light to pass polyester base blue sensitive layer In addition to the color sensitive layers comprised of silver halides and dye couplers, there are filter layers, and gelatin layers designed to keep each color sensitive layer separated so the dyes do not bleed across layers. There are anti-halation layers to prevent internal reflections within the film stock from degrading the images rendered. And it is all supported on a polyester base material. Remember that that characteristic curve for any negative emulsion plots the change in density as it directly relates to a change in the log of the exposure. In simple terms, increasing the exposure usually corresponds to an increase in negative density. I say usually, because once the D log E has entered into the shoulder portion of the curve, the change in density becomes greatly reduced and once the emulsion achieves its Dmax (maximum density) there can be no further increase in negative density. Similarly reducing exposure results in a thinner or less dense negative until the D log E curve enters the toe portion of the curve and reaches Dmin (minimum negative density) represented by the base fog level of the emulsion. Copyright 1997 & revised 2005 Christopher Chomyn page 88

4 We therefore talk about brightness and darkness (luminance) of an image in terms of negative density. A negative presents the areas of a scene by representing bright areas as more dense and therefore darker on the negative, and dark areas as less dense and therefore brighter on the negative. A more dense negative (a negative that has received more exposure) requires more light to be pushed through it to render an acceptable positive image on the print. This requires printing on higher printing lights. A less dense negative requires lower printing lights to render similar results. In this characteristic curve which represents Kodak s 5284 Expression 500 filmstock, one can see that the base fog level is highest for the blue sensitive layer and lowest for the red sensitive layer. It would seem that this has been designed to compensate for the light loss that occurs when each wavelength passes though the emulsion and exposes the appropriate layers and is subsequently filtered out before reaching the blue sensitive layer. It is also apparent that given a neutral scene exposed with white light (light that matches the color balance of the emulsion) the blue sensitive layer will be rendered with the greatest density, thus requiring a higher printer light. But as we all know from looking at printer light reports, the blue layer often uses the lowest printer lights. This is to compensate for the light that is lost due to transmission and absorption as it passes through the layers of emulsion. As one increases the blue printer light, the blue will become less apparent. The red sensitive layer will require slightly higher printer lights in relation to the green and blue lights in order to render a neutral print (one without color bias). Of course, seldom is a scene neutral and without color bias, but this is a starting point to help understand the timing process. From this it would seem that this film emulsion is designed so that the blue will need to be printed up in order to render normal results whereas printing with lights that are straight across (the same number for each color RGB) will likely produce an image that is excessively yellow. Of course the specific printing lights and negative density will be dependant on the intended look of the image, based on the mood, tone and subtext of the material being created. Generally speaking, a more dense negative, which is evidenced by its being printed with higher printing lights, will contain more information and is often desirable. Of course, the specific elements being photographed will have a huge bearing on the negative density, and the resulting image is the final proof of the success of the image. If an image looks good to your eye, rest assured it has been printed and can be printed well again. If an image you see in dailies is different from what you had hoped to see, look at your printer report. If the image is bright, and your numbers are low you can print it down (higher numbers) and it will print as you had intended. If the image is dark and the numbers are high, it can most likely be printed up (lower numbers). Trouble occurs when you want to see a bright image, but the image is dark and the numbers are low. This indicates a thin negative, or a negative with low density, which results from underexposure. It is possible that there was a problem with your exposure and you may not be able to Copyright 1997 & revised 2005 Christopher Chomyn page 89

5 print the image as you had intended without a marked increase in grain, and a reduction in contrast. Also, if your image is bright, and your numbers are high, you may not be able to print down enough to create the image you had intended. This might indicate overexposure. Remember, the printing scale is from 0-50, there is no changing this without changing the trim on the printer. The lesson is this. Dailies do not provide enough information on their own. Printer reports are an indication of negative density, but do not provide enough information on their own. Using the combined information provided by film dailies and printer reports is the best way to gauge your exposures and the resulting negative density. This information should guide you when making any adjustments to your working methodology. Copyright 1997 & revised 2005 Christopher Chomyn page 90