We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
For practical reasons it is, therefore, advisable, when making comparative tests of overall sensitivity, to distinguish between a speed figure relative to a speed comparison of the straight-line portion measured for equal gamma values, and a speed figure relative to the speed comparison of the curved portion which practically takes into consideration the toe section only and which, therefore, is identical to a combination of threshold and shadow speed.
An additional way of expressing speed comparisons of negative types which is commonly practiced, is that of indirectly calculating negative speed from the printer lights required to give a normal print of each negative. As the printer light in general is selected with the intention of giving the print sufficient detail in the high lights, this method of speed calculation refers principally to speed comparison for high negative density portions.
Straight Line Portion
Another characteristic important in the consideration of our problems is the latitude of the negative material expressed by the extension of the straightline portion. Normally it should be assumed that the farther the straight-line portion extends towards the upper end of the characteristic curve, the better it should be regarded in view of the protection it offers against wrong calculation of exposure. In practice, however, it will be found that the laboratories quite often prefer a negative type with a relatively low shoulder break. The reason for this is that the exposure range of the standard Bell & Howell printer with 22 printer lights has a rather limited latitude, and that, therefore, naturally the danger of encountering highlights of unprintable high density is emphasized in cases where negative types are used with high shoulder breaks. The new automatic Bell & Howell printer has an increased range of printer lights which in itself should be considered a needed improvement and a step forward.
Color Sensitivity
In dealing with the subject of color sensitivity of photographic emulsions in relation to visual sensitivity, we have entered the most complex phase of our problem.
At present four types of photographic emulsions are in practical use which are distinguished by different color sensitivity. They are as follows:
Color Blind Emulsion.
To this group belong emulsions which are only responsive to blue, violet and ultra-violet. They are represented in practice by Positive film and Sound Recording film.
Orthochromatic Emulsion.
In addition to the original blue sensitivity, which is an attribute of all Silver Bromide emulsions, this type is sensitive to the yellowgreen range of radiation. Its practical application in the 35mm motion picture field is rather limited at present as it is only used for reproduction of dupe negatives.
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