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Those of you familiar with fluid immersion microscopy know that it is used when the maximum magnification and maximum resolution is required of visible light microscopy. Fluid immersion objectives are fully immersed in the fluid and so is the object, and the air interface is thus eliminated. Fluid immersion scanning utilizes the same technique, as illustrated in the image to the rightt which shows the film immersed in fluid between glass on one side and an optically clear overlay with the same index of refraction as the film on the other. The technique was first used in drum scanners, which required that the film be sparated by a layer of fluid to eliminate the Newton Rings that would otherwise form. With the advent of ScanScience, fluid immersion scanning became available to other scanners as well. Just as dry objectives are not capable of attaining high magnification and resolution, dry scanning is equally subject to the same limitations. Equally, dry enlarging, or dry projecting are similarly impaired. The air interface causes degradation of image quality due to the reflections and scattering at the film grain which is typical of dry scanning (or enlarging, or projecting) as illustrated in the far right schematic. We see thus that the light rays impinging on the dry film are scattered or reflected and that a number of light rays are lost in transmission. On the film immersed in fluid, -the image at the far right, fewer rays are lost in transmission. This translates into greater resolution, contrast, dynamic range, smooth gradation and image richness. Elimination of dust scratches is another benefit. Most dust decreases in opacity when wet in fluid. Those who experience fluid scanning for the first time are like the patient whose cataracts have been removed.
very little time and requires no post operative cleaning and drudgery. In all it saves time as in one operation dust and scratches are dealt with not requiring the application of Digital Ice, which degrades the image. |
DRY SCAN FLUID SCAN
Copyright ScanScience 2006
like the NIKON 8000 is actually due to effect of light scattering at the grain which is picked up in all its glory by that fine scanner. Drum scanners never get blamed for "pepper grain" because with them fluid scanning is standard. Flatbed scanners do not get the blame either, because only a very few of those scanners can pick up grain detail |
| FILM FLATNESS: A CONDITION TO SHARPNESS |
| DRY SCANNING |
- Depth of Field
Scanners optics are close-focusing devices with shallow depth of field. To obtain a
sharp image the film must be placed at the scanner's Plane of Optimum Focus
(POF).
Film, on the other hand, is never flat. Any one that has studied physics knows that
the lateral tension required to make a string suspended between two points adopt
a perfectly straight shape, is infinite. Film flatness can not be attained by
tensioning the film. Overcoming the film's natural tendency to curl requires
applying a perpendicular force to the film through the whole area. The surface
tension of the fluid, provides that perpendicular force in the way that no tensioning
devices can.
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| FLUID SCANNING - ScanScience > |
In Flatbed Scanners the glass comes with the package, and the refraction of the glass bed is unavoidable. Fluid scanning involves an additional glass but the glass need not be in the path between the light emerging from the film and the optics. Epson V 750 scanners are provided with a wet mount tray which require that the film be placed on top of the glass when wet mnounted. This results in double refraction caused the In additional chunk of glass effectively subtracting some of the benefits gained by fluid scanning. ScanScience's simple answer to the problem is to provide an adapter that avoids glass between the film and the sensors. The fluid mounting plate faces the lamp, with the film being placed under the glass. The image going to the sensors is untainted by additional refraction from the fluid mounting plate. REFRACTION AND THE FILM SCANNER Film Scanners have the inherent advantage over flatbeds that they are not refraction limited. The absence of the extra glass, potentially gives film scanners an edge but does not solve the problem of dry film curvature. THE GLASS HOLDER Owners of film scanners try overcoming the film flatness problem by using glass holders. It is physically impossible to attain film flatness with glass only on one side of the film, unless the film curves in such a way as to have its curvature against the glass. When this happens the result is Newton Rings. ScanScience's simple answer to the problem is fluid scanning. With the glass on the side of the lamp so that there is no glass between the film and the sensors. This results in the flatbed scanner not being subjected to double refraction, and the Film scanner to no refraction at all, preserving its inherent advantages.
AN glass has a microscopically rough surface intended to break up Newton's interference reflections which cause Newton rings. When the light reflected from two surfaces at a slight angle and a short distance to each other meet, it can interact constructively or destructively according to their phase, causing Newton Rings. AN Glass therefore can not be perfectly clear glass: if placed in front of the lens it would be detrimental to the image. Taking a picture using AN glass as a filter will show what effect AN has on the image. When AN glass is part of the film carrier in a film scanner, the film is placed against the glass which is in the light path from the film to the scanner sensors. This not only adds the additional refraction of the glass but the degrading effect of an AN surface to the degradation of the image. |
Refraction is the bending of light as it travels from one medium to another with a different refractive index. . Refraction degrades the image since not all light rays are perpendicular to the glass, and instead of pinpoint landing on the sensor as a perpendicular light ray would, it is scattered over several sensors. This corruption of the original image impairs resolution, contrast and saturation.
notable because of their higher resolution and contrast, dynamic range and greater color saturation than dry scans. |
| ScanScience Innovators in Fluid Scanning. Our Innovative Products power the World's Scanners |
to film scanners at 20% of the cost of refractive limited offerings. |
| REFRACTION IN FLATBED AND FILM SCANNERS, GLASS HOLDERS, "AN" GLASS |
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