Modern Classic SLRs Series :
The Focusing Screens - Background Development Effort

 
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Optical Path.jpg Loading.. Finder w/ screen.jpg
The optical path in the New F-1. The center peice of focusing screen was a key element in the system now. Instead of being a conventional focusing aid, it played a prominent role in the metering and some very exciting development was used in making the focusing screen came to the center stage.


In total, the New F-1 offers a full range of 13 individual focusing screens. Categorized by the three metering groups, there are 32 focusing screen/metering system combinations. The entire series is available for center-weighted average and selective-area metering. Only
six (6) screens provide spot metering. The system includes two new Bright Laser Mattes which are nearly 20% brighter on average than the other laser matte screens of the series.

How does these extra bright screen benefiting a photographer ? In the standard to medium telephoto focal range (from 50mm to 200mm) they are 1.5 times as bright, making viewing a more pleasure thing to enjoy. This enhanced brightness pays dividends, especially when shooting in low light and unfavourable condition or better still, some smaller aperture lenses which yields dimmer viewfinder image can be of more comfortable in focusing when used in conjunction. Other interesting breakthrough are the
Cross Split/New Splits formations which facilitates vertical and horizontal format focusing by dividing the subject in both planes. The shape of the subject consequently is no longer a factor in achieving accurate focusing. The standard New Split/Microprism is available for all three metering patterns and does not incur darkening even with slow lenses. New screen like A/B format laser matte is available with engraved corner markings to facilitate cropping.

claudioscreen4.jpg claudioscreen2.jpg
Credit: Image courtesy of Mr. Claudio®. who is a collector for Canon photo gear, he also has an Ebay Section as well as maintaining a website on his own where occasionally trading some photo equipment. Image(s) copyright © 2003. All rights reserved. Please respect the visual property of the contributing photographer.

This unique system of interchangeable focusing screens and metering patterns has added an entirely new dimension to the New F-1 in its direct comparison with its rivaling models by other manufacturers. Now, instead of being limited to just one metering method, you can be ready for any conceivable exposure situation by slipping two or three screens into your gadget bag along with your lenses and film. But as I said, everything has a starting point, these development eventually leads to built in metering seletor that doesn't require any change of focusing screen anymore, as like the
mighty full-featured AE Canon T-90 by Canon, launched merely 5 years later aftert the New F-1 in 1986.

newF1screenopen.jpg
Credit: Image courtesy of Mr. Claudio®. who is a collector for Canon photo gear, he also has an Ebay Section as well as maintaining a website on his own where occasionally trading some photo equipment. Image(s) copyright © 2003. All rights reserved. Please respect the visual property of the contributing photographer.

I remember during the Minolta's X 700 (Will be featured here later in Classic Modern SLRs series) in 1981 (Same year as the New F-1) which has its Acute-Matte focusing screen with focusing technology is comprised of some 2,500,000 microscopic cells, each of which is a conical micro-lens shaped for better light dispersion and, consequently, a 50% brighter, clearer, higher-contrast image that is easier-and faster-to-focus, just a coincidence may be but, Canon's own intepretation was extended into providing metering function as well. The laser matte method of surfacing the focusing screen eliminates light diffusion, and at the same time, guides the light in the right direction. Thus, this process ensures that the maximum amount of light is transmitted to the viewfinder so that the scene appears brighter. The grains of the matte surface are also extremely fine, smoothly shaped, and uniformly spaced, making these screens distinctly brighter and clearer than conventional ground glass screens.

Screen Enlarge.jpg

The Bright Laser Matte
screen in enlarge state, compared with the illustrations on the left.



Although it would seem difficult to top such performance, further improvements have made the focusing screens for the New F-1 system even better than before. Viewfinder brightness is increased by 20% - a full- 1.5 times brighter than the traditional ground glass matte. (Comparisons made within Canon products.) But the real benefits of these new advances are evident when shooting in low light, or when using lenses with small apertures. The. overall increase in brightness makes focusing much easier and more accurate in difficult conditions. Moreover, to eliminate moirb effect produced on the screen by regularly spaced subject patterns, the New F-1 focusing screens incorporate yet another new improvement. Through a slight amount of intentional irregularity in the arrangement of the matte surface grain pattern, moirb effect has been virtually eliminated. The new Bright Laser Matte screens, light changes were made to the grain pattern arrangement, and the surface was textured more smoothly. The result is perfection in screen brightness. A close-up of the Bright Laser Matte screen surface reveals appro. 220 million regular-shaped 22u grains that function as microscopic lenses with extremely accurate interrelational positioning over the entire surface of the screen. This honeycomb structure of micro-lenses is effective in guiding the maximum amount of light to the condenser lens. There is no question that this brightness makes focusing easier: there is no darkening when stopping down, and because graininess is eliminated, the image can be very sharply focused. Bright Laser Matte screens were practically made for low-light and stopped-down photography. They are also a great aid when shooting with slower lenses. Both "S" and "T" types have an overall matte field; there is no distracting split-image circle or microprism collar.

* See next page for full availability of all focusing screens developed along with the New F-1.

The Fresnel lens, a modification of a regular convex lens which condenses the light rays entering the viewfinder and guides them up through the eyepiece. Thus, it is also called a condenser lens. A Fresnel lens is used in place of the usual convex lens due to weight and space factors. If a regular lens were used, the camera's pentaprism would have to be taller, and the actual weight of the camera would be greater. A Fresnel lens, which performs the same function as a convex lens, thus makes the camera lighter and more compact.


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The spacing between ring peaks on a Fresnel lens is significant. In the New F-1 it is only 0.03mm, compared with 0.05mm for the F-1. Consequently, it is nearly impossible to see the rings in the New F-1 finder with the naked eye. More importantly, this tight spacing contributes to the sharper viewfinder image. Normally, a Fresnel lens has a flat area in its center which occupies a diameter of approximately 5.2mm. This flat area produces a slight difference in image magnification between it and the rest of the lens. In the New F-1, however, this area has been eliminated. The center of the multi-coated Fresnel lens used in the New F-1 screens has a convex surface to give equal magnification across the lens. Elimination of this problem has made the New F-1's viewfinder image crisper than many other camera's. Okay, since there are so much fuss about technologies packed behind the development of the screens, what does it matter other than provides a brighter image in the viewfinder for focusing and composing ? Because, the screen is the core element in the New F-1's central metering system and more light needs to accumulate and transmission to the split beam to the SPC for exposure calculations. Refer back to
metering section for more info.

Or
proceeds to NEXT sections on availabilities of the various 32 types of screens.

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