Cameras Focusing Screens and Viewfinders

Most popular SLR cameras have a fixed focusing screen and pentaprism, both of which are more than adequate for day to day situations. Although both of these features make rapid focusing and composition easier, neither can be the perfect answer in every situation. For that reason many photographers choose an SLR with an interchangeable focusing screen, viewfinder, or both. You will find that some of the more expensive cameras have this facility.

Special Cameras Screens

It may be possible to have your camera’s fixed focusing screen changed by the manufacturer or importer if you don’t want the expense of changing your camera system. Another choice of screen may be more suitable for your specialist subject when the ‘general purpose’ screen is a disadvantage. With interchangeable screen cameras you can have a number of alternative screens for different types of photography. Manufacturers like Nikon and Pentax have a range of screens suitable for close-ups and photomicrography, architecture and astrophotography, for example.

Handling Cameras Focusing Screens

Interchangeable screens can usually be inserted above the mirror chamber through the front of the camera (with the lens removed). In the case of cameras with an interchangeable viewfinder, screens are dropped in to position from above the camera top plate with the pentaprism removed. Because the screens are plastic (or thin glass) and are therefore relatively easy to damage, take care not to touch or scratch the surfaces.

Handle the screen by its special tag using the tongs provided for front-inserting screens, or by the protective frame if the screen fits via the top of the camera.

Never use a spirit-based lens cleaning fluid because it will crack or melt the plastic and ruin the screen — they are not cheap. A water-based solution, such as Kodak Lens Cleaner, is suitable. If you have several screens keep them in the individual dust-proof containers provided when you are not using them.

Cameras Viewfinders

For the most expensive reflex cameras there is a range of viewfinders as alternatives to the pentaprism. A pentaprism provides an upright, rightway-round image for easy composition, and is usually fitted as standard on 35mm reflex cameras, but special finders may be more appropriate for particular projects.

There are three different pentaprisms in the Nikon range — non-metering, CdS or silicon — as well as three special purpose viewfinders.

A 6x magnifier is used for close-up photography and for copying. It enlarges the image on the central part of the screen six times. Because the magnifier is not a pentaprism the image appears laterally reversed — just like a mirror image. Diopter correction in the eyepiece is included to allow spectacle wearers to focus accurately without the need to wear glasses.

Cameras with fixed pentaprisms can often be fitted with a focusing magnifier which fits on to the eyepiece. They generally magnify the centre of the screen image two times.

The waist-level finder for many larger format cameras (such as twin lens reflex) is popular for rapid framing of a subject with the camera held at low level.

An action finder provides a full view of the focusing screen with the eye away from the eyepiece — behind or to either side. It is used by sports and action photographers, and by people wearing industrial goggles. It is also useful when the camera is in an underwater housing.

An interchangeable viewfinder connects to the camera top plate directly above the focusing screen. When properly aligned it will click and lock easily in to place. It can only be removed by

Disengaging the locking mechanisms — this can often be a little more tricky than attaching it. When the viewfinder is removed take the opportunity to dust the focusing screen using a blower brush.

Cameras Eyepiece Accessories

You can fit a right angle finder to the eyepiece on your camera. It allows you to view at 90° to the subject, and this is particularly helpful if the camera is positioned at low level, such as on the floor. Of the two types available, only the more expensive ones produce an image the right way round.

If you wear spectacles and have difficulty in focusing, eyepiece correction lenses can be fitted on to the camera viewfinder enabling you to focus accurately without your glasses. Ask your optician about your lens prescription. Some specialist opticians and camera distributors can supply you with the appropriate correction lens to suit your eyesight.

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