ScreenScope Handheld Stereoscope
The ScreenScope is a mirror stereoscope for viewing side-by-side images in the parallel format and suits up to 5 inch wide images separated by up to 5 inches between centers and has a coverage of over 3.5 inches wide and 6.5 inches high. The ScreenScope features chrome plated first surface glass mirrors that present very clear images without ghost reflections or chromatic aberration (color fringing) which is inherent in prism based viewers. The mirrors are set at roughly 45 degrees and are parallel to each other which minimizes the sensitivity to the viewing distance. A stereoscope can project two slightly different images to each eye creating a perception of depth in an image. Some people can master viewing stereoscopic images unaided by looking wall-eyed or cross-eyed but it is difficult to master and can be a strain on the eyes. A stereoscope deflects the images to allow more natural viewing which makes them accessible to the untrained viewer and relieves eye strain. This 3D viewer includes removable lenses which help to focus at close range and these can be handy when zooming in. The high quality mirrors in this viewer give a very clear image and at a great price.
The ScreenScope is made by Stereo Aids in Australia. The handle is removable keeping the package compact.
The eye mask curves around the sides of the eyes to block distractions from the side of the view and this helps increase the immersion experienced. Unfortunately this may also prevent people wearing glass from placing their eye close to the viewer and in this case it offers little advantage. The eye mask is a light press fit and can easily be remove and reinstalled.
The ScreenScope may be used without the eye mask installed and this avoids distortion caused by the lenses and gives a crystal clear image thanks to the high quality mirrors. The lenses are made of crown glass and are a press fit into the eye mask and removing the eye mask also removes the lenses so this allows a quick switch between viewing with and without the lenses. Since the eye mask holds the lenses the eye mask must be installed to use the lenses which may not be ideal if wearing glasses. The lenses can be removed allowing the viewer to be used without the lenses while still benefiting from the eye mask.
High quality mirrors
The ScreenScope has high quality chrome plated first surface glass mirrors. The glass mirrors are very flat avoiding distortion across the mirror. Unlike typical household glass mirrors, which have the reflective surface on the back behind the glass, the first surface mirrors have the reflective metal coating on the front of the mirror. This is critical for avoiding ghost reflections - a back surface mirror generates a ghost reflection from the front glass surface making the image blurry. Since front surface mirrors have the delicate metal coating on the front it is very easy to scratch them and great care must be taken when cleaning. The ScreenScope uses chrome plating for the reflective surface and chrome is relatively hard compared with aluminium however I still advise great care cleaning the mirrors. Try to avoid getting the mirrors dirty, avoid cleaning unless absolutely necessary, use an air blower to blow dust off without touching the mirrors, and if absolutely necessary then wipe very lightly with wet cotton wool using only the weight of the cotton wool. The use of chrome plating for the mirrors makes the surfaces harder and more resilient however chrome appears to reflect less light then say aluminium and the view through the mirrors is noticeably darker than the direct view - this can be compensated for by increasing the computer monitor brightness or just letting the eyes adjust.
The handheld version of the ScreenScope includes a solid handle which is installed through a hole in the base and locks into a socket at the top. The handle may be easily removed for packing. The handle is a good length making it easy to rotate and align the viewer for optimal viewing and it can be held and operated with a single hand.
Viewing stereoscopic images
The mirrors increase the effective separation between the eyes and allow normal viewing of two side-by-side parallel images as a single stereoscopic image and most people will perceive depth in the image. The separation between the mirrors and their geometry are important characteristic of the stereoscope. The size of the ScreenScope is illustrated below from which the rough spacing of the mirrors can be inferred. The mirrors are parallel and at roughly 45 degrees and with this geometry the increase in separation is relatively independent of the viewing distance.
The field of view and aspect ratio are illustrated below - the black perimeter is the ScreenScope eye mask and baffles and in the distance is one half of any example print. It can be seen that the viewer is ideal for portrait photographs.
Image size when viewing with the magnifying lenses
When using the magnifying lenses a image of around 3.5 inches wide and 6.5 inches high is viewable, and with the magnification it appears even larger. The lenses allow close viewing from about 4 to 11 inches, and the exact viewing distance can be varied to suit your eye focus. When viewing at around 11 inches the eyes are focused into the distance, and if you are short sighted then you may need to wear corrective glasses, or use the ScreenScope without the lenses. With the eyes focused into the distance they converge naturally into the distance and image pairs with a separation of around 5 inches are natural to view. This separation supports images up to 5 inches wide however the coverage width is only around 3.5 inches so unless you wish to pan around to take in the full image then it may be best to limit the image width. The image separation may need to be adjusted to suit your eye separation and while this is possible with two separated left-right prints, or when using computer software such as offered by this website, it may not be possible for a framed print or for prints in a book. The coverage height is an impressive 6.5 inches making it ideal for portrait photographs.
Image size when viewing without the magnifying lenses
Viewing images without the magnifying lenses may suit many people and I recommend 3.5 inch wide by 6 inch high images separated by around 4 inches for natural viewing. This size can conveniently fit a 10x8 inch photo frame or a photo book. My experience suggests that this viewing method works for a wide range of people, more that when using the magnifying lenses, and more feedback is welcomed. Note that the image separation for natural viewing with the magnifying lens versus without the magnifying lens is quite different so a choice needs to be made when making prints for which the separation can not be adjusted. If you are experienced as viewing stereoscopic images then you may be able to increase the separation slightly to support wider images but this will require viewing wall-eyed, and is not recommended for print made for general viewing. The non-adjustable ScreenScope is great value and works well for images this size. For viewing larger images the ScreenScope Adjustable model allows the angle of the outer mirrors to be decreases for viewing larger images from a further distance.
Not everyone can perceive the 3D effect in stereoscopic images
People perceive depth differently and the stereoscope uses only differences in disparity to convey the 3D depth in a photograph. While most people with two good eyes will see a 3D effect there are many people with two good eyes who will not see a 3D effect and the degree of the effect is expected to vary. People also perceive depth from relative movement between near and far objects, from geometric and lighting cues, and from the focus of objects.