Why we Rank Stereo Photos

Slideshows of original stereo photography are a highlight of every GGSS meeting. During our slideshows, members and guests are encouraged to rank each stereo photo in a live poll while the stereo photo is displayed and discussed. Results are shared after the slideshow. 

Our intention isn’t to pick winners and losers. Rather, the poll encourages engagement with the photographs and provides helpful feedback for the photographer to grow their stereo skills. 

You don’t need to be an experienced stereo photographer or photography judge to rank our slideshow photos. We appreciate your opinion!  

Ranking Scale 

Our ranking scale spans from “OK” to “Wow,” eschewing a “Poor” option.  

5 – Wow! “Tells a story. Personal favorite.” 

4 – Excellent. “Technically and artistically flawless.” 

3 – Very good. “Strong, well done.” 

2 – Good. “Minor correction…” 

1 – OK. “Try again.” 

What to Look for in a Stereo Photograph 

Follow these qualities as a guide rather than a strict checklist. Weigh your own preferences and experience when evaluating a stereo photo in our slideshows. Our members practice a wide variety of stereo techniques that don’t always fit neatly into these criteria. 

These values are based on a scoring system originally proposed by the Stereo Society of America (an offshoot of the Photographic Society of America) in 1951. They were followed by the stereo division of the Oakland Camera Club (now the Golden Gate Stereoscopic Society) for decades. In the early 2000s we updated our evaluation guidelines for modern stereo photography technologies and techniques.  

Stereo Quality 

• Evaluate the presentation of the subject with respect to depth. 

• Look for a flow from foreground, to midground and then to background. 

• Evaluate the photo’s parallax (see terms below). 

• It should be possible to separate the different depth planes visually. 

• Near objects should appear near. Distant objects should appear far. 

• The stereo effect should be noticeable regardless of the distance of the subject from camera. 

Composition 

• Like 2-D photography, composition is the deliberate arrangement of visual elements within the frame to guide the viewer’s eye.  

• Structural guidelines like leading lines, framing, and a strong focal point create balance. 

• Distinct foreground, midground, and background objects should be perceived in stereo. 

• The composition elements should be placed to take advantage of the stereo effect or enhance the stereo effect 

• Watch for backgrounds distorted by extreme parallax, caused by lenses converging on the subject. 

Color Harmony 

• Colors are arranged to create a visually pleasing and balanced image by using color theory relationships, such as complementary, analogous, or monochromatic palettes, to guide the viewer’s eye and evoke specific emotions.  

• Color combinations prevent visual chaos and strengthen the photo’s narrative. 

• Color changes provide good depth queues. 

Alignment 

• The stereo window is compositional concept unique to stereo photography. 

• The stereo composition should appear “behind” the screen, as if looking through a window. 

• Subjects can come “through the window” into the audience space, but the protruding element should not be trimmed by the borders of the image. 

• The stereo photo should be easy to view, without eyestrain or difficulty converging the stereo pair. 

• The stereo photo should not require the presenter to compensate for major errors. 

• Misalignment in the vertical direction is unacceptable. 

Focus 

• Stereo photographs benefit from small apertures and sharp focus from foreground to background. Soft focus does not provide good depth queues. 

• On macros, watch focus on closest subject as well as center of interest. 

Exposure 

• Minimal blowouts (light areas captured as completely white) or blackouts (pitch-black shadows or dark areas). 

• Side lighting produces shadows that give parallax depth queues. 

• High contrast and large parallax results in ghosting (double images). 
  (It’s almost impossible to avoid ghosting in an image, for example, with a white moon against a dark blue sky with a brightly colored foreground.) 

Terms and Definitions 

Convergence 

The point where the eyes (or lens axis) meet at the same point. Stereo camera lenses should be converged with caution; the distortion that results can make the image difficult to view. 

Hyperstereo 

Some stereo photos may appear to have enhanced depth and miniaturized subjects. It’s an effect created by spacing the lenses of a stereo camera farther apart than the average interocular distance (the distance between the eyes, about 65mm). Many stereo photographers apply the hyperstereo effect intentionally to emphasize the depth of faraway subjects, like landscapes. 

Hypostereo 

A short stereo base, less than the average interocular distance, will allow for up-close or macro stereo photography. 

Mergers 

Also called interference. Stereo photography’s ability to separate objects in z-space allows for compositions that would fail in 2-D. For example, imagine a photo of a thicket of trees; only in stereo will that photo reveal each individual tree rather than a mess of branches. 

Parallax 

The difference between the right and left image. To measure parallax, close one eye at a time and note the difference in the distance on each image from the left edge of the pair to a specific point on a subject. You can also remove your 3-D glasses and observe the screen distances between the background subjects to get a sense of the amount of parallax in a stereo photo. A stereo photographer must keep the screen parallax below the point where the eye has difficulty converging the two pairs into a single image. If the composition requires the viewer to observe the background in preference to the foreground, the parallax is too great. Parallax issues can also lead to discomfort viewing the stereo image. 

Zero Parallax: Subject at the Window 

The distance from the left side of the pair to the subject is the same distance in each image (right and left). If you have a landscape and the background looks like it’s at the distance from you to the screen, and the foreground subject is in the space between you and the screen, the photo should be re-aligned so that the foreground is “at the window” with zero parallax. 

Positive Parallax: Subject Behind the Window 

The distance from the left side of the pair to a point on the subject is smaller in the left image. If you have a landscape and the background splits into double images, the positive parallax is too great and your eyes are diverging beyond their limits. The stereo photographer has selected a camera separation that is too large for the subject. 

Negative Parallax: Subject in Front of the Window 

The distance from the left side of the pair to a point on the subject is larger in the left image than the right image. If you have a landscape with framing tree branches and the branches seem to be suspended from midair in the space between you and the screen, the stereo image suffers from too much negative parallax. The photographer was likely too close to the camera’s subject. 

Pseudo 

Stereographers can reverse the left and right stereo image, intentionally or accidentally. This results in far objects appearing close and near objects appearing far, a sort of inside-out image. Sometimes the subject matter makes this hard to detect. Try flipping your 3-D glasses upside down for an example. 

Rivalry 

If each eye is presented with a different image in a stereo pair, discrepancies between the two photos will cause the visual disturbance “retinal rivalry.” This effect can be used creatively, but is also apparent when one image in a stereo pair has been retouched, or if there was movement between successive exposures.  

Stereo Window 

The borders of an image. A properly composed stereo image places the stereo photo’s subject behind the stereo window.