Guidelines for Guest Judges

Introduction

Never seen a stereo (3-D) photo? If you’ve judged a photo competition before, you’ll feel right at home at the Golden Gate Stereoscopic Society — the fundamentals of subject, composition, and technical execution all apply. We value feedback from judges with fresh perspectives and don’t expect you to become a stereo expert.

Golden Gate Stereoscopic Society members create their stereo images with a variety of synchronized dual camera rigs, two-lens digital cameras, and traditional single-lens cameras using the “cha-cha” method of two offset photos. Photoshop and other popular software tools are used in stereo photography, with some restrictions (most of us use the excellent Stereo Photo Maker application).

TheGolden Gate Stereoscopic Society is a member of the Photographic Society of America, and participating judges can earn points towards PSA stars. General information about judging camera club photo competitions is available from the N4C Judge’s Manual and the PSA’s Understanding Judging in a PSA-Recognized Exhibition web page.

Oakland Camera Club Competitions

Most of theGolden Gate Stereoscopic Society’s monthly meetings include a judged competition. Our competitions typically feature 50-60 stereo photos in three groups, and run about ninety minutes. We present our competitions on a brilliant 55 inch 3-D HDTV. You’ll wear polarized 3-D glasses provided by the club.

A club member serving as presenter will navigate each slideshow for the judge. The Open group starts the meeting’s competition, followed by a Special competition theme.

The number of slides will be announced by the presenter at the start of each group. The judge may choose to either comment on each slide directly, or preview a complete slideshow before commenting on each slide.

Titles are not announced when a photo is displayed, but can be read at the judge’s request.

At the end of a group, the presenter will calculate the number of placements and honorable mentions that the judge will award, based on the Golden Gate Stereoscopic Society’s acceptance chart. The final image in each group is a single-screen stereo thumbnail “lightbox” collection of all of the group’s entries. The judge will select acceptances from this collection, and can request to review any or all of the images full-screen. A scorekeeper will log the judge’s decisions.

Evaluating Stereo Photography

Not all Golden Gate Stereoscopic Society judges are familiar with stereo photography. Members of the Golden Gate Stereoscopic Society appreciate criticism from judges of all photography backgrounds.

These values taken from the Photographic Society of America’s 3D division. Use this table as a guideline rather than a strict checklist.

Percentage of Score
Value
Description
30Stereo QualityEvaluate the presentation of the subject with respect to depth
Look for a flow from foreground, to midground and then to background
Evaluate the correct selection of parallax
It should be possible to separate the different depth planes
Near objects should appear near. Distant objects should appear far
Stereo effect is less noticeable at far distances from camera

20CompositionDistinct foreground, middleground, and background objects should be perceived
Minimum distance jumps from edge of the stereo window to subject matter help avoid having too much parallax in the image
The composition elements should be placed to take advantage of the stereo effect or enhance the stereo effect
20Color HarmonyColor harmony rules for photography are shared with stereography
Color changes provide good depth queues
10AlignmentThe stereo window is an important compositional concept in 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 projectionist to compensate for major errors
Misalignment in the vertical direction is unacceptable
10FocusStereo 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
On macros, watch for distorted backgrounds caused by extreme parallax
10ExposureSide 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 with a white moon against a dark blue sky with a brightly colored foreground

Definitions

Hyperstereo

In addition to the illusion of depth, some stereo photos may appear to have miniaturized subjects. It’s an effect created by spacing the lenses of a stereo camera farther apart than the human eye, in some cases many feet apart. Many stereo photographers apply the hyperstereo effect intentionally to emphasize the depth of faraway subjects, like landscape backgrounds.

Pseudo

Sometimes stereographers 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.

Stereo Window

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

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.

Parallax

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

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 is in the space between you and the screen, the photo should be re-aligned.

Positive Parallax: Subject Behind the Window

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.