Improve your 3D Pictures

With Post-Processing

How to improve the presentation of

your 3d images for competitions

By George Themelis

NSA - June 2013

Two Types of Post-Processing

A. Crop, Adjust Levels (contrast/Brightness)

B. Add/Remove Elements

PSA Division A B

Projected Image OK OK

Nature OK X

Photojournalism OK X

Photo Travel OK X

Pictorial Print OK OK

3D OK OK

Post-Processing Operations

Operation SPM PEP

1. Crop Y

2. Alignment & Stereo Window Y

3. Level/color Adjustment Y

You need 2 programs for post-processing:

1. StereoPhoto Maker (SPM): Software designed to work with 3D images. You can read, view, crop, align, and save stereo images. It works in PC computers only and it is free.

2. General Photo-Editing Program (PEP): There are a lot of pro-grams available for general photo editing (Photoshop, etc), many of which are free. They all do about the same things. My advice is to learn to use one program well and stick with it.

Crop—Why?

1. Remove unwanted/distracting Elements

2. Focus on your main subject

3. Improve composition

4. Change aspect ratio to fit the subject better

5. Change aspect ratio to fit the viewing medium better

6. Look for a picture within a picture (useful shortcuts F: increases picture size to fill the screen, J: Shows picture at full resolution)

Crop—How?

With SPM, use the crop function (Shortcut: B)

A cross hair will appear in the screen and moving around as you move the mouse pointer. Go to one corner to start cropping. Hold the left mouse button down and move the opposite corner. You will see an out-line of the area to be kept. You can release the mouse button and click inside the area to make fine adjust-ments but once you release the mouse button, the image will be cropped. To stop cropping, hit ESC. To reverse a cropping operation, hit EDIT, UNDO (shortcut: Z)

Cropping at a Fixed Aspect Ratio

Click at the pull-down menu next to the cropping button icon. Then click at the “Free Cropping Option”

Check the box “keep Aspect-ratio”. Select the desired As-pect-Ratio (by typing it in the X:Y box). Then OK.

The Stereo Window

The Stereo Window • The stereo window is the frame (edges) of our picture. Every picture

has a frame because it ends somewhere.

• In stereo this frame takes a special meaning. Since our pictures extend in space this frame becomes something of a window into space, hence the term “stereo window”.

• Like a real window, our subject is usually behind this “stereo window” but it can also be “at window level” or extend forward into the “audience space” (this is known as “through the window effect”.)

• The photographer has control over how the scene is located with respect to the window and can use this as part of the composition.

• Good placement of the subject with respect to the window (or good win-dow placement) will improve the presentation of a 3d image. Bad win-dow placement can be distracting and negatively affect the presenta-tion. Learning how to manipulate the window is an important skill.

The 3L Rule A rule that I have found useful for checking for stereo window placement is the “3L Rule” which states “The Left eye sees Less on the Left side of the image.”. If this is true, then the object is behind the stereo window.

To see why this is true, consider a real window. There is an area on the left side that is seen only by the right eye (assuming that everything is behind the window.) So it is true that when looking outside a real window, the right eye sees more on the left side, or (easier to remember), the left eye sees less on the left side.

Where are these letters located with

respect to the window?

Objects WRT Window • The letter B is behind the stereo window, the letter W is exactly at

window level, and the letter F is in front of the stereo window.

• The letter W has exactly the same distance and this is the reason it lies exactly at the window. The letter B is closer to the left edge on the left image and further on the right. You can tell that B is behind the stereo window because “the left eye sees less on the left side”. The opposite is true for the letter F.

• Things are even easier with overlapping images. The rule for window placement now says: If the two images overlap, then the object is at window level. If the right image is on the right side of the left im-age then this object is behind the window. If the right image is on the left side of the left image then this object is in front of the win-dow.

• Let me emphasize again that it is not necessary to view an image in 3d to tell how an object is positioned with respect to the stereo window. All you need to do is to study the relative displacements of the right and left images for this object.

Window Control

• To set the stereo window so that an object is at window level, for example, all you need to do is shift the images horizontally so that the left and right images of that object overlap (or have the same distance from the edge of the stereo image).

• To move the entire scene back (away from the observer), increase the separation of the R and L images.

• To move the entire scene forward (towards the observer), decrease the separation of the images.

The window is controlled by adjusting the horizontal spac-ing of the Right and Left images with respect to each other

Window Control in SPM With SPM you can adjust the stereo window in two ways:

1) While viewing the image in 3d (anaglyph works for any computer moni-tor) press the R or L arrows. Pressing the right arrow (→) increases the separation and pushes the scene back (away from the observer). Press-ing the left arrow (←) decreases the separation and pushes the scene for-ward (towards the observer).

2) Go to “Easy Adjustment” (Adjust, Easy, or just hit “K”). You will see an anaglyph image with the H (for Horizontal Adjustment) bar at the top. Moving the images horizontally via this control adjusts the stereo window.

Since the stereo window does not depend on color, viewing the image in black & white anaglyph is the simplest way (you only need a pair of ana-glyph glasses) to see the image in 3d and set the stereo window. This method is available to anyone with a computer that runs SPM. I use a passive 3d computer monitor and #1 to adjust the stereo window.

After you are satisfied with the location of the stereo window remem-ber to save the image (SPM will not remind you.)

Window Errors Window violation is the situation where an object “goes through the window” but it is being cut by the edges of the window. This cannot happen in real life. For something to go through a real window, it has to clear the edges of the window. A window violation presents a conflict to the brain and it is confusing and undesir-able. We can specify three kinds of window violation:

• Extreme violation: The entire scene is in front of the window. In this extreme situation the window is not well defined and beginners have a hard time recog-nizing what is going on. The image often looks fine except for the “floating edges” (bands on either side of the image that appear to belong nowhere.)

• Vertical violation: This is the classic window violation with the subject being cut by the vertical edges of the window.

• Horizontal violation: The subject is being cut only by the horizontal edges of the window. This is not as severe as the vertical violation and it is sometimes acceptable (except for purists who demand absolutely no violations.)

Window violation is not the only error in stereo window placement. Another error is placing the entire scene too far behind the window for no good reason. Re-member, to move the scene back we increase the separation of the two images. There is a point where the images are separated too much and fusing them be-come uncomfortable (or impossible.) This situation should be avoided.

Optimal Window Placement

For me, optimal window placement happens when the near object is close to the stereo window (or allowed to go through without a violation) and the background can be fused comfortably. There is usually a range that satisfies these requirements and the exact placement of the window is subjective.

Window Placement Guidelines

1) Scene with good depth range: The near object can be placed at window level or made to go through (if it does not touch the edges, i.e. without window violation). 2) Scene with limited depth range: The near object can be placed behind the window, leaving a bit of space between the window and the near object. This “breathing space” emphasizes depth in a scene that lacks sufficient depth on its own. 3) Scene with extreme depth: There is no satisfactory placement of the stereo window. If you place the near object at window level, then the infinity will have too much separation and cannot be viewed comfortably. If you reduce the infinity separation (bring images closer together) then the near object will violate the ste-reo window . My personal recommendation for #3: If there is no way to crop the image to reduce depth (by cutting off distant background or an object too close) then one has to choose between two “evils” - a) extreme separation or b) window violation. If the main interest is in the near object and the background just “happened to be there” then I will go for (a) (frame the foreground well and forget the background). If the main interest is in the background (and a piece of leaf, a tree branch, or a ground object happened to be too close) then I will go with (b) (reduce the separation of the images to fuse the background comfortably and let the foreground violate the window.) But the best advice is to avoid situations like #3 while composing the picture. Do not come too close to the near object without blocking the background.

Auto-alignment with SPM SPM can set the stereo window during auto-alignment. This is possible because the program knows the near and far objects. How SPM handles the stereo window depends on how the preferences are set. Default value will set the stereo window at the near object if the infinity separation is not exces-sive. This is the best choice for the beginner, in my opinion.

What Else Can SPM Do?

We have shown:

• Cropping

• Alignment

• Setting the stereo window (horizontal alignment) Other operations I have found useful:

• Color correction (minimize differences in color between R and L views)

• Rotation (to straighten the horizon)

• Adjust horizontal perspective to straighten vertical lines

• Clone brush (to remove objects that appear in one view only)

Easy Adjustment (K)

Levels/Color Adjustment Is it necessary?

90% of the times an image can be improved (some times just slightly, some times a lot) by adjusting levels.

Is it fair?

• It is fair that some film photographers use Velvia to get more saturated col-ors?

• Is it fair that one can select an option in the camera to increase color satura-tion?

• Since a lot of people use modern digital cameras in Auto mode, it is the camera that makes decisions regarding exposure, not the photographer.

• Is it fair to use SPM to crop and adjust the stereo window? (Why not accept the stereo window choice that Fuji makes?)

• Some people seem to invest more time in photo-manipulation than picture taking.

• Life is not fair in general.

How to go about it

• Buy/download a photo editing program and learn how to use it (read the manual, read a book, take a class)

• Practice!! • Calibrate what you see in your computer monitor with what

you see in the projection screen • Be careful of over-processing

Photoshop Elements 1

Photoshop Elements 5