Improve your 3D Pictures With Post-Processing - 3D-Con

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
Projected Image
Nature
Photojournalism
Photo Travel
Pictorial Print
3D
A
OK
OK
OK
OK
OK
OK
B
OK
X
X
X
OK
OK
Post-Processing Operations
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 programs 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.
Operation
SPM
1. Crop
Y
2. Alignment & Stereo Window
Y
3. Level/color Adjustment
PEP
Y
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 outline of the area to be kept.
You can release the mouse button and
click inside the area to make fine adjustments 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 Aspectratio”. Select the desired Aspect-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 window placement can be distracting and negatively affect the presentation. 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 image 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 window.
• 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 spacing 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 monitor) press the R or L arrows. Pressing the right arrow (→) increases the
separation and pushes the scene back (away from the observer). Pressing the left arrow (←) decreases the separation and pushes the scene forward (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 anaglyph 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 remember 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 undesirable. 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 recognizing 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. Remember, 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 become 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 stereo 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 excessive. 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