How I made Man In Space Using Only SPM

Last night I attended the Detroit 2015 International Stereo Exhibition in our Ohio Stereo club. I saw a picture by Robert Bloomberg showing the Astronaut sculpture in Salt Lake City (see bottom for more details) and a small picture of the Earth was added in the upper right corner. I was there too (in SLC for the NSA 2015 convention) and took similar pictures. As a matter of fact, I entered a picture of the same sculpture in the same exhibition, but it was not accepted.

This gave me the idea so when I came home that night, I created this (click to enlarge if you need to):

Here is how I did it:  First I found my Detroit entry. As I said, I took several pictures of this. I believe I took this particular one using my twin Panasonic LX5 cameras so it has quite a bit of depth. The sculpture is up high so it can be framed with the sky only in the background, or it can be framed with buildings. I tried to avoid the buildings to create the illusion of floating in space. I like this picture because it is “pure and simple”. Here it is:

I then found a picture (2d) of the moon that I took last month using my Questar 3.5 telescope and a Panasonic GX7 camera. The focal length of the Questar is 1350mm and my micro 4/3 camera has a half size sensor so the “full frame equivalent” focal length for this picture is a very long 2700mm, that’s why the moon spills a bit of out of the picture. This is fine because I wanted a big moon. Here it is:

Then I combined the two pictures using StereoPhoto Maker’s “add logo” function. This function is related to the “add text” function that allows you to add titles. The “add logo” function allows you to add a 3d logo to a stereo picture. However, it can be used to add a stereo picture into a stereo picture. Here are the steps involved:

1. Open the Astronaut stereo picture and save it in separate L and R images (“File”, “Save Left/Right images…”) This will be the logo.

2. Load the moon as a stereo pair (“File”, “Open Left/Right images” and then use the moon both times, so you end up with a flat stereo pair of the moon). This is the main picture that will serve as the background. Hit the Right arrow key to adjust the stereo window and push the moon a bit back (at what will be the infinity of the combined pair). I am aware that the moon could (maybe "should") be pushed even farther back but I am afraid the resulting image will have too much deviation. This issue would be alleviated if the astronaut pair had less deviation. Also, I could have used a 3d picture of the moon but this is not appropriate here when the moon is supposed to be far away.

3. Go to the “Edit”, “Add Logo” and work out the menu details to create the stereo pair you want. Here is how the menu that created my stereo image looks (hit enter to enlarge):

Regarding the details in this menu: I hit “Browse”, found my left Astronaut picture (from #1 above), the program loaded the stereo pair. I checked “Use Transparency” and with the color picker that came up I touched the blue background of this picture. I adjusted the sliding scale next to it (set to 6) and hit “Extract”. This eliminated the background from the “logo” picture. I adjusted the “size” of the logo so it fit well with the moon. I adjusted the “Depth” (set to 13) to make sure that the Astronaut is separated from the background and Image position (instead of typing numbers in these fields you can use the mouse cursor, hold the left button and move the image where you want to). And when I was done, I hit “OK”.

This involved a bit of trial and error. When you hit OK you go back to the program and can check your stereo pair (easy in my interlaced 3d monitor). If you do not like the results you can undo the Add Logo function (“Edit”, “Undo” or CTRL Z) and try again. The program remembers the last settings which is nice. Keep changing things until you get it just right.

I have used the “Add Logo” function before, so the entire process took less than 30 minutes. I think this is quite fast for a combined stereo image where a lot of variables (like sizes and relative depth of the two images might) need to be adjusted by trial and error.

One advantage of the Add Logo function: You can see any changes that you make while the Add Logo dialog is opened, in 3d. Click "Anaglyph" next to the Preview (right side). This includes things like changing size, changing image position, and (especially) changing depth.

Note: This was possible only because the background of my Astronaut picture (or whatever you select as “logo”) was uniform and could be extracted. If you have a more complicated picture then you have to use photoshop or perhaps Topaz Remask, a program that does exactly that, removes the background from an image. I have never used layers in photoshop and have not figured out how to use Remask, but I know how to use StereoPhoto Maker.

If you are interested in this sculpture, here is what I found in this source:
http://www.geekpittsburgh.com/art/salt-lake-flying-objects

Michael Bingham returned to Flying Objects in 2014 with an equally ambitious creation entitled The Curious Voyager. Instead of an animal, Bingham chose an astronaut as the centerpiece for the sculpture—replete with a mirrored face mask—with the human space traveler floating upside down as he observes the streets of Salt Lake City below him.

“I’ll admit, I had just not too far back seen the movie Gravity and was really intrigued with that, with just the idea of weightlessness,” Bingham explained to the Herald Journal. “But that’s always been interesting to me. I’ve always been fascinated by astronauts.”

If you enlarge the picture you can see me and fellow 3d photographers reflected in the astronaut’s suit (helmet?). I was there with Ron Fross, John Bueche, Diego Ruiz (check the first picture below - this is what the dedicated photographer will do to get a different point of view), Peter, George Philosophos, Takashi Sekitani, and others. We were taking a tour of Salt Lake City on Wednesday of the convention week and the bus dropped us somewhere in the area. You could not miss this sculpture. I actually have a picture of all these guys photographing the same sculpture. By the way, Ron Fross won an award in the on-side stereo competition with one of his pictures of this sculpture. These are halves of stereo pairs:

How to Measure Stereoscopic Deviation using StereoPhoto Maker

In this blog I will describe three ways to measure the stereoscopic deviation in a stereo pair, using the free software StereoPhoto Maker. This is based on a Tutorial published in the Stereogram 20.2 (October 2015). Stereogram is the newsletter of the Ohio Stereo Photographic Society (OSPS) and it has been published since 1997. For subscription information, see www.ohio3d.com

What is Stereoscopic Deviation and Why Should I Care?

If you look at a stereo pair it consists of two seemingly identical pictures. However, the pictures are not identical, but have small differences in the form of displacements in the horizontal direction. It is these displacements (stereoscopic deviations) that are responsible for the sense of depth when the pictures are seen in stereo. So, yes, you should care :)

Here is a stereo pair. Notice that the house is displaced with respect to the tree. This is easier to see if the two images are superimposed:

Back in the good old slide film days, the only practical way to superimpose images was in stereo projection. Today, this is easy to do with digital images and programs like StereoPhoto Maker.

The deviations vary across the image (see the road in this picture), being zero at the “window” (tree in the figure above) and maximum at the furthest object (house). We are usually interested in the maximum stereoscopic deviation (P, I have used the letter P from "parallax" another term for this displacement). For an image to be viewed comfortably, this maximum stereoscopic deviation must be less than a certain amount, which depends on the viewing method. One popular recommendation for projection is to keep the maximum stereoscopic deviation under 3.3% or 1/30.  Note that P has a value of length and it can be measured on film or a camera sensor or a display, so it depends on the image size, but it is more meaningful to divide this deviation by the image width to produce a ratio or %, which does not depend on image size.

So, now that we know what the stereoscopic deviation is, let's address the question, how can we measure it? But, first, let's load up an image to work with. I selected this stereo pair, a close-up of a butterfly. I took this picture during the 2010 NSA Convention. I would like to measure the maximum stereoscopic deviation and answer the question if this image will project well or cause problems. Here it is (in LRL format, click to enlarge and freeview):

But where is the far point in this image (which is responsible for the maximum stereoscopic deviation)? It seems to be in the lower part of the purse. There is black spot there which is easy to see (and measure). I will consider that to be the far point whose deviation I would like to measure.

1. Using SPM’s Auto Alignment report

After auto alignment with SPM, a window pops up with “Auto alignment values.”  Look for the value reported as “disparity of the infinity points” near the bottom. This is reported as a ratio and in this case it is 1/18. This is about twice as large as the recommended 1/30 value. This serves as a warning that there will be excessive deviation in stereo projection.  Here is how the report looks. I have circled the disparity value:

2. Using a grid in SPM

Dennis Green (of the Detroit Stereo Club) made me aware of this method. First, go to anaglyph (or interlaced) mode to overlap the two images. Then go to View -> Grid Setting (bottom of the menu, see the figure below). Set the V Line to 29 (this will divide the image to 30 segments). With just one look you can see which points are within one segment so have the maximum recommended deviation (1/30) or less. For the maximum deviation (shown below) this method gives a value of 2.5 times the recommended value (2.5/30 = 1/12).

3. Using SPM’s Position Alignment X value

At the bottom center of the SPM screen you see this: Position Alignment (x=0, y=0). If you press the R or L arrow keys, the x value changes (pressing the top and bottom arrows changes the y value). So my procedure for measuring deviation is this: Overlap the images (I like to use interlaced because I have an interlaced 3d monitor). Here is what I see. I have highlighted the far points that I will overlap to measure their deviation:

Use the R/L arrow keys to overlap two objects. Read the x displacement. This is the stereoscopic deviation in pixels. Here is what I get:

Divide this by the width of the image to get the % deviation. Using this method I measured 84 pixels for the far points. 84/936 (image width) = 9% or 1/11, which is close to Dennis’ grid method.

Note: the default displacement is 4 pixels every time you press the arrow keys, but this can be changed to a different value through the “Preference” menu shown here (to get to this menu go: Edit, Preferences, Adjustment).

Changing it to 1 pixel will give you the best possible accuracy. This value will also affect how fast the stereo window changes every time you press the arrows, so you might want to bring it back to the default 4 if you have changed it to 1 (4 works well, 1 is a bit too slow).

Note added later: Pierre Meindre mentioned in photo-3d that if you hold the shift key while pressing the arrows, the adjustment is made in 1 pixels increments, no matter what the default is. In this case, there is really little need to lower the default. As a matter of fact, Pierre increased the default to 10 for fast adjustments and then presses the shift key for fine adjustments. The default value of 4 works for me so it is good to know that I do not have to change this, just remember to hold the shift key when I want fine adjustments. (PS. I have now increased the default, like Pierre has done. This works the best for me. The window moves quickly and when I want to slow it down, I press the shift key.)

One last "trick" when using the Position Alignment method: If you press the Home key, the X and Y values are initialized (set to zero).  You can also use this method to measure Y displacements (there should not be any Y displacements in a perfectly aligned image, but they often are because alignment is not or cannot be perfect).

Comparing the Three Methods

Notice that the SPM alignment report gives a smaller deviation than the other two methods. Using the grid or displacement method is more accurate because it is targeted to specific points. The report is based on image alignment which selects a certain number of points used in the alignment. The far point might have been missed (better: "not included") in the alignment. So the alignment report is good for giving you one quick value for the maximum deviation. If you are using auto alignment, you get this value with no extra effort.

The grid allows you to estimate the stereoscopic deviation in the entire image with one glance.

The Position Alignment method allows you to accurately measure the stereoscopic deviation for specific pairs in the image. It is the most accurate but also most time consuming.

Does the Excessive Deviation Matter?  

This is a very good question. The fact that the maximum deviation is excessive does not mean that the image will have a problem in projection. It depends on how prominent the “offending” (showing excessive deviation) part of the images is.

In this particular image it is just a spot on the purse.  One could use photo editing to remove this spot. The attention of the viewer is focused on the butterfly and the hand. The purse is mostly irrelevant and does not draw much attention. In that respect, this image works, even though it has about 3x the recommended maximum deviation. But if the background is prominent and cannot be ignored, then excessive deviation will be a problem. Knowing the maximum stereoscopic deviation is not enough to decide if an image will work or not. You need to see the entire image and make a subjective call.  No matter if the deviation is a problem or not, knowing how to measure it can be useful.

One last comment: I think this image demonstrates the difficulty in taking a close-up of a small object with the Fuji with B = 75mm. A different camera (Panasonic 3D1 with B = 30mm) or a Cyclopital close-up attachment with the Fuji (B = 30mm) would have been a better tool for this particular picture.

Let me know if you have any comments and make sure that you check my other blogs for 3d stereoscopic information.