Q & A with Balliolman: 3D/Stereo Photography

More stereo posts are appearing in forums, more members are sharing 3D photographs, viewing them, becoming more curious about the format and having a go themselves.

In my stereo threads members have asked about varied aspects of 'shooting stereo' and viewing the results. But the answers are scattered among the threads. The purpose of this thread is to offer a one-stop service for members who may want to know more about the 'how to' of stereo photography. I shall do my best to answer your questions or link you towards the right direction. In doing so I hope to assist you in literally opening up a new dimension in your photography!

There is much I could choose to begin writing about so I shall begin with answering the most direct and simple of questions. Should you want to know more please post your enquiry into this thread and I shall answer as best I can ...

So, what is stereo photography?

Stereo photography is the combining of two similar images to create a third which offers the perception of depth. The two images mimic what each eye sees in the manner we view the world. Therefore, people who can see only with one eye cannot, unfortunately, perceive depth or recreate it in stereo photography.

How is a stereogram viewed?

There are two ways of viewing a stereogram, namely freeviewing or by using a viewing aid.

Freeviewing itself means looking at a stereo commonly in one of two ways: parallel or crossed. The former is the most natural inasmuch the left eye looks at the left image and the right eye looks at the right image. A central image appears giving stereo depth. The effect is impressive. There is one significant limitation with this method. The width of the the stereogram cannot be wider than the distance between the viewer's pupils. Trying to get your eyes to splay further left and right than they are is not recommended! The consequence of this is Parallel stereos tend to be small.

Crossed stereos on the other hand can be viewed in sizes which can be very large indeed -- even poster sized if you wished. Crossed stereos are those which are commonly posted to POTN. In this method the left eye looks at the right image, the right eye looks at the left image and a central image fuses to give stereo depth. With practice this can be done almost instantaneously and effortlessly. The sense of depth is also very impressive though slightly shallower than in Parallel freeviewing.

Novice freeviewers often report sensations of strain at first. Frequently this is the result of straining the eye muscles by crossing eyes too vigourously. This can be made worse by viewing a monitor which is too close. For best results sit 2 or 3 feet away and practice little and often. Some people acquire the knack at once, others have to persist with regular practice -- just as I did -- before their first stereo pings into depth! The watchword is 'relax' and you will achieve your aim in the end.

Anyone with corrected vision can freeview!

There are various mechanical aids available on the market to assist people in viewing Parallel stereos. These vary in price and sophistication. Before mastering P freeviewing I used the Pokescope. It makes viewing a cinch. Another benefit of this device is it allows the viewing of stereos which are too big to freeview.

There is another popular stereo format which requires a viewing aid and that is called "anaglyph". I have only seen one in the forums. This is the fuzzy looking red and blue image type often found in magazines. Spectacles with a red filter for one eye and a blue filter for the other eye are needed for viewing. The great benefit of anaglyph format is that very large images can be viewed and they can be zoomed around giving the viewer the sense of being immersed in the scene -- and all in stereo depth!

Thanks for reading and if you want to know more about any aspect of stereo photography, please, feel free to ask!!

Best wishes,

That is a great discription. I have done 3D imaging for a long time and even delved into 3D video (It can get people really disoriented)

Loki1117 wrote:
That is a great discription. I have done 3D imaging for a long time and even delved into 3D video (It can get people really disoriented)

Hi Jeff, it is good to make your acquaintance! I'd like to see some of your stereos. Why not post one into an appropriate forum? Should you do so, please put "3D" into your thread title as that would help members find it through the search function. As for 3D video that is a whole new ball game ...

I took a look at some of your stereo pictures and they're cool. I stopped after viewing 4 or 5 'cuz I didn't want to strain my eyes too much.

Anyway, I was curious....how did you take these pictures? Do you have to use a special attachment in front of the lens?

PacAce wrote:
I took a look at some of your stereo pictures and they're cool. I stopped after viewing 4 or 5 'cuz I didn't want to strain my eyes too much.

Anyway, I was curious....how did you take these pictures? Do you have to use a special attachment in front of the lens?

Thank you for looking at some of my stereos, Leo! If you are new to freeviewing your decision to look at a handful at first is a sensible one. With practice you will be able to view lots of stereograms no bother at all.

Almost all my stereo work is done by a method called cha-cha (sometimes people use the alternative term 'NASA shuffle') using my DReb. The method is shot, sidestep and shot.

To answer your question, though, now and again I use a lens made by the Loreo company called a Lens in a Cap or LIAC(T). The T denotes the digital version taking into account the 1.6 factor. It is a beamsplitter device which makes your DSLR capable of recording stereograms in Parallel mode. The benefits of the LIAC are convenience and moderate freezing of motion. There are three LIAC stereos in my gallery (and clearly marked so).

Here is a link for the LIAC you may want to look at http://www.loreo.com …ts/loreo_3dcap_​photo.html

The LIAC was the means by which I began taking stereos as it has for many other newbie stereoshooters. One final detail it does not cost much either!

Interesting.

Thanks for the info.

I'll see what I can do to post a couple of my stereograms in a couple of weeks. I am leaving to visit some family tomorrow, so I don't have time for that right now. For my pictures though, I have a slide mount (not refering to film) on my tripod that moves the camera from one side to the other. It is actually meant for balancing a vidoe camera over the center of the tripod, but it works great for stereograms as well as slight focus changes for macro shots.

That sounds promising, Jeff! For other readers the slidebar arrangement is another means by which to produce a two shot stereo. Allow me to explain ...

Almost all my stereos are done with my camera handheld and by my physically stepping sideways. There are inherent problems with this method caused by the inexactitude of it all. Common problems will be shots taken at slightly different levels, rotational problems caused by not gripping the camera into motionlessness, or stepping closer or further from the subject. All these are technicalities which can be dealt with in post-processing -- but wouldn't it be better avoiding them in the first place?

Step forward a slidebar atop a sturdy tripod! All the above problems are prevented. Moreover shots can be taken as quickly as it takes to move the camera the short distance needed - seconds!

Probably the best slidebars which can be adapted to stereo purposes are those produced by Bogen/Manfrotto. They are available in geared and ungeared versions. The former are particularly useful for macro stereo where the sideshift, or stereobase, needs measurement in millimetres. But as you can see from my present signature block I still need to get a sturdy tripod -- until then it is handheld cha-cha for me!

THank you Balliolman for your valuable efforts.

As you said, I am doing cha-cha ( I like the name ) stereo shots. The next step , as I hate tripods, will be focusing more and more on the rotation as the height and forth/back movement are easier to control upon shooting, and later in PP ( cropping and resizing ). More difficult but interesting IMO.

Now let me go deeper in SPM

The point is : TTW, BTW & window violation.
should these parameters ( effects maybe ) be taken into consideration DURING shooting or upon processing the stereo ? I noticed that you always say ( pushed in - pushed out ... Etc ) in SPM.
What I do is the following: I open the two shots, each one in it's place for cross stereo , then from the main window I go to the Alignment Mode, chose a common point ( in a well focused part ) and do the alignment.
Later I go to the Easy Adjustment window, and notice that the both layers ( the red and the blue ) are well layered. I noticed that in your modifications you move the red a little left ( H position slide around 10 steps left ) . IS THAT HOW YOU PUSH THE PICTURE BACK THE FRAME ?

will be back for more questions after I get this point .

Best Regards

The simple answer to that is both during shooting and then in processing. The consideration of depth is an additional factor to consider alongside all others required of good photography. The subject should be thought about its suitability for the desired effect BTW or TTW. For example a doorhandle could be ideal for TTW if, in processing, the window is set just before the flat door. In all cases there should always be sufficient margin around the main subject of a shot to take into account the processing consequences of alignment, setting the window and cropping.

This should mean the left shot on the left and the right shot on the right: in other words Parallel Mode.

Go straight to Easy Adjustments. The common point needs to be in the centre of each chip! Nowhere else will do. This is because it is from this point that the alignment of each chip at its edges will be judged. Slide red and blue over each other. Adjust vertical misalignment and get your central point exactly overlapping. Then using the horizontal slider align similar points on the left then on the right. Eventually all points in your chips should be aligned. If you cannot work this out I shall write a detailed workflow.

Use the top slider in EA. Using the right button pushes back the stereo. The left button pulls the stereo TTW.

I should expect so as there are other details to consider but I shall not second guess whether they are problems for you!

Thank you Balliolman for your comments

I was starting with opposite: lefr to right and right to left : cross eyes mode

Noticed that it was much better in my third pair than in the first one. Clear.

I noticed the different directions as I was starting in cross eyes mode .

Now, Here is the second questioning

Q1: you said that the TTW and BTW are controlled FIRST during shooting. I understand that , for example , in my first pair , this one

http://www.anti-uob.com/up/images/1S.j​pg

the lower petal is pointing out more than the stamina, i.e. closer to the lens. Do you mean that I should've kept the petal and the stamina on the same ( imaginary ) plane ( distance ) from the lens in order to get everything BTW , once I was focusing on the stamina ?

Q2: I spent sometime surfing your stereos in Flickr. I think now I have an idea about objects BTW. I noticed that in most of the pairs there are no close items in the frame. i.e. the close foreground is , somehow, free (ok there seem to be objects close to the lower edge but I think this is upon cropping) . The frames are showing objects in focus only (no closer objects shown) . IS THIS RIGHT?

Q3: On Wednesday I am going in a trip where there should be a lot of landscaping and buildings to shoot and produce stareos.
I want to know in brief, what are the points to be taken into consideration ( regardless rotation and motion ) to make decent stereos and not to find it later at home that I ruined all the chances I will have?

Sorry for this headache I am causing you , but my life's principle is "You gonna do something , you gonna do it right" , or leave it.

Best Regads

kallousa wrote:
Now, Here is the second questioning

Q1: you said that the TTW and BTW are controlled FIRST during shooting. I understand that , for example , in my first pair , this one

http://www.anti-uob.com/up/images/1S.j​pg

the lower petal is pointing out more than the stamina, i.e. closer to the lens. Do you mean that I should've kept the petal and the stamina on the same ( imaginary ) plane ( distance ) from the lens in order to get everything BTW , once I was focusing on the stamina ?

The lower petals are close to the camera so are the stamen. The stamen, if the are the closest objects to the lens, you could choose to use for a TTW shot because none of that part of the image can touch the borders of the finished stereo.

The petals are at the edge of the shot therefore should not touch the border in the finished stereogram. What you now need to consider is the following part of stereo workflow:

Setting the stereo window

The stereo window is the level at which you decide everything in your photos should go behind. This can be anywhere you choose but usually it is some detail which, in reality was close to the lens, because that was part of your artistic judgment of composition.

After alignment choose the detail which will be closest. In my redo of your shot I chose the nearest part of the closest petal. Get the chips at this chosen point overlapping exactly. That is now where you have set the window. It would be strange to view because it would be like viewing a scene in reality with your nose pushing against it. So to make viewing more natural it is necessary to push the stereo BTW so it appears at a comfortable viewing distance. This can be as little or as much as you want. However, the more you push back the more you will diminish overlap, consequently crop your chips, and also make it harder for some people to fuse them when viewing.

The final check when the window is set in EA is to use the flashing button. If all parts are behind the window everything will move left and then right at the same time. If anything at the borders is going the opposite direction then that indicates a WV! To cure that push further back.

The exception is a deliberate TTW shot. I think your stamen could nudge beyond the window and you could get all else behind.

Compare your original and the redo in EA flashing mode and all should become apparent.

The foreground will appear free if it is BTW. You will often find a small detail at the bottom of my stereos which was the mark I set the window by and then pushed back from. All elements in a stereo should be in sharp focus. I often use the hyperfocal ADep function to get that. (Some of the macro stereos in POTN can be difficult to view because of the limited DOF and consequent blurring.)

Keep a steady hand! Vertical misalignment is inevitable so minimise it. Judge your sidestep. With experience you will learn what is the correct distance for a given situation. The sidestep should be 1/30th of the distance between lens and the nearest object you will want in the finished stereo -- which is usually the nearest object in reality. With single camera cha-cha you cannot photograph moving objects. Be aware of movement and try to screen or avoid it. This includes windblown elements. But this is now to open a new learning point -- that of retinal rivalry.

I look forward to seeing the resultant stereos of your trip!

Best wishes,

Hey Balliolman,

Is there any risk to crossing your eyes all the time to view stereograms? Like can you strain/hurt/damage your eyes in any way?

There is no risk to eyesight to my knowledge, JCW122, though I should state I am not medically qualified.

However doctors, including an opthamologist, tell me that freeviewing strengthens eye muscles and can even help some people with specific squint problems.

Experiment with finding your optimal viewing distance from your monitor. The closer you are the more you need to cross eyes; this could lead to strain. So move back to a viewpoint where crossing is minimal.

I can freeview for hours with no adverse effects. Common sense and fatigue suggests when resting should occur!

I bought a package that is supposed to teach you how to correct your eyes and stop needing glasses. Im nearsighted. Anything to not wear glasses right?
Anyway, The focusing you do in to view this is one of the exercises in the package.

Is it helpful? Dunno.
Didnt work for me because it also required that you stop using your glasses.
I can not drive and otherwise function properly without mine.