Methods

Equipment
Technique
Editing

In this sec­tion, we bring to you detailed meth­ods and tech­niques relat­ed to sterepho­tog­ra­phy, from begin­ners and sea­soned pho­tog­ra­phers alike. The aim is to share tips and notes on how to get start­ed on spe­cif­ic meth­ods. In oth­er words, your per­son­al DIY stereo guide.


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Stereo Window basics

written for the stereosite by David Kuntz (Rancho Palos Verdes, California, USA)

Stereo pho­tog­ra­phy is a bit more demand­ing than tra­di­tion­al flat pho­tog­ra­phy, because a poor­ly ren­dered 3D image can be dif­fi­cult or unpleas­ant to view.  So, the stereo pho­tog­ra­ph­er has to take addi­tion­al steps, not required with flat pho­tos, to avoid the prob­lems that lead to view­er dis­com­fort.  The good news is that under­stand­ing a cou­ple of rel­a­tive­ly sim­ple con­cepts will allow you to con­sis­tent­ly pro­duce 3D images that are easy to look at, and have good 3D impact.  And, once you’ve absorbed these ideas, it won’t take you any time at all to rou­tine­ly per­form the actions nec­es­sary to accom­plish this.

What is the Stereo Window?

The series of three pho­tos shown here illus­trate a key 3D pho­tog­ra­phy con­cept that affects view­ing com­fort, name­ly, the stereo win­dow.  Imag­ine that your screen has a rec­tan­gu­lar hole in it, and you’re view­ing the 3D con­tent in this image through it.  That is, you’re see­ing the boy point­ing his fin­ger at you through a win­dow in your screen.  The lat­tice of green lines in each image lies in the plane of your screen; in oth­er words, your eyes see the green lines as being the same dis­tance from you as your screen itself.

In the first 3D image pair (on top), the boy’s hand (which is the clos­est object in the com­po­si­tion to you), appears behind the green lines, or behind this win­dow.  In the next stereo pair (the mid­dle), his fin­ger has been moved clos­er, so that his fin­ger­tip is right at the plane of the win­dow; the exact same dis­tance from you as the green lines.  In the last 3D image (bot­tom), his fin­ger­tip has now come through the win­dow, and is clos­er to you than the green lat­tice of lines.

These three 3D images are all the same pho­to.  So, how did this trans­for­ma­tion in terms of their depth rela­tion­ship to the stereo win­dow (or plane of the screen) between them occur?  The lit­tle red arrows between the pho­tos indi­cate how it works.  If you com­pare the posi­tion of the boy’s eyes in each of the left side images with the left­most green ver­ti­cal line, you can see that the entire image has been moved slight­ly to the right in each suc­ces­sive pair.  The right side image doesn’t move at all.  This is pos­si­ble because the orig­i­nal pho­to has lots of addi­tion­al mate­r­i­al off the left and right edges that is being cropped off here.  

This crop­ping, and how it relates to the win­dow is shown again in the next two pho­tos.  Here, you can see this image is cropped down quite a bit (in oth­er words, there’s lots more in the orig­i­nal image that’s not being shown out­side the frame of the crop).  But, by slid­ing the image left/right rel­a­tive to crop­ping rec­tan­gle (or stereo win­dow), the depth rela­tion­ship of the sub­ject mat­ter with respect to the win­dow is changed.  What is not changed, how­ev­er, is the depth rela­tion­ship of ele­ments with­in the com­po­si­tion itself (such as the per­ceived depth dis­tance from the tip of the boy’s fin­ger to the back­ground).  Those were set when the image was orig­i­nal­ly tak­en, and can­not be sub­se­quent­ly changed.  All, that’s hap­pen­ing here is an adjust­ment in the rela­tion­ship of the image con­tent with respect to the frame it’s con­tained in.  

Why worry about the Stereo Window?

The next series of pho­tos is intend­ed to demon­strate why you should care about the posi­tion­ing of the stereo win­dow rel­a­tive to your pho­to.  In the first one, the flower petals at the edge of the frame are in front of the stereo win­dow.  This caus­es a bit of visu­al con­fu­sion, espe­cial­ly at the left edge of the frame.  There’s also some “shim­mer­ing” at the frame edges, because there’s so much image mate­r­i­al that shows up at the edge of one image that doesn’t appear at the cor­re­spond­ing edge of the oth­er image.  

Too far in front of the win­dow.

In the next pho­to, every­thing is far behind the stereo win­dow.  This again caus­es a bit of “shim­mer­ing” on the left and right sides of the image because so much of what appears at the edges doesn’t match up between the left and right.  How­ev­er, this ver­sion isn’t that unpleas­ant to view.  

Too far behind the win­dow.

The third image has every­thing in the image set just behind the win­dow.  It’s com­fort­able to view, doesn’t have a lot of shim­mer­ing at the edges.

Good rela­tion­ship between sub­ject and the win­dow.

If the dif­fer­ences point­ed out here aren’t obvi­ous to you, don’t wor­ry.  Your sen­si­tiv­i­ty to how the win­dow is adjust­ed depends on a few fac­tors.  First there are indi­vid­ual vari­a­tions in how we each per­ceive stereo pho­tos, and our tol­er­ance for these adjust­ment fac­tors.  Next, the size of your dis­play, and your dis­tance from it, are also impor­tant fac­tors.  If you’re view­ing this tuto­r­i­al on a small phone screen, it’s quite pos­si­ble that you either won’t see the dif­fer­ences between the last three pho­tos, or won’t be both­ered by them if you do.  But, as dis­play size goes up, these dif­fer­ences become much more notice­able and dis­turb­ing.  When viewed on a large screen 3D TV, or if pro­ject­ed on a large screen, even much small­er dif­fer­ences than those illus­trat­ed here can pro­duce a sig­nif­i­cant amount of view­ing dis­com­fort.  The take­away from this is that if you’re only show­ing your images on Insta­gram, you don’t need to wor­ry about all this near­ly as much as if you’re pro­ject­ing them for a crowd. 

How Do I Control the Stereo Window?

So, if you now under­stand the need to set the posi­tion of your sub­ject mat­ter with respect to the stereo win­dow, the next ques­tion is how to accom­plish that.  That turns out to be the easy part.

Two of the appli­ca­tions that can be used to read­i­ly per­form this adjust­ment are the Win­­dows-based pro­gram StereoPho­toMak­er, and the cor­re­spond­ing iPhone/Android app, 3DStereoid (both pro­duced by Masu­ji Suto).  No mat­ter which pro­gram you use, the very first step you should take, before per­form­ing this win­dow adjust­ment, is to “auto-align” your image.  This gets rid of any ver­ti­cal, rota­tion­al, per­spec­tive or oth­er mis­align­ments that can make a 3D image uncom­fort­able to view. 

With auto-align­­ment com­plete, set the win­dow in StereoPho­to Mak­er by going to the “Adjust” menu, and then select­ing “Easy Adjust­ment.”  This brings up a large dia­log box with lots of options, along with your image dis­played in anaglyph (red/cyan) for­mat.  To adjust the win­dow, just use the slid­er at the top of the win­dow (indi­cat­ed in red).  This allows you to move the two images hor­i­zon­tal­ly rel­a­tive to each oth­er.  As explained pre­vi­ous­ly, this will change the rela­tion­ship of your sub­ject mat­ter to the stereo win­dow.  

Anoth­er option in StereoPho­to Mak­er is to stay in the main pro­gram win­dow, and then just use the left and right arrow keys to make this adjust­ment.  Each press of the arrow key shifts the image a small amount, so it’s eas­i­er to use the Easy Adjust­ment menu if a large shift is need­ed in order to get the right win­dow set­ting.  This adjust­ment can be per­formed with your image dis­played in vir­tu­al­ly any for­mat; anaglyph, par­al­lel pair, cross-eye pair, and so on.  So, you should prob­a­bly choose a dis­play method which you are actu­al­ly able to view in 3D.  

In the 3DStereoid app, this same func­tion­al­i­ty is avail­able by select­ing “Edit” from the main menu.  Then, the left and right arrow but­tons (indi­cat­ed in yel­low in the graph­ic) will shift the images rel­a­tive to one anoth­er.

How do you know when you’ve got it right?  Any part of your pho­to that doesn’t have a red or blue fringe (that is, the red and blue images are per­fect­ly over­lapped there) when viewed in anaglyph is right at the stereo win­dow.  This sit­u­a­tion is illus­trat­ed in the next graph­ic, which shows that the right side of the right­most flower in the image has no col­or fring­ing, and will there­fore be exact­ly at the stereo win­dow in terms of depth.  The petal next to that does show a fringe, and won’t be at the win­dow.  It can be help­ful to view your image through anaglyph (red/cyan) glass­es dur­ing this process to visu­al­ize the rela­tion­ship of sub­ject mate­r­i­al to stereo win­dow, or alter­nate­ly, in anoth­er for­mat that you can actu­al­ly view in stereo. Often, a final step of crop­ping your 3D image may be help­ful after set­ting the win­dow.  This can be help­ful to elim­i­nate parts of your pho­to that don’t match up well or are visu­al­ly dis­tract­ing after win­dow­ing has been per­formed.

Conclusion

Hope­ful­ly, this tuto­r­i­al has shown you the need for stereo win­dow adjust­ment and it’s ben­e­fits, and giv­en you a sim­ple, easy to use method for per­form­ing that adjust­ment. The key take­aways to remem­ber are:

  • “Shoot loose.”  That is, be aware when you’re tak­ing your pho­to that you’ll prob­a­bly end up los­ing some of it on top and bot­tom dur­ing auto-align­­ment, and on the left and/or right dur­ing win­dow­ing.  So, pur­pose­ful­ly include a bit more on all sides to accom­mo­date this even­tu­al­i­ty. 
  • The depth con­tained with­in your image is deter­mined when you take it, and can nev­er be changed. What you can change dur­ing sub­se­quent adjust­ment is the rela­tion­ship between you sub­ject mat­ter and the stereo win­dow (the frame of the pho­to).   
  • Always per­form an auto-align­­ment on your 3D image(s) first, before com­menc­ing any oth­er pro­cess­ing oper­a­tions.
  • You’ll often want to per­form a final crop­ping step after win­dow­ing an image to “clean it up.”  That is, crop out any­thing that some­how got cut off by the process or doesn’t look right. 
  • Win­dow­ing can help make your pho­tos eas­i­er to view, and should be done on every sin­gle 3D image you make.  But, it becomes increas­ing­ly impor­tant as you go to larg­er dis­plays.  So, it’s not near­ly as impor­tant for images intend­ed for view­ing on a small cell­phone screen, but it’s absolute­ly crit­i­cal for large screen pro­jec­tion.  But, it’s easy to do, so why not get in the habit right now?
Getting started with Catadioptric stereos (Mirror stereos)

written for the stereosite by Gordon Au, USA

If you already take stereopho­tos using the sequen­tial (‘cha-cha’) method with your phone or cam­era, you’re undoubt­ed­ly aware of its lim­i­ta­tions: your main sub­ject has to remain per­fect­ly still; peo­ple and cars mov­ing in the back­ground cre­ate dis­crep­an­cies; chang­ing light between shots is a prob­lem; windy days can be impos­si­ble. How­ev­er, you may or may not know that adding a small hand­held mir­ror to your stereo arse­nal can help you over­come many of these prob­lems. With the mir­ror reflect­ing half of the camera’s view, you can cap­ture an entire stere­opair in a sin­gle shot, elim­i­nat­ing tim­ing-relat­ed issues. Though it depends on the mir­ror and camera(lens), this is usu­al­ly best for close-up shots:

Zoomed-in cata­diop­tric stereo of a female Bi-Col­ored Aga­pos­te­mon sweat bee, A. virescens

This fig­ure shows the basic prin­ci­ple: the mir­ror reflects one half of the camera’s view (in blue) over to the oppo­site side, where it over­laps with the oth­er half view (in yel­low). For every­thing in the green over­lap area, you get 2 dif­fer­ent views—stereopair poten­tial! Tech­ni­cal­ly, a sys­tem that com­bines a mir­ror and lens like this is called cata­diop­tric.

The trick­i­est part of tak­ing cata­diop­tric stere­os is posi­tion­ing and hold­ing the mir­ror. The basic steps are:

  1. Bring the ver­ti­cal mir­ror right up to the cam­era lens (but not touch­ing it!).
  2. Move the mir­ror to the side, until the near edge is no longer vis­i­ble to the cam­era.
  3. Tilt the far edge of the mir­ror back towards the cen­ter, until approx­i­mate­ly half the cam­era view is reflect­ed.

You can do this on either side — whichev­er is more com­fort­able.

The sin­­gle-mir­ror cata­diop­tric method

The set­up should look some­thing like this:

Mir­ror and cam­era posi­tion­ing

And your raw pic­ture will look like: 

An unprocessed cata­diop­tric shot

When you start out, you will need to fine-tune the mir­ror posi­tion and tilt. I rec­om­mend tak­ing a series of test shots, using the same sub­ject (at ~1–2 mir­ror lengths away), and with dif­fer­ent com­bi­na­tions of mir­ror posi­tions and tilts:

  • Shot #1: mir­ror 0mm from lens edge / 40% of view reflect­ed
  • Shot #2: mir­ror 0mm from lens edge / 50% of view reflect­ed
  • Shot #3: mir­ror 0mm from lens edge / 60% of view reflect­ed
  • Shot #4: mir­ror 3mm from lens edge / 40% of view reflect­ed
  • Shot #5: mir­ror 3mm from lens edge / 50% of view reflect­ed
  • Shot #6: mir­ror 3mm from lens edge / 60% of view reflect­ed
  • Shot #7: mir­ror 6mm from lens edge / 40% of view reflect­ed
  • (And so on…)

To process the shots, sim­ply:

  1. Straight­en if nec­es­sary, so the mir­ror edge is per­fect­ly ver­ti­cal.
  2. Sep­a­rate the two images.
  3. Un-reflect (hor­i­zon­tal­ly flip) the mir­ror image.
  4. Edit the two images as you would for any stere­opair.
    I rec­om­mend using StereoPho­to Maker’s auto-align func­tion

After pro­cess­ing, go back to your notes, and see which com­bi­na­tion of mir­ror posi­tion and tilt worked the best. (What amount of depth do you pre­fer? Which stere­opairs turn out the clean­est?) You might want to fol­low up with more test shots of sub­jects at dif­fer­ent dis­tances.

Beyond ‘get­ting start­ed,’ there are fur­ther details worth dis­cussing about mir­ror stere­os, includ­ing the ide­al mir­ror (size; shape; type: a front sur­face mir­ror (first sur­face mir­ror), which you can find on Ebay), pre­cise pro­cess­ing (crop­ping, match­ing size and focus, cor­rect­ing for key­stone dis­tor­tion), his­to­ry and the­o­ry, and more. Learn about some of these in “DIY Cata­diop­tric Stere­os” a video tuto­r­i­al I made for the Nation­al Stereo­scop­ic Association’s 3D-Con 2020. Also, check out the cor­re­spond­ing gallery and see #cata­dioptric­stereo on Insta­gram for exam­ple shots.

Feel free to send ques­tions through my web­site WorldOfDepth.com, or via Insta­gram. Have fun exper­i­ment­ing, and I look for­ward to see­ing your mir­ror stere­os!

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Gordon Au (New York, USA)

I am an avid stere­o­g­ra­ph­er and gen­er­al 3D exper­i­menter, mak­ing stereopho­tos, stere­ovideos, anaglyphs, extrac­tions, and con­ver­sions, draw­ing upon a vari­ety of sources, includ­ing TV and film, art­work, NASA data, prod­uct reviews, and more. I exper­i­ment with cata­diop­tric stere­os, asym­met­ric fram­ing, video pan­ning / zoom­ing of 3D stills, x‑rays and fog as depth map sources, and more. I am a proud mem­ber of and have pre­sent­ed and/or writ­ten for the New York Stereo­scop­ic Asso­ci­a­tion, the Nation­al Stereo­scop­ic Asso­ci­a­tion, and the Inter­na­tion­al Stereo­scop­ic Union.

Web­site: WorldOfDepth.com
Insta­­gram-pro­­file: World­OfDepth
YouTube-pro­­file: World­OfDepth

Evolving to a twin camera set up

written for the stereosite by Graeme Barclay, Scotland

If you are already tak­ing stereo pic­tures, well done! How­ev­er, if you desire to broad­en your hori­zons by cap­tur­ing more chal­leng­ing images, for exam­ple freez­ing motion, or cre­at­ing dra­mat­ic land­scapes, then a twin cam­era set up may be the answer.   

Like many peo­ple I start­ed in stereo pho­tog­ra­phy with my cel­lu­lar phone respec­tive­ly one cam­era, tak­ing sequen­tial stere­os. While this is ade­quate in many cir­cum­stances where there is no move­ment between the two frames, how­ev­er it is lim­it­ing. For exam­ple, back­ground move­ment, or water move­ment in rivers or the sea ruins stereo pic­tures tak­en using this method.

After three years of tra­di­tion­al pho­tog­ra­phy and hav­ing the advan­tage of work­ing along­side pro­fes­sion­al pho­tog­ra­phers, I soon real­ized I was look­ing to cre­ate high qual­i­ty stereo images. To do this I required two cam­eras and a means to trig­ger them in sync. I also want­ed the flex­i­bil­i­ty to have inter­change­able lens­es to enable a wide range of styles, which also pro­vides the abil­i­ty to add neu­tral den­si­ty fil­ters for long expo­sure pho­tog­ra­phy. 

Setting up

So now I have twin cam­eras. Ide­al­ly, two cam­eras exact­ly the same would be the best plan, how­ev­er, I have a Sony A6300 and a Sony A6400. These work well togeth­er. I mount­ed these togeth­er on a 30cm plate. Next, I need­ed to find a way to link them togeth­er. Sony does make a sync a cable to link these cam­eras, so trig­ger­ing one cam­era auto­mat­i­cal­ly trig­gers the oth­er. While this does work, I also need­ed to trig­ger the cam­eras remote­ly remov­ing any chance of cam­era shake. It is also much more con­ve­nient to be able to trig­ger the cam­eras from a dis­tance with­out any trail­ing cable.

This is what the entire set up looks like, includ­ing extra lens­es.

Remote control

I bought a wire­less set up on Ama­zon as well as two addi­tion­al cables. I cut off the orig­i­nal stereo jack plugs and sol­dered on an ordi­nary stereo jack cable I had. Con­nect­ing the third cable wasn’t as easy, as the colours of the wiring in this cable were dif­fer­ent from the oth­er two. I con­nect­ed an old cam­era and start­ed test­ing to see if this worked while keep­ing notes of the many failed attempts. I do not advise a tri­al and error of this type as it may dam­age your cam­era. It might be advis­able to get cables of the same type so that the colours will prob­a­bly match per­fect­ly or to seek pro­fes­sion­al or advice from your cam­era man­u­fac­tur­er. At least, all this depends much from what cam­eras and what kind of remote con­trol you include in the set up. So you might encounter some­thing sim­i­lar, hope­ful­ly you will not.

Final­ly, it all came togeth­er, and it was work­ing! I could both focus with the half press and fire with the full press of the but­ton. The elec­tron­ic shut­ter release of this type is sim­ple to use and has a pos­i­tive dis­tinc­tion between focus and shut­ter release. Final­ly, this set up allows cable release as well as wire­less release. Chang­ing from cable to wire­less could not be sim­pler. Remov­ing the jack plug from the trans­mit­ter and con­nect­ing it to the receiv­er works per­fect­ly. Instruc­tions to pair the trans­mit­ter and receiv­er are pro­vid­ed and sim­ple to fol­low.

This trans­mit­ter can either be con­nect­ed direct­ly to both cam­eras with the split­ter cable or work togeth­er with the wire­less receiv­er. The small Vel­cro tag is to keep the jack plug in place as it often drops off when left hang­ing.
This cable con­nects both cam­eras to the elec­tron­ic shut­ter release.
This receiv­er is only mount­ed on the stereo rig and con­nect­ed to the stereo cable when I want to release wire­less­ly.

Synchronisation

Now that it is all con­nect­ed, how could I make sure it was real­ly syn­chro­nized? I opened my lap­top, searched for a stop clock and let it run, focus­ing both cam­eras on the screen and fir­ing them.  My first few attempts showed there was 1/20th sec of dif­fer­ence between both cam­eras. For my approach, this was unac­cept­able. This was not only due to my using two dif­fer­ent cam­era mod­els. I began scrolling through each of the cam­era menus, mir­ror­ing every set­ting until I was suc­cess­ful. Both cam­eras were sync­ing per­fect­ly on sin­gle frame and sin­gle focus. How­ev­er, I still can’t get these to sync in con­tin­u­ous focus set­ting, silent mode or in a burst of more than one frame.

Mounting the cameras

Con­nect­ing L brack­ets to cam­eras is extreme­ly ben­e­fi­cial as this makes it eas­i­er to switch from por­trait to land­scape very quick­ly. Shoot­ing in land­scape will pro­vide more flex­i­bil­i­ty when it comes to align­ing images, espe­cial­ly for novices. My per­son­al pref­er­ence is shoot­ing in por­trait. At the point of shoot­ing I am always very care­ful with fram­ing, so I do not crop much of the pic­ture in edit­ing. 

My most recent addi­tion for stereo astro pho­tog­ra­phy is a 600cm base plate, allow­ing a far wider base where there is no close fore­ground to enhance the stereo effect. Enlarg­ing the base­line is also ben­e­fi­cial for land­scape pho­tog­ra­phy.

Sony A6300 in sil­ver and a Sony A6400 (the twins) mount­ed on a base plate.

L brack­ets help to switch from por­trait to land­scape eas­i­ly.
This 600cm base plate allows to enhance the stereo effect of dis­tant objects. 

Advantages of twins 

Whilst the cel­lu­lar phone in many instances will take good qual­i­ty stereo pic­tures, which is ade­quate for social media or web­site gal­leries, there are many dis­tinct advan­tages of hav­ing a twin stereo set up for simul­ta­ne­ous stereo pho­tos.

  • Man­u­al con­trol of shut­ter speed, aper­ture, ISO and focus 
  • Aper­ture or shut­ter pri­or­i­ty or full man­u­al 
  • Freez­ing motion  
  • Con­trol­ling the depth of field 
  • Much larg­er file sizes suit­able for pro­jec­tion 
  • Shoot­ing in RAW files, allow­ing deep­er post edit­ing 
  • Mul­ti­ple lens­es, from tele­pho­to to super fish­eye wide angle 
  • Able to use Neu­tral den­si­ty fil­ters enabling very long expo­sures  
  • Gra­di­ent fil­ters for when the sky is too bright 
  • Con­nect­ing to an exter­nal flash 

All that said, I am no way dis­miss­ing the unique flex­i­bil­i­ty of shoot­ing stereo using the cel­lu­lar phone. Its cam­eras are con­tin­u­ing to improve. Your phone is always with you. There are many apps for align­ing and edit­ing stereo images, the screen size allows for instant free-view­ing, and post­ing on social media is extreme­ly quick and easy.

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Graeme Barclay (Edinburgh, Scotland)

At this point, I’ve been tak­ing dig­i­tal pho­tographs for a lit­tle over three years and stereo pho­tog­ra­phy for around six months. I’m employed with­in the finan­cial sec­tor but have had many years expe­ri­ence in hydraulic engi­neer­ing and over­com­ing tech­ni­cal issues.

Insta­­gram-pro­­file: mys­tere­opics

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