Stereo photography to go — from start to finish in 3 minutes

Creating side by side stereo photos entirely on your smartphone

written for the stereosite by Pascal Martiné, Germany

Introduction

Many stereo pho­tog­ra­phers — espe­cial­ly those who are about to start with the medi­um — will at some point encounter prob­lems when tak­ing sequen­tial stereo pho­tos with their smart­phone. This could be the wrong dis­tance or rota­tion between the left and right image, the has­sle of trans­fer­ring the images to a com­put­er for post-pro­cess­ing, auto­mat­ic size reduc­tion by col­lage apps, etc. There are com­mon solu­tions and guides avail­able for most of these sin­gle steps but this puz­zle might get con­fus­ing or even frus­trat­ing for some. So bet­ter to switch to a stereo cam­era or build a stereo rig even if it’s expen­sive, heavy, and not always with me?

Per­son­al­ly, I real­ly enjoy tak­ing stereo pho­tos of mov­ing scenes with my Canon rig. But most oppor­tu­ni­ties are not worth tak­ing the large bag with me and I also don’t have enough expe­ri­ence to make full use of all set­tings of the cam­eras. That’s why I actu­al­ly hard­ly used my rig for almost two years. In fact, I’ve only used my smart­phone and I def­i­nite­ly am con­vinced that this is a good choice — even for those who want to take stere­oscopy more seriously.

Here are some exam­ples of stereo pho­tos tak­en at unex­pect­ed occa­sions. Luck­i­ly, I have my smart­phone always with me.

Preliminary remarks

This tuto­r­i­al is based on my per­son­al work­flow for cre­at­ing side-by-side stere­os and includes sev­er­al apps for tak­ing, align­ing, com­bin­ing, and post-pro­cess­ing stereopho­tos. From shot to post, all files stay entire­ly on the smart­phone. Depend­ing on the occa­sion I slight­ly mod­i­fy my work­flow by adding, replac­ing, or skip­ping par­tic­u­lar steps. But on aver­age the process real­ly comes down to 3 min­utes to get a fin­ished side-by-side stereopho­to. It needs a lit­tle prac­tice of course, but in the end it’s nei­ther more com­pli­cat­ed nor more time con­sum­ing than final­iz­ing the shots that I took with my rig. Using a ready-built stereo cam­era might be eas­i­er, but I did not try one of those because of the lim­i­ta­tions of a fixed baseline.

That said, I’m using an iPhone 11 Pro and so my expe­ri­ences are iOS-based. But all the apps I’m using are avail­able for Android as well and should work quite sim­i­lar­ly. The same goes for stan­dard edit­ing oper­a­tions like crop­ping or dupli­cat­ing images in your photos/gallery app. More recent­ly, I start­ed using Apple short­cuts to auto­mate cer­tain steps. But indeed, this doesn’t seem to be pos­si­ble on Android. There­fore, in addi­tion to pro­vid­ing the ready-to-use Apple short­cut, I will also explain the indi­vid­ual steps involved.

If any­one could pro­vide detailed remarks on Android, I will be glad to update this tuto­r­i­al later.

1: Taking the photos

As you might already know, the base­line (i.e. the hor­i­zon­tal shift­ing) between the left and right image is cru­cial for the depth and can­not be changed after­wards. There­fore, I rec­om­mend David Kuntz’s arti­cle about find­ing the right base­line for a stereo photo.

For now, what I  want to take away from it is to always take 3–5 pho­tos in a sequence instead of only two. That way, you will have mul­ti­ple stereo pairs with dif­fer­ent base­lines. No mat­ter if you are expe­ri­enced or a stereo begin­ner, you will always have at least one pair with the right depth. Fur­ther­more, if you have two or more pairs with sat­is­fy­ing depth you may be able to sort out those with rival­ries (i.e. move­ments or dif­fer­ences between the two shots that cause flick­er­ing in a stereo view). Final­ly, this method gives you also a kind of cer­tain­ty while you take your pho­tos: instead of think­ing about the right base­line you can focus on a calm and relaxed par­al­lel cam­era move­ment dur­ing your sequence and this will sure­ly result in  bet­ter aligned pho­tos (although pos­si­ble, cor­rect­ing the align­ment is lim­it­ed and caus­es crop­ping of your images).

In addi­tion, I want to rec­om­mend always rotat­ing your cam­era to shoot in land­scape for­mat. Keep in mind while choos­ing your point of view that the aspect ratio of your final stereo image may not be land­scape, but stick­ing to land­scape for­mat ensures that lat­er on you will be able to adjust the stereo win­dow more eas­i­ly. As this sug­gests, stereo pho­tog­ra­phy includes crop­ping in most cas­es. You may be tempt­ed to shoot in upright ori­en­ta­tion, espe­cial­ly when you want to take quick snap­shots in 3D, but you will lose more mate­r­i­al than if you shoot in land­scape for­mat. The only excep­tion I would note is an extreme­ly nar­row image format.

So, after a short while you will end up with hun­dreds of pho­tos on your cam­era roll ready to make you despair. Thus, the next step takes the most patience in the whole process.

2: Finding the stereo pairs

Sure­ly you have heard of the soft­ware Stereo Pho­to Mak­er and the cor­re­spond­ing mobile apps i3DStereoid (or 3DStereoid for Android) which we will use now. It is not pos­si­ble to save files with the free ver­sion but I can promise you it’s worth every cent. Even though they’re some­times a bit cum­ber­some to use, devel­op­er Masu­ji Suto deserves lots of recog­ni­tion for devel­op­ing mul­ti­ple stereo apps inde­pen­dent­ly in his spare time.

There are dif­fer­ent tuto­ri­als and guides avail­able for the app (iPhone-help, Android-help) where every func­tion is explained in detail. There­fore, I will only explain the steps that are essen­tial for this tuto­r­i­al. I always use par­al­lel view because that allows you to use a view­er or print cards. This tuto­r­i­al works like­wise for cross view, but if you want to use this or oth­er dif­fer­ent view­ing meth­ods, the lat­er steps need to be mod­i­fied. When first using the app, please set up for par­al­lel or cross view in the bot­tom menu by tap­ping the eye-icon. As long as you want to fol­low this tuto­r­i­al com­plete­ly, you can­not use the frame fea­ture. Tap on the ‘Main Menu’ but­ton on the top left cor­ner and choose ‘Open Stereo Image’ and nav­i­gate to your pho­tos. Unfor­tu­nate­ly, i3DStereoid won’t remem­ber the last used fold­er so you will have to do this every time. There is a fea­ture for easy flip­ping to the next image but it’s not suit­able for our purpose.

Now you have to select two pho­tos. You can do this by tri­al and error and improve with expe­ri­ence. But you can also free view the thumb­nail images in dif­fer­ent ways: you can fuse adja­cent images, or every oth­er image, or every two images, depend­ing on the grid, though this will require a lit­tle more prac­tice. Depend­ing on the direc­tion of your pho­to sequence the result­ing stereo view will be either nor­mal or invert­ed. But for­tu­nate­ly, either way lets you esti­mate the amount of depth of the stere­opair and there­fore helps you to choose the right one more quick­ly. Keep in mind that stereo pho­tos look shal­low­er at thumb­nail size and will look deep­er at full size. After you have deter­mined the pair with the best depth you can now pro­ceed as nor­mal. Tap­ping on the ‘L‑R’ icon switch­es the two pho­tos so that you can change between par­al­lel and cross view.

3: Aligning the stereo pair

With­out a brack­et to guide the move­ment of your cam­era, it’s almost impos­si­ble to pre­vent ver­ti­cal cam­era move­ment or rota­tion between the left and the right images. This makes it dif­fi­cult or impos­si­ble to view the stereo pho­to, even with a view­er. Luck­i­ly, i3DStereoid has an amaz­ing auto-align­ment fea­ture: just tap the white magician’s hat on the bot­tom menu and you are done.

Optional step: color adjustment

Some­times the col­ors between the left and the right image are dif­fer­ent due to the aut­o­fo­cus of your smart­phone. More recent­ly, i3DStereoid got a sec­ond magician’s hat (the col­or­ful one). Tap­ping on it will adjust the col­ors of the two images to match bet­ter. If you tap once, the left image becomes the col­or ref­er­ence; if you tap twice, the right image becomes the col­or ref­er­ence; if you tap three times, all changes will be undone.

Optional step: vertical cropping

Although I’ve spent a few sen­tences on how to reduce the need for crop­ping, there are some cas­es that require addi­tion­al crop­ping, e.g. if you sim­ply want to remove some­thing from the top or the bot­tom of the photo.

I have to add that I per­son­al­ly pre­fer my stereo pho­tos to all have the same aspect ratio, be it  dis­play­ing them in a grid, or for print­ing them. Sure­ly if you only want to dis­play them on social media like Insta­gram dif­fer­ent aspect ratios won’t mat­ter that much. But if you want to keep a fixed aspect ratio, it is nec­es­sary that we crop only ver­ti­cal­ly in this step, or at least that we crop in a way that the result will still have a wide format.

The third icon on the bot­tom menu opens the ‘Adjust mode’. The stere­opair is dis­played inter­laced and a blue crop­ping frame is dis­played. You can adjust the frame eas­i­ly with your hands.

Note about the stereo window

Let me take the oppor­tu­ni­ty to drop a few lines about the so-called stereo win­dow here because that will be the next step we are about to pre­pare. The stereo win­dow is cre­at­ed by the bor­ders of your left and right images. In addi­tion, their hor­i­zon­tal align­ment will cre­ate a depth rela­tion between the bor­ders and the stereo pho­to. In oth­er words, by adjust­ing the stereo win­dow you deter­mine if your sub­ject is at the lev­el of your screen, lies behind, or even pops out. Like the base­line, the stereo win­dow is essen­tial for a good stereopho­to; how­ev­er, unlike with the base­line, the posi­tion of the stereo win­dow can always be cor­rect­ed lat­er. I high­ly rec­om­mend David Kuntz’s arti­cle on that top­ic to ensure you know how to achieve the desired effect and pre­vent a so-called win­dow violation.

It is just as pos­si­ble to adjust the stereo win­dow in the ‘Adjust Mode’ of i3DStereoid. But since we have to switch to anoth­er app at some point any­way, I per­son­al­ly pre­fer adjust­ing the stereo win­dow lat­er. In par­tic­u­lar, that is because I want to imme­di­ate­ly see the stereo win­dow while I’m work­ing on it. But this is not pos­si­ble with the inter­laced dis­play of i3DStereoid — even though this is use­ful for some pur­pose as well.

4: Intermediate file handling

To export the adjust­ed stereo image, open the main menu again and choose ‘Save Stereo Image’. Since we want to do fur­ther edit­ing you should choose ‘Orig­i­nal res­o­lu­tion’ in the next step. Android users should export the stereo image twice — you will see why lat­er. If you have more sequences that need pro­cess­ing I rec­om­mend repeat­ing steps 2 and 3 now, so that you end up with a bunch of prop­er­ly aligned and cropped stereopho­tos that are saved one after anoth­er on your cam­era roll. That way, you won’t need addi­tion­al time to search through your pic­tures dur­ing the next steps.

a) iOS

Right now, the stereo pair is stored side-by-side in one image file. For fur­ther pro­cess­ing, we need to sep­a­rate them. Luck­i­ly, Apple offers a kind of script­ing tool called ‘Short­cuts’ that allows us to auto­mate process­es like this. I’ve writ­ten a suit­able short­cut for our pur­pose that you can down­load if you open this link on your iPhone. You might need to adjust some set­tings first (more about that here, oth­er­wise pro­ceed as described for Android). After down­load­ing the short­cut, you have two pos­si­bil­i­ties to run it: you can start it direct­ly in the short­cut app, or on your Home­screen, or you can use the ShareSheet. In this case, open the pho­tos app and select all the stereo images export­ed from i3DStereoid. Then tap on the share icon, scroll down and select ‘Divide Stereo Pho­tos’. That’s it.

b) Android

The fol­low­ing fid­dly step might not be nec­es­sary. Still, it could pre­vent exceed­ing res­o­lu­tion lim­its that would cause auto­mat­ic size reduc­tion. So, it’s best to check if skip­ping this step has any effect on your final stereo image. As stat­ed above, you should have two copies of each of your stereo pho­tos. Go through each of the files now and cut off the right part of one copy and the left part of the oth­er. This should be pos­si­ble with Android’s stan­dard edit­ing tools. You don’t need to care­ful­ly cut exact­ly in the mid­dle — this is just to reduce the width.

Now you should have the left and right stereo images one after anoth­er, with the right depth, and per­fect­ly aligned.

5: Adjusting the Stereo Window

Now we have to switch to anoth­er app that is extreme­ly use­ful over­all. Adobe Pho­to­shop Express (iOS / Android) is also a mobile ver­sion of desk­top soft­ware. It is free with some lim­i­ta­tions but with enough func­tion­al­i­ty for our pur­pose. How­ev­er, I rec­om­mend buy­ing a year­ly sub­scrip­tion because this opens a lot of use­ful func­tions for post-processing.

Start the app and nav­i­gate to the ‘Col­lage’ func­tion. After our prepa­ra­tions it’s pret­ty easy to just select the stereo pairs and import them. The Lay­out sec­tion in the bot­tom menu lets you change the divi­sion between hor­i­zon­tal and ver­ti­cal (most­ly just titled G1 and G2). Tap­ping on the ver­ti­cal divi­sion icon again switch­es the two pho­tos so that you can change between par­al­lel and cross view. The aspect ratio sec­tion lets you choose your desired for­mat. I rec­om­mend 16x9 which results in almost square stereo views. The app also lets you direct­ly choose for­mats suit­able for pur­pos­es like Insta­gram posts or sto­ries. (There are many more lay­out or zoom func­tions and plen­ty of online tuto­ri­als to dive into the app.) For now, that’s all we need to start with the stereo win­dow adjust­ment: while you’re free-view­ing the stereo pho­to, tap and hold one of the two images with your fin­ger. Quick­ly slide your fin­ger down out of your view. Now, while free view­ing, move your fin­ger hor­i­zon­tal­ly and watch the stereo image mov­ing for­ward and back in the stereo win­dow. This tech­nique enables you to deter­mine exact­ly the best posi­tion­ing for your photo.

There are basi­cal­ly two sim­ple rules: mov­ing the pic­tures towards each oth­er will bring the stereo view clos­er, and mov­ing the pic­tures away from each oth­er will push them deep­er into the win­dow (when par­al­lel view­ing). By mov­ing both in the same direc­tion you can choose the image area. If a dis­turb­ing blue frame appears, just wait a few sec­onds and it will dis­ap­pear. Some­times you will acci­den­tal­ly zoom in, just dou­ble-tap to zoom out. No mat­ters what hap­pens, you have a com­fort­able undo func­tion available.

If you are sat­is­fied with the stereo win­dow, tap on the share icon on the top of the screen. Then select ‘Save to cam­era roll’. If you nav­i­gate back to pro­ceed with the next stereo pair, you can choose whether to save the col­lage or not.

Again, I would rec­om­mend repeat­ing this step with each of your pre­pared stere­opairs before the next step.

Parallel and cross grids

You may appre­ci­ate show­ing your images in par­al­lel and cross-view right under­neath each oth­er in a square grid as is direct­ly offered in i3DStereoid. I don’t rec­om­mend start­ing with a col­lage of four pho­tos in Pho­to­shop Express for that pur­pose. Instead, work as described using your pre­ferred view­ing method and export the col­lage once. Then switch the two images like described above and export again. That serves for the same stereo win­dow in both ver­sions. After­wards, import both col­lages into a new col­lage with­out any addi­tion­al bor­ders. Sounds com­pli­cat­ed? Well, that may be true. Maybe it’s bet­ter to adjust the stereo win­dow in the ‘Adjust mode’ of i3DStereoid in this case.

6: Post processing

As you will know, Photoshop’s cen­ter­piece is post-pro­cess­ing pho­tos, and the same applies to Pho­to­shop Express. If you choose ‘Edit’ instead of ‘Col­lage’ on the app’s start screen you can re-open the export­ed stereo pho­to, choose ‘Adjust­ments’ in the bot­tom menu, and apply dif­fer­ent effects. Beside expo­sure, con­trast, and oth­er com­mon­ly-known set­tings, it’s espe­cial­ly use­ful to con­trol high­lights and white tones, and sim­i­lar­ly shad­ows and black tones, inde­pen­dent­ly. Try light­en­ing up the shad­ows while dark­en­ing the black tones! Fur­ther­more, I espe­cial­ly rec­om­mend ‘Clar­i­ty’ and ‘Dehaze’. Final­ly, artis­tic col­or adjust­ment is pos­si­ble in the ‘HSL’ sec­tion where you can reduce or increase the sat­u­ra­tion of spe­cif­ic col­ors. Most of these are only avail­able in the paid ver­sion though.

If you’re done, you don’t need to export the pic­ture man­u­al­ly. Just nav­i­gate back and con­firm to save. A new copy will be cre­at­ed. Voilà — that’s your final stereo pho­to ready to post or send anywhere.

Alternatives

If you don’t want to sub­scribe to Pho­to­shop Express or don’t feel com­fort­able using this app, it’s also pos­si­ble to use the built-in iOS or Android image edit­ing in a sat­is­fy­ing way. If that’s the case, you also might need to think care­ful­ly about how you want to adjust the stereo win­dow. Like I men­tioned above, this is pos­si­ble in the ‘Adjust­ment mode’ of i3DStereoid. If you pre­fer the free-view­ing adjust­ment, there are many col­lage apps avail­able. But don’t for­get to check whether they reduce the file size or insert unwant­ed watermarks.

7: Tidy up

Depend­ing on your phone’s stor­age it might be nec­es­sary to delete some of the files that were gen­er­at­ed dur­ing the process. If you repeat­ed step 2 and 3 before start­ing off with Pho­to­shop Express, and did like­wise with step 5, you have your cam­era roll quite orga­nized despite the large num­ber of pic­tures. This makes it easy to choose which ones to delete and which ones to keep. I would only like to give you one piece of advice: you nev­er know where you are going to present your pic­tures at some point. When­ev­er you change the medi­um in which you present stereopho­tos, it can be nec­es­sary to increase or decrease the base­line. So that’s anoth­er advan­tage of tak­ing more than two images, and that’s why you should keep your orig­i­nal pho­tos. You can store them some­where on an exter­nal dri­ve or card.

Conclusion

As I men­tioned above the smart­phone has become my num­ber one device to take stereo pho­tos. Of course, if I need to take simul­ta­ne­ous stereo pho­tos, I take my stereo rig. But even then, I trans­fer the pho­tos direct­ly to my phone, and luck­i­ly, there is a cable for that. This is because of three more rea­sons that I don’t want to with­hold from you: first, I have found a vivid and inter­est­ed stereo com­mu­ni­ty on Insta­gram — basi­cal­ly designed for use with a smart­phone. Sec­ond­ly, the smart­phone is a real­ly good view­ing device, be it for free view­ing, or be it insert­ed into a view­er like the LSC Owl. Even mag­ni­fied phone screens don’t get as pix­e­lat­ed as com­put­er mon­i­tors. Final­ly, not only do I have my smart­phone always at hand to take stereo pho­tos. I also have it read­i­ly avail­able when­ev­er I have to kill time. For those moments, what could be bet­ter than doing a few stan­dard pro­cess­ing steps to get new stereo photos?

These pho­tos required slight­ly more artis­tic post-pro­cess­ing but were still edit­ed entire­ly on the smartphone.