About that unintentional “Dutch angle”
The intentional Dutch angle

About that unintentional “Dutch angle”

How to get your image straight in 10 different photo editors

Do you remem­ber my last arti­cle about the things you can improve on for your next pho­to club com­pe­ti­tion? You remem­ber the unin­ten­tion­al “Dutch angle”? If you want to know what it means, or how to get rid of it, then this arti­cle is for you.

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PART I — “So, what is the problem here, Officer?”

The “Dutch angle”

Also called “Dutch tilt”. Every­one who ever used a cam­era has used this tech­nique, but most peo­ple nev­er knew they did.

This effect is sim­ple to achieve, in fact it is a lot eas­i­er to do than… the oppo­site. If you have a Dutch tilt in your image (or your video, but I ignore that for now), then the image slants to one side and gives you an uneasy feel­ing about it.

The intentional Dutch angle
The inten­tion­al Dutch angle

That is not a prob­lem if you want the view­er to feel that way. The slope should not look like a result of slop­py image post-pro­cess­ing. In that case, any judge would be hap­py to point out the issue because it is easy to see, and easy to avoid, and thus safe to com­plain about.

Let us look at the exam­ple below.

The unintentional Dutch angle

The judge would feel uneasy, but not in the way you want. The ocean will flow off the edge of the world to the left. Nobody wants that, not even the peo­ple who believe the earth is round.

If you want­ed to show off your lat­est beach shot with that mag­nif­i­cent sun­set (it was sun­rise, but that doesn’t mat­ter), then a slight­ly non-hor­i­zon­tal hori­zon line would cause major skin rash to appear on the judge’s face. The judges have to learn how to deal with that oth­er than to throw pro­fan­i­ties into the audi­ence. They could hand out a copy of this arti­cle to the image author, to edu­cate in a more civ­i­lized man­ner. We don’t want to scare away the judges, so what can we do to help them?

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Part II — “How do we get rid of the unintentional Dutch tilt?”

My first answer would be: “Get it right in cam­era when you take the image.”

You can use many helper tools to make sure your cam­era is straight when you take the image. Some cam­eras have inbuilt sen­sors which yell at you with more or less intru­sive mark­ers on the screen: “Warn­ing! Dutch angle!” Some cam­eras have a grid on the screen to help you get it straight and to help you use the “Rule of Thirds”. This is a won­der­ful top­ic for anoth­er time.

You can also use a phys­i­cal spir­it lev­el, pop them on the flash hot shoe, or you can use an inte­grat­ed lev­el in your tri­pod. You have a tri­pod, right?

To cut that short, if you did not get it right in cam­era, you can use soft­ware to fix it in post-pro­cess­ing. That is good news.

The bad news are: straight­en­ing an image will be a destruc­tive process, you will lose pix­els at the bor­der of the image. If some­thing impor­tant is close to the edges, you are in trouble.

Let me illus­trate what I mean. The fol­low­ing screen­shots are from Gimp, they dis­play very detailed what is hap­pen­ing after the straightening.

Illustration of image crop effect
Illus­tra­tion of image crop effect
  1. The thin slant­ed edge shows the image bor­der of the orig­i­nal image after rotation.
  2. The rota­tion was around the cen­ter of the image. You can change that, you can change every­thing in Gimp. Make sure you know how to change it back.
  3. The hori­zon is now lev­el, but…
  4. The soft­ware crops the image to fit it in the out­er bor­der. That is the largest size with no clipped alpha areas (areas which are now trans­par­ent with­out image information).
  5. The check­er-board area is the area of lost pix­els after the rotation.

If you do not crop in the image after rota­tion, you would get this:

Image areas without image information when not cropping image
Image areas with­out image infor­ma­tion when not crop­ping image

The red-marked areas would con­tain no image infor­ma­tion. Some pro­grams can invent pix­els, they use AI (Arti­fi­cial Intel­li­gence) to guess what that area might look like, and add it to the image. That works well for uni­form areas like the sky or water, but less so for detailed areas like the bot­tom left cor­ner. Most pro­grams are not sophis­ti­cat­ed enough to use AI, they only give you the crop option. Or they zoom the image out, either way: you lose pix­el from the orig­i­nal image.

The crop also has two options, one changes the aspect ratio of the result (first Gimp exam­ple above). It keeps the most amount of pix­els. If you opt for keep­ing the aspect ratio of the orig­i­nal image intact, then you lose more pix­els. That would be the com­plete grey check­er-board area around the image lost (see image below).

You see why I said: “Get it right in cam­era when you take the image?

Crop with retained aspect ratio loses even more pixels
Crop with retained aspect ratio los­es even more pixels

Every soft­ware does the straight­en­ing a bit dif­fer­ent­ly. Some use the crop tool to give you the oppor­tu­ni­ty to rotate the image. Some use mark­er lines where you tell the soft­ware what you want to appear straight, and it cal­cu­lates the rota­tion. Some use a rota­tion tool, the user has to crop man­u­al­ly. Or the soft­ware is nice and does it for you. All have the same two actions to perform:

  1. Rotate the image
  2. Crop to fit

The result­ing image los­es pix­els and you need to tell the soft­ware how to do it. Or the soft­ware does it for you.

Let’s have a look at how good the soft­ware helps you with the “sim­ple” task of straight­en­ing an image.

Before I get to this, just a quick tip. If your soft­ware does not sup­port hav­ing some hor­i­zon­tal guide­line, you can use this lit­tle gem of software.

Screen Ruler tool
Screen Ruler tool
Screen ruler in action

The tool is easy to use, it dis­plays an over­lay over your screen. You would use it to mea­sure pix­els on the screen, but it also cre­ates a hor­i­zon­tal line you can move freely across the screen. Change the opac­i­ty to have your image vis­i­ble through the ruler.

I still believe if you need to use it, your image pro­cess­ing soft­ware is not good enough.

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Part III — 10 different programs to straighten your image

I con­fess, I am an image edit­ing soft­ware col­lec­tor. Some­times that is use­ful, but most of the time it is only expen­sive. I will now present you 10 pro­grams I used to straight­en an image. I will tell you how easy it was on my sci­en­tif­i­cal­ly proven scale from 1 to 5 stars, with 1‑star caus­ing skin rash like Dutch angle skin rash, and 5 stars being like a bar of choco­late. Note: I am a Win­dows user, if some­one donates me a prop­er Mac­Book and the soft­ware, it could tempt me to test that on a Mac.

Photo Editing Software under test

This list is in no spe­cif­ic order, all are recent edi­tions at time of writ­ing (June 2020).

  • Paint.NET (free)
  • Affin­i­ty Photo
  • Adobe Pho­to­shop
  • Adobe Light­room
  • DxO Pho­to­lab 3
  • DxO Nik Col­lec­tion 3/ DxO Viewpoint
  • Sky­lum Luminar
  • Gimp (free)
  • Microsoft Pho­tos (comes with Win­dows 10)
  • Pho­to­Scape X (free version)

Buckle up, here are the results:

Note: The results are high­ly sub­jec­tive. It does not tell you any­thing oth­er than how I per­ceive the pure straight­en­ing func­tion­al­i­ty of the soft­ware, includ­ing han­dling of the clip­ping areas. Noth­ing else. It won’t tell you how good the soft­ware is usable for you in general.

★☆☆☆☆ 1‑star rating, symptoms: causes unintentional Dutch angle skin rash. Do not use for straightening an image, it is painful.

Windows Photos

In this cat­e­go­ry: Win­dows Pho­tos. I think Microsoft did not build this piece of soft­ware with image edit­ing in mind, it is more for col­lect­ing and dis­play­ing images. But they have an edit func­tion, so we’ll see if we can rotate the image with that.

First issue was to get the image on the screen, but that is anoth­er sto­ry. Well, after a while I fig­ured it out, but the fact that it took me a while to get one image loaded speaks for itself. Or against me, but I assume for now it was the soft­ware not work­ing as I assumed it would. Here is the screen:

Edit & Create Menu of Windows Photos
Edit & Cre­ate Menu of Win­dows Photos

Click on “Edit”, and you will be pre­sent­ed with this:

Windows Photo UI

When you start mov­ing the straight­en­ing slid­er, it offers you a wide grid as a guide:

Windows Photo UI explained
  1. Use this to get the straight­en­ing slid­er on the right.
  2. Move the slid­er until you believe the image is now straight.
  3. The dark area tells you what pix­el areas you lose dur­ing the process.
  4. Save a copy.

The bare min­i­mum, if you ask me. Skin rash is coming!

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Paint.NET

Next Pro­gram in the 1‑star cat­e­go­ry is Paint.NET. It is also a free soft­ware, and I used it for a long time as a replace­ment for the inbuilt “Paint” pro­gram. I did not use it for straight­en­ing images, I show you why.

You have two options here:

Option 1: Go to the lay­er menu and select “Rotate / Zoom”

Using the Rotate option
Using the Rotate option
An unusual sight for a rotate option panel.
An unusu­al sight for a rotate option panel.

Use the upper slid­er or the up and down arrows to get the image straight. Touch noth­ing else. I could not get the image right with the very coarse slid­er. Try to enter the cor­rect amount into the input box if you want to be more pre­cise. Brrrr.

Bet­ter use the oth­er option, Option 2:

Paint.NET explained
  1. elect the ‘Move select­ed Pix­els’ tool.
  2. The mouse changes into the rotate-hand shape when you are near the cor­ner of your image. Click and drag to rotate the image.

That works bet­ter than option 1, but you still don’t have a guide to check if the image is straight, and no auto­mat­ic cropping.

You can work around the miss­ing guide by adding a lay­er and put a straight line guide there, then select the image lay­er and rotate. Remove the line lay­er after done. It is cum­ber­some, but works as a workaround (or use the on-screen ruler tool).

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★★☆☆☆ 2‑star rating. Symptoms: causes itchy skin.

Def­i­nite­ly some con­tenders here.

PhotoScape X

The good and the ugly thing is the 0:45 sec­ond help video they put on YouTube.

They know why they turned off the com­ments on that video. Please, PLEASE, put a human voice in the video and explain what you are doing. You can hear the mouse clicks, but noth­ing more. They used two sam­ple images, but when they showed the straight­en func­tion on the sec­ond image, a flaw in the soft­ware was very vis­i­ble, so as they want­ed to tell us “Don’t use me, I can’t straight­en severe slant­ed angles!”. What was the issue? In the demo they reached the end of the slid­er when the image was still not lev­el. You would need two pass­es to get that sam­ple image straight. Why would you show that in a pub­lic prod­uct demo?

But it is good that they linked a help video direct­ly from the soft­ware where you need it, so thumbs up for that!

Help video

 

OK, that out of the way, you can still straight­en an image with Pho­to­Scape X, use the rota­tion slid­er con­trol or drag the mouse over the screen, which is bet­ter than Win­dows Pho­tos or Paint.NET, but not great. In my ver­sion the slid­er is a lot wider than in their help video, so it is eas­i­er to get slow rota­tion work­ing. That makes it more pre­cise. But the image re-cal­cu­la­tions are a bit sluggish.

You can also enter an angle, but who knows the exact angle you want to rotate the image? That is not spe­cif­ic to Pho­to­Scape X. Most oth­er soft­ware pack­ages had the same box for enter­ing an angle, it can be use­ful for fine tuning.

When you rotate the image, the soft­ware over­lays a helper grid, and you can also ‘grab’ and rotate the grid by drag­ging it up or down. The grid helps you to see what is hor­i­zon­tal (or ver­ti­cal). If I could change the num­ber of lines, or put my own helper line close to the hori­zon, then it would be eas­i­er to see if the hori­zon is lev­el. You can work around the issue, reduce the height of the pro­gram win­dow (get out of a max­i­mized win­dow first), it will move the grid lines close to the horizon:

PhotoScape X scale
Not close enough 👎
grid line close 👍

How does the inter­face look like?

Screenshot straighten tool location PhotoScape X
Screen­shot straight­en tool loca­tion Pho­to­Scape X

I marked the straight­en tool with the 1. When you click on it, a pop­up win­dow comes up and lets you do your thing:

PhotoScape Explained
  1. Your mouse point­er changes to a grab hand. Click, hold and move to rotate the image around the cen­ter (not marked).
  2. The posi­tion­ing grid.
  3. Use the slid­er as an alter­na­tive to 1.
  4. Enter a num­ber if you know the angle.
  5. Choose if you want to main­tain the image size dur­ing rota­tion or not
  6. Apply change

Short sum­ma­ry: Does the job. The help video is a bit unpro­fes­sion­al. What is the use of the “Main­tain Image Size” option? Get rid of that and spend time on the help video instead. The soft­ware does a lot of things bet­ter than the straightening.

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★★★☆☆ 3‑star rating — feels like eating a bit of cheap chocolate. No skin irritation.

Gimp

Gimp is a tool which tra­di­tion­al­ly does every­thing a bit dif­fer­ent­ly from reg­u­lar win­dows soft­ware. It is a mighty tool in the hands of an expert, but there is also a lot of “get­ting used to it” involved. You can con­fig­ure and re-arrange all the lit­tle win­dows. And you can detach or un-dock them. Learn how to reset things, you will need it.

Let us see if I as a novice user can get it to straight­en an image.

After open­ing an image I found the ‘Rotate Tool’:

Gimp 1
Gimp Explained
Lots of options

Make your­self famil­iar with the options.

  1. “Nor­mal (For­ward)”. What does it do ‘for­ward­ly’? I don’t get it.
  2. “Cor­rec­tive” works more like putting 2 mark­er on the hori­zon and let the soft­ware cal­cu­late the rota­tion. Just with­out mark­ers, but with a grid. For that to work, turn on the Grid by using the drop down (4.) and select sev­er­al lines, maybe 30. When you drag the mouse on the image, you rotate the grid instead of the image. Align the grid with the hori­zon and hit enter. That is all very con­fus­ing, but it works if you fig­ured it out.
  3. I would use “Crop to result” or “Crop with aspect”.
Clip/Crop options

4. Use­ful for when you select option 2. above instead of 1.

The process which worked good for me with Gimp was this:

1. Pull a helper line to the place where you think the hori­zon should be. Close enough is enough. Do that by start­ing to drag the mouse inside the top ruler and pull to the posi­tion you want.

Gimp process 1
Cre­ate a helper line

2. Use Nor­mal Direc­tion, Crop with Aspect, and No Guides:

Gimp process

3. Drag the cur­sor inside the image to rotate the image until straight. The helper line should be close to the hori­zon to be helpful.

Straight!
Straight!

There is anoth­er menu on the screen (not sure how I got there):

Gimp another

This lets you set the angle, and you can also change lots of oth­er things. Best solu­tion for me was to get this out of the way, as it was occu­py­ing screen real estate.

Quick sum­ma­ry: For a novice user there are just too many options, and they have strange names and they van­ish into thin air, nev­er to be seen again. It is very easy to mess up the docked menus.

But Gimp can do the job in sev­er­al ways and one of them might suit you. Maybe it clicks with your brain bet­ter than it did with mine. Com­plex­i­ty con­fus­es me.

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Skylum Luminar 4

Lumi­nar 4 missed get­ting in the 4‑Star cat­e­go­ry. All 4- and 5‑star con­tenders used a tool to sim­ply mark the (crooked) hori­zon, the soft­ware then cal­cu­lates the rota­tion need­ed to get the line straight.

With Lumi­nar 4 you need to man­u­al­ly rotate. And the guid­ing grid changes dur­ing the rota­tion, which could be annoy­ing if it changes just before you get the hori­zon straight. I love Lumi­nar 4 because of what their AI does (espe­cial­ly the sky replace­ment is awe­some!), but the straight­en­ing is not the best I have seen. For paid soft­ware, I was a bit dis­ap­point­ed. Let me show you the process:

Skylum Luminar anim

Please, Lumi­nar team, let your AI team find some­thing bet­ter than that.

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★★★★☆ 4‑star rating — feels like eating a bit of chocolate.

More paid soft­ware here, as expect­ed. First in line is Adobe Lightroom.

Adobe Lightroom

I use Light­room a lot for my image cat­a­log and basic image edit­ing. If you haven’t used it before, there is a tool for lev­el­ing the hori­zon hid­den behind the crop tool, you can find that here:

Lightroom 1
  1. After select­ing your image, go to the devel­op module
  2. Select the crop overlay
  3. Grab the ruler tool with the mouse and drag a line with it across the hori­zon. You do that lit­er­al­ly, detach­ing the tool from the menu:
Lightroom 2
start dragging a line with the spirit level tool
start drag­ging a line with the spir­it lev­el tool
dragged line with the spirit level tool
dragged line with the spir­it lev­el tool
Click ‘Done’ when you are done

When you release the tool after drag­ging the line across the still crooked hori­zon, Light­room rotates the image to make the line straight. Click ‘Done’ to fin­ish the job. You can’t change the mark­er posi­tion after you release the mouse. If you didn’t get it right first time, reset and do it again.

Quick sum­ma­ry: It does the job. ‘nuff said.

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Affinity Photo

Affin­i­ty Pho­to has a lot of the “Look and Feel” of Adobe Pho­to­shop. The straight­en­ing task is sim­ple to do:

UI for straightening in Affinity Photo
UI for straight­en­ing in Affin­i­ty Photo
  1. Select a per­sona which pro­vides the crop tool. Select the crop tool.
  2. Click on the “Straight­en” but­ton and move your mouse to the crooked horizon.
  3. Click and drag the mouse across the hori­zon. When you release the mouse but­ton, the image rotates to straight­en it.

Straight for­ward. The process is very sim­i­lar to what you do in Light­room, but the image is not auto­mat­i­cal­ly cropped. You can do it man­u­al­ly, or you can try to ‘inpaint’ (that is what Adobe calls ‘con­tent aware fill’ in Pho­to­shop) the alpha area cor­ners. When Affin­i­ty Pho­to can’t do auto-crop, why is it not in the 3‑star cat­e­go­ry? Because of the ‘inpaint’ option. Auto­mat­ic crop is nice, but as long as I can do it myself with lit­tle effort, it is not a deal breaker.

I won’t show the ‘inpaint’ here, Affin­i­ty Pho­to has released a use­ful video about the straight­en­ing on YouTube, that explains also the ‘inpaint’ option. Guys at Pho­to­Scape X: this is how a tutorial/help guide should be. The help video is anoth­er rea­son Affin­i­ty pho­to is in the 4‑star cat­e­go­ry for me.

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★★★★★ 5‑star rating — feels like eating a chocolate bar.

I have four pro­grams in the top cat­e­go­ry. First one is Adobe Photoshop.

Adobe Photoshop

Let us see what Adobe Pho­to­shop offers.

Photoshop 1
  1. Select the crop tool.
  2. Select the spir­it lev­el icon for the straight­en­ing tool.
  3. Click and drag across the hori­zon, release the mouse but­ton at the end.
Photoshop 2

After that, you have options before you com­plete your changes (use the tick sym­bol marked with 3).

  1. The rota­tion has cre­at­ed emp­ty areas (if you ticked the ‘Con­tent Aware’ option).
  2. Tick­ing the ‘Con­tent Aware’ box would try to fill these areas with sen­si­ble pix­els. The result­ing image has the same dimen­sions and aspect ratio as the orig­i­nal one, but with invent­ed pix­els in the corners.
  3. Click this to apply the changes.

If you don’t tick the con­tent aware box, it will just auto-crop the image. You lose pix­els as we all know now.

Quick Sum­ma­ry for Adobe Pho­to­shop: Straight­en­ing is easy to do. You can tell Pho­to­shop to fill the oth­er­wise cropped areas instead of crop­ping them. That works well for some images, try it. If it doesn’t work for that image, you can still do a straight crop. Or use one of the many oth­er tools Pho­to­shop offers to get the cor­ners filled. I made a note to write anoth­er arti­cle about that. Should be fun!

What I didn’t like is the miss­ing abil­i­ty to cor­rect the posi­tion of the hor­i­zon­tal mark­ers after you release the mouse but­ton. DxO has that and I think it is useful.

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The oth­er remain­ing pro­grams are all DxO pro­grams. They work nat­u­ral­ly very similar.

DxO PhotoLab 3

DxO Pho­to­Lab 3 is a spe­cial­ist in cor­rect­ing image dis­tor­tions, their straight­en­ing tool is great. Show, don’t tell:

PhotoLab anim

The last two pro­grams are near­ly iden­ti­cal. DxO View­point is the stand-alone ver­sion, DxO Per­spec­tive Efex is the new addi­tion to the exten­sive col­lec­tion of Plug-Ins called Nik Col­lec­tion 3. I’ll show you DxO View­point, but the user inter­face for the Per­spec­tive Efex Plug-In looks exact­ly the same.

DxO Viewpoint / DxO Perspective Efex

DxO Viewpoint anim

These two give me the best expe­ri­ence for the pure straight­en­ing task. Expert job, guys!

It was effort­less to do and had the most accu­rate result.

If the ani­mat­ed GIF above is too fast, here is the UI from the plu­g­in in detail:

DxO Perspective Efex explained

1. Select the Lev­el tool.

2. Move the two mark­er to the still slant­ed hori­zon line, as far away from each oth­er as pos­si­ble. You can repo­si­tion each mark­er after you release the mouse button.

3. When you move the mark­er, you see a mag­ni­fied tar­get area under the now cross shaped cur­sor. If you need more fine tun­ing, press the shift key to get extra slow cur­sor movement.

4. Change the line col­or to make the line more visible.

5. Apply and watch the image now in its straight-hori­zon glory.

There are oth­er meth­ods avail­able in DxO Per­spec­tive Efex/DxO View­point, but I found the process above straight for­ward (pun intend­ed) and very accurate.

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The com­plete exer­cise made me aware that such a ‘sim­ple’ thing like straight­en­ing an image is not so sim­ple to solve for image manip­u­la­tion soft­ware. It has to solve three basic things:

  1. Rotate the image.
  2. Pro­vide a hor­i­zon­tal guide
  3. Crop the image

I think only DxO Per­spec­tive Efex/DxO View­point and Adobe Pho­to­shop felt like they built the tool to help the Pho­tog­ra­ph­er with the task. They thought about the lit­tle details.

What would be on my wish list to make these two pro­grams bet­ter for straight­en­ing an image? I would mix the two.

DxO Per­spec­tive Efex/DxO View­point: add ‘Con­tent Aware’ fill from Photoshop.

Adobe Pho­to­shop: Add the mag­ni­fied cur­sor area from DxO Per­spec­tive Efex/DxO View­point, the change line col­or option, and the shift key to slow down the cur­sor movement.

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Closing words

I hope you learned some­thing about how any image manip­u­la­tion pro­gram would tack­le the straight­en­ing. Even if you don’t use one of the 10 pro­grams, you can still apply the con­cept to your favorite image pro­cess­ing software.

Now there is no excuse any­more for you when the judge com­plains about an unin­ten­tion­al Dutch angle in your image. You know how to get rid of it.

Frithjof Moritzen

Photography Club Enthusiast

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