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.
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.
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 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?
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.
- The thin slanted edge shows the image border of the original image after rotation.
- 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.
- The horizon is now level, but…
- 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).
- 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:
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?”
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:
- Rotate the image
- 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.
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.
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:
Click on “Edit”, and you will be presented with this:
When you start moving the straightening slider, it offers you a wide grid as a guide:
- Use this to get the straightening slider on the right.
- Move the slider until you believe the image is now straight.
- The dark area tells you what pixel areas you lose during the process.
- Save a copy.
The bare minimum, if you ask me. Skin rash is coming!
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”
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:
- elect the ‘Move selected Pixels’ tool.
- 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).
★★☆☆☆ 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!
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:
How does the interface look like?
I marked the straighten tool with the 1. When you click on it, a popup window comes up and lets you do your thing:
- Your mouse pointer changes to a grab hand. Click, hold and move to rotate the image around the center (not marked).
- The positioning grid.
- Use the slider as an alternative to 1.
- Enter a number if you know the angle.
- Choose if you want to maintain the image size during rotation or not
- 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.
★★★☆☆ 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’:
Make yourself familiar with the options.
- “Normal (Forward)”. What does it do ‘forwardly’? I don’t get it.
- “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.
- I would use “Crop to result” or “Crop with aspect”.
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.
2. Use Normal Direction, Crop with Aspect, and No Guides:
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.
There is another menu on the screen (not sure how I got there):
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.
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:
Please, Luminar team, let your AI team find something better than that.
★★★★☆ 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:
- After selecting your image, go to the develop module
- Select the crop overlay
- 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:
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.
Affinity Photo
Affinity Photo has a lot of the “Look and Feel” of Adobe Photoshop. The straightening task is simple to do:
- Select a persona which provides the crop tool. Select the crop tool.
- Click on the “Straighten” button and move your mouse to the crooked horizon.
- 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.
★★★★★ 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.
- Select the crop tool.
- Select the spirit level icon for the straightening tool.
- Click and drag across the horizon, release the mouse button at the end.
After that, you have options before you complete your changes (use the tick symbol marked with 3).
- The rotation has created empty areas (if you ticked the ‘Content Aware’ option).
- 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.
- 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.
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:
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
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:
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.
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:
- Rotate the image.
- Provide a horizontal guide
- 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.
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.
