Screw it! Or rather SKRWT!
SKRWT – an alternative app to PerspectiveCorrect?
The Problem of Falling Lines
Everyone who is in to architectural photography knows the problem. Falling Lines, buildings that threaten to fall out of the picture. Lines that in reality are vertical and parallel – like the face or edge of a building – will in a 2D photo converge in a point outside of the image, opening upwards. The camera lens is subject to the same restrictions as the human eye, that of the central perspective. Other prominent examples are railway lines, or a street, that apparently meet in a point on the horizon. The reason for the effect is that the face of the building is not parallel to the image plane. To achieve that, the camera would have to be positioned at the height of the middle of the building, something that in most situations is impossible. This means that every time you tilt the camera from a street level, you get the impression of the falling lines, and the feeling that the face of the building would be toppling.
With the fixed focal length of the mobile cameras (i.e. 35mm for the iPhone5), that are more suitable for landscape photography and panoramas, you quickly feel the technical constraints when working with architectural photography. Knowing about these, it is possible to work with them, using them when composing the image, and achieve dramatic effects. Often however, you would want to eliminate those kinds of contortions. In traditional architectural photography the necessary procedure is known as shifting. The professional and expensive cameras solve the problem by allowing you to adjust the lens manually so that it is parallel to the image plane. For miniature-cameras there are particular (Tilt)-Shift objectives that are expensive, but operate in the same way.
There are also other areas of photography in which an adjustment of the perspective makes sense. For example in landscape photography, where you could want to straighten the trunks of the trees, or when you are photographing interiors. The same applies to Street-photography and effectually all images in which the composition relies on use of the vanishing point or symmetry. Using symmetry as an element of composition, you can generate order in an image that creates an almost graphic effect.
If you are post-processing your images on a computer, there are special programs or tools, like ShiftN, that offer ways to manually or automatically correct the falling lines. Until now that has been marginally or inadequately possible to do on a mobile phone. With SKRWT (pronounced: „screw it“) there is now an app* that allows this to be done in an easy and precise way.
mobilephotography.de had the exclusive opportunity to extensively test the app before it was officially launched on the 25th of May 2014, and also to have an in depth conversation with the SKRWT developer, Mathäus Jagielski (26).
The idea behind SKRWT is naturally not new, as the above mentioned hard- and software solutions are evidence of. But Mathäus, who works as a freelance photographer and filmmaker for renowned names such as RedBull und REELLJEANS.COM, is a perfectionist. And since becoming a passionate Instagrammer, he was annoyed at the inadequacy of the solutions offered to correct the problem on the mobile phone. As a professional photographer he was not satisfied by the results, and as his frustration grew, the idea of developing an app based on his needs and preferences, one that could meet his high standards, matured. Since the beginning of 2013, he has, with the support of some friends located in a small town on the border to Holland, been working on developing a mobile solution to the problem. Until now, the measure of things mobile phone-wise, has been the app PerspectiveCorrect, which was also developed precisely to address the same problem, by the well-known Phoneographer Misho Baranovic from Australia. In other words an app which SKRWT hast to be on a par with.
How does SKRWT work?
When you first open the App, you are faced with the possibility of choosing between taking a picture with the camera – SKRWT uses the native iPhone camera app – or opening an existing one from the gallery. In contrast to PerspectiveCorrect, SKRWT does not give you the opportunity to do a live perspective control. In my opinion that means that SKRWT is best suited for the post processing of images*. After you have shot or imported the image from the Camera roll, you will find a toolbar at the bottom of the screen, which through swiping allows you to access additional options. Leftmost on the bar you find the „Undo“-symbol which also gives you the opportunity to revert to the original image, next to it, to the right, you access the function that allows you to tilt the image. Contrary to PerspectiveCorrect, you do not control the tilting through swiping the screen, instead SKRWT offers a scale at the bottom of the screen, through which it is possible to control the tilting on a very precise level. The result is shown live in the preview, and you can zoom in by using two fingers, to get a better view and control. By touching the check mark, you confirm the action, and it is possible to make further adjustments. The primary function of the app is of course to tilt the image plane, so that it is possible to achieve the trapezoid correction. This is the perfect tool to countermand the falling lines that are conditioned by the way the camera lens is made, or to exaggerate it, in order to boost the effect. By using SKRWT you can do that both horizontally and vertically.
Additionally there is a tool to correct the so called pillow or barrel distortion, meaning the optical bulging that an image might show towards its edges, an effect that can be likened to using a fisheye lens.
By allowing you to rotate the image in steps of 90° in a clockwise direction, you can adjust the vignette along the sides of the image. The vignette does however take the original image as its starting point, and not the adjusted image that has undergone the trapezoid correction. That means that the app does not create a new vignette, it just allows you to correct the one that originated from the fixed focal length of the iPhone.
The highlight of SKRWT is however hidden in the automatic crop function. In the process of correcting the perspective, the result is a trapezoid formed image, which has to be cropped to form a rectangle or a square. As a result you lose part of the edges of the image. The goal is to keep this loss at a minimum; on the other hand there shouldn’t be any leftover white edges. That can be rather hard and fiddly work because of the small screen, and it is difficult to be as precise as you may want to. SKRWT takes care of the cropping automatically and optimizes the crop so that you lose as little as possible of the edges of the image. There is of course the option to perform this task manually, which also gives you the opportunity to choose the end format of the image, which can be free, or you can use one of the standard image formats. The corners of the crop tool are marked with coloured indicators, and to achieve a precise crop, it is possible to zoom in on the areas you need to look closer at. The crop frame can be moved by using the two finger touch, meaning that you can also adjust the position of the zoomed in part of the image. All testifying to the developers eye for details and will to perfection.
You can also adjust the size and colour of the grid. The finished result then can be saved to the camera roll or be directly shared on Instagram. Another nifty detail is that the image is automatically given a white frame if it does not fit Instagram’s square 1×1 format.
All in all SKRWT* is a powerful tool for perspective correction, which through the use of a scale wheel allows you to achieve very precise results in an easy manner. The app design is clear-cut, functional and self-explaining. Through the time of testing, the app performed fast and stable without crashing. SKRWT* gives you as a user a great tool in your hand to prepare your image for further processing. I think SKRWT* can be seen as a real alternative to PerspectiveCorrect, a must have tool, not only for architectural photography, and I would give it my highest recommendations.
From the 25th of May 2014 SKRWT can be bought for 1,89 EUR in the AppStore. Initially it is an app exclusively for iOS. The developer Mathäus Jagielski says that it is a goal to develop an Android version of the app, but that it will probably not happen in the very nearest future.
And then some basic tips for using perspective correction on images:
Before you start to straighten an image you should check whether or not the original photo lends itself to perspective correction. The human eye perceives the motif just as the camera lens, and there is a danger that you over-edit the image, so that the result appears unfamiliar to the viewer. If you try to adjust images that are not suited, the photographed object may seem deformed (that is especially true for cubic or cylindrical objects that are narrower at the bottom than the top). You can avoid this effect by just slightly adjusting the vertical lines, you are not achieving exact parallelism, but it will seem more natural to the eye. Already as you are taking the photograph there are things you should think of, in order for the result of the processing to come as close to a professional camera as possible:
– Because you lose edge through the cropping of the trapezoid image that comes as a result of the perspective correction, make sure you have a sufficient edge around the object.
– Always set the camera to the highest resolution because you always loose quality through the processing and adjusting of the image.
As part of the launch of SKRWT* in the Tunes store on the 25th of May 2014, mobilephotography.de will start a new mission, “Love for Symmetry”. The people from SKRWT have given us great gifts to give away, and have also been kind enough to provide some promo codes for the App store. For three first-prize winners there is an Olloclip 4-IN-ONE, a Power Bank and a GorillaPod!
Details about the SKRWT-Mission can be found in our missions section.
* Affiliate links.