Designing a slit-scan photography app

Poloska is the personal project we built together with my husband and developer Nik Shanin It’s a real-time photo manipulation app that uses a very interesting photography technique called slit-scan.

A bit of history

Slit-scan technique appeared in the middle of 20th century and was used to determine a winner in sports competitions during a photo-finish. The photo finish is a period of time usually occurring in a sporting race when multiple competitors cross the finishing line at nearly the same time. As the naked eye may not be able to discriminate between which of the competitors crossed the line first, a slit-scan photography can provide a more accurate check.

Unlike the usual photography we all are familiar with, slit shooting does not show the whole captured area at a certain period of time. Instead, it captures the changes but only in a small fragment — a narrow frame, and it shoots for a long period of time (we made the unlimited period of time in Poloska).

For more information about this technique, you can google it as “slit-scan photography”

Pictures taken with Poloska. The moving objects are captured like they look in real life, while the still environment is converted to stripes

But why

The main reason why we decided to build it was our interest in this technique at first. But then we discovered that it could be used in many ways in the modern world as well.

First of all, it can still be used in competitions. The problem with this amazing technique is that the tools it requires to take the picture are expensive, and not every competition organizer can allow themselves to purchase it. It’s also can be quite difficult to find a professional photographer who works with this technique and has the necessary equipment. So we wanted to give the opportunity to small and non-profit sports organizations to use the alt-scan feature to determine the winner easily.

Secondly, we wanted to give the opportunity to everyone to discover this technique and to be able to take slit-scan pictures. As I already mentioned, not many people know about this technique because of the cost of its equipment and the narrow area of its usage at the moment. But think what we could do with it! We could create beautiful wallpapers or collages. We all could, everyone. Just using our phones. And Poloska, obviously.

And now - how

When you open the app, you can see a vertical (you can set it to horizontal) 1-pixel line — the slit. This line is the area which camera would shoot and manipulate in real time. So the result of your shooting would be this 1-pixel area duplicated several times. What you need to do is to keep the moving object in the viewport area. The rest is pretty simple. You tap the Record button and wait until your moving object crosses the viewport area. At this moment you can tap Stop recording and view your creation in the app gallery.

You can experiment by shooting objects that move with different speed. That would create different effects like stretching them or narrowing them. You can also shot static areas if you’d like to receive the photo consisting of stripes only. For a better experience, we recommend using a tripod or holding the iPhone still while shooting. If you’d like to experiment even more you can shot a rotating object in a “moving slit” mode. That would create bizarre twist effects to the object. You can also set different speed or play with horizontal or vertical slit.

3 image capture modes in Poloska: left — vertical slit mode, middle — horizontal slit mode, right — moving (vertical on this screenshot) slit mode

Designing the app

It was a very interesting experience building this app, ( more interesting from the development point of view though 🙃) From the product design perspective, I needed to come up with an interface that would be pretty natively to use, even for people who never heard of this unique technique before. Though I needed to show a little guidance, I also wanted to save it for people to experiment with it in their own creative way. By skipping a heavily designed walkthrough part of the app, I wanted to show that this app is affordable for everyone, and everyone one can freely download and use it.

The challenge in UI design was to create an interface where the main graphical object would be the picture itself. And the whole app interface would be the supplementary area that wouldn’t take much of your attention itself. The best solution became to use the transparent elements and backgrounds that blur the background area that is visible in the camera viewport creating beautiful and unique dynamic appearance.

While I wanted the UI to be invisible and clear, it was decided to add some sounds to help to provide useful feedback. Also, it was crucial to include the camera opening and closing sound indicator in the app. From the accessibility perspective, it’s important to clearly distinguish the start and the end of the soothing because when you tap the record button it’s changing state is hidden behind your thumb.


We were happy to receive our users’ comments and feedback after the release. More than happy we were to know that people download the app and share their thoughts on what we can improve to make it even more useful for them. We appreciate your help and support and we already thinking through the next update.

Stay tuned and download Poloska from the iOS AppStore