All iPhone and iPad cameras have fairly wide angle lenses. This means that you must stand pretty close to the participants to fill out the image when recording a Photo or Video Finish. Sometimes this is an advantage (e.g. indoors), but in most cases it is the oposite. In many water sports like rowing and kayaking it can be difficult to get close to the finish line. And if the participants have different lanes, like in a 100 m sprint, standing close makes it impossible to set a slice width that fits all runners. This because the runners moves with very different speed as seen by the camera.
A solution to this problem is to move further away from the finish line. But if you back away the runners will become fairly small and it becomes more difficult to set time lines and identify runners. Zooming in solves that and can be achieved in two ways: Using the digital zoom or use an external ad on lens on the iPhone/iPad.
In the Finish Set Up you can tap on the camera icon at ”Zoom and Preview”. At the bottom of the camera view there is a slider that enables you to zoom up to 2x (5x when running at 30 fps). Zooming reduces the image quality a little, but the gain in viewing angle usually more than compensates that. The digital zoom doesn’t cost anything and is easy to apply. Unfortunately few seems to have discovered this feature, so I really encourage you to test it out.
Ad on lens
There is a large number of different ad on lenses of varying quality and price range available on the market. But the cost of a decent tele lens is around $50-$100. The add on lens gives a little better quality than the digital zoom, but more importantly, can be combined with the zoom for even longer range. Below I have tested a Olloclip 2x lens and a Manfrotto 3x lens. The Olloclip is sold in different combinations with a wide angle lens and costs around $99. It is easy to mount, but can only be used on an iPhone without a case. To place it on a stand you need some additional fixtures. The Manfrotto has an integrated case with a built in tripod fixture and costs $50.
I used an iPhone 6 running at 240 fps (the effects you see below would have been even more pronounced at a lower frame rate) and placed it on a camera tripod (important when you use tele lenses) . I placed it pretty close (2.4 m to the nearest lane) to fill out the image. I ran in lane 1 and 6 and set the slice width to 8 px so the closest runner looked OK. Below is the photo finish.
As you can see the runner in lane 1 is pretty drawn out, and by standing at same height as the runners I risk that they obscure each other.
Next I moved backwards and up the timekeeper stand. I set the digital zoom in the Preview to 2x and ran in both lanes. The slice width was 8 px as before. The image quality is a bit worse, but the angle is better and the runner in lane 1 looks better.
In the third test I added a Olloclip 2x tele lens, set the digital zoom to 1.5x and moved further backwards. The result shows some further improvements. Unfortunately the timekeeper stand on my small local stadium didin’t allow me to move back more, so I couldn’t test the combination with 2x lens and 2x zoom.
For an easy comparison of the image quality I needed something that looked the same in each run. I therefore brought down my daughter’s old Lego train from the attic. I tested different combinations and moved the iPhone so the train had the same size in the camera view each time. This means that the distance in the 6x image is 6 times further away than in the first image.
The first two images are without an add on lens. The distance in the second image is twice the one in the first. There is some quality degradation due to the zoom.
Next are two images with the Olloclip 2x lens. The first is at the same distance as the second image above, so you can make direct comparison. The image quality is a bit better than the digital zoom and close to the iPhone without lens and zoom. The second image shows that the lens enables you to shoot at 4x the distance, but with a little lower quality.
Here are two clips with the Manfrotto 3x lens. The image quality is similar to the Olloclip.
The last image is again the iPhone without lens and zoom, but taken at the 6x distance, i.e. the same as the second Manfrotto image. This gives some perspective on how much closer the lens and zoom brings you.
For sports like rowing, kayaking, horse racing etc, even the 2-3x tele lenses might not be enough. There are a number of 8x-18x (usually 12x) lenses available on the market. They come from different companies but look similar, so they might have the same origin. They are pretty cheap, around $30, so you can not expect too much. But the image quality in the middle of the image is not too bad, and since SprintTimer only uses the mid part, they are actually better for Photo Finish than for conventional photography.
Below is a Photo Finish of a Dragon boat race shot with a 12x lens (Thanks to Jiri). Click on the image for a larger version.