keystone correction

So I took some photographs using the Olympus keystone compensation on a trip to Montreal. Most of them deal with buildings that are leaning back, which is the classic case when trying to photograph a building. The first set deal with some landscape photographs. In both these photographs I could not move any further back to take the photographs, and both were taken with the Olympus 12-40mm, set as wide angle (12mm or 24mm full frae equivalent).It was possible to correct both images, without loosing any of the building.

keystone correction of photographs — *Originals (left), keystone corrected (right)*

The second case deals with portrait format photographs. In both cases it was slightly more challenging to make sure the entire picture was in the frame, but doing it in-situ it was possible to assure this happened. Doing in post-processing may result in the lose of a portion of the photograph. In the lower image I had enough leeway to position the keystone-corrected frame in such a manner that the building is surrounded by ample space.

Compensating for perspective distortion often comes at a price. Modifying the geometry of a photograph means that less will fit in the photograph. Taking a photograph too close to a building may mean something is cut off.

Horizontal keystone correction can sometimes be more difficult, because the distortion is usually a compound distortion. In the example below, the photograph was taken slightly off-centre, producing an image which is distorted both from a horizontal and a vertical perspective.

Is there a loss in aesthetic appeal? Maybe. Food for future thought.

The Olympus OM-D EM5 Mark IIhas a completely cool feature they call keystone compensation. It’s a kind-of weird name – but dig a little deeper and you run into the keystone effect which is the apparent distortion of an image caused by projecting it onto an angled surface. It basically makes a square look like a trapezoid, which is the shape of an architectural stone known as a keystone. Now normally when you take a photograph of a building, this effect comes into play. Reducing the keystone effect is called keystone correction. There are special lenses that remove this distortion, i.e. tilt-shift lenses. Now Olympus has introduced an algorithm which compensates for the keystone effect. Here is an example of keystone correction (distortion is shown as the opaque pink region).

Olympus has introduced an algorithm on some of their cameras (e.g. EM5ii) which compensates for the keystone effect. First, you have to enable Keystone Correction in “Shooting Menu 2”.

*Turning on keystone correction on an Olympus EM-5(ii)*

Then it’s a simple matter of using the front or rear dial for correction. The front dial is used to horizontal correction, and the rear dial is used for vertical correction. Note that it doesn’t allow for both types of keystone compensation to be used at the same time. If you decide to change from vertical to horizontal correction, you have to reset the vertical component to 0. Frame the shot and adjust the effect in the display using the front and rear dial. Select the area to be recorded using the directions buttons (surrounding the OK button).

keystoneOLY4 — *Keystone correction screen*

The only trick is using the INFObutton to switch between keystone compensation and making adjustments to exposure compensation. In fact if you are using keystone correction often, I would program it into one of the function buttons.

Keystone Compensation mode enables keystone distortion to be corrected when shooting architecture and product photography without resorting to tilt-shift lenses or post-processing corrections in Photoshop.

Crafting Pixels

Vintage lenses, photography and digital imagery

In-camera keystone compensation (Olympus) (ii)

In-camera keystone compensation (Olympus) (i)