I just got a Canon G1X Mark II as a replacement for a broken Canon G12 and was moderately happy about it, until I started to use it for pretty much the same thing I did before: HDR via Auto Exposure Bracketing, using default settings and high resolution. However, not a single one set of three pictures I captured could be aligned using Luminance HDR, which is the (free) software I use for this. I tried to change the image ratio to 4:3, take pictures from far away, but there seems to possible solution. As a matter of fact, some pictures seem a bit displaced, while others, like this one Do not in fact seem to have an alignment problem. Any idea of what can have happened here?
Here are a few things about expecting your camera to auto align shots taken with the camera handheld:
- Different types of motion in different directions or on different axes do not all have the same effect on an image. Particularly, changes in subject distance or lateral movements affect the perspective of the image. Changes in perspective of 3D scenes require vastly more computational power and correction than changes that only affect the angular aim of the camera while shooting from the same optical position.
- Different cameras have different designs for how optical image stabilization is done. Lens based IS can deal most effectively with changes in the camera's point of aim from the same optical position, but can't correct at all for lateral or rotational movements. Sensor based IS can deal with lateral and rotational movements around the lens' optical axis, but don't do as well with changes to the camera's point of aim for longer focal lengths.
- Software alignment tools can easily correct for rotational movements around the optical axis of the lens as well as for changes to the angle of the point of aim, but changes in perspective caused by lateral movements or movements towards or away from the scene are much more difficult to correct, as the perspective is different for each of the bracketed frames.
- At wider angles, zoom lenses often demonstrate enough geometric distortion to make even changes in the precise point of aim that don't change the perspective difficult to align without resorting to distortion correction.
- Ergonomic differences between two cameras may affect how the same basic movements by the hands holding them will affect the alignment of the lens with the scene. This can particularly be the case with cameras where the lens is not placed near the center of the front of the camera.
There's really no substitute that works as well as insuring that all of the images in a bracketed exposure are shot from the same exact position with the camera pointed in the exact same direction. In other words: there's no substitute for a tripod or other stable mount for a camera. IS and auto alignment may often come close, but they'll never be as exact as when the camera is immobilized for the entire series of frames.