Definition
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The optimal viewing scale is determined by the highest resolution
at which an image is of excellent quality, and has no visible defects. |
Scale affects defect visibility
Wrong focus, graininess, processing artefacts can detract from an image's appeal. Viewing an image at a smaller size or scale factor, can make degradations less visible or annoying, improving the image's perceived quality. |
Quality defects reduce image clarity and fidelity
Examples of individual types of defects. The images are heavily degraded on purpose to make it obvious. In natural photos we usually find combinations of defects, which have varying degrees of visibility. In the figure below, the optimal viewing scale of the distorted images is very small.
Finding the optimal scale
Left image: a high-resolution, but overall out of focus, and low-quality image is downscaled to a lower resolution.
Middle: at the optimal viewing scale, the image shows no quality degradation, and essential image details are sharp and clear. The essential details are in the foreground, thus it is acceptable for the background to be out of focus. Right: further downsizing does not improve the quality of the image. |
At the optimal viewing scale:
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In the examples below ...
Each row shows crops taken from the same source image. Each crop is extracted after previously downscaling the source image by a different amount. You can often notice strong degradations at the original size (left-most), whereas the lowest resolution is of excellent quality (right-most image). The OPTIMAL SCALE is often somewhere in between. Note: it is best to view each image as is, do not click to enlarge. |
Artistic intentThe optimal scale of the image on the left is 100%. Even though there are many out-of-focus areas, these are used for improving the feeling of depth. This effect is often encountered in macro-photography (close-ups). The focus is correct, as the frontal plane is in focus, this includes the droplets and flower petals nearest to the camera.
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Participating in the experimentYou will annotate images using a browser-based interface, called Zovi. This allows browsing a collection of images, zooming to select the optimal scale for each, and saving the selection.
Zovi UI controls
Zoom: use the zoom slider at the top of the screen Pan: click and drag the image Next image: press the green arrow button or the right arrow key. |
Steps to complete the work
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2. Select the optimal scale
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It takes about 15 seconds to find the optimal scale/zoom for each image.
Thank you for participating in our study!
Thank you for participating in our study!