PanGazer logo PanGazer – zoom level

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The zoom level (magnification factor) of a view is shown by PanGazer as a percentage, where 100% zoom means that each pel (pixel) in the original image is represented by one pel on-screen.  200% means that each pel in the original image has been extrapolated to 2×2 pels on-screen, and similarly 50% means that each pel on screen represents 2×2 pels of the original image.

PanGazer lets you change the zoom level within a wide range; however that range is necessarily constrained by the window size and shape and by the image type and dimensions.

For a given window and image:

  • Minimum zoom is the smallest zoom level available (that is, the most ‘zoomed out’).
    This is not a specific percentage because image dimensions vary; instead:

    For a spherical image the minimum zoom will normally correspond to a 10mm equivalent focal length lens (130 diagonal angle of view – typical human medium-peripheral angle).

    For other images the window will be filled at minimum zoom.

  • Default zoom is the default for the image, which will be derived from image metadata if possible (that is, the zoom level chosen by the photographer or saved by PanGazer, etc.).
    In the common case when there is no zoom level in the metadata:

    For a spherical image the default will normally correspond to a 44mm equivalent focal length lens (54 diagonal angle of view – typical human angle of attention).

    For other images the window will be filled, as for minimum zoom.

  • 100% zoom is the zoom level where the pel (pixel) ratio will be 100% (that is, each pel in the original image is represented by one pel on-screen, as described above).

  • Maximum zoom is the zoom level where the pel (pixel) ratio will be 200%.  This allows a useful enlargement over 100% zoom without excessive blurring.

 
Notes:

  1. When viewing images using ‘Full screen’, borders may appear around a non-spherical image when, even at maximum zoom, the image is lower resolution than the screen.

  2. For spherical images, pel size is calculated from the number of pels in the image at the horizon.

PanGazer and these web pages were written by Mike Cowlishaw; Please send me any corrections, suggestions, etc.
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This page was last updated on 2021-08-03 by mfc.