Alphatron EVF: The magic number for a better picture quality

The resolution of the 3.5” Retina (iPhone 4) display is 960*640 as you may know.

It is not only higher than the 800*480 resolution but is also a magic number for a better picture quality. For full HD video signals, the EVF-035W-3G will use only 960*540 pixels to match the aspect ratio of 16:9. A resolution of 960*540 is exactly half of the full HD resolution which is 1920*1080. This means that the EVF-035W-3G will have the downscaling factor of 2.0 (1920/2=960, 1080/2=540).

Resolution : 960×540 (518,400 pixels)

  • Exactly ½ of the Full HD Resolution -> Perfect downscaling factor;
  • No Vertical 1 pixel line omission (see cross hatch pattern of 1080i/60 on 800*480 resolution monitor)

 

We call it the ‘Perfect Downscaling Factor’. You can see why this is important if you look at the specification of the
competitors. Regardless of the size, all of the EVF’s (Cineroid, Zacuto and SmallHD) have the resolution of 800*480
which has a downscaling factor of 2.4 (1920/800=2.4) horizontally and 2.25 (1080/480=2.25) vertically.

When you have to downscale full HD video to match the lower resolution LCD panel, there’s a significant difference in
picture quality if the downscaling factor is an integer.

The EVF-035W-3G shows 1 out of every 2 pixels. However, if the downscaling factor is not an integer (i.e : 2.4 or 2.25),
some of the horizontal and vertical pixels cannot be reproduced in a correct way. Hence, fine details, particular those for
accurate focusing, cannot be reproduced.

Of course it’s best if you don’t need to downscale the video from the camera. But, if you have to downscale due to the
limitation of the LCD panel, it’s better to have the downscaling factor of 2 rather than 2.4 or 2.25. You can verify this
benefit simply by loading 1 pixel-width horizontal- or vertical lines in full HD resolution to the monitors or EVF’s.