所以發現很多時候用 2x 的圖片就夠了？：「Capping image fidelity on ultra-high resolution devices」。
會這樣討論主要是發現螢幕特性：
The most modern screens are OLED. These screens boast some really great features like pure blacks, and are marketed as 3x scale. However, nearly no "3x scale" OLED actually has perfect 3x3 pixels per dot on their screen.
因為螢幕不是真的到 3x 的要求，丟 2x 的圖片出去就好，省頻寬又省下載時間：
This means that most OLED screens that say they are 3x resolution, are actually 3x in the green color, but only 1.5x in the red and blue colors. Showing a 3x resolution image in the app vs a 2x resolution image will be visually the same, though the 3x image takes significantly more data. Even true 3x resolution screens are wasteful as the human eye cannot see that level of detail without something like a magnifying glass.
省下 38% 的資料量，32% 的時間：
There's no difference that the human eye can see, but will save 38% on data and 32% on latency on the capped image load for this particular example which is reflective of most images that load on Twitter.
這也另外帶出了其他的想法，如果沒有太多時間研究的話，可以考慮先提供 2x 的就好，不需要特地做 3x 的版本...
