http://www.amazon.com/ASUS-PQ321Q-31-5-Inch-4K-Monitor/dp/B00DJ4BIKA
I’ve found that one which says 140ppi, but it’s a huge monitor. I’d imagine if you scale that down to 22” or so it’ll be much higher dpi. I’m not sure any that small are out quite yet to really know, but they should be coming soon.
The Mac Laptop monitor has 326 ppi and is said to be superb for processing and editing photograph
the rumors are that apple wont make stand alone monitors with that much resolution due to cost constraints but I think theyre waiting for market demand quite franklu
From my favorite photography web site ,,and forum
The big news, of course, is the so-called Retina display. Let’s be clear that “Retina” is simply an Apple marketing term not a standard of any sort. It means a screen (be it on an IPhone, an iPad, or now a Macbook Pro, in which the resolution is so high that the individual dots (screen pixels) are so fine that they are invisible to the human eye. If you are working with a normal screen at the moment, look closely at these letters. If you’ve good eyesight you can just see that each letter is made up of separate elements. They’re very fine, but they can be seen. On the Retina display they’re not just invisible, but the letters on the screen look as if they were printed, they are that sharp.
The screen has a resolution of 2880X1800 pixels. A typical 15” laptop screen is 1440X900. This high pixel count leads to a screen resolution of 220 PPI. This is close to a high quality photo printer’s resolution.
http://www.luminous-landscape.com/reviews/accessories/macbook_pro_retina.shtml