MacBook – Can a MacBook Air support 2560×1600 output via HDMI using a Mini DisplayPort/Thunderbolt to HMDI adaptor

I have exactly same set up down to the MBA 2012 + Adapter and Cable.

It has been working flawlessly since.

So far I used it on 3 different TV models.

In your case I would say it is the adapter, they tend to be flaky (what do you expect for $6).

But, you can take a look in the Console and see what the "Windoserver" is doing when you plug in the cable.

If you live in the USA, go to store like Best buy or Walmart, get another adapter and try it. If it works you have your proof. If it does not just return it to the store for full refund.

You can get full resolution with mini DisplayPort to DisplayPort or mini DisplayPort to Dual-link DVI. Dual-link DVI supports up to 2560x1600 pixels resolution. DisplayPort supports that resolution or even higher.

You will not get full resolution with mini DisplayPort to DVI. DVI is limited to 1920x1200 or something similar. You usually won't get full resolution with mini DisplayPort to VGA.

I do not know whether you get full resolution with mini DisplayPort to HDMI. I think it depends upon your graphics card.

Bottom line. I would recommend using mini DisplayPort to DisplayPort.