New iMac screens - Pixel density considerations

The new value machines amongst the new iMacs are the Core 2 Duo 21.5" models unless you want a fast GPU. They are quite a bit smaller than the 27-inchers, but they can be more ergonomic, they are still full 1080p HD resolution, and just as importantly they have a much larger pixel size than the 27" models. The larger pixel size can be a significant advantage for a desktop, especially for an OS like Snow Leopard which is not resolution independent. In order of increasing pixel density (or smaller pixel size):

15" G4 iMac: 1024 / 12" = 85 ppi
24" iMac: 1920 / 20.4" = 94 ppi
20" iMac: 1680 / 17.1" = 98 ppi
17" iMac: 1440 / 14.4" = 100 ppi
21.5": 1920 / 18.7" = 102 ppi
27": 2560 / 23.5" = 109 ppi
13" MacBook Pro: 1280 / 11.3" = 113 ppi
12" G4 iBook: 1024 / 9" = 114 ppi

As I no longer have the eyes of a teenager, my favourite desktop pixel density for web surfing in Safari is somewhere around 90-100 pixels per inch (ppi). That includes the 20" and 24" iMacs, with the 21.5" coming in very close at 102 ppi. I had a chance to check out the 21.5" and 27" iMacs in person and I found the 21.5" more pleasant for general surfing than the 27" at normal desktop seating distances, at least with Safari. While it's true the 27" is still a lower pixel density than the laptops, people generally sit closer to laptop screens so the higher pixel density is less problematic for laptops than desktops. Luckily, while this is a problem for Safari, it's not as much of a problem with Mozilla Firefox, since Firefox is more easily adjustable. The 27" iMac might just be enough to push to me to Firefox as my primary web browser on the Mac.

We can only hope that the new 27" screen is a hint to full resolution independence to come in OS X 10.7.

Best 27" bang for the buck is the Quad

Despite some expectations, the dual-core iMacs may not actually be the best value in the 27" iMac line.

The price advantage of the Core 2 Duo 27" iMacs is in large part due to the much lower end AMD Radeon 4670 GPU option in those machines. However, the Radeon 4850 is roughly twice as fast, helpful with applications like gaming, Aperture, and Final Cut Studio, as well as OS X features like OpenCL°. If you want to take advantage of that GPU power boost from the Radeon 4850, then the price comparison becomes very interesting.

3.06 GHz Core 2 Duo - US$1849 / CAD$1964
3.33 GHz Core 2 Duo - US$2049 / CAD$2184
2.66 GHz Core i5 Quad - US$1999 / CAD$2099
2.80 GHz Core i7 Quad - US$2199 / CAD$2319

Out of that group, the Core i5 quad-core machine is the best deal. In fact, it's even cheaper than the 3.33 GHz dual-core model (which I suppose might make sense, since the 3.33 GHz Core 2 Duo CPU is actually significantly more expensive than the 2.66 GHz Core i5 CPU). While 2.66 GHz doesn't seem that fast, Hz for Hz, Core i5 is faster, and there are four cores too. Furthermore, in dual-core mode, Core i5 can ramp up to as high as 3.2 GHz using Turbo Boost.


But bang for the buck be damned. I've ordered the Core i7 quad-core iMac. It will be nice having eight logical cores (!) in my iMac, even if only for bragging rights.


°Both the Radeon 4670 and 4850 support OpenCL, but the 4850 will be faster. Apple Canada and Apple UK (among other international Apple pages) erroneously do not list the Radeon 4670 as supporting OpenCL.


However, Apple USA has recently updated its OS X tech specs page to include the 4670.