What are the differences between the displays used in the Intel-based "Aluminum" and "White" iMac models? What is the viewable angle and the brightness of each?

When Apple introduced the original "Aluminum" iMac line on August 7, 2007, there was immediate outcry from some readers disappointed that the iMac "Core 2 Duo" 2.0 20-Inch (Al) and "Core 2 Duo" 2.4 20-Inch (Al) models had a lower-quality 6-bit "glossy" display with a reduced viewing angle compared to the 8-bit display in the 20-Inch "White" models that these systems replaced. Some disappointed customers went as far as filing suit against Apple over the issue.

Subsequently released 20-Inch and 24-Inch Aluminum iMac models use essentially the same display, but the 21.5-Inch and 27-Inch models use ones of better quality (and differing dimensions, naturally).

Identification Help

If you're not sure which Aluminum iMac you have or need to identify prior to purchase, these models can be most readily identified externally via EMC number (located inconveniently under the "foot" supporting the computer) and in software by model identifier.

These models also can be identified by their serial number using EveryMac.com's Ultimate Mac Lookup feature.

21.5-Inch & 27-Inch Aluminum iMac Display Details

The 21.5" and 27" Aluminum iMac models all have better quality displays than earlier Aluminum ones, but there has been a tiny bit of variation.

The "Late 2009" iMac models -- the iMac "Core 2 Duo" 3.06 21.5-Inch (Late 2009), "Core 2 Duo" 3.06 27-Inch (Late 2009), and "Core i5" 2.66 27-Inch (Late 2009) -- have "glossy" TFT active-matrix LED-backlit LCD displays with 1920x1080 and 2560x1440 native resolutions (21.5" and 27" respectively, 16:9). Both displays are 8-bit and use IPS (In-Plane Switching) technology, a considerable improvement for the 21.5-Inch configuration compared to the 20-Inch models replaced. However, it is worth noting that the 27" models are brighter than the 21.5" models (375 cd/m2 compared to 320 cd/m2).

The "Mid-2010" iMac models -- the iMac "Core i3" 3.06 21.5-Inch, "Core i3" 3.2 21.5-Inch, "Core i3" 3.2 27-Inch and "Core i5" 2.8 27-Inch -- have displays that are quite similar to those in the "Late 2009" line that they replaced. All are 8-bit "glossy" TFT active-matrix LED-backlit LCD displays with 1920x1080 or 2560x1440 native resolutions (16:9) and all use IPS technology too. The 27" models are even the same brightness (375 cd/m2), but the 21.5" models are slightly brighter than those replaced (330 cd/m2 compared to 320 cd/m2).

For the "Mid-2011" iMac models -- the iMac "Core i5" 2.5 21.5-Inch, "Core i5" 2.7 21.5-Inch, "Core i5" 2.7 27-Inch and "Core i5" 3.1 27-Inch -- Apple did not release official brightness information, but the company did reveal that these displays are the same size and have the same contrast ratio and viewable angle as the "Mid-2010" line. In its customary teardown iFixit confirmed that these models use the exact same displays as their predecessors, so it is safe to conclude that the brightness is the same as well.

The education-only "Late 2011" iMac model -- the iMac "Core i3" 3.1 21.5" Late 2011 -- also uses the same display as the "Mid-2011" models equipped with 21.5-Inch displays.

Display Summary Chart

Display size, brightness, contrast ratio, and viewable angle is provided on each individual iMac specs page but to make comparison easier, this information on the stock models also is provided below in a chart:

* Horizontal viewable angle/vertical viewable angle.

† These models use "glossy" displays.

‡ Please note that on August 7, 2007, Apple reported the brightness of the display in these systems in "nits" but quietly changed it a few days later to "cd/m2".

§ Apple originally reported the brightness of the display in these systems as "380 nits" but changed it a few days later to "385 cd/m2."

In the US, site sponsor Adorama sells new iMac models with free shipping. Other World Computing sells used and refurb iMac models at bargain prices with free shipping, as well. Finally, if you need to sell an iMac, A+ BBB-rated Cash for Your Mac will buy your older iMac with an instant quote and prompt payment.

In the UK, site sponsor Hoxton Macs sells used iMac models with a one-year warranty and free next day delivery throughout the UK. Delivery across Europe also is available starting at just £9.99 for two-day delivery to France and Germany.

In Australia, site sponsor Mac City likewise has a variety of used iMac models sold at low prices and available with a free warranty and fast shipping across Australia.

What does "nits" mean as a unit of brightness? How does "nits" compare to "cd/m"?

"Nits" and "cd/m2" candela per square meter, but often reported as just "cd/m" -- are both effectively identical measures of luminance. On August 7, 2007, Apple published the brightness of the displays used by the original "Aluminum" iMac Core 2 Duo models in "nits" but quietly changed this a few days later to the previously used "cd/m2" standard. For more information, please refer to the Lighting Design Glossary.