Why does the Canon 1D Mark III cost more than the 1D Mark IV?

Question

Why does the Canon 1D Mark III cost more than the 1D Mark IV ? According to snapsort it looks like the Mark IV is better.

Mark 3: $7995 http://www.amazon.com/Canon-1D-Mark-III-Digital/dp/B000NP1C5O/

Mark 4: $5399 http://www.amazon.com/Canon-EOS-1D-Mark-IV/dp/B002TG3ZYQ/

And also on Canon's website:

Answer

The EOS 1Ds Mark III is Canon's top-of-the-line full-frame DSLR: 21MP; 45 AF points; dual DIGIC III processors.

The EOS 1D Mark IV (that's 1D, not 1Ds) uses a 28.1 × 18.7mm sensor which is smaller than a 36 x 24mm full-frame, but bigger than the 22.3 × 14.9 mm sensor in the Rebel, 60D, 7D, etc.

The main tradeoff with the 1D Mark IV vs. the 1Ds is that you get a slightly lower image quality but continuous 10 fps shooting vs. only 5 fps on the 1Ds.

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What is EOS iTR AF?

Question

I have read references to this feature on some Canon DSLR cameras and am wondering what benefits or uses it has.

Answer

Canon has introduced a new feature coined EOS iTR AF - Intelligent Tracking and Recognition Auto Focus on the Canon EOS-1D X DSLR.

The camera attempts to detect the locations of faces and focus on these in the scene or alternatively it can identify subjects of a particular color such as in sporting events for example. Face detection is given the highest priority, but if this lock fails it will fall back to looking for the color information.

The default AF mode for the EOS-1D X uses phase detection AF information, but the secondary option uses the face and color detection of the iTR AF. This feature is achieved by using information from the RGB metering sensor as part of the AF system.

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