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Focus Accuracy

The A900 frequently front-focused with the ZA 135mm f/1.8 Sonnar on multiple A/B comparisons/trials, making focus bracketing a necessity, not the easiest task with a 135mm lens at f/1.8, using its AF-optimized focusing in manual mode (less precision than with an mechanical helicoid). Focus shift was checked at close range on the 135mm f/1.8 Sonnar, and found to be absent.

Making a valid comparison between the A900 and Canon 1Ds Mark III proved challenging—

The lack of Live View on the A900 made accurate focus tedious to achieve. The A900’s standard focusing screen is usable but not designed for “pop in pop out” manual focus. Sony does offer an alternative screen which is likely to be better for manual focusing.

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focus focus 
With ZA 135mm f/1.8 Sonnar @ f/1.8: 9/9 autofocus front-focus.

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