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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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Since 2006, Diglloyd Advanced Photography is the authoritative review and reference for DSLRs and their lenses: Canon and Nikon primarily, but also Pentax and some medium format. Reviews of key DSLRs are included, but the primary focus is on lens performance. Also included is a wealth of technique and workflow approaches.

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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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