Oly 75 1.8 Why?

Started Aug 5, 2012 | Discussions thread
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Re: partially incorrect
In reply to Harold66, Aug 6, 2012

Harold66 wrote:

t. Thus, a lens like the 75/1.8 is quite important and helpful because its combination of longer FL and fast aperture maximizes DOF control within the m4/3 system.

For the record the somewhat longer focal length of 150mm over 135 has NO influence on the DOF for a given sensor/film format and focusing distance

You've mis-understood. The comparison isn't between the "somewhat longer focal length of 150mm over 135mm", but rather between the Oly 45/1.8 (90mm equiv) and 75/1.8 (150mm equiv).

First of all, 75mm is not just a "somewhat longer focal length" than 45mm. Secondly, the difference in focal length does have a considerable influence on DOF. The Oly 45/1.8 focused at 10ft at f/1.8 yields a DOF of 0.79 ft, while the Oly 75/1.8 focused at 10ft at f/1.8 yields a DOF of 0.28 ft.

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