Margin of error with fast glass (pic)

Started Aug 21, 2008 | Discussions thread
VRII Senior Member • Posts: 2,529
Re: Margin of error with fast glass (pic)

If by "Margin Of Error" you are referring to razor thin DOF, then it's very misleading to attribute it only to "fast glass" which I guess you mean wide open F/stop.

In this example you really pushed the limits on the 4 factors which affect DOF, the F/stop is only 25% responsible.

1-) Long Lens (180mm)

2-) Wide Open ( F/2.8)

3-) Close focusing distance to the subject ( 6 ft)

4-) Full Frame Sensor

So the margin of error IS NOT only the fast glass, even at F/8 you would still have a very shallow DOF all other items being equal.

This is the problem that many amateurs encounter by reading these forums and salivating over fast glass because they think that it is "the only thing" that has an effect on thin DOF, whcih I think is one of the most misunderstood / misexplained factors of photography.

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