What is equivalence good for?

Started Jul 25, 2014 | Discussions thread
Great Bustard Forum Pro • Posts: 42,228
Teach correctly from the get-go.

cainn24 wrote:

mostlyboringphotog wrote:

I am presenting my case that rather than telling the confused person that f/2 is equivalent to f/4, when he puts on the 4/3 f/2 lens on FF (do you see where I'm going with this?)...

Where do you get the idea that equivalence has any practical relevance to someone who is only concerned about the performance of a single system with respect to itself?

Teach beginners the good old exposure triangle. Teach them equivalence when they start asking questions about relative performance across formats.

That's a pretty simple, pretty reasonable strategy, wouldn't you say? And if you agree that it is, can you explain to me who you are actually arguing with, and what you are actually arguing about?

When a beginner reaches the stage where knowing about f-ratios, shutter speeds, and ISO settings are important (that is, a "real beginner" should start out in Auto Mode and Auto ISO), then teach them correctly from the start.

Teach them that higher f-ratios result in more narrow apertures, and that more narrow apertures result in a deeper DOF as well as less light falling on the sensor (and thus more noise) all else equal.

Teach them that faster shutter speeds result in less motion blur as well as less light falling on the sensor (and thus more noise) all else equal.

Teach them that the ISO control is used simply to get the desired brightness for the photo.  Higher ISO settings give an indication of the noise in a photo by informing you about the relative amount of light falling on the sensor.

When they are interested in comparing to other formats, explain that the same f-ratio results in different aperture diameters on different formats for a given AOV, resulting in a different DOF and a different amount of light falling on the sensor.


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