SURVEY - Do FT / mFT users know the difference from "full frame"? Replies wanted!!

Started Apr 26, 2013 | Discussions thread
Great Bustard Forum Pro • Posts: 39,708
Re: OK, I've read Great Bustard's "Equivalence FAQ"

JosephScha wrote:

Its URL was given in a previous post in this thread.  (It was posted on the Olympus forum, under a previous user name for the same person)

I am now enlightened.

As he clearly defines it, "Equivalent images are simply images which have the same perspective, framing, DOF, shutter speed and display dimensions."


and "Fully equivalent images will be made from the same total amount of light.  ... the noise will be the same for equivalent images...

For equally efficient sensors.

...but not for the same exposure."

Correct, where the exposure is the density of the light falling on the sensor as opposed to the total amount of light falling on the sensor:

So, that is clear.  Now, it is up to each of us to decide whether this is worth our time to think about.

Equivalence is only relevant if you are comparing different formats.  If you are working within a format, there's no reason to invoke Equivalence.

Clearly, I was thinking about 50mm lens on FF and 25mm lens on 4/3 to span the same angle, but that is not what he's aiming at.

But it is part of it.

I was aiming at having equally bright images - I would say equal exposures, but then we'd have to argue about that - which would require the same f stop at the same shutter speed and ISO.

See gollywop's outstanding article on this point:

The images would have different noise.

And different DOF.

So, now that I understand that equivalent images on same efficiency sensors will have the same noise but not the same exposure...

Yes.'s clear that I was not talking about the same thing at all.

I am very sure that whatever you call the concept I'm thinking of it is useful to me.  I'll work on understanding how equivalence as defined in the FAQ is useful to me.

This post in the mFT forum, which is a more up-to-date version of the Equivalence FAQ you read, was received well:

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