"Equivalence" demonstrated: Canon 5D and Panasonic GX1

Started Apr 27, 2013 | Discussions thread
Great Bustard Forum Pro • Posts: 38,511
Re: "Equivalence" is not "Equivalence" - try a new terminology.

pavinder wrote:

Great Bustard wrote:

I asked earlier today:


In terms of the visual properties of the final photo, what parameters do you think are "more equivalent" than the parameters I have used [photos with the same perspective, framing, DOF, shutter speed, and display size]?

From where I sit, I find it ironic that so many would be happy to define "Equivalent" as photos with the same AOV and exposure, despite the fact that they would have rather different visual properties.

What do you think?

Personally I think one needs to choose between

a) visual properties (DOF, framing, bokeh, etc), and

b) technical properties (noise, camera settings, quantum stuff).

I tend to agree.

Shutter speed is a technical point.

I disagree -- it pertains to motion blur which is a visual property.  For sure, if there is no motion in the scene it is irrelevant, but it's relevant more often than it isn't, methinks.

The same applies to DOF -- if the whole of the scene is within the DOF at any aperture (astrophotography, for example), then DOF is irrelevant.  However, DOF matters more often than it doesn't.

As are focal length, aperture, ISO.


One can look at two photos, compare them aesthetically and declare them "visually equivalent" without ever needing to know the shutter speed or focal length etc.

Again, motion blur.

In any case to me it makes little sense to define some visual properties as important and relegate others as not important to the discussion.

Well, Equivalence doesn't do that.  It talks about visual properties that can be made equal, regardless of the system, and then adds in:


If the sensors are equally efficient, this will result in the same total noise.  If the mFT (4/3) lens is twice as sharp as the FF lens, and the 1.6x lens is 1.6x as sharp as the FF lens, the sensors have the same pixel count and AA filter, then all will capture the same detail.

Of course, with more stipulations, you can add in more visual properties.  However, there is a significant difference between "equivalent" and "equal".

But if the discussion is kept to aesthetic vs technical then it becomes much easier.

I kinda think that's exactly what Equivalence, as defined, does.

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