"Equivalence" demonstrated: Canon 5D and Panasonic GX1

Started Apr 27, 2013 | Discussions thread
Great Bustard
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Re: "Equivalence" is not "Equivalence" - try a new terminology.
In reply to pavinder, Apr 29, 2013

pavinder wrote:

Great Bustard wrote:

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.

I absolutely agree that shutter speed, aperture etc. are critical in affecting the visual properties of an image - that's why we shoose them accordingly.

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.

Maybe I wasn't clear with my point - that yes, shutter speed affects the visual properties such as motion blur on a moving subject.
Similarly with a static subject, shutter speed is irrelevant.  1/15 at f22 vs. 1/125 at f8 - here the aperture is what makes the difference in terms of DOF.

But I can nevertheless look at and compare two photos taken with different cameras at different settings and say they are "visually equivalent" without needing to know what actual shutter speed/aperture/etc was used in each photo.  I can still say they look the same because they have the same framing, perspective, lightness, DOF, blur etc. without needing to know any of the numbers.

What I'm saying, however, is that if there is "enough" motion in the scene, and the shutter speeds are not the same for both systems, there will be a noticeable difference between the photos.  This is why shutter speed is one of the five parameters of Equivalence as I've defined it.

No, not all scenes have "enough" motion where shutter speed matters, just as, no, not all scenes have "enough" DOF where aperture matters.  But, if DOF is to be considered a visual element that should be equal for Equivalent photos, then so should shutter speed.

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:

http://www.josephjamesphotography.com/equivalence/#equivalence

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.

...which is why I suggested using two different terms to avoid people confusing things.

It's like arguing the question "What is Art?".  People have their own interpretations.  Some say only painting and sculpture are Art.  Others include photography and video.  Others allow installations as Art.  And there are also people who do things like cook food in a gallery and call it "Art".

But if we at least agree on "this work is a painting", "this is an installation", "this is a performance" etc. then we are much closer to finding out why we might disagree on the question of "is this thing we're looking at a work of Art?".

Similarly to say "these 2 photos are visually equivalent but not technically equivalent" is far more helpful than to just argue about whether they are "equivalent" under some all-encompassing definition.

So, what are your parameters for "visually equivalent" and what are your parameters for "technically equivalent"?  I mean, next thing we know we're going to be talking all sorts of "equivalences" for size, weight, price, AF speed/accuracy, build, etc., etc., etc.

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