Aperture - Equivalence or Equivalency?

I would phrase it differently: Equivalence isn't about making photos that look the same; rather, it's about the settings on different formats that result in photos where certain important visual qualities (perspective, framing, DOF, and motion blur) are all the same. From there, we can see if one format or the other offers advantages with regards to these (and other) properties that are preferable for our photography, with regards to equipment choices. Obviously, if one system can get us a better photo than another system can by not using Equivalent settings, we would certainly do so.

That's not exposure. Exposure is what the lens projects toward the sensor. Much of that light never gets detected.

That's a fair distinction to make, especially when comparing newer cameras to older cameras. For example, let's say we shot the same scene with the ["ancient"] Canon 5D and the modern Canon R5 at f/4 1/400, both using the same lens. The exposure will be the same for both, but the recorded exposure will be twice as high for the R5, as the more modern sensor records twice as much light projected on it as the older 5D.

turn up DRO on sony or shoot slog 3 and its a total different ball game to expressing lightness.

Wow! That TOP article really hit a nerve!

I did not expect it to be taken so seriously; it seemed to me to be largely satirical and very much his personal opinion (as is most of TOP's content), not something to get worked up over.

No, the article was not "largely satirical", not by a long shot:

This will probably annoy a few people, but I'm sorry, I think it's true, even if it's not true of you. I personally think the equivalent aperture fallacy mainly exists because it relates to status and prestige. It's usefulness for many (not all) of those who promulgate it is in asserting that one can achieve shallower DoF with a "full-frame" (FF) camera than others can using smaller-sensor cameras even if the latter have the same speed or slightly faster lenses. ("My FF ƒ/1.4 lens is better than your Micro 4/3 ƒ/1.2 lens.") At root it's a way of showing off a claimant's ownership of expensive equipment, and there's not really much more to it than that.

That is absolutely not sarcasm, nor is anything else in the article.

Another article from the TOP website was cited over on DPR which has sparked up the weekly equivalence debate:
www.dpreview.com/forums/post/67647242

Quite entertaining. Jim Sterling and I have been batting it back and surprisingly, the thread hasn't been locked, yet!

I'm afraid I'm confused -- Tom Caldwell has assured me numerous times that everyone already understands Equivalence (therefore, I don't need to keep posting "corrections" to misunderstandings and misrepresentations, even sandboxing me to save me the trouble), yet the article makes the claim:

3. Focal Lengths Have Equivalents, Apertures Don't
...
What is not correct is to claim that this ƒ/1.7 lens is the equivalent of a full-frame 150mm ƒ/3.5 lens! There is a technical term for that—"utter nonsense."

So, is Ctein being "sarcastic" again? 😁

By the way, you quoted a great rebuttal in your reply!

Well, I am glad to find support from those who are well versed, and often go back to your excellent essay to obtain good source material!

As for the m4/3 forum, it is one long conga-line of equivalence denialists.

Here's another recent thread that went right off the rails:
www.dpreview.com/forums/post/67644821

The attacks on Hogan are more amusing. I never see threads started to attack him on the Nikon forums. He goes down very hard on Nikon regularly.

I do not get, or maybe I do, this brand loyalty, that we see on many forums. When I felt Nikon were slipping downhill with the quality of their products, I had no problems switching to Olympus/Panasonic, using the best bits of both brands. One gets sucked into the fanboy syndrome a bit, but when I picked up a Nikon Z7, I had no problems trading in my M43 gear. I get upset too when some fanboy who uses another brand tells me that what I am using is junk.

Equivalence denial is just a symptom. The real problem is that a vocal group M43 users on that forum have an inferiority complex regarding the gear they use, and feel their choices need defending against the "big boys".

It might just be better to post pictures showing that you can take great pictures with that still very valid system

Yes, the level of defensiveness there is quite extreme.

You're right of course. And I do that (post photos) over on L-mount-forum.com. I don't post photos on the m4/3 forum because if they are not birds in flight taken with an OM camera, there is nil interest.

I just haven't quite weaned myself off the m4/3 forum because it's a circus and I can't help but reply. I expect that it will be forced soon when I join the ranks of those who have been banned.

The DPR M43 forum is the Crack Cocaine of photo forums. It became a habit when I used M43, and then posted on the weekly thread. There is a small vocal group who turn the place into an entertaining circus of the absurd. It is difficult not to reply to the idiocy that gets posted in certain threads. Yes, facts get you banned by the surly ringmasters who love to crack the whip against facts. I tried not to got involved, but sometimes it was just to much, and then the inevitable ban arrived.

But it is easy to get sucked into this stuff. It was not until I picked up a demo Z7, and actually shot some frames with it, that I understood that M43 is not the wonder solution that some people claim it to be. This thread that I copied to my Blog got me banned. I thought it was pretty balanced, explaining the advantages of both systems.