[teknopaul]

"This is nuts: it’s akin to saying that the milli- prefix should have different meanings depending on whether we’re talking about meters or liters."

Were were here recently with "mega": Sometimes mega is squared as in megapixels. Sometime not as in megabytes.

No biggie.

Db in audio is a relative scale and that makes perfect sense. If you mixer goes + or - 6db that makes sense but can't be measured as power, your mixer might not be plugged in to any speakers so relation to real power is moot in the digital realm.

3 eq bands with -+6db makes sense too. Doesn't need to be precisly specified to be of immediate value, +-12db is clearly something else and users know what.

[StableAlkyne]

> Sometimes mega is squared as in megapixels. Sometime not as in megabytes.

Even worse is Mega in Megabytes could be 1,000,000 or 1,048,576 and it's more or less up to you to know what's what

(Yeah, there are formally megabytes/mebiibytes/MiB/MB, but I honestly cannot recall the last time I heard anyone use anything other than just "megabyte" for 2^20 bytes... Or even wanted to refer to exactly 1,000,000 bytes. Other than decades ago when disk manufacturers wanted to make their hardware seem higher capacity than it really was)

[klysm]

I see MiB in usage a lot and I always make the distinction myself

[BlueTemplar]

Wait, when did they stop ?!

[strbean]

I think the biggest issue by far is that many of the different contextual uses for dB are all in the same domain, or very close.

When you're talking about the loudness of sound, in the same exact context you might care about SPL, perceived loudness, AND gain.

If it was just a matter of "in electrical engineering / physics, dB implies this unit + baseline, when dealing with acoustics, it implies this other unit + baseline", it would be less problematic.

[jameshart]

Megapixels aren’t ‘squared’ though?

Ah, unless you’re trying to make ‘pixels’ the same unit as in ‘pixels per inch’…

The problem there isn’t how ‘mega’ is applied but how ‘pixel’ means both an area pixel as well as the linear size of a pixel.

[perching_aix]

> Sometimes mega is squared as in megapixels.

Is that right? A pixel is a 2D object already. It's not like e.g. with centimeters, where it's a 1D unit, so it becomes centimeters squared to form a 2D unit.

[davrosthedalek]

it's (cm)^2, not c(m^2). If there would be the one-dimensional equivalent to pixels, say pix, then 1pixel = 1pix^2, and then 1 megapixel = (kpix)^2

[perching_aix]

After putting significantly more effort than perhaps socially acceptable into this, I completely agree so far, but I'm still horribly confused about GP's point about "mega" being a "squared unit in megapixels".

That to me implies that "mega" in "megapixels" is a planar ("[pre?-]squared") scaling factor, but it's... not really? Are those even a thing?

I think this is what the debate is about at least. Mega does line up with kilo squared, but that's not because mega becomes a planar scaling factor, but because it just so happens that 1000 times 1000 is 1 million. It's kind of a coincidence? Like it's literally 1 million pixels, that's what's being meant. Just like with cm squared, the ohhhhhhhhhhhhhhhhhhhhhhhhh

[davrosthedalek]

I believe the point is that in "centimeters squared" you also square the cm. So it's 1/100 of a meter, then squared. While the mega in megapixels applies to the area. So presumably there are two length multiplied to be a pixel, and then you have a million of those.

I don't think it's a very deep point, and I would say the mega is not squared, but the centi is squared.

[perching_aix]

What finally clicked it into place for me was trying to perform a unit conversion. It's kind of annoying cause we don't really use mega with anything squared usually (I don't recall anything at the moment at least), which added to the confusion.

When one converts from square kilometers (km2) to square meters (m2), one needs to undo the kilo (x1000) not once, but twice, accounting for both dimensions. So as you say, it's actually here where the scaling factor is secretly squared, it's k2, just not written out. Hence despite kilo being a 1000x bump, you need to divide by 1 million, because it's actually squared in kilometers squared.

So if mega in megapixels was behaving "normally", that would imply similar semantics, so to convert into kilopixels, you'd divide by 1000 not just once, but twice. But no, 1 megapixels is 1000 kilopixels. I guess the idea is that instead of being "secretly" squared it's "explicitly" already "square" as a result? So instead of resolving to mega2 pixels2, it's just mega pixels, since pixels is 2D, and so squaring it is unnecessary.

I think I get it now at least, but yeah, I agree with your sentiment. It actually reminds me, when I first learned converting between units of area in primary school, I had quite the troubles with wrapping my head around it exactly because of this.

[davrosthedalek]

Yes, and I think it just depends where how you read the square. For cm^2, we mean that we square a centimeter, not that we have a centi of a meter^2. But a hectare is really a hect of ares, so 100 ares. Here the square "is baked in" into what comes after the modifier.