When I think of my 12, F2, 17, 25 and 45mm 1.8 , they all seem both smaller and lighter than this 35mm by some margin?

'Course once you start factoring in actual performance, build & features, the resolution of the body behind the lens, subjective preferences over rendering, etc. then it's a whole other ball of wax. But when it comes to UWA thru normal there's plenty of similarly sized lenses across various formats, at least if you're really paying attention to what's available across different mounts.

If you take construction into account the 24 F2.8 is plastic, so unsurprisingly it’s going to be light, and it’s slower optically at 2.8. But I do take your point about size and weight in general overal.

A further thought, the size and weight issue argued on the basis of equivalence can be misleading.
Take the Olympus 17mm F1.2 Pro and the Panasonic 35mm F1.8. If you mounted the Panasonic on a M4/3 camera you would have a 70mm lens with a equivalent DoF of F3.6, the Ilympus of course would be 34mm F1.2 .
I’m betting that the you can’t get a 12 Mm F2 in FF that weighs as little as the Olympus or is as small.
Yes I know the equivalence argument , but when. You look at what the lens is in its self, and use that as a comparison FF either don’t exist or they are larger.

" Take the Olympus 17mm F1.2 Pro and the Panasonic 35mm F1.8. If you mounted the Panasonic on a M4/3 camera you would have a 70mm lens with a equivalent DoF of F3.6, the Ilympus of course would be 34mm F1.2 . "

If that's what you think, there's some serious flaws in your understanding of equivalence, no offense. The Pana lens if it could be mounted on a M4/3 camera would act as the equivalent of a FF 70/3.6, just like the Oly 17/1.2 is acting as the FF equivalent of a very pricey very beefy 34/2.4.

Equivalence doesn't work any differently with one lens vs another, you're just not using the full image circle with certain lenses on certain formats.

You can in fact get cheaper/faster wides on FF than what's available for M4/3 (and I own that 12/2 BTW, and the 17/1.2 too tho it'll be sold in the near future), often without any significant size sacrifice. One of the examples with the most direct equivalence is the Sony 20/1.8 G vs the Voigtlander 10.5/0.95.

^ One of those two is sharper wide open, slightly cheaper, better corrected, lighter, and AF to boot... Guess which. The 12/2 is equivalent to a 24/4, so the 24/2.8 G is in effect a stop faster (tho it's making more heavy use of software corrections to get there, OTOH it's whether sealed and several hundred dollars less than the Oly).

M4/3 can have a size advantage with various teles (35-100, 75/1.8, longer zooms) and a couple other zooms (14-140, 12-32, 9-18) for which there's just nothing remotely comparable size wise, and of course with body size/variety if you actually opt for some of the smallest available, but with UWA thru normal primes any advantage has largely evaporated.

I'm keeping my 12/2 BTW, probably the only M4/3 lens with a pretty decent resale value that I won't be using much and still decided to keep, cause for video it's still pretty tough to beat Oly IBIS. Okay but stable video beats high IQ shakycam...

^ One of those two is sharper wide open, slightly cheaper, better corrected, lighter, and AF to boot... Guess which. The 12/2 is equivalent to a 24/4, so the 24/2.8 G is in effect a stop faster (tho it's making more heavy use of software corrections to get there, OTOH it's whether sealed and several hundred dollars less than the Oly).

M4/3 can have a size advantage with various teles (35-100, 75/1.8, longer zooms) and a couple other zooms (14-140, 12-32, 9-18) for which there's just nothing remotely comparable size wise, and of course with body size/variety if you actually opt for some of the smallest available, but with UWA thru normal primes any advantage has largely evaporated.

I'm keeping my 12/2 BTW, probably the only M4/3 lens with a pretty decent resale value that I won't be using much and still decided to keep, cause for video it's still pretty tough to beat M4/3 IBIS. Okay but stable video beats high IQ shakycam...

I thought the F stop was an optical function? The 12 mm F2 is exactly that in terms of light gathering, only when used on m4/3 the crop effect is to multiply the focal length by 2 & the DoF looks like F 4.
The voightlander is a lump, metal and is manual, so size and weight will be different to an AF lens.
I’m not disagreeing about equivalence , I am saying equivalence is based on a sensor differences .
Now I have not scoured the lens line up of every format , but I have not seen an actual 17mm focal length at F1.2, or F1.8, or a 12mm F1.4 or F2 in FF. that costs & weighs less or about the same in comparable quality. In terms of size weight comparisons based on actual Focal Lenght and max Aperture the m4/3 are smaller

Yeah f-stop just describes a ratio, f2 is f2 when it comes to exposure but total light gathered is still dependent on sensor size (you've got that right I think but are somehow jumbling it when it comes to looking at lenses), so equivalency isn't simply about DoF - it applies to everything.

Thus a FF f2 lens will behave the same as an f2 M4/3 lens on the same sensor size... Why would you then conclude the FF lens is equivalent to x2 the f-stop when used on a M4/3 camera but not the M4/3 lens?

If anything wider/brighter designs are somewhat more challenging to execute on the smaller sensor, hence the price of the 12/2 & PL12 when FF 24/1.8 lenses are often much much cheaper. If you shoot a FF 24/1.8 on a FF body it'll end up with the same noise as a M4/3 12/0.9 lens would on a M4/3 body, given the same exposure.

All else being equal... ISO 200 on M4/3 should look like ISO 800 on FF, etc.

If anything the Voigtlander being manual should give it an advantage since it frees up some parts of the design, but that's countered by the metal build to an extent and more broadly by how challenging designs that wide/bright are on smaller formats.

Take the Laowa 14/4 and the 7.5/2, the 1mm equivalent FL difference aside they're pretty much directly equivalent and just about the same size, both are manual, the FF one is a little heavier but on their respective sensors they'd produce similar looking images and cost pretty much the same.

The faster wides and UWAs on larger formats simply end up offering a wider performance envelope, you can take something like their 12/2.8 or 15/2 and end up with more total light gathered (thus a less noisy image), or stick with the smaller slower options.

So we agree the speed of the lens is just a ratio and has nothing to do with the sensor ?
The DoF also not dependent on sensor size , it is dependent on the size of the aperture and the distance from the subject .
There really is no issue unless you create one. I don’t even try to recreate a FF equivalency in my head when shooting M4/3, if I want more or less DoF I either get closer to my subject or use a bigger aperture. To be clear the FF look is not a standard and therefore there is no need to ape it.
I still can’t see any lenses with a 12mm Focal length and a maximum aperture of F2 or F1.4 primes in the FF line up that are as small , light and in the case of Olympus, as cheap.

I'm not making an argument in favor of either format btw, if I didn't plainly state it before I see upsides to both and I shoot both. I don't see the size advantage to wide thru normal M4/3 primes tho, specially if taking equivalence into account. 'Course the FF bodies are for the most part pricier so the argument can't be made in a vacuum.

There's no M4/3 prime as small as my Sony 24/2.8 or SY 45/1.8 that's actually equivalent (the 12/2 & PL25 are the closest in size but they're 24/4 & 50/2.8 by equivalence), but there's also no FF 150/3.6 as small as the Oly 75/1.8 (some of the vintage 135/3.5 lenses actually get close and might outresolve the Oly on a high MP body but I like my AF and my tiny M4/3 bodies)...

There's definitely no FF 85/3.4 lenses with the MFD of the Pana 42.5/1.7!

https://m.dpreview.com/learn/2799100497/equivalence-in-a-nutshell

https://m.dpreview.com/articles/2666934640/what-is-equivalence-and-why-should-i-care/2

" I still can’t see any lenses with a 12mm Focal length and a maximum aperture of F2 or F1.4 primes in the FF line up that are as small , light and in the case of Olympus, as cheap. " -George

I can agree with everything before that, I'm not sure what you're trying to say at that point tho... I take it to mean that you're happy with your M4/3 camera, it's performance, and the look achievable; that's great! Why would a 12mm FF lens matter then?

My point is simply that if you're gonna compare lens sizes across formats (which is what you did originally) then equivalency matters.

You can achieve exactly the same look and noise levels and everything else with a 24/4 FF lens (on a FF body) as with a 12/2 M4/3 lens (on a M4/3 body), and in fact the 24/2.8 & 24/1.8 FF lenses can be as small as the 12/2 M4/3 lens and are very very often cheaper ('course the bodies aren't).

The only point I am making is equivalence is not like for like, the lenses are not the same . If you want to compare lenses by weight, size and cost etc, then the focal length and aperture should be the same.
I say this because the design of the lenses may not be the same if you only go on equivalence

" If you want to compare lenses by weight, size and cost etc, then the focal length and aperture should be the same. "

Why would you compare 24mm equivalent wide lenses vs wildly UWA 12mm FF lenses tho? That doesn't make any sense to me, if the aim is to compare what you'll use across different formats to get the shot then equivalency practically has to be factored in, if for FL at least.

You yourself started off by comparing the 35mm FF lens against stuff like the 17/1.8 & 25/1.8...

I did indeed compare two different things . I came to the view that saying two different things could not be directly compared. Hence use the same focal length and Maximum aperture is a like for like comparison when considering weight size and cost.

" Hence use the same focal length and Maximum aperture is a like for like comparison "

On paper and in theory maybe, if you're more interested in talking about lens design than their practical use and value. The former didn't seem like your original intent tho.

" when considering weight size and cost. "

If that's a factor then I don't see how doing so makes sense; weight, size and cost imply how it'll be used matters, you aren't gonna use a M4/3 12mm lens for the same things you'll use a FF 12mm lens... Why even bother comparing them then? It's academic...

My FF & M4/3 75/1.8 lenses are pretty much the same exact size and one is heavier simply cause it's metal (the Oly), not sure who would care. FF one ran me $300 and the M4/3 one ran me $500-something as a refurb.

At the tele end the image circle seems to have much less impact on lens size.

Price is ultimately what the market will bear, sometimes unfortunately that leads to $800 f2 lenses like the 12/2. I bought it refurb, would've never paid retail for it... I actually think the 75/1.8 is worth the high asking price somewhat more (wish I'd bought it sooner tbh!), tho stuff like the SY 12/2 and Sigma 56/1.4 are easily a better value even if they're transplanted APS-C designs.

I still don't see how you can make much of an argument in favor of the 12/2 tbh, I really like it but it's one of the worst values in the system... M4/3 teles can have an advantage because there's not a lot of slow FF teles like say that new Canon 100-400 f5.6-8 or the Sigma 90/2.8... The wides are facing a lot more competition and overlap between formats IMO.

DPR did already compare the Nikon & Sony ones (somewhat) in their (rare) written reviews for each one. Chris is surely waiting for the 28mm to make a roundup, and since no one is making new ones besides Fuji/Nikon he's got nothing to work with! :P

Leica is obviously Hanse’s trash. Just like everything past his number 1!

"Why no Leica 35mm apo SL f2?" because it's not f1.8?

because its to much money, like @Bigsensorisbest said I'm on the breadline... haha

@Bigsensorisbest I think Sony has a lot of great tech but they are missing the art of the whole process. Everything feels to clinical and not aspirational.

Banana. 1.8 and 2 are effectively the same. Nikon had a spell of releasing F2 lenses instead of f1.8 in the AI range..