An ultra-fast zoom that might actually be feasible?

So, we always see "Why can't we have a 24-70mm f/1.8 IS?" threads and the like, and we all know the reasons why we can't have such a lens. But would someone with more optical design knowledge tell me if the following would be mildly possible?

A 50-85mm f/1.8 (or maybe variable aperture, like 1.4-1.8 or 1.4-2)
-or-
A 35-50mm f/1.8 (")

I love my Sigmalux, but on my 40D it was often too long, and now on my 5D2 I find it's often a little too wide. In the last month, there have been several times when I'd have KILLED to have just that extra little bit of reach/subject separation. But I can't really bring myself to pay for and then carry around two primes that are so (relatively) close to one another. But I'd LOVE to have them both at the ready.

So why isn't THIS a possibility? Clearly there'd be no purpose in having a 35-50mm zoom with an aperture even as fast as 2.8...but when you've got the equivalent of two fast primes without the need to change lenses, don't you think that'd be worth some extra dough? I can't imagine that a 35-50 would be THAT enormous...maybe about the same as a 24-105 or a Brick?

Another thing; I wouldn't even need a "zoom" per se...I'd be happy with a lens that could just snap back and forth between the two FLs. However, I have no idea if this would make any difference as far as construction goes.

So tell me...is this another idiotic fantasy or is it feasible? Would any of you buy one?

I would pay BIG money for a 2.8 24-105L Zoom.

Make it a 20-100 at F2 and it'll probably be the only lens I use.

I know it'll be big and heavy but so's carrying an 85L, 35L, 24L and a 70-200 MKII

a 24-135 f2.8 has been my dream lens for years.

Gel wrote in post #11173236
Make it a 20-100 at F2 and it'll probably be the only lens I use.

Which is probably the exact reason one wont be created...you have 1 lens that does the work of 3 or 4 lenses..you only buy 1......not 3 or 4..company loses money in the long run

digirebelva wrote in post #11173597
Which is probably the exact reason one wont be created...you have 1 lens that does the work of 3 or 4 lenses..you only buy 1......not 3 or 4..company loses money in the long run

not if that one lens is equal to or more than the sum of the 4 lenses.

Gel wrote in post #11173236
I would pay BIG money for a 2.8 24-105L Zoom.

I know it'll be big and heavy but so's carrying an 85L, 35L, 24L and a 70-200 MKII

Tamron actually made a 28-105(or 135..i forgot which) f/2.8 at one point

its sadly very VERY soft...But it wasnt as big as you'd think (iirc its about the same size/weight as a 24-105, maybe a hair heavier)

So yeah, a 28-105 f/2.8 might not be impossible actually, Whether or not such a lens is a -necessity- im not sure

KenjiS wrote in post #11179473
Tamron actually made a 28-105(or 135..i forgot which) f/2.8 at one point

its sadly very VERY soft...But it wasnt as big as you'd think (iirc its about the same size/weight as a 24-105, maybe a hair heavier)

So yeah, a 28-105 f/2.8 might not be impossible actually, Whether or not such a lens is a -necessity- im not sure

if it had IS, i'd get it ... around/within 2k usd

mike cabilangan wrote in post #11178463
not if that one lens is equal to or more than the sum of the 4 lenses.

Thats a tall order...and would probably carry a prohibitive price (for a lot of us) to boot..since they are not going th eat the R&D on something like that..would be interesting though..

mike cabilangan wrote in post #11179606
if it had IS, i'd get it ... around/within 2k usd

I think its doable for $1800...

I think the problem is that the price tag becomes ridiculous. Why pay $1500 for a 2x f1.8 zoom when you could buy 3 f1.8 primes for that?

tkbslc wrote in post #11334643
I think the problem is that the price tag becomes ridiculous. Why pay $1500 for a 2x f1.8 zoom when you could buy 3 f1.8 primes for that?

Heh, my suggestion wasn't even 2x! More like...1.7x. Sadly your price figure is probably right. If the lens had the IQ of, say, the Nifty and the 85 1.8, along with similar build quality to the latter, I'd figure they could keep it under $1k (and I'd probably pay around $700 for such a lens). But there's no way they'd do that and not make it an L...so kiss cheapness goodbye.

But to be honest...I WOULD rather pay $700 for a Nifty and an 85 1.8 in one lens than $450 for a Nifty and an 85 1.8. The convenience would be worth the extra $250. It's too bad it'll never happen!