Why No f/1.4-2.8 Zooms?

I understand why there are fixed aperture zooms, but since the digital age, the actual need for those has diminished since you can just stop the lens down to f/2.8 throughout the zoom range.

Anyways, with lenses like the 24-70mm and 70-200mm, the largest aperture is 25mm and 71mm wide respectively. if they designed the lens to utilize that same size aperture, then we would have a 24-70m and 70-200mm f/1.0-2.8.

I understand that you would probably have a fair amount of vignetting and spherical aberrations at f/1.0, but at f/1.4, 1.8, or even 2.0 it would clean up a fair amount. So is a f/1.4-2.8 zoom lens too much to ask for with today's technology?

i think you have aperture and zoom range mixed up a 24-70mm f2.8 L has an effective aperture of 2.8 throughout the zoom range of 24mm to 70mm. and to answer your question, to engineer such lenses would be ridiculous, not to mention, they'd cost a pretty penny and weigh more than any of us would care to shoulder.

I'm sure there are technological problems. Glass making hasn't advanced very much, if at all, in decades.

Then, if you could build such a lens, it would be large, very heavy and very expensive. Companies are in the business of making a profit so they would have to see what kind of market there would be for such a lens, factor in the estimated price of design and production. I'm sure they've done their homework which is why such a lens does not exist.

The size should be the exact same along with the weight. The size of the aperture at 70mm is the approximate size of the aperture needed for a 24mm f/1.0 lens (actually a little larger). The lens can already physically change it's focal length to 24mm, so nothing should be different.

The 24-70mm for example has an aperture size of 25mm at a focal length of 70mm. Change the focal length, but keep the aperture the same size and you have a 25mm aperature at a focal length of 24mm which would be a f/.96

I'm guessing that it's because nobody would want to carry around an 80 lb (36 kg) lens.

I have wondered about that. Obviously the aperture is pretty wide at 70mm, why can't they keep it that wide at 24?

I dunno. Olympus is now selling some f/2.0 zooms. If I was shooting photos for a living and making good money off of it, I would have some of those.

In reality, I wonder if they are worried it would take away from prime sales. Even if it made the 24-70 cost $3000 (assuming double cost of what most f/2.8 zooms cost between Canon, Nikon, and Sony) they might lose a lot of sales of 35L, 50L, etc.

I think the aperture also has a relation to the front element. I forgot about that. I think there is more involved than focal length/size of aperture = aperture f number.

laydros wrote in post #7637047
I think the aperture also has a relation to the front element. I forgot about that. I think there is more involved than focal length/size of aperture = aperture f number.

From Wikipedia, "[The f-number] expresses the diameter of the entrance pupil in terms of the focal length of the lens; in simpler terms, the f-number is the focal length divided by the "effective" aperture diameter."

I've often wondered about this myself. There must be some technical limitation, and not the usual "it would be too big/heavy," because the necessary glass already appears to be there. Remember, the OP isn't talking about f1.4 at the 70mm end, he's talking about f1.4 at the 24mm end, where it would appear enough glass already exists.

Do we have any optical engineers that can explain this?

FWIW the only 35mm zoom that breaks f2.8 that I know of is the Tokina 28-70 f2.6-2.8, the one with the Angenieux pedigree. I believe Olympus 4/3 zooms get away with apertures larger than f2.8 thanks to the smaller image circle; ultimately, they trade off the extra aperture for reduced light gathering area.

Mike Deep wrote in post #7637207
I've often wondered about this myself. There must be some technical limitation, and not the usual "it would be too big/heavy," because the necessary glass already appears to be there. Remember, the OP isn't talking about f1.4 at the 70mm end, he's talking about f1.4 at the 24mm end, where it would appear enough glass already exists..

Exactly.

At 70mm f2.8, the lens is open 25mm. if the blades didn't close down as you zoomed out, it would be 25mm f1.0. Same size lens.


Its most certainly possible, its whether or not it would introduce a ton of other issues (vignetting, CA, distortion, etc) that is the question.


Or, maybe it would just cut into the sales of fast primes.

Tokina once had an 28-70 2.6-2.8
Angenieux once introduced 28-70 2.6 for Nikkor AF and Canon EF.

I often wonder abt that too, might be because there are too much glasses/elements which decrease the intake of light.

The lens closes down mechanically when you zoom out with another aperture I believe. If there a way to take out that extra mechanical aperture so you can shoot at 24 f/1.0?

Anyone up to hacking a brick?

If you look at slower variable zooms, the aperture diameter still shrinks quite a bit. So there must be some design limitation that makes it difficult to do what you are suggesting.

For example, the 18-55 IS f3.5-5.6. 55/5.6 is about 10mm aperture size, but 18mm/3.5 is about 5mm. So the aperture opening is closing half way. 70-300 f4.-5.6 has a 53mm opening at 300mm and a 18mm at 70mm. We don't really have any evidence of a lens design that can keep the aperture opening size fixed while changing focal length. It is likely hard to channel the same amount of light down a tube while the focal length changes, so you have account for collecting less + the massive vignetting.

Perhaps something like a variable max f2-2.8 would be more realistic and within the scope of similar designs.

Well if the 24-70L closed down by 1/2, the aperture size would be 12.5mm which would equate to an f/1.92 at 24mm which is about f/1.8 and Canon would probably market it as such.

Okay, good thing i happened upon this thread. There's so much misinformation here, I'll attempt to straighten you guys out, as follows:

On second thought....