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02-23-2010, 10:02 PM   #1
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Why there is no zoom lens below f/2.8?

Hello everyone,

Just interested why there is absolutely no zoom lenses below f/2.8? So much f/1.2-1.8 primes in every range from 20mm to 200mm... Why no zooms?

I'm a happy owner of FA31 f/1.8 and cannot imagine I will have to deal with slow f/2.8 on my beloved evening streets of China. Or perhaps it isn't so slow as I think it is...



02-23-2010, 10:37 PM   #2
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I would say, its probably because zooms target a particular crowd of people. If you make them too fast they, will also get really huge and its likely that they will no longer be as appealing to the target audience and sales are not going to be as great. But then again, I could be wrong...
02-23-2010, 10:45 PM   #3
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Olympus have them.
ED 14-35mm f2.0
ED 35-100mm f2.0

Canon has a patent too. But consider the 2.8 is already quite costly, I wonder how much the f1.8/2 will cost.
Canon EF-S 17-55mm F2.0 IS USM??????????So-net???
02-23-2010, 10:46 PM   #4
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QuoteQuote:
I would say, its probably because zooms target a particular crowd of people. If you make them too fast they, will also get really huge and its likely that they will no longer be as appealing to the target audience and sales are not going to be as great. But then again, I could be wrong...
I'll second that. Have you ever handled 2.8 zooms? They're already quite big and heavy (say, a typical 70-200/2.8 weighs about a kilo and 200-300 grams)

Olympus has zooms that are faster than f/2.8 - the 35-100/2.0 (weighs 1.6 kg without tripod ring) and 14-35/2.0 (900 grams). Both of them are heavier than their 2.8 counterparts by 300 grams or so - while camera bodies are smaller and lighter.

02-23-2010, 10:51 PM   #5
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QuoteOriginally posted by pbo Quote
I'll second that. Have you ever handled 2.8 zooms? They're already quite big and heavy (say, a typical 70-200/2.8 weighs about a kilo and 200-300 grams)

Olympus has zooms that are faster than f/2.8 - the 35-100/2.0 (weighs 1.6 kg without tripod ring) and 14-35/2.0 (900 grams). Both of them are heavier than their 2.8 counterparts by 300 grams or so - while camera bodies are smaller and lighter.
Yeah, I understand it will be heavier. However that's not a constructional limitation as I imagine, as there are relatively fast pancakes. Maybe the cost / performance / engineering efforts are really out of balance for this kind of lens I dream about. And I'm not a pro, doubt I would go for more than $1.5k even for such a fine glass.
02-24-2010, 04:53 AM   #6
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The difference between f1.8 and f2.8 is a little more than a stop. What that means is that if you shoot at 1/30 of a second at f1.8 you will shoot (roughly) at 1/15 of a second at f2.8. For whatever reason, over time f2.8 has been the maximum for zooms.

You are wrong about the construction costs. Currently the 16-50 f2.8 runs 850 dollars. To get it to f2, it would be twice the size and cost more than 2000 dollars.
02-24-2010, 05:27 AM   #7
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QuoteOriginally posted by wlachan Quote
Yes, but since the 4/3rds sensor is smaller and generally a stop behind in ISO performance, this is effectively almost exactly equivalent to f/2.8 in APS-C.
02-24-2010, 08:00 AM   #8
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QuoteOriginally posted by Karellen Quote
Yeah, I understand it will be heavier. However that's not a constructional limitation as I imagine, as there are relatively fast pancakes. Maybe the cost / performance / engineering efforts are really out of balance for this kind of lens I dream about. And I'm not a pro, doubt I would go for more than $1.5k even for such a fine glass.
Faster zoom will not only be bigger and heavier, but also WAY MORE expensive!

Consider this: the faster a lens gets, the more complex it gets to correct the abberations of a lens. As a zoom already affords a lot more design and production effort and cost than a "simple" prime lens, can you imagine, how costs would explode if you add one full f-stop more!

With the currently fast zooms of usually f/2.8 we look at 12-15 lens elements and usually some esoteric highly refractive glass (ED/SD/UD etc. glass) With faster zoom colour correction alone would need to be done by even more highly refractive glass. And increasing spherical abberations would afford the use of even more aspherical lens elements. If you pay now 1000USD for a 70-200/2.8 I would expect a 70-200/2.0 in the vicinity of 4000USD. If you already pay 1800USD for a Nikon 70-200/2.8 you would probably pay 6000USD for the f/2 equivalent.

How many of these lens would be sold? And then there is the additional cost of more massive tripods needed, bigger bags, bigger filters etc.

Ben

02-24-2010, 08:34 AM   #9
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QuoteOriginally posted by Karellen Quote
Yeah, I understand it will be heavier. However that's not a constructional limitation as I imagine, as there are relatively fast pancakes.
Yeah but pancakes are primes, an f/2 zoom to cover the APS sensor is going to be CRAZY big and heavy .... not to mention expensive. Something like a 17-50 f/1.8 ... you're looking at a lens so big and heavy it's almost a tripod only affair.
02-25-2010, 11:20 PM   #10
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big and beefy

You have to consider: what does f-stop mean, aperture-wise?

The f/number is a ratio of focal length to aperture opening. At f/2, the aperture is 1/2 the focal length. I'm holding a SuperTak 55/2; focal length is 55mm, aperture wide-open (f/2) is 27.5 mm; front lens diameter is about 33mm. To make that an f/1 (ignoring all necessary corrections), the rear lens and aperture would be 55mm, and the front lens would be correspondingly larger, as would the lens body. A slower lens, an Industar (Russian) 50/3.5, is little more than a pancake. Fast means fat.

So, think about designing a fast long lens -- a prime, not a zoom. We'll make it a simple long lens, no fancy folded elements. We want a 300/1.5. The rear element needs to be 200mm across -- that is EIGHT INCHES!! The front element would probably be 250-300mm -- TEN TO TWELVE INCHES!! Even with aspherical plastic lens elements, that's gonna be one heavy, clumsy SOB. Make it a zoom, with distortion corrections at every focus, and it gets worse, much worse.

Long fast lenses are physically difficult and economically hazardous, at least.

EDIT: MY NUMBERS ABOVE RE: LONG FAST LONG LENSES ARE WRONG! For a 300/1.5 lens, it is the FRONT element that must be 200mm (8 inches) diameter. Rear element size will be much smaller. (I was tired, I didn't think straight, I'm sorry.) That's still a mighty hunk of optics. Don't drop it on your foot.

Last edited by RioRico; 03-02-2010 at 04:44 PM. Reason: humiliating self-correction
02-26-2010, 12:28 AM   #11
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Well, there is this Angénieux 28-70 f2,6 designed for film. Not sure this is really an improvement over a f2,8 lens, not even sure that it exists in Pentax mount.
02-26-2010, 12:39 AM   #12
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I can only say what everyone else has said.. more focal length and a lower aperture means more weight and big dollars.

Look at Canons 24-70mm f/2.8.. I'd absolutely love to have it, but it's bulky as all hell and does not sell below $1500.
02-26-2010, 03:24 AM   #13
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QuoteOriginally posted by Zav Quote
Well, there is this Angénieux 28-70 f2,6 designed for film. Not sure this is really an improvement over a f2,8 lens, not even sure that it exists in Pentax mount.
There is also a Tokina with the same f/2.6 max. aperture. But that is not a real advantage over the standard f/2.8 zooms, just about 1/4 f-stop. I guess, if it was an "improvement" Tokina would still produce it, but it was superseded by the more common f/2.8 version.

Ben
02-26-2010, 05:46 AM   #14
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QuoteOriginally posted by Ben_Edict Quote
There is also a Tokina with the same f/2.6 max. aperture. But that is not a real advantage over the standard f/2.8 zooms, just about 1/4 f-stop. I guess, if it was an "improvement" Tokina would still produce it, but it was superseded by the more common f/2.8 version.
Then there's the M42 Zenit 17-69mm f/1.9 manual zoom lens for Krasnagorsk 16MM cine cams. But a 16MM or Super16 frame is much smaller than even a 110 frame, let alone an APS-C sensor. So yes, it's a Pentax screwmount, but I suspect the vignetting would be unbearable even on a Pentax 110 SLR. I'll try to find specs on that lens...

Look here [ The Krasnogorsk-3 (K-3) 16MM Film Camera - Filmmaking ] at that lens on a windup K3 cine cam, and you see that it's short but wide. Looks like a fun camera to use.

format ----- frame size -------- diagonal (min. image circle)
-------------- -------------------- -----------
16MM ------ ~10.25x7.5mm -- 12.7mm
Super16 --- ~12.5x7.4mm --- 14.5mm
110 format: 17x13mm -------- 21.4mm
ApS-C dSLR ~25x16.7mm ---- 30mm

EDIT1: The lens is called the Meteor 5-1 (or maybe Meteor 3-2). I'm still looking for specs. I search eBay for METEOR ZOOM LENS and find various offerings, all CHEAP CHEAP CHEAP and probably unusable on our SLRs. Bother...

EDIT2: Here [eBay.ph: METEOR-3-2 ZOOM LENS 1.9/17-69mm FOR KRASNOGORSK-3I (item 230369372265 end time Mar 18, 2010 21:39:23 PHT) ] is the lens on eBay. From the fuzzy photos, the rear element looks to extend quite a way into the camera body. A SLR's mirror probably wouldn't like that very much.

Last edited by RioRico; 02-26-2010 at 06:26 AM.
02-26-2010, 06:07 AM   #15
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QuoteOriginally posted by mattdm Quote
Yes, but since the 4/3rds sensor is smaller and generally a stop behind in ISO performance, this is effectively almost exactly equivalent to f/2.8 in APS-C.
At a given ISO, f/2 is still f/2 though and will give faster shutter than f/2.8. Just to clear it up for others

Last edited by Andi Lo; 02-26-2010 at 02:37 PM.
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