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My friend was talking about the 28mm, 70mm, and 200mm Nikon primes that he considers to be the "holy trinity" of lenses. Another friend asked why not just make a single 28-200mm zoom lens instead? I know typically zoom lenses aren't quite as sharp as prime lenses, but even so, some zoom lenses like the Nikon 28-70mm are very high quality. So I wondered, why not produce a lens that can be ideal for shooting in almost any setting; Something with a huge focal range and a super low F/stop, like a 18-300mm f/1.2 with IS?

Surely it would be expensive and a lot of glass, but lots of people would be willing to pay for such a versatile lens. What would the potential drawbacks of making a lens like this?

Ryan
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There are multiple drawbacks to why this isn't feasible, but it pretty much comes down to economics.

The biggest one is the market, sure you could possibly technically create one but the cost would so ridiculously high that it would be far out the reaches of most mortals. It would also be so ungainly to use that it probably would lose more of the market there, especially if it weighs the same as a small elephant and you need a specialist trailer mount to move one. I can't imagine rocking up the wedding and asking the vicar if you can drive your vehicle down the aisle just to use it!

The time and engineering required would be other factors, larger lens elements are grown from crystals which takes a long time, especially the crystal required for a front optic of 300mm f/1.2 (check out this question here with a picture of a 300mm f/1.8 What is the Canon PE Mount? to grasp the size). You would need multiple elements just to get the zoom.

The R&D alone would probably cost more then they would ever hope to earn back by selling these lenses making it economically nonviable for the manufacturer. Don't forget the years taken to manufacture the prototypes alone.

Crazy Dino
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See Is it physically possible to build a long zoom (17-300 mm for example) at an aperture value of around 1.4 or 1.2? for 95% of the answer (in summary, it'd be so ridiculously expensive and so large that it is effectively impossible).

But that's not all! Suppose we discovered a treasure trove of lenses made by aliens — so many that any photographer can just have one for the asking. And the alien technology used allows them to be the same size and weight as a typical 24-70mm f/2.8 lens today.

I still wouldn't take one.

Well, okay, maybe I would, but I'd still prefer smaller and lighter primes to carry around all day. The Nikon 28mm f1. 8 prime weighs 330g, while the 24-70mm f2.8 zoom is over a kilogram. Even if I have the equivalent total weight in primes in my backpack, I don't have it around my neck. And I can always opt to travel light — which I couldn't with the alien omega lens.

And that particular prime is on the heavy side — consider the Pentax DA Limited 70mm, which clocks in at 130g with the included lens hood.

mattdm
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Firstly, different peoples' concept of perfect may not be the same as other peoples' sense of perfect. As you suggested yourself, to your first friend, the 'holy trinity' might be perfect for them, but not for your other friend who prefers a zoom covering the same range.

Secondly, it will depend on what is being photographed, by who, the prevailing lighting subject, and action conditions. A wide angle (e.g., 28mm) prime might be better in some subjects and conditions, while a versatile telephoto (e.g., 70-200mm) zoom might be more practical for other subjects and conditions, depending on who's photographing, what specifically they're shooting, and what their preferences are for doing such shots.

As far as your suggested 18-300 f/1.2 is concerned, you may be prepared to pay $10K + for, and be strong and fit enough to carry such a (perhaps 10 kg) lens around your neck for several hours, but there are probably other who wouldn't. There is/are one or more 18-300 zooms in existence (Nikon AF-S DX Nikkor 18-300mm F3.5-6.3G ED VR , Sigma AF 18-300mm F3.5-6.3 Contemporary Series, Tamron evemn make a 16-300mm F/3.5-6.3 Di II VC PZD ) with a more modest max.aperture, because that's probably what the manufacturer may have considered to be the best value / balance of price / aperture to be sellable, portable, manufacturable. Again, as you said yourself, the issue of sharpness for such focal length range combo at F1.2 could be difficult to achieve acceptable sharpness performance for a reasonable price, and portability.

David Barry
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    $10,000 is a vast underestimate. Sigma makes a 200-500mm f/2.8, and that's $26,000 — and much easier to make since it's all telephoto and much slower. – mattdm Apr 27 '17 at 21:10
  • @ mattdm, OK maybe $100K then, but probably too much for average Joe Phot to be willing to invest in, let alone carry. – David Barry Apr 27 '17 at 21:19
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    My guess is 10 or 100× that even — and heavier too. Not just too much for the average photographer, but unreasonable for a business or even most governments. Basically, I agree with your point but I think it's even more extreme. – mattdm Apr 27 '17 at 21:34
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First, the longer the zoom range, the harder it is to maintain a sharp image with low distortion throughout the range.

Second, the longer the zoom range, the heavier the lens. For example, Canon's 28–300 lens weighs almost four pounds, versus only 1.5 pounds for a 24–105.

I'm hoping that diffractive optics will be the holy grail in that space, but time will tell.

dgatwood
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  • I'm not disagreeing with your point in the large, but on a case-by-case basis, there's still room for engineering to shine. For instance, Nikon's 28–300mm lens (same ƒ/3.5–5.6 aperture range) weighs just under half the weight of the Canon (1.76 lbs, specifically), and seems to compare favorably. – scottbb Apr 27 '17 at 23:20
  • The Nikon lens is a mostly plastic consumer lens, whereas the Canon lens is a mostly metal L lens; it makes more sense to compare lenses that are designed to ostensibly be similar build quality. But yes, there's definitely room to improve weight-wise. But of course, the original poster wanted an f/1.2 lens at 300mm. – dgatwood Apr 28 '17 at 18:32
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First, you are right about the Nikon 28-70mm, it’s a super duper lens. Besides, most digital images will only be scrutinized on a 72 dpi monitor. My meaning -- all that wonderful resolution goes out the window. Now a professional gears up to make big prints on paper – that’s a different story.

The zoom lens is a complicated gismo, many moving parts needed to shove lens elements about. Plus each doubling of the focal length results in a 4X decrease in the brightness of the image forming rays.

Suppose you shoot an image at 18mm focal length, and 100 units of light arrived at the image plane. What happens if you zoom to 36mm and make no other changes? The image brilliance drops to 100 ÷ 4 = 25 units of light. Now zoom again to 72mm; the light loss is now 4X more = 25 ÷ 4 = 6.25 units of light. Zoom again to 144mm, the image brightness is 6.25 ÷ 4 = 1.6 units of light. Zoom again to 300mm and the light loss is 1.6 ÷ 4 = 0.4 units of light – that’s a total loss of about 256X units of light. See how that goes?

OK – we must make an adjustment to maintain the light level at the image plane. We must somehow increase the light capturing ability of the lens. We are talking about increasing the working diameter of the lens. What must the working (apparent) diameter of the aperture be to allow a 300mm lens to function at f/1.2? Answer -- 300 ÷ 1.2 = 250mm. Oh my – that’s 10 inches diameter, see how that goes?

We can make a 300mm f/1.2 lens. These are used in astronomy, but you won’t be walking around with one of these in your pocket.

Alan Marcus
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It would be too big and expensive. There is no market for a lens like that.

osullic
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