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Going back decades, well-heeled amateur and hobbyist photographers have lusted after fast prime lenses. Partly this is just human nature. In the days when most cameras shipped with standard 50mm F1.8 or F2 lenses, it was inevitable that such photographers would long for something a little more exotic. A little faster, more expensive, and more ‘professional’. For photography obsessives that grew up idolizing the famous LIFE magazine shooters of the late 20th Century, it was natural to aspire to own those kinds of lenses, despite their price.

There is still a demand for F1.4 and faster lenses, but that’s not the same thing as saying that there is a need for them

Partly though, the appeal of fast lenses is practical – regardless of your ability level or income. They let in more light, and more light, even today, is always good. In the film days though, you really needed every stop. For a long time, anything above ISO 400 was considered ‘fast’, and shooting so-called ‘high speed’ film involved compromises, in color rendition, grain and contrast. For photographers that needed to work in changing conditions, an F1.4 or even F1.2 lens was valuable insurance against missed opportunities created by a lack of light. Never mind that many of the F1.4 and F1.2 lenses of the film era were pretty soft wide open – a slightly hazy photo is better than no photo at all.

But today, two decades into the ‘Digital Century’, is there still a need for ultra-fast lenses?

One of the ultimate drool-worthy lenses, the Leica Summilux 35mm F1.4 (this example is from the 1970s) is the most compact F1.4 lens that Leica ever made for its M-series rangefinders. Its small size, light weight, and the premium attached to F1.4 means that it has long been a favorite of professionals and wealthy amateurs. Never mind the fact that at it can’t focus closer than 1 meter, can’t accept normal filters and doesn’t really get sharp until F2.

Fast lenses continue to sell, and technically of course, the F1.4 and F1.2 (and faster) primes of today are far superior to the designs that came before. Standout examples of the current state-of-the-art include Canon’s superb RF 50mm F1.2 and EF 35mm F1.4L II, Sony’s GM 24mm F1.4, and Sigma’s 35mm F1.2 ‘Art’ among many others. Tamron’s new 35mm F1.4 is another stunning lens, and don’t let a Pentax fan catch you suggesting that the FA* 50mm F1.4 SDM AW is anything less than perfect. Technically speaking, all of the lenses I just mentioned are among the best of their type that you can buy.

Canon’s EF 35mm F1.4L II USM is a stunning lens – in fact arguably the best 35mm prime on the market. If you’re a Canon shooter, and you’re one of those people that really needs F1.4, this is the lens to get. But for most of us, it might be overkill.

Clearly, then, and partly for that reason, there is still a demand for F1.4 and faster lenses, but that’s not quite the same thing as saying that most photographers still have a need for them. I suggest that these days, with the modern BSI-CMOS sensors inside most full-frame interchangeable lens cameras, the average full-frame photographer will be fine with F1.8. And might actually be better off.

To explain why I think that, I’ll break down the three traditional arguments in favor of fast lenses:

1: Faster lenses let in more light, and more light is always good.

This is a fact. More light is never a bad thing, and the 2/3 of a stop which demarks an F1.4 lens from an F1.8 lens is not insignificant.*

Consider the practical implications of shooting at F1.4 versus F1.8: First, you’ll be able to shoot at faster (shorter duration) shutter speeds. Assuming a constant ISO sensitivity, an increase in 2/3 of a stop of aperture means the difference between shooting at a shutter speed of 1/25th of a second and shooting at 1/15th.

That’s potentially quite handy if, for example, you’re shooting with a 28mm lens. Without any form of stabilization, you’ll probably be able to hand-hold your shot at 1/25th, but you might struggle at 1/15th. So in marginal light, shooting at F1.4 will give you a little bit more peace of mind.

This portrait of everyone’s favorite dog was shot wide open, on the Nikon Z 50mm F1.8 S. Belvedere is sharp, there’s no CA anywhere, and foreground and background are pleasantly blurred. The high performance of the Nikon Z6’s BSI-CMOS sensor means that even at ISO 1,400, noise is barely an issue (and could be reduced even further with a little more NR in Adobe Camera Raw). ISO 1400 | 1/250 sec | F1.8

The second practical implication is that more light coming in through the lens means that assuming a fixed shutter speed, you can shoot at lower ISO sensitivity settings. Two thirds of a stop is the difference between ISO 640 and ISO 400.

But do you care these days about the difference between shooting at ISO 640 and ISO 400? Or ISO 1,600 and ISO 1,000? Or even 160 and 100? The increased performance of modern sensors at high ISO sensitivity settings means that the days when you really needed to keep your ISO ultra-low for acceptable results are (fortunately) over. As such, when it comes to light gathering, the advantage of an F1.4 lens is less important now than ever before. That’s assuming you’re shooting with one of the new generation of BSI-CMOS sensors, of course, with dual-gain architectures.

2: Faster lenses make for more attractive images

But of course you know all about F-stops, and the reason you’re interested in an F1.4 lens is not for its technical advantages when it comes to pushing your exposure envelope, but for its aesthetic advantages. Specifically, shallower depth of field and blurrier backgrounds at maximum aperture.

This is fair enough – if you consider two lenses of the same focal length, one an F1.4 and one an F1.8, the F1.4 lens will deliver blurrier backgrounds, assuming a constant camera to subject distance. Physics again.

F1.8	F1.4

However, the difference between the appearance of background blur at F1.4 vs. F1.8 isn’t as great as all that. It’s highly dependent on camera to subject distance of course, but in general, I’ll bet that most people, if they saw a photograph shot at either F stop setting in isolation, would be unable to identify the aperture setting you used.

Look at the example above. The image on the left was shot at F1.8, the image on the right was shot at F1.4. The crop is from an area just to the left (her left) of our model’s head.

The two images look different, certainly. But are they that different? Meanwhile, the marginal increase in depth of field at F1.8 over F1.4 may actually be advantageous for some photographic situations – especially portraits like this, where even a slight sharpness difference between your subject’s eyes can be distracting.

3: A faster lens stopped down is sharper than a slower one is wide open

Traditionally, this is true. No lens is technically at its best when shot at its maximum aperture. Stopping down a touch is good practice if you want to achieve better overall sharpness, cut down vignetting, minimize some common aberrations, and you don’t mind losing a tiny bit of background blur in return.

This portrait was shot straight into the sun, on Nikon’s Z7 with a new Z 85mm F1.8 S attached. Wide open, this image is sharp across the frame, contrasty, and while there is some flare in evidence, you really have to go looking for it. This is not the kind of performance that we would traditionally associate with an 85mm F1.8. ISO 64 | 1/2000 sec | F1.8

Again though, these days, you may find that the difference between an F1.4 lens stopped down to F1.8 and a good F1.8 lens wide open is minimal. Looking at the best of today’s crop of F1.8 primes their performance wide open is extraordinary. When examining images from the Nikon Z 85mm or 50mm F1.8 S or the Sony Sonnar T* FE 55mm F1.8 ZA, its obvious that compared to the ‘kit’ primes of the old days, they’re in a different league. Some of this is down to the increased design flexibility that mirrorless technology brings in terms of automatic software corrections, but not all.

At the end of the day, an F1.8 prime that is sharp and contrasty across the frame, which offers pleasant bokeh and lacks significant fringing when shot wide open is – I would argue – a much better value proposition than a more expensive F1.4 or F1.2 lens which needs to be shot at F1.8 or F2 for optimal results.

Disadvantages of ultra-fast lenses

Hopefully I’ve challenged some of the conventionally accepted advantages of faster lenses, but to further bolster my case I want to look at their outright disadvantages.

There are three: size, weight, and cost.

Lenses with a maximum aperture of F1.4 or faster are typically larger, heavier and as I’ve hinted at above, more costly than F1.8 or slower equivalents. The image below, showing Canon’s EF 50mm F1.8 STM next to the RF 50mm F1.2L USM is an extreme example, but nevertheless, if you see a 50mm F1.2 (or F1.4) and a 50mm F1.8 in a particular company’s lineup, you can bet that the F1.8 will be the lighter, smaller and cheaper of the pair.

I don’t want to pick out (or pick on) particular brands here, but Nikon’s Z-mount prime lens range is worth looking at in the context of this discussion because it currently only consists of F1.8 options (pending the arrival of the manual focus 58mm F0.95 Noct, which is a bit of a special case).

Two lenses, both made by Canon, one for DSLRs on the left, and one for mirrorless, on the right. The biggest reason for the size difference between these two is their maximum aperture. The lens on the left is the EF 50mm F1.8 STM, while the lens on the right is the RF 50mm F1.2L USM. The RF lens is one stop brighter than the EF lens. One stop brighter, and a whole lot heftier.

Of Nikon’s three currently available Z-mount lenses, the Z 50mm F1.8 S and Z 85mm F1.8 S are, in my opinion, optically outstanding in almost every way that a photographer should care about. The Z 35mm F1.8 S isn’t quite in the same league when it comes to CA suppression, but it’s still excellent. The combined cost of all three of these lenses is $ 2,250 (not inclusive of tax). That’s only $ 150 more than the MSRP of Canon’s admittedly stunning, but undeniably massive RF 50mm F1.2L, shown above. Meanwhile the combined weight of the three Nikon lenses comes in at only 300g more than the Canon 50mm on its own. And around 800g (about 1.7lb) less than the expected weight of one Nikon Noct, (pictured at the top of this article) if you’re playing that game. We don’t know how much the Noct will cost yet, but let’s assume it will be significantly more than $ 2,250…

If you want a really fast, flagship prime lens, be prepared to pay for it, in more ways than one

Clearly this is an imperfect comparison, drawn only to make a point. But hopefully you do get my point: If you want a really fast, flagship prime lens, be prepared to pay for it, in more ways than one. And ask yourself first – how much do you really need that extra stop or two of light?

Just one more thing…

Speaking of price brings me to a flaw in my argument – or at least to a caveat: The fact that all other things being equal, an F1.8 lens is likely to be cheaper and smaller than an F1.4 or F1.2 equivalent is unsurprising, and in itself proves nothing. What has proved surprising to some of our readers is that fact that the best of today’s crop of F1.8 primes for mirrorless systems are more costly than their D/SLR-era F1.8 equivalents. In fact, in some cases they’re more costly than their F1.4 D/SLR-era equivalents.

Nikon’s Z 85mm f1.8 S, for example, costs almost exactly twice as much as the still-current AF-S 85mm f1.8G. Meanwhile, the AF-S 50mm F1.4G is a fine lens, and still available new for around $ 400 – that’s 2/3 of the cost of the Z 50mm F1.8 S. Sony’s new FE 35mm F1.8 costs $ 750 – that’s more than Sigma’s 35mm F1.4 ‘Art’ – still one of our favorite fast prime lenses, even seven years after its introduction.

Sharp and free of distracting flare even when shot almost wide open, Sony’s new FE 35mm F1.8 is one of the most useful lenses for Sony’s mirrorless interchangeable lens system. ISO 100 | 1/400 sec | F2.2 Photo by RIshi Sanyal

Why is this so? The reasons are various. There’s the the overall loss of value in the digital photography industry which has seen volume at the low end of the market disappear, driving the prices of high-end products up. The need to recoup some of the R&D costs of developing entirely new mirrorless mounts, the fluctuation in the value of the Japanese Yen over the past decade or so, and other factors.

$ 800 spent now on one of the current crop of state-of-the-art mirrorless lenses buys you more than $ 800 ever has

But let’s not lose sight of a really important fact, independent of all that: The newer lenses mentioned above tend to be superior to equivalents that came before. While $ 800 is clearly a lot more cash than $ 400, $ 800 spent now on one of the current crop of state-of-the-art mirrorless lenses buys you more than $ 800 ever has. As such – especially if you’re a Nikon Z or Sony FE mirrorless shooter – I would argue that it’s time to leave behind the old idea that faster always equals better and take this opportunity to downsize.

Look out for part 2 to this article, if I ever get time to write it – ‘Hey Canon and Sigma, how about some more compact, high-performance F1.8 primes?’

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* In fact, 2/3EV is the difference between APS-C and full-frame.

Articles: Digital Photography Review (dpreview.com)