27 June 2018
It won’t be too wrong if we say that in photography most things are happening in 20-100 mm focal length range. We deliberate whether 20, 24, 28 or 35 mm lens is better but in truth, they all have a certain magic that we can recognise. Their particular focal length defines it.
The word magic is becoming overused, but there is merit in seeing the association with a focal length.
From the most-things-happening range, ultra wide angle lenses branch off on the shorter side and telephoto lenses on the longer one. The two groups behave oppositely in how they project a scene, and they both are more distinct in this than what we see with lenses in the normal range. The UWA lenses will have a reputation of being the most extreme in this regard. But we want them to do extreme things, and I would say they do it in an intuitively right way via more than one form of projection.
Long or super telephoto lenses then seem to start somewhere from 300 mm in the focal length range. The shorter ones we call telephotos and often split them into medium and short telephotos as their angle of view widens towards 50 mm. All the telephotos are valued lenses. They break boundaries of distance, lending you silent wings (think of a pocket helicopter) that can in an instant cross the terrains and spaces impossible to navigate through, bringing your viewfinder close to the objects, animals or people.
Nikon has been creating some elite, relatively large aperture (fast) and expensive telephoto lenses during the short digital era. Slow lenses of this kind, however, whether versions with a variable or constant aperture, have long been an ugly duckling in the modern photo industry and particularly so in Nikon lines. They were either of inferior quality or didn’t materialise at all. Some essential f4 telephotos (we can see these as semi-slow or semi-fast) appeared after considerable delays, like the 70-200/4 VR. The 300/4 was equipped with the VR just three years ago.
This f4 300 mm prime, however, wasn’t an ordinary update. Some will agree with me that no lens update is quite ordinary to us, but this lens that had something called phase Fresnel lens inside employed a design that reduced the primary limiting factor in the use of the telephotos - the size and weight. It is mirroring a similar application of diffractive optics Canon has also been working with for some time. And what’s more, the new technology was aimed at a broader audience cost-wise.
This seemed to have marked a change. It was soon confirmed by the appearance of a conventional, albeit to that day also unusual, Nikkor 200-500/5.6 VR lens. The f5.6 is generally considered a slow aperture although in the practical world the 500 mm f5.6 is closer to being semi-fast, just as the f4 180-400 mm is relatively close to being semi-fast telephoto at 400 mm.
The change wasn’t happening in isolation. It coincided with the Third-Party makes signalling more interest in the segment which they have already shown by launching novelty zooms that were compact and capable of good to excellent results, reaching to 600 mm and all that in more and quality build versions. More Nikon patents for phase Fresnel primes of longer focal lengths were reported, and a few days ago Nikon announced the development of 500/5.6 PF (phase Fresnel) VR.
I saw that as a promising development and excellent news as I always thought that the slow telephotos are somewhat neglected group of lenses albeit a very potent one. I was among the first to own Nikkor 200-500/5.6 VR and Sigma 100-400 OS C lenses (or 24-120/4 VR, Canon 70-300 L IS for APS-C format and long-awaited 70-200/4 VR after owning the Canon version already). We will use Nikon first but put excellence above the brand when it comes to it.
The new PF 500 lens will come with the f5.6 aperture which to some opens a question. Does it make it slow? Slow means a small aperture, less bright lens in the equipment jargon. I would say that it depends. If you are a user of the fast f4 500 mm with a set of teleconverters and established ways for using it, you might tend to consider f5.6 slow for a 500 lens and thus less ideal. But is that the case for broader use and outside of special uses? Or where these lenses made excessively fast for the overall configuration needed in their time, and also because the noise control/picture quality was a fair deal worse at higher ISOs?
A photographer will always admire fast glass, nothing has changed in this. A scene of a subject in African savanna in the context of the environment and a broader sense of the place taken with a 400/2.8 or 180-400/4 can't be replicated with a slower lens and indeed, an alternative with a lesser blur and subject separation can have it tough to compete with that (although it may be found an attractive option in other and slightly different cases). I would concentrate on this with the fast telephotos.
Short telephotos like 105/1.4 have no less power in creating a unique picture within the realm of its focal length use. Bokeh is a critical part of the quality with the telephoto lenses. It, in many ways, shapes the picture, not least because the delicate de-focus transitions are common in most photographs taken with the telephotos.
And we should mention some other applications where the absolute speed of the aperture is important part in a given equation rather than any factors that form in the field.
But having thought about the long lenses and the aperture for some time, and about the maximum aperture with relation to other things we get with telephotos, I would rethink the slow telephoto label as well as the status associated with these specifications. Because although in different ways, it seems that these lenses are just as exceptional as their faster cousins and because in practical photography there are inferior tools but there are no inferior specifications.
As mentioned the third-party manufacturers took advantage of better means of building and designing the lenses and changed the established ways in this segment as they moved deeper into original equipment manufacturers (OEM) space. This came partly as a result of the low priority the slow-lens concept had among the OEM. The third-party turned their attention to these lenses because they saw that these specifications are artificially underrated and consequently understated, quite unrightfully so. They thought they deserved more attention from both sides, from the manufacturer and the user. And the users didn’t need to be encouraged twice.
Nikon that, just as any other company, is first a business and only then a base for its adoring fans, knows well about the value of fast lenses (resolution over the noise control is another corresponding preference), but they also can’t afford nonsense with this. The advantage of holding these designs off was gone, and it no longer is good business. What’s more, the alternative solutions for compact telephotos have been in the works, so it more than makes sense to engage seriously in this somewhat vaguely defined area.
Another change, which was touched on and that we can spot, is in an argumentation that the telephoto lenses use higher shutter speeds and hence the extreme focus on the large aperture before anything else. While the shutter speed point is generally a valid one, the advances in picture quality at higher ISOs we get mean that we can opt between the ISO setting and the ideal depth of field (DOF) more freely. This translates into a reduced need for large apertures with lenses with which we typically fill the framing. We can now use higher ISO values with less negative effects on the image quality. We also have better noise reduction software. These are changes that, similarly to the situation with the third-parties, will keep their course in the same direction so apart from strictly specialised uses the telephotos aren't asking for faster apertures nearly as much as it used to be.
Depth of Field
The availability of lighter, slower but longer lenses also offers better options when it comes to choosing whether to crop by a format (such as APS-C) or with the file (135 format). The latter bringing an added benefit of subject isolation/shallower depth of field the former can never match for the same framing with a given lens. Working with the two systems, therefore, offers different options; along with a different style, approach and the results in this regard.
That brings us to a dilemma of even greater depth of field control (narrower or shallower DOF) in 135 format and a need for a fast aperture. The choice of many - mounting the telephoto on the APS-C format - says about the need for a shallower DOF in a typical telephoto lens scenario. But one can still be demanding more for their specific, aesthetic reasons. So is a slow f8 lens on Fx 135 format disadvantaged when it comes to DOF?
One of the reasons photographers use APS-C cameras with telephoto lenses is that it gives them more reach and that without crippling one’s ability to move, react and handle the lens effectively. While these reasons have largely become moot due to increased resolution of Fx sensors and more compact telephotos available, they hint at the relativity and the practical value of a fast aperture for DOF with the telephotos. These lenses are specially designed, often optimised and predominantly used to fill the framing with one’s subject or with its part. So let’s try to imagine a scenario like this but use not a 500 mm telephoto for it, but a 35 mm lens. If one can’t visualise it, they can take a 35 mm lens and get this sort of framing with it. One can be then easily reminded how ridiculously close they have to be for this framing, how extreme it is. Their f8 or f10 stop will leave them with a very shallow DOF indeed. With the telephotos, we get this result all the time, especially if we want to. Cropping (an option with Fx vs Dx format) will make the effect milder, but cropping is less and less needed for reach as more and longer focal length lenses are available in a trend that is set to continue. In the typical scenarios the telephoto is used for, that is, the photographer fills a significant proportion of the image with the subject, the DOF at f5.6 is already prohibitively thin. And as the experience tells us, if the object or its part intended to be in focus, is even smaller size, f8 is barely enough for the desired DOF for the distance has been reduced even more. Examples:
700/8 3/14 A Closer Look
One related aspect we can also notice is that because the telephoto (and UWA) lenses project in a specific way, the compression effect that we get with the telephotos has subtle impacts on perspective, on how out-of-focus elements and the bokeh are typically developed, on how a subject is rendered including the perception of the DOF and in terms of the overall signature (way) the lens models the subject against and with the surroundings. This is the telephoto look the photographs shot this way have, and this also seems to be having effects on the way we perceive DOF with these lenses.
f4, f1.4 and the phase Fresnel
Coming back to the fast lenses, the semi-slow/semi-fast f4 lens (the sound of that will depend on whether it is a 100, 200 or 500 mm lens) offers a great balance in DOF control for reasonable cropping while shining in shooting subjects set deeper in the environment when one does insist on a stronger shallow DOF effect. Let’s note here in a simplified way that the bokeh quality can be more important than a more intensive blur. The aforementioned Nikkor 70-200/4 VR forms what we call larger bokeh shapes than the Sigma 100-400 OS lens (at the same aperture) yet its bokeh behaviour can be considered inferior in comparison as it can show faults in the bokeh (I call this 'abrasive grain') coming typically through in the background in some scenarios. The later has smaller bokeh features, but it creates a quality painterly type of bokeh void of the fault that I prefer (crossing into a slightly different topic this way, the specifics for this lens include 'photographic spark bokeh' in the foreground which in combination with sometimes too calm or monotonous backgrounds makes for valued results). The f2.8 and f2 telephotos are mostly restricted to medium telephotos reflecting the rule of less tight framing that is practical with shorter lenses (my favourite lens in this regard that I don’t own at the moment is then the Nikkor 105/1.4E). The fast telephotos also make combinations with the teleconverters. The resulting set of combinations and the lens on-its-own option make these distinct specialist tools.
Today though, even at the current level of ISO control, with the 135 format resolution and with better DOF control (the growing number of high quality slower telephoto lenses) these lenses moved more to an extreme and their fast apertures can often be regarded as excessive. Especially in the light of other important things that define the use of the telephoto such as the weight, size and the price.
For the PF lens and from the aperture point of view, a well done 500/5.6 PF has preconditions for becoming another revolutionary lens that takes advantage of becoming sufficiently different and can capitalise fully on this technology. The semi-fast f5.6 is on a fast side regarding the DOF and plays a critical role for both types of thus more defined lens groups as well as for the user who is offered a better choice for particular uses. A non-standard aperture f6.3 500 mm lens would not be bad at all if not for the concern of using it with 1.4 x teleconverter, but that with conventional designs. Fractional differences here can have tangible implications for use of the lens. On the contrary, a faster f4 500 mm phase Fresnel lens could, in my view, harm the project(s) and fail to address the competition’s offerings.
Having an option of both (the f5.6 and f4 500 PF lenses) is then a different proposition, though that is not an option we could talk about today. *ETA The ultimate telephoto PF prime for a balance of reach, handling and effective framing would be, in my view, 600 mm f5.6 in combination with 1.4 x teleconverter.