HDR - Part 12 - The Right Side Of Lenses

There are a number of reasons why people like old lenses, and they’re all very valid. Cameras and lenses so good they’re invisible are a recent development. Most of the best films ever made, by default, predate today’s spotless pictures, and artists have always been a rebellious bunch in any case. This, though, is an article about why it’s not always a good idea to rebel, at least without knowing exactly what we’re getting ourselves into.

It’ll be no surprise to anyone that anything that can be wrong with a lens – contrast, minimum focus distance, breathing, consistency – is all likely to be even more wrong with older designs. The intent here isn’t to issue some sort of blanket decree against old glass, but to encourage people to properly test lenses out. That can take time that sometimes isn’t afforded, especially on small productions, but differentiating the character of a lens from the flaws of a lens is a complicated and largely opinion-based process that requires a bit of attention. What we want is all of the character and none of the fuzziness – because at some dangerous, unpredictable point, those can be more or less the same thing.

Optimal Lighting is Everything

That happens because most of the world’s most sought-after lenses – the Panavision C and E series, and Cooke speed panchros were designed in a period where film speeds forced directors of photography to light their shots to a healthy stop. Given how sensitive modern cameras can be, it’s not really clear why modern shoots often run lenses so near to wide open. Perhaps it’s a lack of light; perhaps it’s a (sometimes questionable) desire for super-shallow depth of field. Either way, the rule of thumb is often that a lens performs best closed down two or three stops from wide open, though generally not at more than f/11, after which sharpness can become limited by diffraction in the tiny aperture in most designs.

That’s not what many people are doing in 2020, though, and the results from older glass are not necessarily that pretty. Everything, new or old, works better stopped down a bit, but modern lenses are designed much more with wide apertures in mind, and they fall off less in quality. The bottom few stops on mid-century lenses should probably be considered only for dire emergencies. The artifact of running lenses wide open is poorer sharpness and contrast, as well as an increase in various aberrations and consistency issues. The solution should always be to achieve a reasonable light level for a shot – with LED lighting and modern cameras it’s never been easier – but especially with older glass. Otherwise, the biting contrast of something like Blade Runner may recede into an unattractive grayish mush, even if we’re using the exact same glass.

Practical Considerations

Sometimes, old lenses have practicality issues, too. There are sets of lenses around which make it very difficult to photograph a shot of someone sitting at the wheel of a car and talking to someone out of the window. We might pull out the 50mm and discover that the minimum focus distance forces us to be rather further away than we had intended. Things are in focus, but we’re not really getting the frame we wanted. So, we might grab, say, an 85mm lens, back up to achieve something like the same framing, and – oh. The 85mm has an even longer minimum focus distance, and we still don’t have quite what we set out to achieve.

As with issues of running very wide apertures on old lenses, some of this issue comes from the expectation of the designers. People who built lenses in the 1940s, 50s and 60s didn’t expect people to shoot so many closeups; they didn’t expect so much location shooting in small, under-lit domestic premises. These lenses were built to shoot giant vistas or impressive song-and-dance numbers in expansive sound stages. In those days, people didn’t endlessly shoot huge facial closeups, partly because we do less of that for cinema. That’s a TV thing, and there was certainly no idea in the mind of the person who designed the lenses that they’d be used for the small screen.

Minimum focus issues can be solved with diopters, and there are some great examples of anamorphic photography with diopters in films such as Star Trek: The Motion Picture. Still, diopters have problems of their own. In the end it might just be worth considering a lens designed in living memory that can focus on objects closer than the moon.

Sharpness Illusion

Let’s talk about sharpness. All lenses, young or old, perform better in the middle of the image. Corner falloff is worse, of course, in more primitive designs, and it’s particularly bad in situations where we might be using electronic imaging sensors that are bigger than the film frames that older lenses were designed to cover. That doesn’t just mean huge, full-frame sensors; the term “super-35” is often used to describe electronic sensors that may be fairly close to the size of the old film frame, but they often aren’t exactly the same dimensions. Sometimes, that’s really quite noticeable.

Stills lenses, designs intended to work on 35mm stills cameras, often project a large enough image to cover some of the biggest sensors around, which explains why they’re an increasingly popular target for rehousing. Lenses intended for motion picture work, though, naturally project a much smaller image. Sometimes they’ll throw out some light that hits the corners of a large but roughly-super-35 sensor. Whether that light represents an attractive image is another matter.

Sensor Incompatibilities

There are also some specific characteristics of imaging sensors that represent a straightforward incompatibility with older glass. Ever thrown an old lens on a modern digital stills camera and noticed that it tends to vignette green? That’s because old film lenses didn’t have to bother too much that all of the light rays, of all colors, were hitting the sensor at right angles. If that’s the case, the lens is image-space telecentric. When that isn’t the case, as is frankly more usual, different colors of light may arrive at the sensor at different angles. Some digital sensors have the tiny sensitive part of each pixel buried at the back of quite a long pit, so it simply can’t see light that’s coming in at a steep angle. If only magenta light is coming in at a steep angle, and everything else is coming in at a shallow angle, the image vignettes green.

It’s not a nonexistent issue on film. The three (or more) layers in a color negative stock inevitably have a thickness, so any light that’s coming in at a very extreme angle can create blur between them. Even so, it’s subtle – a blur, rather than an outright vignette – and many older lenses don’t bother fully correcting for it. Perhaps worst of all, it’s a characteristic of lenses and sensors in combination – it’s not really possible to test if a lens vignettes a particular sensor or not without running careful tests.

Consistency Rules

And finally, the biggest bugbear: consistency.

Anyone can light a simple facial closeup of one actor on a single lens. Shooting the rest of the sequence, the scene and the production so that they look like they’re part of the same world is where skill comes in. Consistency in filmmaking is a huge topic, but for now let’s suffice to say that older lenses tend to be less consistent than newer ones. That’s true both between lenses within a range, and even between lenses intended to be identical, so picking out a set tends to involve a lot of testing. Consistency problems can arise only at certain lens settings, or only in certain kinds of light. Three 50mm lenses of a given type may match well, but a fourth may be of a later, different design, despite being described identically. This can happen with any lens but is likely to be a far bigger problem on old ones.

It’s especially an issue on re-purposed stills lenses, which often weren’t really built with crucial matching in mind in the first place.

In the end, there are a huge number of ways in which a lens might fail and many of those are worse in older designs. We could talk about breathing – the tendency to zoom in and out slightly as the focus moves. There’s even the fact that very old lenses can literally go yellow and produce slightly tinted images, or cemented layers of glass may start to fall apart, and of course older elements are also more likely to be damaged by excessive cleaning or worse. Actually, tiny chips in lens elements can make shockingly little difference to the image, but it’s hardly ideal.

Lens for the Job

There are a lot of alternatives. Some manufacturers have made lenses specifically designed to flare or produce other interesting optical effects; that’s really the only reason anyone has to shoot anamorphic anymore, since we can achieve the wide frame with fewer compromises in other ways. Modified versions of modern lenses are often more expensive than the conventional types, though, so we might just as easily reach for filtration, the use of atmos, or even go right back to basics and discuss production design and color scheming.

All that remains relevant no matter what, of course, and none of this is any reason not to take vintage lenses if they produce the desired results. It is, though, a reason to make very, very sure that they do produce the desired results, and that they do so consistently, easily, and in a way that’s compatible with the production being shot. Testing is everything.

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