This guide tackles common, complex, and often misunderstood challenges of technical photorealism.
Photographs that show great detail, even when examined up close, can enhance the viewing experience. This effect isn’t necessary to create a compelling image, but it is often desirable, and it can be elusive.
Images shot on film with vintage cameras can produce enormous amounts of sharpness and resolution — but that’s not the default, even if you’re wielding a premium point-and-shoot.
Besides, you don’t need to spend large sums of money on a fancy lens to improve your photos. Though quality optics play an important role, there are many more significant factors.
These 23 tools and techniques summarize some of the most effective ways to improve sharpness and resolution in your film photography. They’re ranked based on their potential and include practical advice with appropriate references.
Navigating the technical aspects of photography can be challenging — no thanks to the abundance of jargon, unclear or inconsistent definitions, and over-reliance on isolated scientific measurements in a complex real-world environment.
Nevertheless, I’d like to cover two basic properties as they can help you understand your photography objectives better: image fidelity and image quality.
Image fidelity can be synonymous with image resolution. This property describes how far we can zoom into the image before we stop seeing discernable details (in the case of fidelity, we’re also comparing the image to the actual reality). It’s affected by the lens, film grain, scanner lens, and scanner output (pixel count).
Image fidelity has been historically difficult to boost during post-production. While the latest developments in computer vision and machine learning can “guess” what a better-resolving version of an image would look like, these tools introduce various errors, and their effectiveness is questionable.
Image quality can have multiple dimensions (as described in NASA Ames Research Center paper by A. Ahumada, C. H. Null). Acutance is responsible for our perception of sharpness and is one of those dimensions.
Acutace measures the edge contrast between objects in a photograph. High acutance will help text appear more readable or small details more discernable — without actually increasing image resolution. Acutance can be measured, and it can be changed after the photo is taken.
Sharpness is our perception of legibility, a combination of image resolution and acutance. An image can be made to look sharper even if its resolution hasn’t been affected. It’s also possible to have a high-resolution image of something that isn’t sharp. A sharp image can be made to look sharper if its fidelity is increased.
This paper (Hewlett Packard Laboratories by D. A. Silverstein, J. E. Farrell) describes the relationship between image quality and image fidelity and how they affect our perception of sharpness.
An interesting side-effect of shooting film is that the grain can increase our perception of sharpness as it affects acutance. Grain with well-defined edges has a lot of acutance (you may’ve noticed that image sharpening software can also make images look “grainy”). But film grain can also have well- and weakly-defined edges (thus be less or more sharp) and its fidelity will vary with the size of the granules.
This guide covers ways to improve the quality and the fidelity of your mages separately or in combination to form sharper images.
◽︎◽︎◽︎◽︎◽︎⇠What is this?
The tools and techniques in this guide will help you improve your images to various degrees. It may be impossible to apply all of them to a single photo — but there’s no need to do that. This is why I’ve added a simple rank graphic next to each title that signifies its potential effectiveness:
A full bar ◾︎◾︎◾︎◾︎◾︎ means the tool or technique described can be very effective, whereas a nearly empty bar ◾︎◽︎◽︎◽︎◽︎ means that only marginal improvements are expected. These grades are based on personal practical experience.
◾︎◾︎◾︎◾︎◽︎ Sharper lenses.
Being the first step in the pathway that transforms light into a photograph, your lens has a very strong influence over the final result.
Simple plastic lenses, damaged lenses, or ill-designed lenses will produce less contrast and resolve fewer details on film — which may be hard or impossible to improve after the fact.
It’s also helpful to understand that most lenses, even plastic ones, can produce results with negligible imperfections. With a proper technique, it may even be possible to create very legible images using a pinhole camera (i.e., no lens at all). To understand how well a modern lens renders an image, compare any of your results to the ones I got from a hand-made lens of sugar — which may be the (unintentionally) blurriest and most distorted photos online.
Portrait of Betty on Gingerbread 1. Not sharp but scanned in high-res.
Even if you’re planning to display your images as a large print, you may be able to convince your audience that your photos are sharp with a cheap lens, poor scan, and mediocre print. If the onlooker is far enough, they won’t notice these imperfections because of the limits of human vision.
However, if you intend to look at your photos up close, your lens choice is important:
Glass¹ lenses with high-quality coatings, good manufacturing standards, and smart design will often produce better results. Conventionally, prime lenses (fixed focal length, no zoom) are considered to be sharper/better-resolving than zoom lenses. Extremely wide and long² lenses can be more challenging to build as sharp as a normal lens (35mm-85mm on a full frame or ~55mm/645+ on medium format).
The above heuristics are not 100% reliable. Well-produced image samples that resemble intended use are more helpful, and so are well-written reviews. Information about the lens’ chromatic (and other) aberrations, flare resistance, and geometric distortion can be helpful in your understanding of how sharp a lens may render your photos. However, you can influence some of those distortions without changing the lens.
¹ — This article is a good overview (with references) of why plastic may not be a desirable material for photographic lenses. In short, plastic’s relative limitations to glass are the narrow range of refractive indexes, lack of homogeneity, lack of physical hardness (scratch resistance), thermal expansion, moisture absorption, and chemical reactivity.
It’s also worth noting that high-end modern plastic lenses exist. One example is the Polaroid I-2 and the other is virtually any mobile device.
² — To clarify, a wide lens is a lens with a focal length shorter than the shortest normal focal length (35mm on a full-frame); a wide lens produces images with a wider angle of view. A long lens would have a longer focal length than the longest normal (85mm on a full-frame) and it would produce images with a narrower (sometimes referred to as “zoomed-in”) angle of view.
◾︎◾︎◽︎◽︎◽︎ Chromatic aberration.
Like a prism that spreads light into a rainbow, glass in camera lenses tends to do that with every point in a photo.
A photo made of rainbows 🌈 is a lot of fun to say! Unfortunately, the effect is rarely considered appealing in real life.
Chromatic aberration, which results from various wavelengths (colours) of light refracting in glass at different angles, can be seen in photos as blue or rainbow fringing. This fringing can radiate around the image edges with high colour contrast (like the deep-brown branches and green leaves on a deep-blue sky background), or it can form defined bands.
An example of chromatic aberration forming with Minolta MD Zoom 35-70mm.
On typical black-and-white panchromatic film, chromatic aberration can still be visible as blurry or unnatural edges. However, if you shoot orthochromatic film (like Ilford Ortho 80 and Film Ferrania Orto 50), chromatic aberration will be reduced. Orthochromatic films are not sensitive to red light; thus, that part of the rainbow is excluded, reducing the size of the [rainbow] fringes around the edges. Using a colour filter with your black-and-white film can also help reduce chromatic aberration.
Wide-angle lenses, which include many zoom lenses with short minimal focal lengths, are more prone to chromatic aberration. So are simple lens designs that lack correction, such as plastic singlets (single elements) in disposable/reusable cameras. This is another heuristic that is best supplemented by an actual lens review.
You can also try to avoid chromatic aberration by selecting your scene and your light. The less colour contrast (i.e., overall contrast and the presence of deep primary colours), the less chromatic aberration will manifest in the image.
Flares happen when light reflects off the glass elements and lens components. These effects may be desirable in some situations, but they can contribute to contrast reduction and colour casting.
Even if there are no visible flares in your image (whether they’re outside the frame or if you cropped them out), your lens may be muddying the details of your photograph as their effect can spread in a large radius around the characteristic geometric shapes.
Lens flare intensity and spread depend on your lens and the light causing the flaring.
