I read a lot of articles and blogs about film vs. digital, and which is “best.” In my opinion, that’s sort of like comparing a hammer to a saw, and asking which is best. The answer is that they are different tools and if you are going to build a house (or a photo portfolio) you’re best off using both. The trick is know which tool to use when.

One central problem that pops up in many of these discussion is a lack of clarity regarding the technical aspects of the photograph. One photographer may be perfectly happy with the results of his digital images, and that may be because his subject matter and technique play to the strengths of digital. Another may find digital to be unacceptable, precisely because her photos don’t play to the strengths of the platform. Until you define what factors affect image quality, you can’t analyze how well different platforms perform in light of those factors.

Fortunately, we don’t have to figure this stuff out all on our own....

In The Negative Ansel Adams outlines three factors that impact image quality. These are acutance, resolution, and grain (or ‘noise’ in the digital realm.)

Let’s look at each of these factors and see how digital and film perform in regards to them.

Acutance is the ability of the medium to record ‘sharp’ edges. So what is a sharp edge? A sharp edge is an abrupt change in contrast. Lay a silver razor on a black backdrop. The transition from silver to black takes place extremely abruptly. If you hearken back to your high school geometry days, and think of the razor and background as making up a plane (a two dimensional series of points), in theory the edge of the razor would be defined by a silver point directly next to a black point – 100% acutance.

Of course, it doesn’t work that way in the real world. No matter how good the optics of the lens, 100% acutance never happens, but excellent lenses can produce very high degrees of acutance.

And then there is the recording media. In broad terms, digital really out performs film in rendering high acutance images. In theory, pixels side by side, could make abrupt changes in contrast. However film, with its layers of silver halide crystals, can never render the same degree of edge sharpness. I saw this most clearly when I started shooting snowflakes digitally. Visually, snow crystals are very edge intensive, and acutance is an essential element creating high quality snowflake photographs. No matter what film I used – including many excellent emulsions like Fuji Velvia 50 or Kodak E100S - the degree of acutance was just not as high in the film images.

So in terms of acutance, digital generally beats film.

Resolution is the ability of the image to record fine detail. Let’s say you are shooting a wide-angle shot of a field of wheat. Think of the fine detail present in that shot: the thousands of wheat stalks, the seed heads topped with tassels. Even though digital cameras increase their megapixels daily, film still holds the edge in regards to being able to record fine detail.

I’m not talking about 35mm film here – even though even it has greater resolution that most digital cameras. But medium and large format film have a tremendous advantage over digital in terms of resolution. For example, a 6x7 cm medium format exposure, scanned at 3200 dpi, produces a digital file greater than 64 megapixels in size. These images have far more resolution for two reasons – they capture vastly more data, and the image projected onto the film is significantly larger (higher magnification) than a digital capture.

At the time of this writing (2006) even 35mm film has greater resolution that most digital SLR’s . Medium format film captures have significantly greater resolution, and large format is a whole order of magnitude greater yet.

So, in the resolution department, film wins hands down - but it only wins big if you are willing to step beyond the 35mm format.

Lastly comes noise or grain – which for the sake of simplicity I’ll just call “noise” from now on. Noise is defined as random changes in contrast and color independent of the subject matter in the exposure.

Both film and digital exhibit higher noise levels at higher sensitivity (ISO) levels. High speed films tend to be more grainy, and digital cameras set to their highest speed levels tend to produce very noisy images. In addition – small sensor digital cameras are generally noisier than larger sensor cameras, which is why digital SLR's generally outperform small format digi-cams.

Different types of film can produce markedly different levels of noise or grain. Some films – like the now discontinued Tech-Pan, Royal Gold 25, and Kodachrome 25 – had extremely fine grain. Others – like Kodachrome 200 or Royal Gold 1000 – were incredibly grainy.

While it’s difficult to generalize, I think it’s safe to say that at comparable ISO settings, digital SLR’s will outperform the best films in regards to noise. Again, I draw on my experiences shooting snow crystals, which have large areas of open space. The noise levels on shots captured with my Pentax *ist-D are significantly lower than the level of noise on exposures taken on Fuji Velvia 50. Similarly, I now routinely photograph close ups of botanical or insect subjects with the *ist-D set to ISO 400 – with noise levels comparable to what I used to see with ISO 100 transparency film.

The complication in understanding noise arises out of the concept of the “signal to noise ratio.” In other words, the more information presented in the photo – the greater the signal – the less noticeable the noise. The less information in the photo – the less the signal - and the more noticeable the noise. Practically speaking, that’s why you see the effect of noise or grain in a photograph of a clean blue sky, but notice it much less in a shot full of information – like the wheat field mentioned above. The upshot is that noise is less of an issue in some shots, based on the content of the image, than in other shots.

One final comment on noise: the grain in film, particularly certain Black & White films, can produce a pleasing and interesting effect. I think that to some extent that’s because we are used to seeing it, and we attach certain cultural connotations to old-fashioned photo grain. But I also think that film grain has a regularity to its pattern that makes it easy for the eyes to accept it and see past it. Digital noise, on the other hand, seems to be less regular and even. It seems to be more distracting that film grain, so it’s fortunate that it is less pronounced.

So, in the area of noise or grain, digital generally wins out over film, but with many caveats.

So how does all this come together?

As I see it, digital really shines in situations where low noise and high acutance are the essential elements of the image. Snow crystal photos are an extreme example of this type of image, but they really illustrate the respective advantages of digital media. In thse shots you have large areas of negative space, where noise can be really prominent. You also have lots of edges to the crystal structures, and those edges need to be as sharp as possible to make the shot work.

I also find that digital works very well with insect close ups. If you think about the structure of an insect, you have lots of edges - body segments, wings, antennae, etc - but not the degree of fine detail that calls for high resolution.

On the flip side, film really excels with high resolution, high detail subjects. This is particularly the case with medium and large format film exposures. Landscapes – especially those with lots of foliage or other fine details – are ideally shot on film. The weakness of film – high grain level – is minimized by the tremendous amount of detail in these sorts of shots. I really need to emphasize that when "a lot of detail" is indeed "a lot of detail." Seriously - photos of skyscrapers or houses, for example, don't dontain a tremendous amount of detail. Unless the paint is peeling or something like that. On the flip side, as subject like this ditch with all the srubby and brambly woods around it, really does have the level of detail to derail digital exposures.

So we come back to the question posed at the start of this rather long blog – which is “best”? Film or digital? The answer depends on what subject you are shooting. Personally, I utilize digital for close ups and most general shooting, but switch to medium format for landscapes and scenics. Capturing these diverse subjects are, essentially, different tasks. And so, it makes sense to use a different tool accomplish each. Just like using a saw for cutting, and a hammer for pounding.