Learning the basics of color negative film photography



Having learned photography on digital cameras, film feels to me like a really unpredictable animal. With digital, there is the instant feedback of immediately seeing the resulting image. A film camera is much more of a black box. You frame the image, press the shutter, and blindly hope that what you’ll see in two weeks is something vaguely like what you want now.

Recently, I came across these words about technique:

Technical mastery is freedom. When we can control our process and know what results we will get, we will be free to create whatever kind of photograph we want. We don’t have to bracket and hope for the best. We don’t have to wonder if our image will turn out. With the proper technique, we know. 

Cory Miller, “Mastering the Zone System – Part 1: Zone System Metering”

I like this idea a lot. I want to know.

After I shot my recent first roll of film, I decided to spend some time actually reading up on film photography technique. This post is an attempt at summarizing what I’ve learned so far. Some details might be a little inaccurate but the general ideas should be correct.

Note that all of this applies mainly to color print (i.e., negative) film, and may not apply to other types of film (reversal, i.e., slide; black and white).

I haven’t had a chance to try all these things out yet. I am not an expert!

Main Takeaways

Coming from digital to film, I naively just assumed film photography would be basically the same as digital photography, except with magical soft vintage colors and a bit more dynamic range and fewer sliders to mess with in Lightroom. It turns out that this is mostly very wrong!

Avoid underexposure.

In digital, if you overexpose and blow out a highlight, there’s no recovering that part of the photo. Overexposure is dangerous. I learned to avoid it, and I found with my digital cameras that shooting with a little bit of negative exposure compensation (like -1/2 EV) often got the image closer to how I wanted it.

Film is the complete opposite! You can wildly overexpose, like +6 stops on Portra 400 wild, and the final image will come out looking mostly fine, maybe just a little less contrasty. Conversely, underexposing film by not very much (a stop or two) results in grainier, muddier images.

From https://petapixel.com/2016/03/29/exposure-affects-film-photos/

There’s lots of creative decision-making in scanning.

A digital image begs to be edited. Once I discovered the power of the Lightroom sliders, it was hard to resist making the photos look the way I wanted – exposure, colors, curves just so. I probably spent more time at my computer than I did behind my camera.

Film, by virtue of being a real, physical medium, seemed less malleable. Since it’s grounded in the truth of a physical thing, I thought that there would be a “correct” way any particular negative scan should turn out. Just reproduce it how it is in reality, but inverted. The camera-to-negatives-to-scans pipeline seemed simple. I was aware of burning and dodging and pushing and pulling, but those are things you opt into, extra unnecessary creative liberties.

But it turns out that there’s massive latitude in the process of turning negatives into positive scans, and there’s no opting out – choices must be made by someone. Color balance, color temperature, overall brightness, all choices that have to be made. Many labs will take your preferences into account when doing scans.

So I think it’s fine to make additional small adjustments and color corrections to film scans – you’re not deviating from the truth, because there wasn’t really one to begin with.

Maybe in the future, I’ll want to get into doing scans at home, to have control over that part of the process too.

It’s interesting to understand what happens with film that makes the above true. The rest of this post digs into that a bit.

How Film Works

Film is basically a thin sheet of plastic covered in light-sensitive silver halide crystals. The crystals react when light hits them such that they become darker when developed.

There are some larger crystal grains and some smaller crystal grains. The big grains are more sensitive to light, because they are more likely to be hit by enough light to be developable. The smaller grains are less sensitive to light.1

This is why higher-sensitivity (higher ISO) films appear more grainy, because the grains have to be physically larger in order to be more light-sensitive; conversely, it’s also why lower-sensitivity films have higher resolution and can show finer detail.

I like these graphics from Richard Photo Lab2:

From https://www.richardphotolab.com/blog/post/film-grain-and-pixelation
From https://www.richardphotolab.com/blog/post/film-grain-and-pixelation

During the developing process, grains that weren’t exposed to enough light to be developable get washed away. This is why underexposing film causes the image to turn out grainier – more of the smaller grains get removed (because they didn’t get enough light), leaving more of the bigger grains. It’s also how pushing film works: You leave it in the developer for longer, so it has more time to find and develop the smaller grains.3

Characteristic Curves

After a certain point, it becomes less and less likely that a given photon will find its way to a crystal grain that hasn’t already been exposed. This nonlinearity is why film is more tolerant of overexposure than digital: As it is exposed to more light, it becomes less sensitive. Contrast is reduced, but there’s no such thing as blowing out the highlights.

This behavior can be plotted as a characteristic curves, with light exposure on the horizontal axis and density (how dark the negative is) on the vertical axis.

I like this one, which compares the characteristic curves of typical film vs. typical digital4:

From https://www.scotty-elmslie.com/uploads/5/6/3/3/56337819/film_vs_digital_characteristic_curves.pdf

The horizontal axis is in exposure zones, with middle gray at 5.0. The referenced article has a nice, more detailed discussion on this topic. The article was published in 2017; I think digital has maybe some advancements in dynamic range since then, but I’m not sure.

We can see the film characteristic curve has a “shoulder” at the top, when the highlights become less sensitive. The author concludes that usable digital dynamic range is about 8 stops, while for film it’s about 12, and both are less than what our eyes can do (18-20 stops).

The Scanning Process

After developing, a lot of variables and choices are made by the person doing the scanning.

The scanner/technician corrects for different densities of film (e.g., as mentioned above, if your film is more exposed, then it will be darker = denser). The light being shined through the film can be made stronger or weaker as needed to get a usable scan. This is why an overexposed image can have a scan that looks basically the same as the correctly exposed image: The negative was more dense, but the scanner corrected for it by increasing the strength of the backlight.5

Additionally, the technician makes corrections for color balance (green/magenta; warm/cool). For color print film, there’s a lot of latitude for color correction, and it’s not really necessary to use filters to correct this in-camera. You can shoot a tungsten-balanced film in the day and a daylight-balanced film under artificial light and both can be made to turn out about the same.6

Further Reading

These articles have nice visual examples of overexposure vs. underexposure in film:

Film characteristic curves as published by manufacturers often have the horizontal axis in lux-seconds. This article has some discussion on how to convert and interpret that: https://www.filmshooterscollective.com/analog-film-photography-blog/a-practical-guide-to-using-film-characteristic-curves-12-25

To really get your exposures right, you can use the Zone System to make sure that all areas of the image you care about will be exposed for adequately. This seems like a good intro: https://www.35mmc.com/02/05/2016/overexposure-latitude/#Density_correction_in_the_scan