Skip to main content

Tone or custom curves: an explanation

UPDATE 28 March 2008: Although I wrote this article almost three years ago I have notice that is visited almost every day. So a quick update. I now shoot with Canon cameras although my wife and fellow pro still uses Nikon. Both manufacturers make great cameras.

I use Lightroom to develop my RAW images and shoot using the most neutral setting. I'm happy with the results and I don't use custom curves when shooting anymore. Still the information below may be useful and the principals of science apply as they always will.

ORIGINAL START OF ARTICLE

I often use tone, or as they are also known, custom curves on my digital slr. Other photographers have asked me to explain what they are. So here's my brief overview.

I do most of my digital photography nowadays with a Nikon D70 digital slr. It's light, doesn't cost the earth and does all I need it to. The quality, if you know how to extract it is superb and can happily be used for everything from magazine covers to superb large prints. This explanation of tone curves is based on my experience with the D70.

Back to basics

Each film has a characteristic curve. Kodak explains a characteristic curve: "It shows the relationship between the exposure of a photographic material and the image density produced after processing."

So what about digital

The same principle applies to digital photography. Here, unlike film, a large part of the processing is done in camera, even when you are shooting raw. You cannot duplicate a digital tone curve, as far as I am aware, during post processing because it relates to how light captured is handled directly after it hits the sensor, ie digital film.

Nikon explains it as follows: "As photographs are saved to the memory card, they are processed to adjust the distribution of tones in the image, enhancing contrast. Tone compensation is performed by means of tone curves that define the distribution of tones in the original image and the compensated result."

Simply put tone curves can:
  • increase contrast
  • reduce contrast
  • alter the way colours behave under different lighting situations
  • brighten mid- tones
  • extract more detail out of highlight areas
  • brighten shadows
Custom curves are especially used to achieve the last three bullet points. Nikon provides excellent built in curves but the D70 and D100 when used with the normal tone curve, sometimes look like they're underexposing the mid-tone areas. Now you could try compensating by increasing exposure but this would be at the cost of highlight detail. A good tone curve can boost your mid-tone areas, lighten up shadow and keep more detail in your highlights - and that's why I like them!

But a word of warning. Getting them right is not easy. The adjustments have to very subtle or you'll spoil the colours and tonal balance. The curve has to be kept as linear as possible in the mid-tone areas.

Custom curves are by no means always the best solution. In high contrast scenes you'll probably want to try the Nikon's low contrast curve and in misty scenes you'll no doubt want to boost contrast with high contrast curve. The D70 also has built in curves for landscapes and portraits. No doubt other DSLRs will have similar options. But the benefits of using custom curves will be the same.

The key thing to remember is that unlike film, digital photography requires some of the normal darkroom lab work to take place inside the camera.

Nikon's D70 requires the custom curve to be loaded into the camera while it's tethered by usb cable to a PC/Mac running Nikon Capture 4 software . At the moment you can only load one custom curve at a time. As with all things the custom curve business is, if you'll pardon the pun, a rather steep learning curve. Just something you've got to keep trying out in different circumstances.

Please let me know if you've found this article useful.

Paul Indigo

Comments

Anonymous said…
I found this most informative, thanks!
12:29
Anonymous said…
Very helpful Paul - came here via your EPZ post.
Thanks Merl
16:19
Post a Comment

Popular posts from this blog

The Story Behind the Stories in My Photography

 Thank you for taking the time to explore my work. Photography, to me, is a meditative act—an opportunity to be fully present and notice the smallest details. The interplay of colour and light, the textures and shapes, the shift of an expression, a gesture — these subtle moments bring me pure joy. They are why I love storytelling and creating visual poetry. Every image in my portfolio is born from a moment of connection or curiosity. Whether I’m in a bustling city street, a quiet room, or a remote location, I aim to create photographs that resonate with empathy. Take "The Cyclists," for example—what appears to be a simple scene of people pedalling along the pier transforms into a visual symphony of movement and stillness, the hurried energy balanced by the serene focus of the riders. This interplay between action and calm often draws me in. I’m drawn to capturing the essence of a person—their inner world, not just their outward appearance. My approach often dances between the...
Post a Comment
Read more

Overcoming creative block and self doubt

Every photographer, for that matter every creative, I've ever met comes to a point when they're not happy with the work they're producing. The pendulum between creative highs and dry spells swings continuously. For some the cycle is long and the bouts are quite mild for others the feeling of doubt about their work can be a crushing experience which returns all to frequently. It's actually quite healthy to have these periods of doubt because it can often be the beginning of something new and interesting which takes you further than you thought possible. Creatives in the commercial world have to always perform and although they may agree looking back that they've had a few patches where their work was less good, they always seem to bounce back. A very few creative geniuses deliver such high quality work that their poorest attempts still surpass the rest of us. But I have never heard of anyone, from tortured soul of Van Gogh to the supreme showman and genius, Salvador ...
22 comments
Read more

What You Photograph Reveals How You Think

  Photography is often described as a way of seeing. Less often do we talk about it as a way of thinking. What you choose to photograph, and just as importantly what you ignore, quietly mirrors how your mind works. Some photographers are drawn to faces, micro-expressions, emotional spikes. Others chase atmosphere, light, mood. Then there are those who gravitate towards structure, systems, order, the invisible logic holding a scene together. None of this is accidental. The camera becomes a sorting tool. It reveals what your brain prioritises. Where others see chaos, you might see alignment. Where some look for drama, you look for balance. Geometry, repetition, flow, layers, these aren’t just visual preferences, they’re cognitive ones. Strong graphic images tend to come from people who think spatially. Who notice how things relate before they notice what they mean. Lines before labels. Structure before story. And yet, the best images rarely stop there. They gain depth when human pres...
1 comment
Read more