Curve transformations and the perfect picture

Like everyone else, we've given you relatively simple-to-use screens for general brightness, contrast and colour adjustment, as a lot of the time simple controls are all that you need for you to improve your images. Sometimes though, these simple controls just don't give you enough flexibility to achieve the results that you are after, and it's at these times that you need to turn to using curves.

With curves you can define a non-linear transformation with respect to any attribute of the colours in your image. For instance, if you wanted to increase the brightness of the shadows without affecting the midtones or the highlights too much, then you would simply enhance the curve at the left-hand (darker) end and leave the right-hand (lighter) end unmodified.

You don't have to remember these mapping of curves to results though, as we've given you a drop down menu of effects, and a slider bar to determine how much of the effect that you want, which in turn will produce the curve for you. You can then tweak it if you want to by tugging at the control points to get just the look that you are after. Complete control.

We've talked before about brightness, and how a lot of professional image-editing software out there mishandles it. This is true too of Photoshop's curve editing feature, in that it only allows you to modify red, green and blue together, or each separately. We do that with Imagina too, except that we also allow you to modify hue, saturation, brightness, luminance and indeed the alpha channel in your image. Without the additional option of brightness, using curves to modify the brightness without altering the colour balance would be next to impossible.

One problem that no-one seems to make any attempt at handling is when you amplify a very dark colour to become much brighter than it was originally. Often this will hugely exaggerate very minor colour differences into massive colour distortion. Take a pixel with no red or green, but just 1 bit of blue in it. In reality, you would not be able to visually determine the difference between this colour and the darkest black. Take that colour and invert it (amplify it massively), then you would see super-bright blue rather than the white you might have been expecting. This kind of colour amplification can just ruin your image and cause you no end of headaches.

Think of Imagina as Anadin. We've this sweet little tick box called "dark to light colour preservation". It ingeniously looks at what you're trying to do with your curve editing and if it thinks you're going to amplify colours that are almost black into something much brighter then it effectively converts those colours to their equivalent grey before it does so, on a smooth sliding scale of course. This gives you a nice smooth transition that avoids all of that nasty colour distortion - an example of which now follows.

A typical image that features dark colours before being inverted.

Now the same image but having been inverted.	And this time with colour preservation turned on.

You can easily see the awful colour distortion that amplifying colours can produce in the left-hand image. Equally obvious is just how much nicer the right-hand image is with our colour preservation in action. Note that the inversion we've used here is a "brightness" inversion rather than a "colour" inversion. Colour inversion is easy and doesn't produce distortion, but it does change the colours, from blue to yellow for instance, which often is not what you want. We've not seen any other software that allows you to do a brightness inversion, possibly because of the problems that it can produce that we've highlighted here. So with us you've won twice over, once with the fact that we've given you the feature to achieve it, and again with the fact that we've allowed you to achieve it successfully where others have feared to tread.