August 8 2016
Lightroom has an easy to use tool for selective exposure adjustments of a photograph. This is because not all areas of a photograph need the same type or amount of adjustment.
The purpose of selecting sections of a photograph for adjustment is to compensate for the inability of cameras to capture the full range of light levels in a scene. When we look at a scene our eyes adjust as we look at different parts, but a camera has to make do with the one setting. Instead, the adjustments are made afterwards in software such as Adobe Lightroom.
This is not compensating for poor photographic technique, it is important to capture as much detail as possible. Particularly not to overexpose the highlights because if they are lost then there is no way to recover them. Another important consideration is using the raw image file and not an already processed jpeg format image file. Raw files contain more information than jpegs about the scene, giving greater scope for adjustments in Lightroom.
Selecting an area for adjustment
The Lightroom Basic panel in the Develop module uses a brush tool to select the adjustment area by “painting” it on the image using the pointing device. Commonly this is a mouse, but I use a Wacom graphics tablet with a pen-like pointing tool.
Users choose a paint colour to show area selected, an overlay of the image. The overlay colour is toggled on and off with the ”O” key. Colour to select area and hide to see the image and adjust the exposure.
It is possible to create a number of selections, they can be separate or overlap. To help there are four paint colours available to help here, Green, Red, White, Black.
It is easy to adjust a painted selection using the eraser end of the tablet pen or go into erase mode and use the mouse.
Change the size and feathering of the on screen paint brush. Use a large size for broad areas and reduce the size for fine work around the edges.
Lightroom has two adjustable brush sizes, A and B so it is easy to switch quickly from a large brush to a small brush and back without having to use the slider adjustments. This also allows a quick switch between feathering sizes.
The zoom level of the working image alters the apparent size of the brush, the greater the zoom level the smaller the brush appears. This means not having to change brush size as you zoom in to make fine adjustments.
Feathering is a gradual tapering of the effect of the brush on the underlying level of adjustment to provide a gradual blend between the adjusted area and its surrounds.
Setting the flow rate alters the amount of paint applied to the selection area. This influences the intensity of Lightroom adjustments, so parts of the selection receive more or less of the adjustment.
The Density slider has a similar effect to the Flow slider. Reduces the amount of paint, and therefore the amount of adjustment applied to a particular area of a selection.
This stops the brush from accidentally painting over edges of objects in the image. Only use it while finishing the outside edges of the selected area. Leaving it on for broad interior selections risks it reacting to edges of objects meant to be fully selected, for example, clouds in the sky.
Typically this is in a landscape photograph where there is bright sky over the top of a wooded mountain range. The trees on top of a hill are often are uneven with lots of gaps around and inside their basic shape. One trick is to leave an unselected gap between the top of the hill and the sky. Then apply a second selection to this gap but adjusted at a lower intensity using the flow and density controls. This is a gradual transition between the sky and the solid hillside and trees below.