If you want to quickly tweak an image and move on, without making a big time commitment (iPhoto, Aperture, and Lightroom) or juggling a milion editing options (Photoshop), try Preview. This free Apple program comes loaded on your Mac and has a robust set of imaging tools. You can adjust an image’s tone or colour, and even select objects within the shot to copy or cut.

Customise the interface
A good way to get a feel for Preview’s functions is to customise the top toolbar. Go to View > Customize Toolbar, and you’ll see icons for zooming, selecting, cropping, rotating, and even scaling. Drag the tools you will use most often to the top toolbar so they’re ready when you need them.

Next, go to Preferences (Preview > Preferences), click on the General tab, and select Open Groups Of Files In The Same Window. This allows you to work on multiple images at the same time in Preview.

Test this setting by selecting a handful of pictures and dropping them on the Preview icon. You’ll see a column of thumbnails displayed in the sidebar, with one image featured in the main window. If you want to add another picture to the line-up, drag it to the sidebar and let go.

Control-click or right-click in the sidebar, and you’ll be presented with options for sorting the thumbnails or choosing how many columns you want them displayed in. If you don’t like the default sorting options, choose None from the contextual menu and drag the thumbnails into any order you want.

Batch processing
You can also perform basic batch processing on multiple images with Preview: for example, just Cmd-click on two or more thumbnails in the sidebar, and then apply the Rotate command. The rotation will be applied to all the selected images in the sidebar.

If your images are too big and you want to sample them down, Cmd-click on the thumbnails of the images you want to resample, go to Tools > Adjust Size, and choose the new dimensions you want to use for the photos. Preview will resample all selected images. 

Tonal and colour adjustments
Most photographs could use a little tonal or colour adjustment. Bring up the Adjustment Inspector by holding down Cmd-Option-C, or by selecting Tools > Adjust Colour. You’ll be presented with eight individual controls to help you improve your photograph. 

Start by clicking on the Auto Levels button right below the histogram. More often than not, this will give you an immediate improvement. Fine-tune the tonal adjustment by moving the three triangle pointers beneath the histogram. The left one is for dark tones, the right is for highlights, and – you guessed it – the middle pointer is for mid-tones.

To correct the colour, click on the eyedropper icon beneath the Temperature slider, then click on a white or grey area in the picture. If you want to fine-tune this adjustment, use the individual Temperature and Tint sliders.

Select with the Smart Lasso
You can select an object and isolate it by using the Smart Lasso tool. Click on the Select icon in the top toolbar, then choose Smart Lasso from the pop-up menu. Carefully outline the object you want to isolate with the Lasso. When you let go of the mouse button, Preview will fine-tune the selection for you and display ‘marching ants’ around the object. To isolate it, go to Edit > Invert Selection, then press the Delete key. Boom: your background is gone.

You can also copy and paste these smart selections into other images. Instead of inverting the selection, press Cmd-C to copy it, then go to the image you want to add it to. Press Cmd-V to paste the object into the new image. Once you’ve pasted the object, you can still move it around.