Preview's Photo Editing Tools Could Be All You Need

A topic that frequently surfaces in the Mac user orbit, especially among veteran Mac users, is what image editing application makes the most sense to use as an affordable replacement for an old copy of Photoshop.

What about Preview?

You say you didn't know Preview had photo editing tools? The Leopard and Snow Leopard versions do.

It's not Photoshop - not even close. However, it may well be all the image-correction software many casual users need. These days, Preview is a lot more than a graphics viewer, incorporating some handy dandy image correction tools that are not only user-friendly and intuitive to use, but also work really well.

Consequently, if the main reason you need an image editor is because you take digital photos or scan transparencies or prints onto your computer and want to optimize them, you may not need a traditional third-party image editor at all. Preview can probably do the job for you.

Check out Preview's Tools Menu. If the last time you checked was in OS X 10.4 Tiger or older, you'll note that there are some new selections.

Say you've downloaded of photo from your camera, and you're not quite happy with the exposure, color rendering, or other picture attributes. For example, here's a photo of my truck. It's straight out of the camera (it's an old 3.2 megapixel unit). To my eyes, both color saturation and contrast are washed out, it has a greenish color cast, and it isn't as sharp as it might be.

Open the image in Preview (I'm using Snow Leopard) and choose Adjust Color from the Tools Menu. A floating translucent black color and exposure adjustment palette (reminiscent of the appearance theme in the Pixelmator image editor ) will appear, with seven sliders that facilitate adjustment of exposure, contrast, saturation, temperature, tint, sepia (!), and sharpness.

That gives you a lot of adjustment range, but the Snow Leopard version of Preview is actually dumbed-down somewhat from the Leopard version, which also included sliders for brightness, black level, and white level.

These sliders give you have real time feedback, and I find that they work beautifully. I love to play with all possibilities, and after my adjustment efforts, my truck photo now looked like this. It definitely has more contrast pop, and I like the color balance better, and I was also able to make it significantly sharper. (I like contrasty pictures.)

However, if you're pressed for time or are not quite sure what adjustment/correction effects you would like, just click the Auto Levels button, and the program will make its best guess as to optimum values, automatically adjusting the sliders. You can still tweak individual qualities if you wish before saving the image.

What impresses me is how sophisticated this is and how well it works - and all from one simple palette, showing other image editor developers how it should be done. In fact, I'm not sure that this isn't the all-round best tool I've ever used for this sort of image correction. It's certainly the most convenient and has added a great deal of value to the Preview application from my perspective.

But there's more. Preview now has an image scaling and resizing tool as well, allowing you to conveniently and quickly change a photo's resolution. Just select Adjust Size from the Tools menu and either manually enter the desired dimensions in the provided fields or pull down the menu and choose one of the resolution selections provided. You can also change the resolution of your picture (number of pixels per inch) by setting it in the resolution box.

As with similar tools in image editor applications, you can also select Scale Proportionally, and the height value will automatically change when you enter a new width value (and vice versa), so your picture will keep its original proportions.

The Select menu gives you several options for selecting portions of a picture, including extraction of part of an image from a simple one-color background - such as a person standing against a clear blue sky - or even a busy background.

There is also a Reassemble Image selection. When it's turned off, Preview will adjust the image's size by making the existing pixels bigger or smaller, but it will not change the number of pixels. However, with Reassemble Image turned on, Preview will add or subtract pixels as necessary to scale your photo up or down, averaging the colors of neighboring pixels when you are scaling up.

Of course, if you need to do more advanced correction, such as red eye or spot removal, or retouching, you'll still need an application like Photoshop Elements or Pixelmator - or maybe the image correction tools in iPhoto will do - but the above-described features are not the totality of Preview's initiating capabilities by any means.