Six Tips for Using the Centered Loupe Option

by Andrew Darlow

With the Aperture 1.5 update came an additional feature within the Loupe tool called "Centered Loupe". The original Aperture Loupe tool was, and still is an excellent way to check focus and detail on images of any size, including thumbnails, but the Centered Loupe is more flexible and it feels more natural to me (more like a real loupe). It can serve as both a focus check tool as well as a "before and after" window for edits made in the adjustments HUD.

Following are a few tips and suggestions for using the Centered Loupe option. I recommend following along with your images. For the purposes of this tutorial, I will call the Loupe, when in non-Centered Loupe mode, in "original Loupe" mode.


1. First, display the Loupe tool in one of the following four ways: Under View>Show Loupe; by pressing the ` key (the key is in the upper left-hand corner of your keyboard and that's my preferred way to access it); by choosing the Loupe icon in the top right corner of the browser (it looks like a gray circle); or by ctrl/right clicking-then choosing "Show Loupe." The Loupe will appear in original Loupe mode, unless you had previously changed it to Centered Loupe mode. Aperture remembers the last state the loupe was in. While you are in original loupe mode, another option when ctrl or right clicking is to choose "Detach Loupe from Cursor (shortcut is the ~ key)." This makes it similar to the Centered Loupe tool. However, I much prefer how the Centered Loupe functions.

Next, enter Centered Loupe mode (while still in original loupe mode) in one of the following ways: Select View>Use Centered Loupe; Use the keyboard shortcut: Cmd + ~; or Ctrl/Right Click and choose "use Centered Loupe."

2. You can then display color values (RGBL), which will change as you hover over different areas of your images. There are three ways to do this: The first is to select View>Show Color Value in Loupe; the next is with a keyboard shortcut (Option + ~ ); and the last is by Ctrl/Right Clicking and choosing Color Value in the contextual menu. This tool is especially helpful for determining blown out areas (RGB values of 255), or very dark areas. However, the box can be distracting, so keep in mind that you have another RGBL readout at the top of the Adjustments HUB that serves the same purpose.

3. Next, decide at what size, zoom level and in which position you want the Centered Loupe to be. This will change from image to image and will depend on the subject. The size of the "magnifying glass" can be adjusted easily by clicking, holding and dragging on the bottom right of the tool (white area). The small contextual menu (see fig. 1 below) makes it easy to adjust the zoom percentage. There are other options in the contextual menu as well. I generally use 100 and 200 percent to judge image sharpness.


fig. 1: The Loupe tool in Centered Loupe mode with the contextual menu showing.

If the Centered Loupe tool is sized down to a relatively small circle, the small arrow in the corner that displays the options will disappear (see fig. 2 below). Just click in the bottom right gray area, and hold the ctrl key (or right mouse click) to access the contextual drop down menu. If you place your mouse over the magnifying glass area of the Centered Loupe, the scroll ball on the Apple Mighty Mouse, or scroll wheel on most mice will cause the center area to increase or decrease in zoom level. Like most things in Aperture, there are also shortcuts for zooming and for adjusting the size of the Centered Loupe.


fig. 2: Centered Loupe mode shown when it is too small to display the small contextual menu icon.

4. Another great feature of the Centered Loupe option can be accessed by clicking and dragging inside the Centered Loupe (see fig. 3). This will temporarily create a circle in the center of the Loupe surrounded by a shaded area based on the zoom percentage you have selected. And at the same time, while you are choosing the "focus area," the whole tool can be moved around the screen. When you release the mouse button, the area in the center will enlarge to the zoom percentage you specified.


fig 3: Clicking and dragging inside the Centered Loupe.

5. Now for the real fun (drumroll, please). If you are in Centered Loupe mode, any adjustments made using the Adjustments HUD (for example, White Balance or Edge Sharpening) can be seen inside the Centered Loupe area, which makes it an instant before and after comparison tool. Just click on and off the HUD adjustment item or items to see the before and after effect. Depending on the system you're using, and the adjustments you choose, the adjustments may take a few seconds to redraw.

This tool is especially helpful when reducing chromatic aberration in RAW files. The adjustment for chromatic aberration in the HUD is called Chroma Blur (under RAW fine tuning and circled in red in fig 4a (top). Fig. 4b (middle) shows an area of a RAW frame with some chromatic aberration, and fig. 4c (bottom) shows the same image after applying a Chroma Blur radius amount of 3.3.


fig 4a (top), fig 4b (middle) and fig 4c (bottom)

6. If you choose "Focus on Cursor" from the contextual menu, instead of Focus on Loupe, the tool works in a very similar way, but the center of the loupe will sow the areas where your cursor is hovering. This is not as good a choice for checking before and after adjustments (as described in Tip 5) because there will be no image visible inside the loupe while making Adjustments. I find the Focus on Cursor option ideal for checking focus on thumbnails.

I hope that these tips help you to get the most from the improved Loupe tool. The real power of the tool comes with experimenting with it until it becomes second nature. I look forward to hearing how you use the new Loupe features.

All demonstration images ©Andrew Darlow. All Rights Reserved.


Peter Frings
2006-11-30 11:30:35
A nice touch is that you can reposition the loupe to where the cursor is by holding the ~ key for a longer moment; you don't have to grab the loupe at all. Move mouse, press ~ and boom (:-) the loupe moves into place...