One of the most useful features in Aperture for studio photographers is the ability to shoot tethered. Tethered shooting allows you to connect your camera via its USB cable directly to your computer, and when you begin shooting the resulting photos are immediately loaded into the Aperture library and displayed on your screen. There are a number of advantages to shooting tethered.
First of all, you get a nice big display to view your images on, while on a shoot. This can be invaluable when shooting in the studio as it makes it much easier to evaluate things such as critical focus and the tonality of your images. Secondly, if you have clients present during the shoot it allows them to see the images on a bigger screen rather than the LCD screen on the back of your camera. There's also the added bonus of having the images already captured on your computer, so you don't have to download them off the card later. In addition, you have an extra backup, as most cameras will record to the card at the same time.
Unfortunately not every camera can shoot tethered, and not every camera that can shoot tethered is supported by Aperture. The good news is that most cameras that can shoot tethered are supported. Apple maintains a list of supported cameras on its website. You can find it by going to the following address:
http://support.apple.com/kb/HT4176
You will also need a USB cable of a decent length, and an open USB port on your computer. I would also suggest going directly into your computer. If you connect to the USB port on an external keyboard, for example (if you're going into a desktop), there may be speed issues, and I've seen cases where hubs can cause problems too. Most people though will more than likely be shooting into a laptop when shooting tethered. The best thing to do is thoroughly test any setup you plan to use before you use it in a mission-critical situation. If possible, the photographer should also have backup equipment available. At least have an extra set of cables to be used if there are connection problems between camera and the computer.
You should also be careful when setting up your camera and laptop. It can be surprisingly easy to pull one or the other and damage them. If you're shooting handheld, you may want to secure your laptop somehow, or at the very least make sure you have a good length on your USB cable. A common setup is some kind of a T-bar mounted on a tripod with a laptop stand on one side and a tripod mount on the other side. These are available commercially from a number of different manufacturers.
To start a tethered shooting session go to the File menu and choose Tether | Start Session. This will bring up the Tether Settings panel:
You may notice that this is quite similar to the options in the import dialog, and that's because they are pretty much the same. At the top, you have the option of Store Files for where to store your files. If you don't have a project selected when you start a session, Aperture will create a new one and name it with the date and time when you started the session. The Store Files option is the same as when importing normally, and gives you the option to store the files in the Aperture library (managed) or in a location of your own choosing (referenced). You also have the option to rename the files on import and this might be something you want to consider when doing a studio shoot. The Metadata section is the same as the import dialog, and again you have the ability to apply presets and set information at this stage. You also have the option to back up files as they're imported and the ability to apply an effect. These options are all the same as the standard import dialog.
Note
A note on RAW + JPEGs
One thing that you might notice is missing though is the option for RAW + JPEG pairs. Unlike a standard import, when shooting tethered, RAW and JPEG pairs are not combined and are treated as separate files. If you have RAW + JPEG enabled on your camera, and start shooting tethered, you will get two images every time you press the shutter button.
Once you have your settings set in the Tether Settings panel, click on the Start Session button to begin your session. This will bring up the tethered shooting HUD. Pressing the Capture button on the HUD will cause your camera to take a picture and for it to be immediately imported into Aperture. You can also use the shutter button on your camera.
Note the small checkbox on the bottom left-hand side of the tether HUD that says Auto Select. With this checked, every time you take a picture it will automatically become the currently selected picture. So, for example, if you are viewing an image in the viewer, it will be loaded and displayed as soon as you take it. If it's unchecked, only the image you currently have selected will be displayed. If you're shooting and nothing is changing on screen, make sure that this hasn't been accidentally unchecked.
When shooting tethered, your display settings are persistent, so if you zoom in 1:1, for example, it will stay zoomed in when the next image loads. This makes it very handy for checking focus. You can also use the Loupe if you would prefer. When shooting tethered, all the other features of Aperture remain active, so you can make adjustments, enter metadata, and so on, all while in a tethered shooting session. This can be very useful if you need to check out potential adjustments and looks on the subject that you are shooting with, while still in the middle of the shoot. This avoids the problem of having models waiting around till afterwards while you test out ideas, in case you need to reshoot something.
Note that you can also close the HUD at any time and continue to shoot tethered, but you will have to use your camera's shutter button. To return to the HUD if you close it, choose File | Tether | Show Tether HUD.
Once you have finished your shoot, to end the session simply click on the Stop Session button on the HUD and your session will be finished. You can also finish a session by choosing File | Tether | Stop Session from the menu.