Filter output in logcat by tagname

use this:

adb logcat -s "TAGNAME"

In case someone stumbles in on this like I did, you can filter on multiple tags by adding a comma in between, like so:

adb logcat -s "browser","webkit"

Another option is setting the log levels for specific tags:

adb logcat SensorService:S PowerManagerService:S NfcService:S power:I Sensors:E

If you just want to set the log levels for some tags you can do it on a tag by tag basis.