  We present a 40 minute time series of filtergrams from the red and the blue
wing of the \halpha line in an active region near the solar disk center. From
these filtergrams we construct both Dopplergrams and summed ``line center''
images. Several dynamic fibrils (DFs) are identified in the summed images. The
data is used to simultaneously measure the proper motion and the Doppler
signals in DFs. For calibration of the Doppler signals we use spatially
resolved spectrograms of a similar active region. Significant variations in the
calibration constant for different solar features are observed, and only
regions containing DFs have been used in order to reduce calibration errors. We
find a coherent behavior of the Doppler velocity and the proper motion which
clearly demonstrates that the evolution of DFs involve plasma motion. The
Doppler velocities are found to be a factor 2--3 smaller than velocities
derived form proper motions in the image plane. The difference can be explained
by the radiative processes involved, the Doppler velocity is a result of the
local atmospheric velocity weighted with the response function. As a result the
Doppler velocity originates from a wide range in heights in the atmosphere.
This is contrasted by the proper motion velocity which is measured from the
sharply defined bright tops of the DFs and is therefore a very local velocity
measure. The Doppler signal originates from well below the top of the DF.
Finally we discuss how this difference together with the lacking spatial
resolution of older observations have contributed to some of the confusion
about the identity of DFs, spicules and mottles.
