ANY method of deinterlacing video drops quality below is a chart from the German wiki, which ilustrates well what happens, when you try to combine the two fields of a video - the source of problem is, that - if anything moves in front of the camera - each field contains a different content... so, how to make from two different pics a single one... ?

a) Weave: show both fields simultanously.. nice idea, but what happens, when both fields show a different content (something did move, as our fotographer to the left)? you'll notice jitter, steps.. works only with converted Film, where both fields contain the same content.. 

b) Skip Field: blurred, due to loss of half vertical information: you skip a field, and you double the lines of one field, or, advanced, you interpolate the missing line between the two lines of one field.. 

c) Bobbing: each field gets a full frame.. instantly, you have twice the amount of data/file size and you have to double the speed of playback.. otherwise, your video gets slowmo.. smooth movement, but some content could 'shake vertically'.

d) Blending: a multistep process: interpolate the missing lines for each field; then interpolate both fields (now frames) to one frame.. nice idea, but.. blurrs again.. 

e) Adaptive: kinda blending, but calculates with a number of frames before and after the actual calculating frame.. tons of computation. avoids sideeffects of blending and bobbing, only avail on pro systems.. 

f) Motion Compensation: latest.. often to be found in state-of-the-art flatscreen TVs: here, there's first an analysis, what parts of the frame do move; then, different parts within the frame get a different method of deinterlacing.. not moving parts get weaved, moving parts get Adaptive Deinterlacing.. 

Yepp.

Modern flatscreens, TFT, Plasmas, OLEDs,.. do not display interlaced video. As your Mac. Watching interlaced video on a computer always shows 'jaggies'. A flatscreen TV avoids this, by sampling the fields, and use one of the methods mentioned above to create a full sized, deinterlaced pic.

.. and it gets even weirder: modern flatscreens allow different framerates, as the so popular 24fps .. which is the native framerate of Film.. in PAL Land, we just sped up Film on transfer to video/PAL. In the US and Japan, the transfer of 24 to 29.97 was always a complicated process => drop of quality.. when the display allows a variable framerate, you avoid all that trouble. 

BEFORE you do anything, and I mean: before you purchase a camcorder!, think about your preferred way of delivery! 

if your camcorder allows to switch interlaced <<>> progressive, think again.