Hi Sophie
As Rafael says no need to convert, can I just add you are probably best off if you work in a 442HQ sequence as if you render everything to 4444 you will end up with some huge files and possibly experience some playback stuttering depending on the speed of your drives.
best wishes
Neil
http://www.patience.tv
8 Core MacPro, Kona 3, Tangent Wave, Mackie Universal Symphony 6.5 or MC V 7 with Symphony option. FCP7, Color, Media creation and conversion. Adobe Encore DVD creation and authoring.
i7 2.7 Gig MBP (non retina) 16Gigs Ram Blackmagic Monitor Mini Symphony 6.5 or MC v7 with Symphony option FCP7
7TB raid 5 fibre storage.