Hi, I have footage at 50i and 25p. The majority is 50i. I have tried viewing both in Premiere: the 25p in a 50i timeline and vice versa. The 50i footage looks pretty soft in the 25p timeline (I'm assuming it just plays one field?) and the 25p also is softer in the 50i timeline but not as bad (not sure how the 50i timeline is interpreting the 25p material). I haven't made any adjustments to the sequence settings - just let the software determine them from dropping the material in. So my question is what is the best approach here and is there a way to convert 25p to 50i prior to sequencing without too much loss of sharpness?

I should say that at the end of the day I will probably convert it all to progressive for web upload but that will involve converting to 60p (or would 30p be better here?) for the web but I'd rather leave that till the end.

If its for the web make it all 25p.
converting 25p to 60p or 30p for that matter will be a pita.
Why 30/60p?

Because all computer screens are 60Hz so movement for all PAL frame rates (25p, 50p, 50i) looks rough.