[eeyore]

Originally Posted by MonArk

Thanks for such definitive responses. I take it that an adapter/converter will lose as much quality as I will save by not having to crop even if I start with the L series 70-200?

you could get by with a 1.4 tc - but that would only give you 98-280 f5.6 and a decent quality TC would cost you nearly as much as a 90-300 f5.6 lens (probably more if you bought the lens s/h)

dont go with a 2xtc as not only will optical quality suffer but it would be an effective f8 140-400 so your af would pack up in all but the brightest light.

you could go with a 2xtc if you swapped the lens for a 70-200 f2.8 but that would cost more in total than just buying the 100-400