I'm planing to buy reflector 5 in 1 types but I cant choose size. I will take photos of couples ( wedding shoots) so there will be 2 or 3 person to light. My wife will hold reflector (as an assistant) :) So photos will be body portraits, I saw some examples of videos from youtube there is oval reflectors and they light very good.
But I cant decide on, which size I should buy?
very large size like 48"x72" or normal size 40"x60"
Canon Eos 1000D, canon 18-200mm f/3.5-5.6, flash, umbrella, tripod
My choice would be as big as photographed objects visible through viewfinder...
let me explain: The reflector casts the reflection - the size of reflection (with flat reflector) is cca the size of reflector itself... So if you are trying to light a scene of three people waist-up side-by-side - you will need reflection at least 180cm wide and 80cm high, to provide uniform fill for whole frame (with smaller reflectors parts of image will not get the fill light...) The size is as well important when trying to use the 5-in-1 reflector as a diffusing panel for sunlight - simply the "shadow" of the reflector has to fall on every part of person/group photographed...
So the size of reflector somehow defines how big objects you can photograph with it... But with the size grows the price, so when the price is too much for you than I would turn-on the gray mass and would go for DIY... (-as I did soooo many times :) )
(Off course you can bend the reflector to cover bigger area or focus the reflection to smaller area... but spreading the light across bigger area is decreasing intensity of fill and requires some skills or tools... so I am not going deeper into it... )