I think answering yourself these questions might help....


1.) How many shots do you think you will shoot in a given 'shoot'?


2.) Will you shoot in Raw, JPG, or both?


3.) Will you will have access to a storage device of some kind. Laptop, portable media device you to download to on the spot, etc.


4.) Is speed shooting (many shots quickly of a moving subject) is a need.


5.) Do you want to play it safe and have backup cards for the purpose of card failure or subject organization?





So, how many shots you will take in a shoot based on what type of file you are saving in and how long you will go without having access to a storage solution should determine how much capacity the card needs. I'm shooting the largest file of both types on a 50D, so I'm going to guess my average picture will consume 25megs. I'll get 40 shots per gig. I tend to shoot about 450 pictures in a day in certain situations (England vacation for example). My old 4gig card from my old 300D won't cut it at all. I also shoot fencing (of the sword variety) sometimes and want the speed of a fast cart. So, I bought a 16Gig IV.


In looking at multiple cards I had something of a dilema. I have a small laptop (12" 5lbs) that I have used up to this point to download cards to, and it's fine for leaving in the car or hotel room (it was bought specifically for travel). I wanted to still have the ability to save a lot of photos but not have to bring the laptop with me and was considering buying additional cards. I had also been looking at portable storage devices I could download the CF right to. At first I didn't think the cost of the storage devices was justifiable... but when I considered a 32gig card was $250 and the 160gig Wolverine was $300 it suddenly became very cost effective.


Now a while ago I stupidly left my 16gig IV CF card at home and had a Camera with no card in it... so I went to a nearby store and bought a 32gig III card, but I had more cash flow at that point. So now I have a card that has much more storage space that I use for 'normal shooting' (i.e. I don't plan on taking a lot of consecutive shots of a moving subject) and my 16gig IV. And, yes, the speed of writing on these two cards DOES make a noticable difference.