I am about to upgrade my Pentax "ist"DL to the K-7. My problem is that I was looking at the sigma 50-500 to go with it, but when I went shopping the guy suggested I go for the new Sigma 120-400 as it is a bit faster, lighter(for hand held & low light shooting), is a bit sharper and around $800 cheaper.
My original reason for going for the 50-500 was mainly more for the lower end option but also good to have that upper range. I have done some OS travelling and now going to Africa in August and found in the past having to change lenses from long-short-long can mean the loss of the shot and having the versatility of the 50-500 would allow me to be able to only have to take the one lens away.
Would the 120-400 give me enough range for general shot? or would I need to still have a shorter lens on hand?
Is my thinking all wrong?
Unsure please help.