These are difficult question to answer because what lens to get/use depend on what you are going to photograph, so I will just write some reflection on my two zoom purchases after got my kit.
First there is two main types of shots of creative photography: Storytelling shots and subject isolating shots.
In the storytelling ones we keep much or all in focus because different elements possible in different distance from the focal plane play together. In the second one the main subject is in focus and every thing else is blurred, usual the background but seen cool ones where the foreground also can be. You know the type, think flower and portrait shots!
The two important factors in achieving one of the two types is focal length and aperture, both are attributes of your lens not your camera so that is why I will be writing about it here!
This is what interests me the most!
Good news: Aperture is not that important here if you go really wide or long! That is good news because the most tricky stuff in creative photography is to get the right aperture for the shot you want to make. Aperture sure play a role in getting a large depth of field: f/16 - f/22. More good news: All lenses has the small openings, cost nothing to make a small hole!
But in the very short and long aperture play less of a role!
Lets take the wide angles first:
Ultra wide is cool, 10mm/11mm is the king of coolness!
First of all, the importance of wide angles is not to capture things in the wide (sometimes it is) but to compose in depth!
The reason is that when you go wide enough you pretty much get everything in focus from close to far even dropping way below f/16 something you may have to do because there is not enough light for above f/11...
Using the wide focal lengths you should think what to put close (really close often!), in the middle and far away because you absolutely can get it all (in focus) even with the smaller f numbers!
Here is an all in focus ultra wide shot:
Focal length 11mm and f/11. So f number lower than 16 and if I shot it today I would probably chosen f/8 that is the Sigma 10-20's optimal aperture from an image quality point of view and I can guarantee all would been in focus!
So what with telephoto shots? Same thing but at a different scale! Now you put the 'near' far away from you and then the middle and far is gonna be far to... Then also stuff get into focus even if you drop way below f/16.
You know I have had fun with the churches and a yellow building in Bergen doing this ;-) Here is a 'all in focus' tele shot of mine:
Focal length 135mm and f/9. Notice f stop is in the "optimal optical" range of f/8-f/11, no need to go above f/11 to get 'all focus', I do not think I could have blurred foreground church from my chosen viewpoint!
Isolating main subject
Here aperture becomes important, it starts f/5.6 and lower (lower f numbers larger opening). And here there are different between zoom lenses! The expensive ones has more low f numbers than the cheap ones but all got f/4 and f/5.6 that will often do it.
Here is flower shot of mine doing the blur thing:
Focal length 135mm and f/5.3, here the aperture is important!
But a tele zoom with f numbers from 2.8 (seems to be the 1.4 of the long!) does give more creative exposure options in this area of creative shooting...
Another consideration with the zooms is whatever they keep their apertures in their zoom range, it is the signature of a pro tele zoom that it keeps f/2.8 all the way...
With that in mind the Sigma 70-200 f/2.8 MACRO looks darn good on paper: Lowest f number is f/2.8 in all it's zoom range and it do not come with a pro price tag! The image quality reviews say is good value for the money.
But you read a lot about focus problem (particular on Canons it seems to me!) with this lens, you may have to go back to store and get a new one! Still I was half way in the door to get this one but in last second got the Nikkor 70-300 AF-S VR f/4.5-5.6, why?
- Saved me between 2000 to 3000 NOK!
- Extra 1000mm
- I love the VR (I guess IS in Canon language) a lot but could have lived without it.
- Dropping the lowest f numbers makes it light (fast tele got glass man!). I like to go pub hoping with the camera in ready position ;-).
I know you did not ask about ultra wide zooms but I thing this is something all should consider, sure if you are only going to shoot birds then you can forget about it...
I love the tele zoom but if had to have only one I must have selected my Sigma 10-20. Good news is that all the independent lens brands (Sigma, Tokina, Tamron) all got excelent afordable ones!
And final words that should been read between lines in above: We do not shoot in any of the "Program modes", everything on the wheel but M, A and S is a waste of place: The camera is not a mind reader, it will probably not choose the right aperture/shutter speed for the shot! Thumb rule is you got typical six combinations of speed and aperture to choose from, art of photography is that you decide.