Who hasn't heard the saying
The photographer takes the picture and not the camera, or
A good photographer will make good images regardless of the gear he uses? While these statements are basically true, I believe it is important to use the right tools for the job.
Here's what I use:
A seemingly quite unspectacular piece of gear with the overall lowest image quality of all my lenses, yet there is something about this lens which is difficult to describe. The images it produces are regularly the most impressive I receive from my whole kit due to its extremely wide-angle field of view on a full frame camera. This article shows a somehow similar observation, stating that a 16-35mm lens was used for more than 50% of all the Reuters press photos in 2012.
Tip: If you need best IQ this lens can deliver use it at 28mm f/11.
This is likely all the standard zoom you'll ever need. Prime lens sharpness and contrast through the whole focal range already at f/2.8, fantastic color rendition and creamy bokeh – what more can you ask for?
This standard prime lens is the only piece of my former entry level kit that I didn't sell until today. Why? Because sometimes it comes in handy when you want to go light or you need the 50mm prime typical wide aperture - all with very stellar IQ. Additionally the very affordable price speaks in its favor, but is paid for with very far below average build quality. This lens is also known as the yogurt cup for obvious reasons.
When you are a Canon shooter the decision for a telephoto zoom lens is naturally a hard one since there are so many high quality alternatives in Canon's lineup. I chose the 70-200 f/4 L IS above the cheaper 70-200 f/4 L because image stabilization is a very important feature especially in long focal length lenses, and above the 70-200 f/2.8 L IS II because of weight and size reasons. IQ is on prime lens level on all the white 70-200s.
Although giving it some serious thought I couldn't come up with anything in this regard. This is simply a great lens.
Exploring the tiny things that surround us is one of my greatest photographic passions. The 100L shines with exceptionally high IQ even for prime lens standards right from f/2.8 and even slightly improving at f/4. I prefer it to the 180L because of its better handhold ability due to shorter focal length and IS, because of its size and weight advantage, wider aperture and faster AF. While we are on this subject, I have occasionally heard that the AF performance is typically for a macro lens not up to the performance of other L lenses. In my opinion this is far from the truth since if you use the focal range limiter the 100L focuses effectively instantaneous and just as quick as my other lenses.
Again I can't think of anything I don't like in this lens.
When you arrive at the point where you're thinking about buying a lens like this you should better have a specific goal you'd like to achieve in mind. This is not for the casual weekend shooter. You really need to show some effort and dedication to justify the price tag and to haul this thing around the whole day. But if you are serious, I can't think of anything that can give you more pleasure to use and more spectacular results than a super-telephoto lens. IQ of this lens is second to none – it easily beats all my other lenses and reaches perfect sharpness and contrast wide open.
It may be hard to believe but I use this lens exclusively hand-held and the relatively low weight in this lens class (3190g) was the main reason I chose it over the 600L II. What also helps a great deal is the 4 stop image stabilization which lets me use it with shutter speeds up to 1/20th of a second (see the image of the deer at dusk below). The new IS mode 3 is especially helpful in action situations where the stabilization is only engaged precisely during the exposure and not while looking through the viewfinder.
A teleconverter extends the focal length of a lens while reducing its aperture. I usually use them on the 500L which results in a 700mm f/5.6 (1.4x) or a 1000mm f/8 (2x) lens. When using the 1.4x AF performance and IQ do not noticeably decrease, the 2x shows clearly visible worse IQ and AF only works quite slowly and tends to hunting. Additionally the 5D Mark III focuses a combination with a maximum aperture of f/8 with the center AF point only.
The first row of sample images below were captured using the 1.4x III, the second row images were made with the 2x III in place.