The first rays of sun were reaching the flowers, but there was still a lot of dew. I wanted to isolate as much as possible the two flowers from background, so I set the lens at 300mm and I placed myself at the right distance to get the desided composition. I've mounted the lens on tripod (the 28-300 is pretty big - it has a tripod collar and you mount the lens on the tripod, not the camera) and I've taken the photo at ISO 100 and f/5.6, the widest aperture of this lens at 300mm.

It was the fist time that I used this lens and, honestly, I didn't expect much, in particular at its weakest setting (wide open at 300mm) - I have been amazed my the results. Even though I wouldn't say that it is razor sharp as a prime, the image quality is really good for an 11x zoom!

The super zooms are some of the most complex lenses - they need advanced optics to cover such a wide range of focal length. They are very versatile lenses, but the tradeoff is a loss of image quality - usually, 18-200, 28-300 and other similar zooms have poor sharpness, strong artefacts and low contrast.

That said, the Canon 28-300 is an anomalous super zoom: Nikon, Olympus, Sigma and Tamron offers lenses with similar range, but the specs are very different from the Canon. The 28-300 L costs four times more than any other superzoom, it weight three times the Nikkor 18-200 and it is twice as long. That's not all: it is also the only superzoom that offers weather sealing, professional built quality, 1:3 reproduction ratio and push-pull zoom. All these peculiar characteristics make the Canon 28-300 a pretty unique lens. Canon has labelled this lens as "L" - a professional lens - and they have sacrificed the small size and light weight to be able to offer "professional grade" image quality. In my opinion, this is the biggest disadvantage of an otherwise wonderful lens - a 1.7 kg lens is not really an "all around, carry everywhere" lens. In this respect, the Nikkor 18-200 VR is much better, it is so small and light that you can really carry it always with you; on the other hand, the image quality of the Nikkor is not on par with the Canon L lens.

A 100%, processed, crop from the photo taken at 300mm, wide open at f/5.6. 

Even in the field of nature photography, the 28-300 can be used for a wide range of subjects, from landscape to macro and wildlife. The renowed nature photographer Joe Mc Donald is a big fan of this lens - I highly recommend to give a look to his test report. Its range of focal length is ideal on a FF camera - on the Canon 5D or 1Ds3 you have everything from wide angle to a good tele. If you need more focal length, you can even use this lens with a 1.4x TC to get a 420mm f/8, even though there will be a visible loss of image quality (Canon states that the 28-300 is not compatible with TCs, but actually you can use them at the longer focals: you just have to pay attention to not zoom back to 50mm or shorters settings, otherwise you may damage the lens). On APS-C cameras as the Canon 40D, you get the equivalent of a 48-480mm, so you lose the "all around" character of the 28-300, and you need to couple this lens with wide angle, as the Sigma 10-20 or the Canon 10-22. The only advantage of APS-C cameras is that they use the "sweet spot" of the 28-300, that is the central area, so you won't see softness in the corners. That said, I think that overall this lens fits much better a FF camera than and APS.

I admit that I've been tempted to buy the 28-300 L IS many times, but I've decided to keep the 24-105 IS and the 100-400 IS since they offer a wider range, and I like the possibility to carry with me only one of them when I don't need both. On the other hand, if you need this range and you are often in situations where you can't quickly swap lenses, the marvelous 28-300 is the lens for you!