zenosprey wrote:I am new to the group, have been searching a lot and have not found answer for my situation. Delighted to find so many knowledgeable folks! I have a Canon Xsi and bought the Tamron 28-300 XR VC so I could have it all! Now I would like to get a smaller lens and something that might take sharper photos. I use the telephoto quite a bit with birds and bringing landscape elements closer. I am often close to the max of the telephoto.I also do a lot of cropping which affects the crispness. My budget does not feel comfortable with a $2000 plus lens. Nor can I carry around a super heavy lens with a tripod.
One person said in buying a lens for sharpness one should aim for the high end divided by the low end to equal 4 or less. I do not understand this ...but that would mean my Tamron is 10+. I am working on understanding the technical issues more after using a 5700 Nikon and then Canon IS3 digital camera.
I would appreciate some suggestions for my next lens.
I wouldn't call myself an expert, by any stretch, but shoot Canon also and have a bit of experience with them. You're correct about the 28-300 being 10+, and the old rule of 4 or less goes way back to when zooms were first manufactured. To be frank, they were more than pitiful! Over time, they've improved quiet a lot, but the old rule still applies if looking for the best possible quality. Of course, we can go the limit and say never use a zoom at all because non-zooms are the sharpest. Just use your feet to zoom instead. That's all good, and well... but I'm generally lazy and prefer having options.
Most people will advise that it's better to go with the best possible lens you can afford, simply because you'll end up replacing anything less than what you really want. I've been there, and done it several times, which resulted in costing more in the end. Lenses, unlike bodies, aren't out of date in a year or two. In fact, good quality lenses can last decades if taken care of. They're the primary investment you'll make in photography, or should be.
You didn't say what you were expecting to photograph with the new lens, so it's difficult to suggest. If by smaller you mean toward the wide angle side to use for landscapes, there's several which could serve well. Without going too wide, the EF 17-40mm f/4L USM is around $700.00. For the price, it's an excellent choice, capable of rendering sharp photos with good contrast & color. And since it's an EF series, it will still work if you update to a full frame body later. Canon has also released a few newer lenses with image stabilization recently, including a 17-55 IS if I recall right. But I'd highly suggest staying with their "L" series if at all possible. They're better built, including seals for extra protection. And they have better quality elements to correct distortions, with extra coatings to control flare.
If you're wanting to stay with a longer lens, the EF 70-200 L is among the sharpest zooms produced. They offer several versions, including an f/4 and f/2.8. Both can be purchased with, or without IS. The f/4 without image stabilization is reasonable at around $700.00 or less, and the price goes up from there. The 2.8 version should work with Canon teleconverter, but the f/4 doesn't. However, a Tamron Pro 300 1.4X should work fine. With a 1.4X, you lose 1 f/stop of light, but the quality would likely be superior to your current lens, and close to the same range at 280mm with converter. But if you feel your 300mm isn't long enough, you might prefer waiting and replace it with the EF 100-400mm f/4.5-5.6L IS USM later on. Price is a bit higher of course, at around $1400.00. It's also somewhat bulky, but with the IS you can avoid using a tripod in many situations.
If you can offer a bit more information, you'll get suggestions closer to your needs. Hope this helps a wee bit.
Good luck, and happy shooting.