What should I look for when buying a lens?

[JustAnEngineer]

On the Canon side, the EF-S 18-55mm f/3.5-5.6 IS lens included with the EOS Rebel XSi kit has much better image quality than the 18-70 lens included with the Sony α-series (the Photozone review of the Sony lens shows astoundingly-bad purple and green fringing). Add the $90 "nifty fifty" EF 50mm f/1.8 lens to your kit for low light and portrait work, and you're off to an excellent start without breaking the budget. The 50mm f/1.8 is well-loved for combining good quality glass and a wide aperture in a cheap plastic body. It is Canon's lightest and cheapest EF lens, yet it can still provide good image quality.

Unfortunately, cheap telephoto zoom lenses usually aren't good, and good telephoto zoom lenses usually aren't cheap. I'll have to defer to the members here who have experience with the value-priced telephoto zoom lenses to know which provides the best bang for the buck. Measure all of them against the $1700 EF 70-200mm f/2.8L IS USM, and they'll look inexpensive and easy to carry, anyway. The Sigma 70-300mm F/4-5.6 APO DG Macro recommended by Overread is $249, vs. $149 for the non-APO version that you initially asked about.

Take a look at the lens reviews here:
http://www.photozone.de/Reviews/Canon%20EOS%20Lens%20Tests
http://www.the-digital-picture.com/Reviews/

P.S.: The field of view crop factor for Canon's DSLRs with APS-C size sensors is 1.6 rather than the 1.5 factor for Sony or Nikon.

 

[F1addict]

On the Canon side, the EF-S 18-55mm f/3.5-5.6 IS lens included with the EOS Rebel XSi kit has much better image quality than the 17-70 lens included with the Sony α-series. Add the $90 "nifty fifty" EF 50mm f/1.8 lens for low light and portrait work, and you're off to an excellent start without breaking the budget. The 50mm f/1.8 is well-loved for combining good quality glass and a wide aperture in a cheap plastic body. It is Canon's lightest and cheapest EF lens, yet it can still provide good image quality.

Unfortunately, cheap telephoto zoom lenses usually aren't good, and good telephoto zoom lenses usually aren't cheap. I'll have to defer to the members here who have experience with the value-priced telephoto zoom lenses to know which provides the best bang for the buck. Measure all of them against the $1700 EF 70-200mm f/2.8L IS USM, and they'll look inexpensive and easy to carry, anyway. The Sigma 70-300mm F/4-5.6 APO DG Macro recommended by Overread is $249, vs. $149 for the non-APO version that you initially asked about.

Take a look at the lens reviews here:
http://www.photozone.de/Reviews/Canon EOS Lens Tests
http://www.the-digital-picture.com/Reviews/

P.S.: The field of view crop factor for Canon's DSLRs with APS-C size sensors is 1.6 rather than the 1.5 factor for Sony or Nikon.

Did you find that APO version on ebay for $250 if not where? If its $100 and is really better then I'd get that seeing as its below my $300 limit.
And I think I've pretty much decided on the Sony A300. To me, I simply can't justify the extra $100-$150 for the XSi for not to many more features. And in all the tests I've seen and read, they were scored nearly identically. Besides, as far as image quality goes. I think both of them would end up being an improvement over my Canon SX100 point and shot.
Plus the sony kit lens combined with the sigman 70-300mm will give me the whole range from 18-300mm. I'll still upgrade later on to a wide angle lens and perhaps switch the kit lens for something better thanks to the info you have provied me. Eventually I'll certiantly want higher end lenses but for now my budget simply won't allow for them. But for now I think I will be able to be happy with the A300+Sigma 70-300mm APO combo.

 

[JustAnEngineer]

You probably want to check prices on-line at B&H Photo Video, Adorama and Amazon.

I'm afraid that the chromatic aberration with the Sony 18-70mm f/3.5-5.6 lens would be unacceptable. You might want to forgo it and get a third-party lens right from the get-go.

 

[F1addict]

You probably want to check prices on-line at B&H Photo Video, Adorama and Amazon.

I'm afraid that the chromatic aberration with the Sony 18-70mm f/3.5-5.6 lens would be unacceptable. You might want to forgo it and get a third-party lens right from the get-go.

chromatic aberration?
what is that?

 

[JustAnEngineer]

Look at the last photo at the bottom of the analysis here:
http://www.photozone.de/sony-alpha-...0mm-f35-56-dt-review--lab-test-report?start=1

CA is when the lens doesn't focus all of the wavelengths of light together, but spreads out the spectrum like a prism does.

 

[prodigy2k7]

some parts of the light spectrum, rays are being bent... Rays arent precise... Basically you get some glorinw on the edges... sometimes red purple green blue etc...

Sorry, that is a educated guess, I could be wrong, but im sure it has to do with the lens construction, the curvature of each element in a lens and what the lenses are made of etc...

http://en.wikipedia.org/wiki/Chromatic_aberration

 

[F1addict]

hmm!?
are there any Sony users with this lens that can verify if this is a problem for them?
I still don't like the higher price of the XSi, I can always get the Sony, use it for a few weeks then decide if I need to replace the kit lens and wait a while before getting the zoom.

 

[Bifurcator]

All lenses have CA dispersion and distortion. How much or how little is the question. Thus benchmarks.

It's shows it's ugly head in some circumstance or another to some degree or another to every photographer and especially every budget shooter.

 

[F1addict]

All lenses have CA dispersion and distortion. How much or how little is the question. Thus benchmarks.

It's shows it's ugly head in some circumstance or another to some degree or another to every photographer and especially every budget shooter.

So what your saying is while I may see the problem in my pictures, another photographer doing a different type of photography may not see it or may not see it as badly?
Its worth the risk. If I see it badly I'll just buy a different 18-70mm lens from sigma or just a different Sony one or something. And I'll wait a little while longer before I buy the 70-300mm lens. I have my 10x optical zoom point and shot if I need it and an 80-200mm lens for my old Minolta X-370 (before you ask, no that doesn't fit the Sony, its not an Alpha mount its and MC/MD mount)

 

[prodigy2k7]

I have the kit lens i never see it... I only see it sometimes with my 75-300 on telephoto end

 

[Bifurcator]

So what your saying is while I may see the problem in my pictures, another photographer doing a different type of photography may not see it or may not see it as badly?

Well different subjects show it differently. For example one way we lowly users test dispersion CA is photographing leaves in shadow against bright sky and look for the red/cyan and blue/yellow fringing. We can notice vignetting by taking a shot of solid colors. And we can see distortion by photographing something with straight lines or fine lines - especially near the edges of photos. There are other things to consider too. Each one of these things call them problems or optical characteristics, can be more or less apparent at different apertures. This complicates testing and makes single image examples just about useless. Everytime someone posts example images of typical photography to "show what the lens can do" I just laugh - it's meaningless. Controlled testing is needed and it won't be a "pretty picture" or "good photograph" in almost all cases.

Its worth the risk. If I see it badly I'll just buy a different 18-70mm lens from sigma or just a different Sony one or something. And I'll wait a little while longer before I buy the 70-300mm lens. I have my 10x optical zoom point and shot if I need it and an 80-200mm lens for my old Minolta X-370 (before you ask, no that doesn't fit the Sony, its not an Alpha mount its and MC/MD mount)

Yeah, if you have money and time to throw at it then just do whatever. If you want to learn about the qualities that define lenses and select the best within your budget then do that. For me I learned when I was young that equipment matters allot in reaping maximum enjoyment. Whether it's target rifles, skis, tennis rackets, surfboards or running shoes - good equipment makes a pretty big difference. Knowing the differences adds appreciation and helps you to understand function - both of which can affect skill.