Quote Originally Posted by Daniel Browning


Quote Originally Posted by clemmb
I checked the ISO charts for 28, 35 & 50mm. The 24-105mm looks sharper to me.

You did not perform the comparison correctly. Read the [url="http://the-digital-picture.com/Help/ISO-12233.aspx]Chart Help Page[/url] where it says this:



<p style="padding-left: 30px;"]Lenses should be critically compared to each other only with test samples from the same camera body..


(Emphasis mine.) This is really important, because the 24-105 would look much worse if the chart had a 50D body. For example, look at the 28-135. On that lens, both bodies are available in the test:


[url="http://the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?FLI=0&amp;API=0&amp;Lens=116&amp;FLICom p=0&amp;APIComp=0&amp;LensComp=116&amp;CameraComp= 474&amp;SampleComp=0&amp;Camera=453]28-135 on 1Ds3 @ 28mm f/3.5 vs 28-135 on 50D @ 28mm f/3.4[/url]


See how much worse the 50D looks? If the chart for 50D+24-105 was available, you'd see that it is worse than 50D+17-55.
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I hear what you are saying and it makes sense so I did a test of my own.


First I looked at Bryan's ISO chart comparison between the canon and tamron 17-55. It looks to me like the tamron is a little sharper than the canon.


I own a tamron 28-75, tamron 17-55 and two canon 24-105s. My 17-55 is a little sharper than my 28-75. I think I have a good copy.


I tested the tamron 17-55 and my 25-105 both on my XTi(same body). Both lenses wide open(tamron at f2.8 &amp; 35mm, canon at f4 &amp; 35mm), same ISO, etc...


The 24-105 is noticably sharper.


I know my test is not scientific but I have always gotten sharper photos from my 24-105.


Mark