skibum5 wrote: ChrisRD wrote: Harry.C wrote:
The ISO 12233 test is not some arbitrary test developed by the owner of that site, and unless you are arguing the owner is performing the tests erroneously then I think we can rule out that option.
When referring to the \'nature of the tests\' as a possible variable I was thinking more along the lines of the difficulties inherent to photographing a flat target with a lens that is not really designed for photographing flat targets in order to determine how good it will be at photographing targets that are not flat.
I\'m not a lens designer nor do I have much technical knowledge about lens design so I have no idea how much this may be a factor (if at all).
Harry.C wrote:
As I mentioned before, the fact copy-to-copy variation exists is something that should be seen as a negative towards the lens manufacturer, not the poor soul who is trying to provide a standard for which to compare lenses against each other. Trying to account for copy-to-copy variation would mean exponentially more work for the site owner and also the ability to obtain 30+ of each lens.
I don\'t think anyone was trying to blame Bryan for copy variation...he\'s actually made an effort to test multiple lenses for several of his test runs.
I think the point some of us where trying to make was that you have to take the ISO crops with a grain of salt...probably largely because of copy variation and because it\'s not practical to test a large number of lenses in this fashion.
\"However, I\'m not totally satisfied with the Canon EF-S 17-55mm f/2.8 IS USM Lens results - the 17-55 under-performed in the comparison tool images in my opinion. And the cheap Canon EF-S 18-55mm f/3.5-5.6 IS USM Lens performed better at the wider focal lengths at the relatively short distance than I would expect to see from this lens - it over-performed in the comparison tool. \"
interesting thing he brings up in that the 18-55 IS actually really is rather crazy sharp, it\'s easy to think oh a cheap kit, and while it may not deliver the most stunning large-scale contrast and colors, it really is pretty sharp, honestly it seemed sharper than my 24-105. And the fabled 17-55 IS, if you look at some other reports and tests, while it is very sharp, it actually has often tested just a bit under many of the other top lenses (although the 17-55 has the lowest CA on the wide side for sure)
so, oddly enough, the one pair of results he questions, is the one I suspect may actually be dead on
The iso test does show that 17-55 does perform better at f4 than the 18-55 at f4. You are likely comparing 17-55 at f2.8 vs 18-55 at f4 which is not a valid comparison. Most really fast lens do worse wide open, but its nice to have the f2.8. So the iso charts do reflect my understanding.
Thats what I like about the iso test. A lot of what you hear on forum\'s is just a repeat of what people heard from someone else without verifying it.
For example, what you will find using the iso test is the new 24-70 v2 at f4 is better than the 24-105 at f4 until about 35mm but after that they are basically equal with 24-105 obviously being way being way better from 70-105. And this gap disappears to almost nothing at f8 at 28mm. But if you listen to feedback on forums this is all summarized down to 24-70 being way better. A more nuanced view is that its tougher to build a wider zoom but a wider zoom is more useful. So the big difference is f2.8 vs f4, reach, and weight.
Jan 08, 2013 at 12:10 AM
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