Perhaps I am asking a very basic question concerning zoom lens performance (related to design and/ or manufacturing). Please bear with me and share your experience.
Do the zoom lenses exhibit uniform pattern in terms of focusing accuracy, sharpness, contrast, etc. throughout the zoom range?
Canon zooms typically show best sharpness in the midrange while quite many Sigma zooms are at their best at the extreme ends while certain areas in the midrange are horrible, e.g. 300mm wide open with the 80-400 OS and 35mm until f11 (!) with the 18-200 OS.
On the other hand, the Sigma 18-200 OS is sharper at the same apertures than the 70-200f2.8L IS at 200mm, especially at near focusing distances!
The 200f2.8L II is sharp no matter what the focusing distance (even with extension tubes) while 70-200's are typically less sharp or even soft near the minimum focusing distance (at 200mm). This is the price you pay for flexibility of a zoom. No matter of calibration will get rid of that because it is part of the lens design (can you say "compromises").
astrolucida wrote:
On the other hand, the Sigma 18-200 OS is sharper at the same apertures than the 70-200f2.8L IS at 200mm, especially at near focusing distances!
The 200f2.8L II is sharp no matter what the focusing distance (even with extension tubes) while 70-200's are typically less sharp or even soft near the minimum focusing distance (at 200mm). This is the price you pay for flexibility of a zoom. No matter of calibration will get rid of that because it is part of the lens design (can you say "compromises").
I disagree with this soo much.
I tested an 18-200 OS in Jessops a while back to see what it would be like in terms of performance for travelling.
I WAS SHOCKED AT HOW BAD IT WAS. The centre didn't touch my 70-200. The corners well. I don't know if I tested a bad one but considering I was comparing 200mm F2.8 to the sigma OS at F11 I would say it was conclusive. I bought a G9 and used my 10-20 as my wide angle with it on my 30D for holidays
My 17-55 IS is consistently sharp throughout all settings.
My 70-200 2.8 IS is the same when it is focused properly - more the camera than the lens.
My 10-20 is also the same although it has more corner fall off, but then it is 1/2 the price of the 17-55 and 1/4 of the price of the 70-200
My EF 24-105, 70-200 f4 IS, 17-40, and 24-70 (just sold) are all excellent and have not needed calibration. Had a new Tamron 28-75 (now sold) that was calibrated several times to improve it. Tokina 12-24 (sold) was calibrated once and was fine afterward.
I have and regularly use the following L-zooms: 17-40/4L, 24-70/2.8L, 24-105/4L IS, 70-200/4L IS, 70-200/2.8L IS, 100-300/5.6L. I bought all of them new, except for the 100-300L, and they're all exactly as they should be. That's not to say that they're perfect lenses and that some of them don't vignette at the wide-open wide end, but they're all as sharp and accurate as they should be.
i've not had trouble with any of the zooms i purchased from canon. my only gripe is that, aside from the 70-200 4/IS, none of them perform on the level of tip-shelf primes.
Just to show exactly how good my 70-200 can be at certain apertures the below picture has been shot at 200mm F5.6, Live view MF at 10x, 1/80th I think.
Processed in DPP, RAW sharpness = 3, RGB sharpness = 200 - this is what I would use for printing to give punch and snappyness
Fred Lindsey wrote:
I tested an 18-200 OS in Jessops a while back to see what it would be like in terms of performance for travelling.
I WAS SHOCKED AT HOW BAD IT WAS. The centre didn't touch my 70-200. The corners well. I don't know if I tested a bad one but considering I was comparing 200mm F2.8 to the sigma OS at F11 I would say it was conclusive.
I tested both lenses at 200mm, at the same apertures, using a 30D. Even wide open at f6.3 the Sigma was sharper than the 70-200f2.8L IS. Imatest results showed, for the whole frame, 1860 for the Sigma and 1818 for the 70-200, so not a big difference, but considering the price differences of the lens, a significant one. In the corners the difference was larger, with Sigma again being sharper.
However, the situation reversed at 135mm, where the center sharpness was about the same but Sigma lost clearly at the corners (75% of the sharpness only). At 100mm, again the center sharpness was about the same while in the corners Sigma had only 50% of the sharpness of the 70-200!
When compared with the 17-55, again the center sharpness was almost the same (90-100%) but in the corners only 20-30% of the sharpness, except at 18mm, where it got 85-100%. Even worse, at the midpoint between center and corner, the Sigma had only 50-70% of the sharpness - thus the very sharp area was extremely small in the center.
The lack of sharpness in Sigma seemed to be astigmatism-related. At least it was blurry in an ugly way, not just soft, but somehow distorted. Thus, even if it showed equal sharpness in the center to the 17-55 and 70-200, at the same apertures, it was very soft at some focal lengths, for most of the image area.
This is why I sold the lens. It was a very nice low light 18f3.5 OS and near-macro 200f6.3 OS lens, but I could not stand its low image quality as an 35f11 OS lens! Thus, a very uneven performer, restricting the available apertures far too much. This does not seem to be a calibration issue, because others have experienced similar performance.
1) 17-40mm f/4 work right out of the box
2) 24-70 f/2.8 perfect after Canon's re-calibrated
3) 24-105 f/4 IS work right out of the box
4) 70-200 f/4 IS perfect after Canon's re-calibrated
The only zoom I own is the 70-200/2.8 IS. I find it sharp wide open and it just gets sharper, it really is a workhorse lens for me and I wouldn't be without it. It was sharp out of the box but I would say it did benefit from a little calibration tweak when it went for service.
