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Old Jan 22, 2005, 5:13 AM   #11
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pcimaging wrote:
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The Sigma is heavier although I do not know how much so. That lens is only a little more expensive than the Canon...
This isan apple/orange comparison

Off course it's heavier (+ more expensive)like all f/2.8 lenses are... The max f-stop isa ratio ofthe diameter of the lens opening to its focal lenght: Ifthe max focal lenght is the same (ie 200mm), but the aperture is larger -> the diameter of the lens has to be bigger -> the optical elements are now larger (to collect more light) -> need more metal to keep the entire thing whole (hence heavier) by design!

A fairer comparison is Canon own70-200 f/2.8's: the Sigma is not heavier here but it's actually lighter on the $
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Old Jan 22, 2005, 5:01 PM   #12
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I've trialed the Sigma EX 70-200mm 2.8 and the Canon L 70-200mm 2.8. Also have used the Sigma 70-200mm and 120-300mm with a 1.4x TC. I believe the Sigma 70-200mm's performance is all but indistinguishable from the Canon 70-200mm, except at 70mm where theSigma is a bit soft at 2.8, at least in my experience. (The Canon softens up at 70mm/2.8 too, just less than the Sigma.) You will probably get light fall-off wide open with the TC.

I really like my Sigma 70-200mm for shooting youth sports and outdoor team/family candids. I've done some indoor soccer work with it as well, and manage decent results, but oh the lighting in these places ... it's just darn hard shooting.
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Old Jan 23, 2005, 6:04 PM   #13
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Well now I'm starting to get cofused! I thought I had made my mind up and was going to get the "F4' and decide later on either the 1.4 or 2.0x extender but now after reading this info about the F/4 problem with focusing and noticing a number of almost new f/4's for sale on ebay, I'm starting to have second thoughts. Maybe I should look into the new Tamron 200-500/5-6.3 DI LD-IF. Thr test results I've seen on the Bob Atkins website rate it quite high. What I want is a long zoom that will blow up to 13x19 size. I sell a few prints but the quality of the lens has to be good for that size print.

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Old Jan 23, 2005, 9:16 PM   #14
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Wow, now that's like an apple / watermelon comparison! I think that the 70-200's fit a different bill -- some reach, but also useable for general photography. The 200-500 is of course out of that picture altogether -- it's all about reach (and you shouldn't even consider hand-holding it). I think this is how you need to consider these. The cropped DSLR's may make the 70-200 range a little less useful than in the past, as it changes from a general purpose to more of a "reach" lens. That's unfortuante. Fortunately, the 50 1.8 fills some of that gap... If a lot of reach is what you're after, then you should compare the 200-500 to other zooms that cover at least 400, and also some primes in that range. E.g. the 400 f/5.6 L is a very nice option if you can live without a zoom.

http://luminous-landscape.com/review...tten-400.shtml

Don't be too worried abouta few reports of focusing problems with the 70-200 f/4 L. This lens probably sells in the thousands of units, and, yes, there are a few stumbles (as there probably are with any but the non-bargain individually tested lenses). I think that the potential issue of some duds can be addressed well, and only in this way -- by testing or trying your own sample, and exchanging / servicing it if you have a problem. Bob Atkins also has a page on how to test for focusing problems.


What would I do in your place? Probably see if I could get my hands on that Tamron, a Sigma in that range, perhaps a Canon 100-400 L, and a 400 f/5.6 L prime that would serve as a reference for comparison (assuming that I'd be willing to buy any of these lenses). I would pick a dealer and salesperson, and start a relationship, and commit to buying something, and just deciding which one over some time. If the best stores do not have stock ona lens, I'd ask about trying some of the others first, and then asking about ordering in the missing one with an option to return.
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Old Jan 23, 2005, 9:28 PM   #15
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Thinking about the 1.6x DSLR crop further, I'd probably also consider the 300 f/4 L (IS), which is recommended elsewhere on this forum, and also quite popular and successful from the following reports:

http://www.photo.net/ezshop/product?product_id=333
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Old Jan 24, 2005, 1:36 AM   #16
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All Canon lenses might have the back focus problem with a particular body. My 70-200f2.8L IS did - the lens was always soft until I sent it in for calibration - which Canon did for free. Can't guarantee they'll do the same for you, but Canon has great customer support and I suspect they want this problem taken care of.

I'm guessing, but I think thefocus problem comes from two things: it depends somewhat on the camera's focus algorithm (how it finds focus) and the lens factory settings of distance. If the lens settings are slightly off an a camera body uses an aggressive (fast) focus algorithm, bad things can happen. Most SLR's use fast algorithms because we (the customer) want fast more reflexive cameras. So focus algorithms have gotten too smart for some situations. The camera images the current focus setting - then moves the lens focus a little. From these two points the body extrapolates to a "good" focus and moves the lens there. If teh lens is miscalibrated, even slightly, focus can be off.

ps: The 70-200 f4 is sharper than the f2.8. Slower lenses always are. But in the mid latitudes, f8, f11, bboth lenses are equals, with the f2.8 perhaps a touch sharper. Check out Canon's lens MTF charts. Something no other manufacturer shows.

http://consumer.usa.canon.com/ir/con...p;modelid=7345


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Old Jan 24, 2005, 7:53 AM   #17
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TDM_Canon_User wrote:
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Check out Canon's lens MTF charts. Something no other manufacturer shows.
FYI - http://www.sigma-photo.co.jp/english.../70_200_28.htm
It looks to me like there's an MTF chart for every lenses... :idea:


On another note calibrating a lens to a particular body is not kosher IMO: What if you have multiple bodie(s)? If a lens focus fine on an EOS-3 or EOS-1 before, it should focus equally good on a 10D or a 20D -> If there's a front/back focus issue with a camera, then that particular body need to be 'adjusted' not the lens (otherwise the lens is 'matched' to 1 particular body, but not the others)... Also when a TC is used, the lens distance to a body is 'modified'; and when a close-up filter is attached to the front of a lens, the body 'need' to adjust for this 'modification' as well...

Someone posted a picture of the AF adjustment screw in lower right corner of the camera's mirror box in a previous post - http://ghonis2.ho8.com/rebelmod9.html
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Old Jan 24, 2005, 8:39 AM   #18
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NHL wrote:
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If a lens focus fine on an EOS-3 or EOS-1 before, it should focus equally good on a 10D or a 20D -> If there's a front/back focus issue with a camera, then that particular body need to be 'adjusted' not the lens (otherwise the lens is 'matched' to 1 particular body, but not the others)...
While I would like what you state, NHL, to be the reality of the situations concerning body/lens focus problems, it just seems like the reality is that it is more complicated than that.

What if my 20D body focuses perfectly with some of my lenses but not a few other of my lenses. Wouldn't adjusting the body so that it focuses correctly with the ones that didn't focus correctly before result in having the previously correctly focusing lenses to now focus incorrectly?

I don't pretend to know all the details of how the manufacturers have implemented autofocus. A simple feedback loop seems sufficient to my simpleton brain but perhaps the reality of the situation is that it is more complex than that and a camera body and lenses must be considered as a "system" (and adjusted as such) to get the best performance from the combination...
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Old Jan 24, 2005, 9:28 AM   #19
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geoffs wrote:
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I don't pretend to know all the details of how the manufacturers have implemented autofocus. A simple feedback loop seems sufficient to my simpleton brain but perhaps the reality of the situation is that it is more complex than that and a camera body and lenses must be considered as a "system" (and adjusted as such) to get the best performance from the combination...
That's my whole point... Will it be 'another' system when I buy a 1Ds mrkII or a 40D in the future?

Which 'combination' is correct then? or a lens has to be constantly adjusted... with each 'new' body? (then it won't be compatible with my older EOS-3 or 10D anymore)

Can you swap the lenses with your friend's (or the store) 20D and determine which is faulty? :idea:
ie the same lens has to work on all interchangeable bodies!
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Old Jan 24, 2005, 3:43 PM   #20
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NHL, I should be getting my new (after exchange) 70-200 f/4L lens today or tomorrow. Right now on my 20D, my 17-85IS and 300 f/4L IS with or without 1.4xTC focus well. If the new 70-200 still does not focus up to the performance of the other lenses I will be reconciled to two actions:

1. Try some other 70-200 lenses from friends on my 20D and let them try mine out. Similarly, at the same time, why not let them try out my other lenses to see how they focus on their bodies.

2. As unpleasant as it may be, I will probably end up sending in the 20D body and ALL of my lenses to Canon servicing for them to be calibrated as a system.
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