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Old Aug 30, 2006, 12:05 PM   #21
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I'm going to add some thoughts to this discussion :blah:

First off, I have about a 50/50 mix of Canon Lenses and Sigma lenses - including L lenses. So, I don't have a bias one way or the other.

I will say, however, it is important to judge a lens on it's individual merits not on the manufacturer name alone - I think everyone would agree there - generalizations are fairly pointless (e.g. Sigma is always as good as Canon at 1/2 the cost is a stupid statement).

Now, the second point is this: make sure you get advice and do research on how a particular lens performs under the conditions you will use it in. This is important. As an example, let's take something in the 24-70 2.8 range. In doing research on lenses for this type of lens I kept running into 2 lenses: Canon's L version and Sigma's version. I was fortunate to get some advice from experienced photographers who I trust and this is what I found: The Sigma was optically just as good as the Canon (this coming from an experienced photog that used both in the real world not just pixel peeping at a single unscientific test or looking at MTF charts). So that was great - in fact, he ended up selling his Canon and keeping the Sigma. But, he admitted the Sigma focus was muchslower in low light than the Canon - not important for him since he wanted 2.8 for DOF not low-light. But he also shot some sports with it and confirmed indeed if he needed a lens for low light sports the Canon was the better choice. Now, that happened to be the genre I was going to use the lens for. So, low light focus speed - which a lens contributes to - was an important attribute. So, he agreed for my purposes the Canon was worth the extra money - but for his it wasn't. If I didn't need the focus speed, the Sigma would be the better option because the better build and focus speed of the Canon wasn't enough to justify the cost difference. People that hadn't used both under low light sports shooting might never know about the difference since focus speed is not something you regularly see in reviews.

So, which lens was better depended on the purpose.

In comparing the Canon 70-200 2.8 to Sigma 70-200 2.8, optical performance, build quality and focus speed of the Sigma was about 95-99% of the Canon in about every condition I could find. So, in that case the $400 savings was worth the 1-4% performance difference.

So, what I'm saying is: sharpness may not be the only thing to consider. Now, you could argue with the findings I listed above - and I'm sure people will. But I think the concept I'm trying to get across is still valid: Just like buying a camera body - when you buy a lens you should know what features are important to your style of shooting and look for opinions from folks who rigorously use those features in evaluating a lens. Another example of this type of thing is the bokeh of a lens. Not all lenses with the same aperture value produce the same quality bokeh. So, for some folks where bokeh is important you will want reliable opinions on bokeh quality. The quality is directly related to lens design - so two different 2.8 lenses will likely produce different bokehs - which one is 'better' may be important to you. And it may be more important than say focus speed. So, you may select a lens that has better bokeh and slower focus speeds because that's what is important to YOU.

So, beware of generalizations - look at each lens on a case by case basis and make sure you're looking at the features important to YOU.

Just my thoughts on the whole: OEM vs. 3rd party lenses and which is better.
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Old Aug 30, 2006, 12:14 PM   #22
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Earlier today I mentioned the high quality of the Pentax 50-200mm lens. To backup that statement up I wanted post a photo sample taken with that lens. MT
I'm sorry MT, you often give great advice, but surely you can see that from the image you posted it's basically impossible to tell whether the lens is any good at all?

The picture is full of horrible artifacts (as it appears on this website) they could come from a range of different factors. The lens may be very nice or it may be rubbish. Judging from that picture it's impossible to tell.


So, beware of generalizations - look at each lens on a case by case basis and make sure you're looking at the features important to YOU.
I agree 100%.

Sharpness is always the single criterion that beginners focus on, but for my photography is one of the least important factors. In fact MTF measured sharpness is the first thing I look for, and if it reaches a certain minimum standard I then put it out of my mind completely. As long as a lens is reasonably sharp, for the kind of photographs I take it really doesn't matter very much how close it gets to perfect.

If I need a sharp photo it usually coincides with the requirement for large DOF, so it's easy enough to stop down to f8 or f11 where even unsharp lenses usually perform well enough to be hard to distinguish from much sharper lenses.

For me AF speed is probably the single most important issue, I HATE slow focus lenses.

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Old Aug 30, 2006, 12:39 PM   #23
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For me it is the CAs, purple fringings, vignettings, bokehs, design, and auto-focus performance that matters the most to me. I also pay attention to the sharpness and distortionsofcouse, but not before the first list comes first.:idea:

Obviously the very first thing I look out for is thewidest F valueand lens reach (Focal length)! Such as 16-80 F/2.8 (In my dreams!):-)
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