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Old Nov 9, 2010, 9:10 AM   #21
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it is a big difference on a long focal length prime, but on such a short length prime that 20% is not allot with a 28mm or 30mm. 20% of 100mm but we are really working with such a small distance that it really does not matter.

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Old Nov 9, 2010, 9:53 AM   #22
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You are missing what I'm saying, with a prime of this length and "working at more normal distances for that sort of lens, between 6 and 10 feet" then it is a gain that can be seen. If you are using it for more distant subjects you are not going to notice much.

20% reduction in DOF is 20%, doesn't matter if we are talking 30mm or 100mm.
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Old Nov 9, 2010, 3:44 PM   #23
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you are missing what I am saying also, 20% of a short focal length is not as big as the 20% number makes it seem.
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Old Nov 9, 2010, 3:46 PM   #24
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I've honestly no clue, what do you mean by 20 of a short focal length, I'm referring to the change in DOF, nothing to do with the different focal lengths of the two lenses.
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Old Nov 9, 2010, 3:49 PM   #25
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I am going by your number.
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Old Nov 9, 2010, 3:57 PM   #26
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Sure, I'm talking about a 20% difference in DOF (well just over). Why is that any less important than a difference of 20% in the DOF of longer lens when used within its optimal range?
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Old Nov 9, 2010, 4:03 PM   #27
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because the point where 1.4 and 1.8 will keep the whole frame in focus with infinity is so short with a 28 or a 30. That it really does not matter much. Also with the shorter distance. Increasing the separation form the background form the subject to increase shallow dof is very little in reality, that is is very easily done. It can be achieved by moving the subject 1 foot further away form the background.
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Old Nov 9, 2010, 4:55 PM   #28
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I can see this is going nowhere so I won't state the major facts again an leave it for the OP to ask for clarification if so desired.
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Old Nov 9, 2010, 5:02 PM   #29
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I think the OP got both points already. And sees that each lens has it's advantages and disadvantages. And form other threads the op is considering FF down the line, and the sig is something that does not serve double duties.

We will not agree that the 20% is huge or not huge, base on the differences in preference and shooting styles. So I agree to just disagree on this point.

Quote:
Originally Posted by yohy View Post
Thanks! Great pictures.

This makes sense, generally, although I read that the Sigma is better against bright light (http://www.lenstip.com/253.11-Lens_r...M_Summary.html), which makes me wonder if the Canon is really better for outdoors.....

In the end, I think the lenses look very similar, and that you are right on target: (1) the Sigma wins out for indoors/low-light and DOF; (2) the Canon wins out for versatility (FF/APS-C and maybe outdoor/indoor) and lower distortion and astigmatism.

I don't like that both lenses seem to have issues with CAs. In the end, I will probably go with the Canon, but the Sigma sure is tempting for indoor work because I need every stop I can get to get light onto the APS-C.

Hmmm.... decisions decisions.
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Old Nov 9, 2010, 5:39 PM   #30
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I think I understand, and I appreciate both of your comments. Hearty thanks!

SIGMA: I think the Sigma is a (slightly) better lens for what I want in the next three months of traveling. Whether in absolute or percentage terms, the DOF difference does seem to be a lot to me (no disrespect, shoturtle -- your advice has been very valuable). At 6', if I'm snapping a quick, spontaneous scene at a party, 2" of DOF can make the difference between getting one person's head in focus vs. having the non-subject next to them partially in focus. And at 3', 20% difference at a restaurant could mean the difference between getting the entree plate in the picture vs. getting the entree plate plus a glass in the picture. Sure, I can move in to get less DOF, but that's a different framing.

CANON: I think the Canon will save me money in the long run -- not just because of the FF, but the filter size is a common one among Canon FF lenses, so even the $100+ I spend on filters will be useful later too (note: even if I don't get the FF camera, this will be more cost effective because I can use the same filters for other 58mm lenses).

Hmm. My inclination is to get the Sigma and pay the piper if and when I get a FF camera. If I'm hard up for money at that time, well, I probably won't get the FF camera anyway... And I want the best shots I can get in the meantime.

Thanks again, guys, for your great debate. The adversary process really does bring out the truth!

Last edited by yohy; Nov 9, 2010 at 5:44 PM.
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