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Old Nov 8, 2010, 7:16 PM   #11
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there is not really a big difference in shallow dof between 1.4 and 1.8. that is only 1/3 of a stop. But mention in the other thread, the sig will not transition over to a FF like a 5d3.
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Old Nov 8, 2010, 7:55 PM   #12
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there is not really a big difference in shallow dof between 1.4 and 1.8. that is only 1/3 of a stop. But mention in the other thread, the sig will not transition over to a FF like a 5d3.
Thanks, Shoturtle. You are right that it makes sense to get a versatile outfit. That said, I have 2.5 months of travel coming up (I am between jobs), and so the value of my current equipment now is greater than its value in a year when the 5dIII comes out. I don't know whether I'll actually buy a 5DII or 5DIII in a year..... Of course, in the end you are right that if the 28 1.8 and the 30 1.4 are more or less on par, then I should get the 28 1.8.

Although the difference between 1.4 and 1.8 is only 1/3 stop, the Canon's results aren't that great wide open, whereas the Sigma's are. Thus, if this lens is to give me good pictures with shallow DOF, I wonder whether the Sigma is better after all (even if I take a hit in a year when I can't use it on my new FF....
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Old Nov 8, 2010, 7:59 PM   #13
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The thing about shooting wide open with primes are you really do not shoot wider then 2.8 during daylight hours. So if you are planning to use it outside, the canon is more consistence stop down. Now if you do plan to shoot indoor and do shoot at 1.4-2.5 the sig has the advantage in sharpness.

They are both good lenses.
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Old Nov 8, 2010, 8:12 PM   #14
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This is what you can expect with the 28 1.8 at 1.8 and 2.8.

the first 2 are 1.8 the 3rd at 2.8
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Old Nov 8, 2010, 10:11 PM   #15
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The thing about shooting wide open with primes are you really do not shoot wider then 2.8 during daylight hours. So if you are planning to use it outside, the canon is more consistence stop down. Now if you do plan to shoot indoor and do shot at 1.4-2.5 the sig has the advantage in sharpness.

They are both good lenses.
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, 1:30 AM   #16
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ST, at those sort of distances then sure you won't see any difference, actually you won't see any real shallow DOF at all, most of the photo will be in focus.

If you are working at more normal distances for that sort of lens, between 6 and 10 feet then you will certainly see a difference. Assuming 30mm for both to take the framing out of the equation then we get the following.

Range 6ft, f1.4, DOF = 0.65ft
Range 6ft, f1.8, DOF = 0.82ft

Range 10ft, f1.4, DOF = 1.82ft
Range 10ft, f1.8, DOF = 2.30ft
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Old Nov 9, 2010, 1:36 AM   #17
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yes there is a different, but not a huge different. As you numbers indicate. Maybe 4-5 inches at 10 feet and under 2 inches at 6 feet.

But each lenses has it's strengths and weakness.
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Old Nov 9, 2010, 1:45 AM   #18
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You are taking the ratio out of the equation. At 6ft we have 2.04" difference between the two, that's over a 20% reduction in DOF from f1.8 to f1.4.

At 10ft it is a shade under 6" difference.
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Old Nov 9, 2010, 1:51 AM   #19
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but the distance is so small that a simple lean in or out can actually compensate for it. So while it is 20% in the real world with these short focal lengths it is really not a huge difference.

Even between a 50 1.4 and 50 1.8 which I have both. The difference can be made up my one step forward or backwards.

PS the photos were not meant for dof example, but the softness question that has been brought up on this thread and another thread the op started. The sigma is sharper wide open, but that lead changes as the lenses are stop down.
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Old Nov 9, 2010, 2:37 AM   #20
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Quote:
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but the distance is so small that a simple lean in or out can actually compensate for it. So while it is 20% in the real world with these short focal lengths it is really not a huge difference.

Even between a 50 1.4 and 50 1.8 which I have both. The difference can be made up my one step forward or backwards.

PS the photos were not meant for dof example, but the softness question that has been brought up on this thread and another thread the op started. The sigma is sharper wide open, but that lead changes as the lenses are stop down.
I'm not sure what you are talking about re the lean in or lean out. I'm talking shallow DOF, getting more out of focus/faster out of focus fall off behind/in front of the subject, moving won't compensate for that. If talking landscapes then sure no difference, if talking close up work, subject separation etc then having over a 20% benefit is big.

As for softness, a web size photo is never going to show a difference. Why a resized photo is no use in showing camera quality

With stopping down, that's all well and good to get sharp, if you want stopped down sharp, I personally rarely care too much about that, I want sharp when open wide, for me that's the main reason for buying a fast piece of glass. Sigma has it right with the 30mm f1.4 and 50mm f1.4 (I've not yet seen the resuts of the 85mm f1.4) so my hat goes off to them.
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