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Optics/Depth of Focus question.
Can anyone make sense of this for me? I took two shots, one with my 17-55mm, and one with my brother-in-law's 24-70L. Both shots were on my 7D, both shots were at f/2.8. The 17-55mm shot was at 1/40th, and the 24-70L was at 1/50th. The 17-55mm was dialed to 33mm, and the 24-70 was at 35mm. Below are the two shots. To my… -
Re: Optics/Depth of Focus question.
so in the 24-70 shot the shirt logo is out of focus (far away) but the couch details on left side are in focus (closer). On the 17-55 shot it is reverse. I can't really say one has more DOF then the other..I think the easiest explanation here is that the focal point was not the same in both pictures...24-70 focus point was… -
Re: Optics/Depth of Focus question.
Thanks, Ziggy! That's really helpful. As usual, when your data doesn't match up, go back and look at your assumptions. I wonder if some of this is purposeful. One of the great things about the 24-70 and 24-105 lenses is the background. Part of that is well designed blades and optics, but maybe part of it is smaller than… -
Re: Optics/Depth of Focus question.
From what I can see on my screen, it seems as though the 24-70 shot has more clarity and definition overall. I know the 17-55 is known to be "just like an L", but the fact is, it's not. Additionally, your focus subject (the pooch) appears to be a tad closer to the body of the person holding it in the second shot (17-55).… -
Re: Optics/Depth of Focus question.
So is the lesson here, that DOF and quality of bokeh are not 100% connected? I'd wager that the larger amount of glass in the 24-70 gives you slightly smoother bokeh. I would, however, also wager that this was not a precise test, as it did not involve truly immobile subjects. To definitively resolve this, grab a tripod,… -
Re: Optics/Depth of Focus question.
Well, glad I'm not crazy. And your explanation does make sense, except isn't that identical to saying that the effective focal length is different? Now, that could very well be, but it would mean that 35mm is not 35mm between lenses. I'm not a pixel-peeper; to me, given an excellent level of sharpness available on every… -
Re: Optics/Depth of Focus question.
I noticed the same thing when I switched from a 24-70L to a 17-55/2.8IS on my old 40D, the difference is real. I had both lenses together for a brief time and I did some tests which showed this. I think it has to do with two things, 1, I believe the 17-55 sits closer to the sensor, and 2, I believe the 17-55 projects a…
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