jcolwell Online Upload & Sell: On
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jcolwell wrote:
I've owned four of the five EF 70-200mm lenses.
...The one-stop difference in shutter speeds between the two isn't what it used to be,
docsmiles17 wrote:
You mean f-stops instead of shutter speeds, right?
Nope. I mean shutter speeds, at maximum aperture. When you're limited to "lower" ISO values, then the difference in maximum shutter speed between an f/4 lens at f/4, and an f/2.8 lens at f/2.8 can be very important. For example, if you're shooting night sports on a field with so-so lighting, the typical amount of light is about 7 EV (exposure values). At ISO 100 and f/4, the shutter speed for 'correct exposure' is about 1/8 sec. - way too slow for sports. So, you crank up the ISO. If you take it to ISO 1600, then you're getting a shutter speed of 1/250 sec, with the f/4 lens (at f/4). That's kind of marginal for field sports. I like to keep it above 1/400 sec. If you're shooting in the same conditions (EV 7, ISO 1600) with a f/2.8 lens at f/2.8, the shutter speed is one stop faster, and is now at 1/500 sec. That's in the sweet spot.
Now that I have a1DX, I can crank up the ISO to 12,800 and get shutter speed of 1/1000 sec on a f/4 lens, at 7 EV. The one-stop difference in (maximum) shutter speeds between a f/2.8 lens and a f/4 lens ain't what it used to be.
Of course, TANSTAAFL. In low light, the f/2.8 lens will generally focus faster and sometimes more accurately than the f/4 lens. The differences will depend on the specific camera and lens in question.
Until recently, I used 24/1.4L and 35/1.4L lenses for shooting events in low light, in order to get decent shutter speeds. Then I got a 1DX and sold these two f/1.4L lenses. It turns out that I really never used the super-wide apertures on wide and very wide angle lenses for DOF control - only for shutter speed. I figure my 1DX is as good at ISO 12,800 as was my 1DsIII at 3200; that's a three-stop advantage. The difference between my 24-70/2.8L II and 24/1.4L ~ 35/1.4L is two stops. So, I have a one stop advantage (in shutter speed) by using f/2.8 on my 1DX, as opposed to f/1.4 on my old 1DsIII. OTOH, I'm keeping my 50/1.2L and 85/1.2L II, because I often use them wide open for DOF effects.
Edited on Nov 23, 2013 at 10:29 AM · View previous versions
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