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 p.1 #6 · Real World Focal Length Difference onLong End? | |
thekid1 wrote:
My son is now into crew/rowing. I am looking at lenses for a longer reach. I have the 70-200 and was looking at the 1.4x or 100-400. On a 1.3 crop it is 364 vs 520. It sounded like a lot but I went to a couple of sights that compare focal length and the difference did seem that big. The differences in focal length at the short end made a big difference but seem to have less of an impact at the long end. I have a Mark II and a Rebel. With the 1.6 crop that could take my 70-200 out to 448.
I was just wondering if at the long end, a difference in focal length of 350 vs 450 is a big difference in actual practice.
On the same camera - so we don't have to worry about pixel density differences, the 100-400 @ 400 will be a lot better choice than a 70-200 + 1.4. and will put 2x as many pixels on the subject and the subject will look ~ 40% bigger.
Comparing the Rebel (8MP) and the 1D II is a bit different as the pixel densities need to be taken into account. The 8.2MP Rebel has 60% higher pixel density than the 1D II and is thus effectively a sqrt(1.60) = 1.28x TC in itself compared to the 1D II. Thus if you use a 70-200 + 1.4x =112-280 on the Rebel it would be like a 112-280 x 1.28 = 143-358 on the 1D II. So you'd need the 100-400 on the 1D II to do any better in reach (or a 70-200 + 2x) than the rebel.
Using the 100-400 on the rebel would be like using a 128 - 512 on the 1D II.
Why don't you see if the 70-200 + 1.4 on the rebel is long enough and has good enough AF. Ideally if you have the money the 100-400 on the 1D II will be a better combo in reach and AF.
Pixel density is more useful than FOV when comparing different cameras to assess reach.
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