It does look very good for the price. It looks good compared to the 400mm f/5.6 prime lens as well but of course the 600mm f/4 prime is much better (costs more than 10 times as much too!) I expect they will sell in large numbers.
It does look very good for the price. It looks good compared to the 400mm f/5.6 prime lens as well but of course the 600mm f/4 prime is much better (costs more than 10 times as much too!) I expect they will sell in large numbers.
I can see the AF being an issue. Once you are passed the focal length where it goes from f/5.6 to f/6.3, all but your center point AF won't work. I tried the 100-400 with a 1.4 TC on Tuesday (f/8). Generally impressed that the AF was as good as it was, but there was definitely an impact.Originally Posted by Jayson
Unless I decide to chase GBH's in rookeries in April/May, I won't need a tele until June. So hopefully Canon will release something like a 400 f/5.6 IS or the 100-400 L II. But if not, the Tamron is really looking tempting.
Nope, the AF system will work as with an f/5.6 lens, because the lens lies to the camera and says it's f/5.6 even though it's really f/6.3.
So with the Tamron all the AF points will work after the lens is f/6.3, or just the center point? I was thinking it may just be the center point (with the assistance of the points surrounding the center).
Edit...just reread your post and I think that is exactly what you are confirming. Interesting. So, are the issues we are hearing about with AF from ~500(410?)-600 mm isn't due to being reduced to the center point on 5DIII/1DX. It is due to less light hitting the AF points but the camera still using those AF points?
Edit #2: I think I was having an idiotic moment with this post. Fortunately, I didn't operate any heavy machinery yesterday.
Last edited by Kayaker72; 02-28-2014 at 01:09 PM.
Yes, they'll all work. With your 5DIII, an f/5.6 lens and 1.4x TC, only the center point (and 4 expansion points) are active because that's how the camera is programmed to behave with an f/8 lens. If you tape the three pins specific to the TC contacts, you'll find that the camera ignores the TC, thinks there's an f/5.6 lens attached, and you'll get all 61 points with the center 21 being cross type. Same idea with the f/6.3, but no tape required because the lens is doing it's own masking.
As you say, the AF points don't work as well with the narrower aperture - it's not so much the amount of light, because they don't work as well even in full sun, it's more that the narrower aperture doesn't provide as large a physical spread of light (to drive the phase difference) from a given point. When you look at an AF sensor, the f/2.8 lines are more widely spaced than the f/5.6 lines - that's the wider baseline that provides greter accuracy, but also requires a wider aperture to spread the light sufficiently.
Just went through Bryan's comparisons, even looked at the 400mm options on the APC center for the similar field of view. My experience is exactly inline w/ these comparisons. I will stay w/ my conclusion that this is a lot of bang for buck.
I need to get the micro adjustment on the auto focus right. Just haven't had time to fiddle with it.
If you see me with a wrench, call 911
And the review is out:
http://www.the-digital-picture.com/R...-USD-Lens.aspx
All in all, seems like a very nice option.
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