kris_hartman

<p>David, but you DO need to compensate for aperture when using a full frame lens on a crop factor body. The EFFECTIVE f-stop changes because you are only gathering a percentage of the total light that the lens lets in on the sensor (62.5% on a Canon APS-C). When you throw away 37.5% of the photons that the lens is gathering, the effective aperture HAS to change. That's the same reason that really fast lenses have such large front elements. They focus the light on the same size of sensor that a slower lens will, but the image from the slower lens will contain many less photons than that of the faster lens.</p> <p>Don't take my word, here's a video explaining it from Tony Northrup, who is the author of the best selling photography book on the planet for the last several years.</p> <p> <p> </p>

<p>David, actually the f-stop of the Tamron lens is slower than that on the 80D. Have to remember to apply the 1.6 crop factor to the aperture as well as the focal length. That puts the effective wide open aperture of the Tamron at 10, and the effective aperture of the Canon 70-200 f/2.8 with the 2X converter at 9. Neither are going to let in a ton of light, but such are the compromises you have to accept when you use a crop factor body with a full frame lens.</p> <p>As far as the AF speed between the 7D Mark II and the 89D goes, they aren't as much different as you might think. I rented both for a month before I settled on the 80D, and put them through some pretty hard testing. While the 7d Mark II DOES have dual processors, I found them to be nearly equal in decent light. The Mark II WAS noticeably faster and more accurate in lower light situations, but that's why I have the 6D. Both the 80D and the 7D Mark II use digic 6 processors (Although the Mark II has 2), and have dual pixel AF and all cross type AF points (45 for the 80D and 65 or 6 for the Mark II). With the same lens, I found them to have similar AF speeds with good light even with moving subjects. I DO miss the 10 FPS burst rate though, but 7 fps isn't horrible, and while the Mark II has a bigger buffer, I rarely shoot that long of a burst. On the other hand, I LOVE my touchy flippy screen. I do some video and the 80D is MUCH better for that. </p> <p>I'm solidly in the enthusiast, but not even close to professional camp, so I don't think a 5D Mark IV is in my future any time soon. Heck, I think that the only reason that I switched from a 5D Mark II to a used 6D for my full frame was that I was tired of having to deal with both SD and CF cards. </p>

<p>If you look carefully you can get a decent used 5D MkII for under $600 and a 6D for a couple hundred more. Of the two, the 6D has a slightly faster burst speed and better low light capability. Plus the 6D is a bit smaller and lighter. If you aren't currently using a full frame, and have a camera that uses SD cards the 6D uses SD cards, while the 5D MkII uses CF. I've had both a 5D MkII and a 6D, and while CF is faster, it's nice not having to have multiple card types. Another thing to consider is that the 5D doesn't do video at all, while both of the others do.<br /> <br />Either body is going to be LIGHT YEARS ahead of the original 5D.</p>

<p>I've also been looking at this Sigma and the Tamron. The sport is about twice as expensive, plus it's like 3 pounds heavier, so I have personally ruled that one out,<br /> From the research that I've done, the Sigma contemporary is really great on full frame, but has a bit of a problem with AF hunting on APS-C bodies in lower light. I shoot with both a 6D and an 80D, and am leaning toward the Tamron for this reason. The prices are VERY close between the two.<br /> Currently I'm shooting with my 80D, a Canon 70-200 F/2.8 and a 2X converter when I need a long lens, but unfortunately that limits me to the center AF point. Either the Sigma or Tamron 150-600's will give me 200mm more reach without the converter, and I can use all of the AF points.</p>