01-10-2014 07:24 PM
01-10-2014 08:17 PM
I haven't even touched a 6D so can't comment on it but I used a 7D for 2 full seasons shooting R/C flying events. You lens needs will be different than mine so just how close & how far out do you hope to cover? (The 7D AF did very well at R/C)
01-10-2014 10:46 PM
Definitely the 7D for a lot of reasons....
Fast, accurate autofocus. More usable peripheral AF points. Up to 8 frames per second. Plus a crop camera gives "free telephoto effect".
Also less money, so you can put more into top performance lenses.
01-10-2014 11:48 PM
The 6D has a fairly basic focusing system. The 7D (and even the 70D) will be much faster. The lens you use will matter... a camera with a fast and accurate focusing system wont do much good if the lens has a slow focusing motor.
USM focusing motors are the fastest -- but even these have a few variations and performance varies by lens model.
A typical phase-detect AF point (generically -- not speaking about any specific camera) is a single axis sensor. It detects if something is mis-focused based on the alignment of the subject after running the light through a splitter which separates it into two halves or "phases". If the phases "align" then the object is focused. It turns out the orientation of the focus sensor axis matters and can be fooled if the subject has a linear pattern running in the same direction. Often times you may be shooting objects with a pattern of lines running in the same direction as the focus sensor axis and the sensor can be fooled into thinking things are focused when, in fact, they are not.
To solve this, some focus points may be 'cross type' -- which means the camera detects phase in two axes simultaneously.
On the 7D (and 70D), the cameras have 19 point AF systems and ALL 19 points are "cross type". On the 6D there is an 11 point AF system, and only the center point is "cross type". The 7D (and 70D) are both much better at dealing with "action" shots.
The 7D has a slightly better focus system than the 70D in that it's able to use expanded AF points and can also use more constrained 'spot focus'. When focusing subjects with low contrast (not much of a pattern to them), using expanded focus points can help. Spot focus is good when the focus point you want to use has lots of contrasty detail ... but you don't want to use the standard focus because the object is very near something which is at a different focused distance. For example... if I want to focus on your eyeball (eyes have lots of contrasty detail) but I want to make sure the camera doesn't mis-focus by locking on your eyebrow (which is a little bit closer than your eye), then I can use the more constrained "spot focus" mode. The 70D does not have those variant modes that the 7D includes.
The 6D is a "full frame" camera with considerably better low-light performance in that you can shoot at much higher ISO while still keeping noise low. The 7D doesn't do nearly as well in low light (it does ok... just not nearly as good as a 6D). But the 6D is not optimized for "action". The 5D III is optimized for both low light AND action. It doesn't have the fast continuous burst framerate of the 7D... but it has a much more sophisticated focus sytem (it basically has the focus system of the flagship 1D X with a few minor exceptions. The 5D III isn't *quite* as good, but close.
As for lens... you'll want a snappy focusing lens and given that RC cars tend to be on the small-ish side, you may want a 70-200mm. Ideally... an EF 70-200mm f/2.8L IS USM II would be hard to beat... but that is an expensive lens. The EF 70-200mm f/4L USM is a very good lens with a competitve price tag considering it's performance. There is also an image-stabilized variant of this lens. Most people will tend to think of image stabilization as a feature which helps you when the shutter speed is low -- and of course when shooting action the shutter speed will be high. One might conclude that IS isn't very useful in this sitatuion and just adds to the price tag. HOWEVER, it turns out that BEFORE you shoot the image, the camera needs to focus. It's hard to focus action when the camera is moving around. So it turns out... image stabilization actually helps the camera achive focus lock faster EVEN when shooting high-shutter speed action photography that doesn't otherwise benefit from image stabilization.
01-11-2014 11:28 AM - edited 01-11-2014 11:53 AM
01-11-2014 02:43 PM
This is one instance where picking the right lens will be difficult. I don't think 70 mm will be wide enough on a crop body & it may not even be wide enough on a FF. That leaves either the 24-70 or 24-105 as good choices but you can't use the IS on the 24-105 when panning. You won't be able to frame these things tightly when they are close to you so think carefully about the lens & borrow if you can for a test on just how wide you'll need as a minimum.
01-12-2014 09:35 AM