Para esportes é preciso AF rápido e bons FPS, acho que a NEX-3 e NEX-5 não dão conta do recado...
Talvez a NEX-5
R ou 6...
E a Nikon 3100 é só 2.9 FPS
http://www.dpreview.com/reviews/sony-alpha-nex-6/9"Outdoors, the NEX-6 was able to track moving subjects surprisingly well - even when
shooting at 10 frames/second. We shot ten burst sequences of an approaching bicycle
(with a rather busy background behind him), and the NEX was able to track the subject
about 70% of the time. We'd expect a better hit-rate from true phase-detection AF
systems, but from a camera of this type, we're impressed."
http://photographylife.com/reviews/sony-nex-5r"As I have pointed out in the beginning of this review, the Sony NEX-5R has a brand
new “hybrid” autofocus system, similar to what the Nikon 1 system has. This hybrid AF
system is a combination of phase and contrast detect AF, which allows for much
quicker AF acquisition than only contrast detect. Thus, the AF performance of the
NEX-5R has improved dramatically when compared to its predecessor. At first, I was a
little skeptical about this. But as I played with the camera more and more, I
realized that AF definitely did get a noticeable boost. I then compared AF speed
between the NEX-F3 and the NEX-5R to see how much faster the new AF system has
gotten. In good light conditions, the NEX-5R acquires focus about twice faster, which
is remarkable. It is still better in speed and accuracy in low light conditions, but
not by much. While I found the NEX-5R to perform pretty close to the Nikon 1's hybrid
AF, the Olympus OM-D E-M5 still gets an upper hand with its AF in terms of AF speed
and accuracy though (to be discussed in the upcoming review)."
http://www.dpreview.com/reviews/nikond3100/9We tested the D3100's continuous shooting using a fast Lexar Professional 8Gb 133x
SDHC card, with the camera set to manual focus and a shutter speed of 1/500 sec at
ISO 400. The camera consistently maintains a 2.9 fps shooting rate regardless of file
format, und unlike recent Nikons at this level, turning on Active D-Lighting has
little impact on the number of frames you can shoot before filling the buffer.
Notably, the burst depth with DRO 'On' has increased dramatically, from the D3000's
mere 5 JPEG frames to a very much more useable 20 frames.
The RAW buffer is a quite reasonable 8 frames, even when shooting JPEGs concurrently.
Once the buffer is full the camera will continue to shoot sporadically at an average
rate of around 1fps when space becomes available again, with occasional pairs of
closely-spaced shots.
Even turning on the D3100's 'Auto Distortion Control' feature (which corrects the
JPEGs for the lens's barrel or pincushion distortion) has little impact on speed. In
JPEG with ADL On too, the camera will still shoot at 3fps for 10 frames, then
'throttle back' to about 1.6 fps and keep on shooting at this reduced rate for at
least another 20 frames (which is arguably a more intelligent way of doing things
anyway). In RAW + JPEG, Auto Distortion Control has essentially no effect on
continuous shooting.
JPEG (ADL Off): 2.9 fps for 24 frames, then approx 1 fps; 19 seconds to recover.
JPEG (ADL On): 2.9 fps for 20 frames, then approx 1 fps; 19 seconds to recover.
JPEG (ADL and ADC On): 2.9 fps for 10 frames, then approx 1.6 fps; 19 seconds to recover.
RAW: 2.9 fps for 9 frames, then sporadic shooting as buffer clears; 13 seconds to recover.
RAW + JPEG 2.9 fps for 8 frames, then pairs of frames at ca. 4 second intervals; 23 secs to recover.
Overall this is a perfectly respectable performance, but in no way class-leading. For
example the Pentax K-x is substantially faster at almost 5 fps, and the mirrorless
Sony NEX-3 and -5 can shoot at 7 fps.
