I have had a 650D, 7D, and now have a 6D so why the changes?
The 650D was a great camera for many reasons but one lens I had just wasn't sharp. After LOTS of reading, then testing I found the lens suffered from forward focus, which meant it was focusing in front of the auto focus point. This can really matter with a long lens as depth field can be very small. With the 650D there was only one thing that could be done - return the lens to Sigma, preferably with my body for adjustment of the lens to focus correctly. And include a fairly chunky fee + insured postage etc etc.
So after more investigation I upgraded to the 7d. A different build quality camera altogether. It has mag alloy body frame instead of plastic. This can make a difference - image quality is not only optics and electronics - the distance between the lens mount and the sensor plane is fundamental also. With a metal body it can be manufactured and maintained more readily than a plastic one.
But most importantly, the 7D had micro adjustment for auto focus. This meant that any lens which moderately front or rear focuses can be adjusted withing the body on an lens by lens basis by the user.
Also the 7D could use my 2 favorite EF-S lenses, the 10-20 and 18-200.
Why did I later move onto a 6D? A relative dropped and damaged the 7D. And after the repair it was just fine but for me it was never the same. I had also recently come back from my holiday of a lifetime and there were lots of photos where i asked the perennial question 'where was that taken'. Also I was becoming more interested in natural low light photography. The 6D fitted the bill because of the full frame sensor, micro focus adjustment, on-board GPS, and also on-board wifi.
Ignoring everything else, whats the advantage of full frame when the pixel count is similar? If a sensor is 20Mpx the resolution is the same whether the sensor is full frame, 1.6x crop, or even a modern top-end phone?
The BIG difference is the pixel size. On a full size sensor the pixels are almost twice the size as a cropped sensor. In low light and/ or high ISO it is significantly more sensitive to light, the effect of which is a lot less
noise. Just consider the sizes:
full frame 36x24mm, area 864
cropped 23x15mm, area 346 (typical
so 36:23 is about 1.6x crop but area is over twice (so pixel size/area is similarly so.
So in no particular order, here's my
comparison of full frame vs. cropped body, assuming metal body and micro focus adjustment, similar sensor pixel count:
* smaller and lighter
* can use EF or EF-S lenses
* A given lens is 60% 'longer zoom' 400mm becomes 640mm
* EF-S lenses are lighter than full frame lenses so less weight and bulk to carry
* To cover a given focal length range (eg 10 - 600) will require significantly less lenses, cost, weight etc.
* shutter is physically smaller so often has higher burst shutter rate and sometimes higher max speed.
* super low light image quality (signal to noise ratio of large pixels) long exposure and/or high ISO
* EF lenses have smaller zoom range so typically the optical quality is less prone to distortion such a chromatic aberration, lack of corner sharpness etc
There are other differences of course but they are not necessarily full vs. cropped body specific, and naturally if you wait for the next release of any given body it will be better and will leapfrog the other models/ oposition (ain't life like that from phones, to cars to cameras to everything
To look at my own list why did I get a 6D at the time? From my perspective I now find that with the body and lenses I have,any problems with an image can clearly be seen to be mine - either technique, composition, or process they are not down to the kit that's for sure. Also, as an very enthusiastic amateur, because I wanted to and I could
What would I do now? with the lenses I had I would be very interested in the 7Dmk II particularly if wildlife/ sports photographer