7D vs 5D3 noise @ ISO400

[MichaelHodges]

I haven't shot the 1DX, but it looks like an awesome camera. 

What's nice about the 7D versus full frame is large prints. I found I was cropping too deeply with the 5D's, and this was affecting print quality at the sizes I prefer to print.

Another poster mentioned the wacky auto focus. I had one of those 7D's, too (and a peeling grip). Luckily, Canon was able to fix both.

Since fine-tuning my 7D, I find myself lusting less and less for camera bodies. Yes, it's a pretty noisy camera, but Lightroom does a masterful job of keeping detail while removing noise. I'm much more interested in location, location, location.  I doubt I'd even upgrade to the 7DII.

[AlanF]

 The amount of noise you get in an image is based on the amount of light being emitted by the object. Noise (for the most post) is a result of the quantum properties of light in that light exists as a gausian distribution of photons, light isn't emitted uniformly but photons hit an object at random. The difference in light and dark areas in an image resulting from noise are caused therefore because in the light area you had 16 photons and in the dark area you had say 9. Because of random probabily the light from your subject doesn't arrive at a uniform time..

Photon noise is caused by the number of photons collected during exposure being small and hence subject to statistical variation. The number collected follows a Poisson distribution, not a Gaussian. The Poisson distribution approximates to a Gaussian when the number becomes very large, and noise is then no longer a problem. The noise varies as the square root (sqrt) of the number of photons collected, N. So signal/noise varies as N/sqrtN, that is sqrtN.  Although an APS-C pixel is smaller in area by approximately 1.6x1.6 times, and thus collects 1.6x1.6 less photons, the sqrt dependence of signal/noise on N means that it is only 1.6x noisier than an FF pixel for photon noise, which is the dominant noise source.

[Kiboko]

My 7D replaced a 1D MKIIn, an 8MP camera, (cost well over £2000 when new), - the 7D was a revelation yet the 1D was very much a professional camera at the top of the pecking order when I first got it.
And all this talk of high ISO and noise! When I used film, (not SO long ago - all my travel and wildlife images are still with Latitude stock library), I shot on Fuji Velvia, 50 ISO, rated at 40 ISO, or Provia, rated at 80. Latitude's current submission requirements state "ensure ISO does not exceed 200 unless absolutely necessary." So I shoot at 100, sometimes 200, and infrequently, if necessary, at 400 ISO. How easy photographers have it these days with the availability and functional use of high ISO's, - yet expectations are SO high, - I wonder how they'd cope if they suddenly found themselves with Velvia loaded in their film camera? I reckon we'd see a load of blurry images!

[AlanF]

If you specialise in photographing squirrels noses at iso 3200 at 30 yards and doing 100% crops, then the 7D is not for you. But, here is one of my favourite photos: a kingfisher caught leaving his roost at the speed of a rocket using a 7D with f/2.8 300 II plus 2xTC III at 1600 iso, 1/4000, f/8 in Raw with absolutely no noise reduction. It is the whole frame. When you pixel peep you see the noise, but you don't need pixel peeping to see this photo.