ISO Sensitivity / Noise levels (contd.)
In-camera High ISO noise reduction
The DSLR-A900 provides four different levels of high ISO noise reduction; Off, Low, Normal and High. As you can see from the graph below there's a huge gap between 'Off' and 'Low' and very little difference between the three 'on' settings. The reason is simple; the A900's sensor is just plain noisy, and to get even close to acceptably noise-free output the camera has to do some fairly intense noise reduction processing. Looking at the crops from out-of-camera JPEGs it's obvious that there is some noise reduction even when you use the 'Off' setting (though it does seem to be truly off for raw files).
Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis (note that the standard deviation scale here has been extended 1.5x compared to the graphs on the previous page).
Noise reduction crop comparisons (ISO 1600 - 6400)
| Off ISO 1600 |
Low ISO 1600 |
Normal ISO 1600 |
High ISO 1600 |
|---|---|---|---|
    |
|||
 |
|||
| Off ISO 3200 |
Low ISO 3200 |
Normal ISO 3200 |
High ISO 3200 |
    |
|||
|
|||
| Off ISO 6400 |
Low ISO 6400 |
Normal ISO 6400 |
High ISO 6400 |
    |
|||
Noise reduction on RAW image files
When we reviewed the Alpha 700 one of our biggest - in fact one of our only - complaints was that Sony was applying noise reduction to raw files, making something of a mockery of the whole point of 'raw' files in the first place. Thankfully Sony soon saw sense and released a firmware upgrade for the A700 allowing you to turn the high ISO noise reduction off altogether, and this is also the case with the A900. What you can't do, unlike any other camera, is shoot RAW + JPEG and only have the camera's noise reduction applied to the JPEG (keeping the raw file 'uncooked') - it's all or nothing.
Below you will find comparison (100% crops) of the four noise reduction options (off, low, normal and high), Each was shot in raw and developed using Adobe Camera Raw (4.6) with both noise reduction sliders set to zero (so the raw conversion isn't adding any noise reduction at all). Although it's hard to be totally sure it would certainly appear that the new 'Off' setting really doesn't apply any NR to the raw files (the output is certainly full of chroma and luminance noise). We found that the ISO 6400 was only really useful for black and white shooting (where the graininess isn't a big problem) as the chroma noise is simply too intrusive for anything but the smallest print.
| A900 RAW NR OFF ISO 1600 |
A900 RAW NR LOW ISO 1600 |
A900 RAW NR NORMAL ISO 1600 |
A900 RAW NR HIGH ISO 1600 |
|---|---|---|---|
    |
|||
|
|||
| A900 RAW NR OFF ISO 3200 |
A900 RAW NR LOW ISO 3200 |
A900 RAW NR NORMAL ISO 3200 |
A900 RAW NR HIGH ISO 3200 |
    |
|||
|
|||
| A900 RAW NR OFF ISO 6400 |
A900 RAW NR LOW ISO 6400 |
A900 RAW NR NORMAL ISO 6400 |
A900 RAW NR HIGH ISO 6400 |
    |
|||
Raw noise compared
Finally let's take a look a the raw output of the Alpha 900 next to the Nikon D700 and the Canon EOS-1Ds Mark III (we'll update this section to add the new EOS 5D Mark II as soon as we have it). Removing any in-camera noise reduction and processing the images using Adobe Camera Raw (again without NR) gives us the nearest thing to a 'level playing field' for assessing the relative noise levels of each camera's sensor. Unsurprisingly the D700's larger pixels give it a distinct advantage here, and show clearly that at higher ISO settings it's not all about pixel counts - the ISO 6400 output retains noticeably more detail than the Alpha 900 with visibly lower noise. But it's also worth noting that at ISO 1600 the three cameras are broadly comparable (Sony has more chroma noise but also the most resolution). At ISO 3200 Canon shows that its in-camera JPEG processing does a far better job at removing noise without destroying information (and that the actual noise levels in raw are lower than Sony's).
| A900 RAW NR OFF ISO 1600 |
Nikon D700 RAW ISO 1600 |
Canon EOS-1Ds Mk3 RAW ISO 1600 |
|---|---|---|
   |
||
|
||
| A900 RAW NR OFF ISO 3200 |
Nikon D700 RAW ISO 3200 |
Canon EOS-1Ds Mk3 RAW ISO 3200 |
   |
||
|
||
| A900 RAW NR OFF ISO 6400 |
Nikon D700 RAW ISO 6400 |
Canon EOS-1Ds Mk3 RAW n/a |
  |
||
