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Raw and Raw Conversion

Supplied software

The PowerShot S90 is provided with the Canon EOS Solutions Disk which includes:

  • Canon Digital Photo Professional 3.7 - Advanced image processing tool, described below.

  • Canon ZoomBrowser EX 6.4 - Easy to use image browsing and organization with a unique interface. Includes rudimentary image editing, printing and e-mail. This latest version of the software also provides some very basic video editing. (Image Browser on Mac platform)
     
  • Canon PhotoStitch 3.1 - Panorama stitching utility. 

Digital Photo Professional is an image workflow and RAW conversion application that provides for the browsing and management of images in a folder structure as well as tagging, rotation etc. In addition it also provides an extensive range of RAW conversion features which include digital exposure compensation, white balance, tone curve, color, picture style, sharpness and lens correction parameters.

A number of different tools can be accessed from the tools menu. The Quick Check tool allows you to browse through a selection of images and assign check marks to them. The Trimming tool can be used to apply a crop to an image (the image itself is not modified, this is simply saved in the recipe).

The Stamp tool works in a similar way to the clone stamp or healing brush in Photoshop (although it is primary designed for the removal of light or dark blotches).The Rename tool can be used to change the filename of a selection of images based on a rule set. Finally you can convert multiple RAW files at a time using the batch conversion tool.

Digital Photo Professional has a comprehensive feature set. It combines file browsing with RAW conversion, including exposure, white balance and noise reduction fine-tuning. It also includes a variety of options for reducing chromatic aberrations. Luminance and chroma noise reduction can be set independently, allowing a good level of control over the noise/detail balance in high ISO shots.
Tone curves can be adjusted for each color channel separately. The lens aberration window offers correction of light fall-off, chromatic aberration, distortion and color blur.

RAW conversion

As is the case in our DSLR reviews, we will compare the appearance of the camera's JPEG output to that of the supplied RAW converter and Adobe's Camera Raw converter which, as a part of Photoshop, Photoshop Elements or Lightroom is probably the most widely-used third-party converter. As the output from ACR using the default settings is so soft we've included an example with increased sharpening (Amount 100, radius 0.5, detail 40). Finally we've also included a range of other RAW developers to see if there's any more we can get out of the file from a detail point of view.

  • Digital Photo Professional 3.7, Default settings
  • Adobe Camera RAW 5.6 (Camera Standard profile)
  • Adobe Camera RAW 5.6 (Camera Standard profile + increased sharpening)
  • DCRaw (run inside Graphic Converter), Default settings + Unsharp Masking
  • Iridient Raw Developer 1.8.6, Default settings
  • Capture One 5.1, Default settings
  • JPEG - Large/Fine

Sharpness and Detail - raw converters compared

With very careful processing you can eke a touch more detail out of the S90's raw files than is captured in the JPEGs, but honestly you're going to have to look very, very closely to see it. This is mainly down to the quality of Canon's JPEG processing and the visual differences shown below reflect the differing levels of sharpening applied more than anything else. Shooting raw does allow you to cut out the camera's noise reduction (which you can't turn off), and this will pay a dividend in finer lower contrast detail.

As mentioned previously ACR 5.6's default output is very soft, though the resolution is there; you just need to use considerably higher small radius sharpening to see it. Canon's own DPP is, by default, doing a little too much sharpening (though you can of course turn this down), and the easiest way to get optimal results without too much tweaking is probably Capture One (though only by a whisker).

Digital Photo Professional -> TIFF (Default settings)
ISO 80 studio scene 100% crops
Adobe ACR 5.6 RAW ->JPEG (Camera Standard Profile)
ISO 80 studio scene 100% crops
Adobe ACR 5.6 RAW ->JPEG (Extra sharpening (100,0.5,50)
ISO 80 studio scene 100% crops
RAW Developer RAW->JPEG (Default settings)
ISO 80 studio scene 100% crops
DCR RAW->JPEG (Default settings + USM)
ISO 80 studio scene 100% crops
Capture One RAW->JPEG (Default settings)
ISO 80 studio scene 100% crops
JPEG out of camera, Fine quality setting (all settings default)
ISO 80 studio scene 100% crop

Resolution

These crops demonstrate that more detail is available from the RAW converters than can be obtained from JPEG. That said, a lot of this detail could be described as 'false' (produced beyond Nyquist), although frankly the majority of the time this is useful as it improves the appearance of 'texture'. The ACR output is significantly softer than either the JPEG or the output from DPP but this is, in part, a result of DPP's over-keen approach to sharpening (and ACR's almost ridiculously conservative approach). Again the best balance between 'clean' and 'sharp' - when using the default settings - is probably that produced by Capture One.

JPEG from camera Digital Photo Professional (RAW)
Adobe Camera RAW 5.6 (RAW) Capture One 5.1 (RAW)

Real word advantages

Because Canon's JPEG engine is really quite good (if, perhaps, a little keen on sharpening), there's little resolution advatge to be gained by processing from RAW. But shooting raw isn't all about resolution and the ability to fix white balance, minor exposure issues and to choose your own tone curve, sharpening, saturation and noise reduction settings is what makes it so invaluable.

And there are benefits to be had from processing high ISO images from RAW. The camera itself offers no control over the level of noise reduction being applied (which is an unusual omission on a camera aimed at a fairly sophisticated audience), and its default settings are not exactly optimal. Thankfully, DPP - and most of ther raw conversion software - allows separate control of chroma and luminance noise reduction, alllowing you to fairly easily produce images as you'd prefer them.

Fine Detail, low ISO

Virtually all compacts (and a good few SLRs) use a small amount of noise reduction even at base ISO, which has the effect of smoothing away fine, low contrast texture in the scene. In this respect the S90 is actually pretty good, and you have to look really hard to find anything in the raw files that's missing from the JPEGs, and even when you do you're unlikely to see the difference at normal viewing magnifications.

In the example below the JPEG has lost a little texture in the distant grass, some of which is recoverable from the raw file if you use a small radius/high amount unsharp mask. Be aware, however, that doing so will introduce a little more grain to the image, even at base ISO.

ISO 80 JPEG from Camera
ISO 80 ACR Conversion, sharpened for maximum detail.
100% crop 100% crop

High ISO Noise and Noise Reduction

The S90 may be slightly better than the average compact at high ISO settings, but at the highest settings (above ISO 800) the sheer amount of noise in the raw files means that you're often best sticking to JPEG and accepting that high ISO work is for small prints only. That said, the S90 does use heavy noise reduction and if you prefer grain to blur you will get sharper detail (and preserve more low contrast texture) if you shoot raw and turn off luminance NR. Ultimately, like all compacts, the upper reaches of the sensitivity range are never going to be pretty when viewed this close.

ISO 3200 JPEG from Camera
ISO 3200 DPP conversion ( Luminance NR 0, Color NR 20)
ISO 3200 ACR conversion ( Luminance NR 0, Color NR 25)

Shadow noise

The examples above are taken from a well-lit studio scene, possibly the least likely use of very high ISO settings. The raw output looks even worse in really challenging low-light conditions, where blue channel noise can become very intrusive (this is shooting under tungsten light, so there's not a lot for the blue channel to pick up).

By clipping the blacks we can remove a lot of it (this is what the camera does with JPEGs), but you need to use some very heavy chroma NR to get rid of the colored speckles altogther. Even so, much more luminance detail can be saved, so you'll get a little more resolution and sharpness shooting raw and removing Luminance NR, which, if nothing else, makes the S90 useful for high ISO / low light black and white photography.

ISO 3200 JPEG from Camera
ISO 3200 ACR Conversion
100% crop 100% crop

Dynamic Range / Highlight Recovery

One of the key benefits of shooting raw with a digital SLR is that you can make use of the entire dynamic range captured by the sensor by removing the (often quite harsh) tone curve applied in-camera to JPEGs from the process, and to compensate for modest under and (more importantly) over exposure. Compact cameras, even good ones, simply don't have the reserves of dynamic range in raw files, and you'll struggle to rescue clipped highlights.

As the examples below show, there's a little headroom there - using negative digital exposure compensation (in ACR) on the JPEG simply darkens all the existing tones and introduces over-saturation and posterization. Applying the same negative exposure compensation to the raw file brings back a touch of highlight detail not seen in the JPEG - maybe half a stop or so, but don't expect miracles.

JPEG from camera
JPEG with -1.75 EV digital exposure comp
Raw (ACR Default) Raw (ACR with -1.75 EV digital exposure comp)

RAW files for download

Here we provide RAW files, both from the review and the sample shots we take, to allow you to apply your own workflow techniques and see whether your experiences match ours.

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