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RAW headroom

Experience has told us that there is typically around 1 EV (one stop) of extra information available at the highlight end in RAW files and that a negative digital exposure compensation when converting such files can recover detail lost to over-exposure. As with previous reviews we settled on Adobe Camera RAW for conversion to retrieve the maximum dynamic range from our test shots.

As you can see the default Adobe Camera RAW conversion delivers less dynamic range than JPEG from the camera (a more contrasty tone curve and less noise reduction in shadows). It's possible to get considerably more than this out of the file, (for example, our ACR 'Best' parameters) but doing so results in a very flat, totally unrealistic (and certainly 'unphotographic') image. The point is that this additional information is there if you wish to selectively recover and blend-in this detail from a series of differently processed versions of the raw file.

  • ACR Default: Exp. 0.0 EV, Blacks 5, Contrast +25, Curve Medium
  • ACR Auto: Exposure -0.95 EV, Recovery 8, Blacks 0, Brightness 0, Contrast 0, Curve Medium
  • ACR Best: Exposure -2.05 EV, Recovery 0, Blacks 0, Brightness +150, Contrast -50, Curve Linear

Settings Usable range
JPEG 8.9 EV
ACR Default 7.4 EV
ACR Auto 9.3 EV
ACR 'Best' 11.5 EV

To test how much exposure latitude the raw file actually gives, we took a photograph of a scene that contained a wide tonal range in raw mode at the recommended exposure, and made a JPEG copy in camera using the raw processing interface in the retouch menu. The reason we did this, rather than shoot JPEG+raw simultaneously, is that when the D3000 is set to simultaneous capture, the JPEG is set to its lowest - 'basic' - quality, and compression artifacts at this setting make extreme levels adjustments impossible - or at least unattractive.

As we can see from the images shown here, although large areas of the sky appear clipped in the original file (and are indicated as such on both the camera's and Adobe Camera Raw's histograms) a lot of tonal information can be recovered using digital exposure compensation in Adobe Camera RAW. The JPEG file fares less well, and although there is some tonal information in the bright sky, any attempt to recover it results in posterization pretty quickly.

What this exercise shows is that even when the D3000's histogram shows highlights as being clipped, a surprising amount of detail can still be recovered from these areas if you shoot in raw mode. What you can't do, however, is get all that much back from JPEG files, either recorded 'natively', or when created from raw files in-camera. The best way to ensure that highlight detail is retained in JPEGs is to keep a weather eye on the camera's histogram and take advantage of the D3000's +/-5EV exposure compensation.

Adobe Camera RAW
default conversion
100% crop
Adobe Camera RAW
-2EV digital comp.
100% crop
JPEG Fine
In-camera conversion from raw , default settings
100% crop
Adobe Camera RAW
In-camera conversion from original raw file, -2EV digital comp applied in Adobe Camera RAW
100% crop
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