Previous page Next page

Dynamic Range

Our Dynamic Range measurement system involves shooting a calibrated Stouffer Step Wedge (13 stops total range) which is backlit using a daylight balanced lamp (98 CRI). A single shot of this produces a gray scale wedge from (the cameras) black to clipped white (example below). Each step of the scale is equivalent to 1/3 EV (a third of a stop), we select one step as 'middle gray' and measure outwards to define the dynamic range. Hence there are 'two sides' to our results, the amount of shadow range (below middle gray) and the amount of highlight range (above middle gray).

To most people highlight range is the first thing they think about when talking about dynamic range, that is the amount of highlight detail the camera can capture before it clips to white. Shadow range is more complicated; in our test we stop measuring values below middle gray as soon as the luminance value drops below our defined 'black point' (about 2% luminance) or the signal-to-noise ratio drops below a predefined value (where shadow detail would be swamped by noise), whichever comes first.

Picture Style options

The D300S, in common with the whole Nikon DSLR range, makes use of Picture Styles - image parameter presets that can be saved, tweaked and swapped between cameras. Initially the D300S has only four Picture Styles though these can be modified or additional ones created using the supplied computer software. As you can see (and as detailed in the 'Grid' view in the Picture Styles menu screen), the contrast - and hence the tone curves - differ between each of the settings.

Active D-lighting

A feature that now appears in all Nikon DSLRs is Active D-lighting - a system that modifies metering and adjust contrast at a local level in order to maximize the amount of dynamic range information squeezed into the JPEG file. Because the image-processing side of that equation depends on the image being shot, our test may not reflect the effect you'll see (we've also conducted some real-world tests), but they do help show what the camera's doing.

ISO Sensitivity and Dynamic Range

The base sensitivity of the sensor used in the D300S is ISO200. There is also a Lo 1.0 mode that attempts to mimic ISO 100 but it's effectively just ISO 200 over-exposed by a stop. The result is that the sensor becomes saturated and clips to white quite easily, limiting that mode's dynamic range. For most applications, you'd be better off buying a neutral density filter if you need slower shutter speeds than ISO 200 will allow.

Beyond ISO 200 the highlight dynamic range remains a fairly stable 3.8 stops above middle gray. The shadow range appears to increase but this is most likely to be a result of noise reduction dropping noise to below our cut-off threshold. Even so, around 8.5 EV of dynamic range with nearly 4 stops above middle gray is an impressive result.

Sensitivity Shadow range Highlight range Usable range
ISO 100 equiv. -5.0 EV 3.1 EV 8.1 EV
ISO 200 -4.6 EV 3.8 EV 8.4 EV
ISO 400 -4.8 EV 3.8 EV 8.6 EV
ISO 800 -4.8 EV 3.8 EV 8.6 EV
ISO 1600 -4.8 EV 3.8 EV 8.6 EV
ISO 3200 -4.7 EV 3.8 EV 8.5 EV
ISO 6400 -3.7 EV 3.7 EV 7.4 EV

Dynamic Range compared

The D300S is competitive without managing to stand out from its peers - there aren't any cameras in its class that can significantly out-perform its 3.8 EV of highlight dynamic range (the bit that tends to be most noticeable when out shooting - blown-out skies tend to be more distracting than blocked-in shadow regions). The closest competitor is the Sony DSLR Alpha 700, which is no great surprise as it's based around a closely-related sensor.

The Canons and Pentax have optional extended highlight modes that increase dynamic range by amplifying their sensors less (to prevent bright regions clipping so easily) in a way that's comparable to what Nikon is doing at ISO 200 and above. However, since we compare noise with the cameras exhibiting their default behaviors, it would be unfair to compare the dynamic range of these extended highlight modes, since they could be expected to generate more noise.

Camera (base ISO)
Shadow range
Highlight range
Usable range
Nikon D300S -4.6 EV 3.8 EV 8.4 EV
Canon EOS 7D -5.0 EV 3.3 EV 8.3 EV
Pentax K-7 -5.7 EV 2.9 EV 8.6 EV
Canon EOS 50D -4.8 EV 3.5 EV 8.3 EV
Olympus E-30 -5.1 EV 3.8 EV 8.9 EV
Sony Alpha A700 -4.9 EV 3.9 EV 8.8 EV

The wedges below are created by our measurement system from the values read from the step wedge, the red lines indicate approximate shadow and highlight range (the dotted line indicating middle gray).







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 usual the default Adobe Camera RAW conversion delivers less dynamic range than JPEG from the camera (a more contrasty tone curve). The best we could achieve was just over 10 stops (10.1 EV) of total dynamic range, more importantly exactly one stop of that is in highlights.

Settings Usable range
JPEG Default 8.4 EV
ACR Default 6.8 EV
ACR Auto 9.1 EV
ACR 'Best' 10.1 EV

To test how much exposure latitude the raw file actually gives, we intentionally over-exposed an image (by 3EV) to ensure that highlights were clipped well beyond the level that could be incorporated into the JPEG file. We then used digital exposure compensation on the raw file to see to what extent those highlights could be recovered. We found that you got no additional information beyond around -1.25 EV, and even at this point the color accuracy of the recovered areas is imperfect.

To check that this incorrectly rendered detail should have been recovered by -1.25 EV of exposure compensation, we compared this RAW conversion to another version of the same scene that had originally only been overexposed by 2EV (i.e. one stop darker than the previous image). In this less exposed RAW file, all of the color in the brickwork could be brought back with -0.25 EV digital comp, so it's clear that there is less than 1.25 EV of reliable information beyond that which appears in the default output.

Given that the default ACR conversion yields around half a stop less highlight dynamic range than the default JPEG, it's fair to say that the best you're likely to get out of a RAW file exposed based on the camera's metering is around one extra stop of dynamic range in the highlights.

ACR with -1.25 EV digital comp. (of +3EV image) 100% Crop
ACR with -0.25 EV digital comp.(of +2EV image) 100% Crop

 

Previous page Next page

Comments