Test method: How we measure dynamic range

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One of the most important parameters in a digital camera is its dynamic range. Dynamic range in photography describes the ratio between the maximum and minimum measurable light intensities (white and black, respectively). Once your subject exceeds the camera's dynamic range, the highlights wash out to solid white, and the darks become solid black. Cameras with a large dynamic range are able to capture shadow detail and highlight detail at the same time. Cameras with a small dynamic range provide you with blown-out highlights and shadows. concert304

Dynamic Range Measurements

Our Dynamic Range measurements consist of shooting a calibrated 28 step wedge with 14 stops total dynamic range (Dmax=4.2) which is backlit using a daylight lamp. A single shot of this step wedge produces a gray scale wedge from the camera's clipped white point down to a clipped black point. Imatest computes a number of different dynamic range measurements, based on a variety of image noise thresholds. These noise thresholds are specified in terms of f-stops in the final image. GrayWedge

Total Dynamic Range

The total dynamic range is limited by the bit depth of the sensor and by the camera-noise. In theory, a 14 bit camera sensor could reach a total dynamic range of 14 stops. However, in the dark areas the amount of noise limits the total dynamic range. Many readers believe that the total dynamic range is an important image quality parameter; the higher, the better! However, the total dynamic range is of very little relevance to real-world photography, since a large part of the dark tonal range is obscured by noise.

 

Petra-small
Click on the image in order to see the preserved detail in the starry sky.

Useful dynamic range

What you care about as photographer, is how much detail you can pull out of the shadows before image noise becomes too high. At the same time, you wish to maintain detail in your highlights.
That's why we pay more attention in our reviews to the useful dynamic range of a camera. We report Imatest's dynamic range on the 0.1 f-stop limit as the useful dynamic range.

4darkzones

JPG dynamic range

We test the dynamic range of RAW files without using any noise reduction and the dynamic range of jpg files with standard noise reduction on. Doing this, we maintain the highest possible detail of the image in the RAW files and obtain at the same time an indication of the sensor performance without noise reduction. The useful dynamic range of jpg files are a good indication of the effectiveness of noise reduction in the camera.


EOS-5D-Mark-III-review-usefull-dynamic-range-final

Some cameras offer an extended low and/ or high ISO setting. The extended low ISO setting produces less noise, but also decreases dynamic range. Some extended low ISO settings actually overexpose the image by a full f-stop, which decreases the signal to noise ratio. This can be seen in the useful dynamic range of the Canon 5D MK2 in the image above.

RAW dynamic range

The useful dynamic range of RAW files without noise reduction is a good indicator for the sensor performance. The usable dynamic range of RAW files is in our reviews generally higher for full frame digital SLR cameras compared to the other cameras, due to larger pixel sizes in full-frame sensors.

The jpg files, because of in-camera noise reduction, seem to perform better in our reviews than the RAW files. Yet that is not so. If you carefully adjust contrast, sharpening and noise reduction of RAW files, you will always obtain a usable dynamic range, better or equal to that of the jpg files.

NikonD3200-dynamic-range

Sufficient-Dynamic-Range

What about the dynamic range reported by other websites?

There are a few websites that report the dynamic range of cameras, like Dpreview, DxO-mark, Imaging resource & Colorfoto. Generally speaking, diferent test procedures, test methods and software are used for the measurement of dynamic range by these websites. Therefore the dynamic range measurement results of different websites can not be compared directly. Camerastuffreview and Imaging Resource apply a similar testing procedure and both use Imatest for the dynamic range analysis. Imaging Resource reports the dynamic range of 100 ISO jpg files with standard noise reduction applied. These results are often comparable with the Camerastuffreview dynamic range analyses for jpg files. We report however, an average dynamic range of jpg files for the 100 - 6400 ISO range.
The dynamic range measurements of RAW files by Camerastuffreview and Imaging Resource are less comparable, since Imaging Resource applies noise reduction to the RAW files and Camerastuffreview doesn't. The dynamic range for RAW files reported by Camerastuffreview, therfore, are lower.

Ivo Freriks
Author: Ivo Freriks
With Camera Review Stuff I hope to make a modest contribution to the pleasure that you get from photography. By testing cameras and lenses in the same way, evluating the results and weighing up the pros and cons, I hope to help you find the right camera or lens.

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