What Is Dynamic Range
In photography, dynamic range refers to the range of light intensities that can be captured in an image, from the darkest shadows to the brightest highlights without losing information.
Measuring A Scenes Dynamic Range
To measure the dynamic range of a scene using a light meter is straightforward. We start by measuring the darkest part of the scene we wish to hold detail. We then take a reading of the brightest part of the scene we wish to hold detail in and then subtract one from the other. This will then give us the dynamic range between these two points
Here we have a typical scene where we want to determine the dynamic range to see if the scanner is capable of reproducing it without losing any information.
Let’s say for example we want to include the tree and clouds in the final image after the sun has gone behind the cloud.
Reading the low values
First, we take a reading of the darkest part (the tree trunk) which in this case gives un an EV reading of 6
Reading the high values
next, we take a reading of the brightest part (the clouds) which in this case gives un an EV reading of 12
If we now deduct the low value from the high value (12-6) we end up with 6 which tells us that the dynamic range of the scene is 6 stops.
Film Scanner Dynamic Range
The dynamic range of a film scanner refers to its ability to capture and differentiate between the darkest and lightest tones in a film image. In essence, it represents the range of brightness levels that the scanner can accurately detect and reproduce.
In the context of film scanning, a scanner with a wider dynamic range can capture more detail in both the shadow and highlight areas of the film. This is particularly important for preserving the subtle difference of tones in the original image.
A scanner’s dynamic range is typically measured in terms of density range, which quantifies the range of optical densities that the scanner can distinguish. Optical density is a logarithmic measure of light absorption, with higher values indicating darker areas on the film.
Epson V800 Scanner
According the the manufacturers blurb, The V800 scanner achieves its excellent dynamic range through various technologies such as its high-performance Dual Lens System, which automatically selects the optimal lens for different media types, and its advanced Matrix CCD Micro Lens technology, which enhances light gathering efficiency.
Epson V800 Dynamic Range Test
After rearranging the darkroom, I came across a Stouffer 21-step step-tablet which I had forgotten about so I decided to scan it on the Epson V800 scanner and see just how much of a range it could produce.
The Stouffer consists of 21 individual calibrated patches, each representing 1/2 stop apart. Aimed with this information, it was relatively easy to determine just how many stops the scanner capable of producing.
Scan of the Stouffer Step Wedge
I scanned the Stouffer step tablet and then opened it in Photoshop which allowed me to see just how many of the individual steps I could see separation in.
After a careful examination of the patches, with my calibrated monitor, I could see separation as far as patch 16 although I had to study this last patch carefully.
Each patch represents 1/2 stop so this means that my Epson v800 scanner is capable of reproducing around 7.5 stops of dynamic range. Personally I am going to cap it at 7 stops because the last patch although visible was pretty hard to see.
Clicking on the image of the Stouffer Tablet will enlarge its view.
Using our scene example above which we measured to have a dynamic range of 6 stops tells us that my scanner could comfortably scan that dynamic range with a full tonal range.
What this tells us
By knowing what dynamic range the scanner is capable of allows us to make judgements when out in the field. For example, if we had measured a dynamic range of say 9 stops then we would know that it would be more than likely that we would be unable to produce a full tonal range scan with detail in both the low and high values.
In this situation, we would have to decide what sacrifices to make, maybe retain detail in the sky at the cost of losing detail in the tree trunk or vice versa.
