Dynamic Range

I've been anxious to get things started but, typically, the weather's been really dull for most of the week! Yesterday, I decided to go out and take some pictures anyway, and make a start on the first couple of projects. I'd read through the first section of the course materials in detail, and it seemed that the instructions for the first project were clear and that it would be quite straightforward. As this is my first attempt at any of the OCA modules, I was pleased to be starting off with something manageable.

However, as will become apparent, things weren't as easy as I'd predicted!


The first task was to use the camera to measure the brightness in various parts of a scene. Here is the scene I chose:

 

The areas that I judged to be the darkest, a midtone and the lightest are numbered 1,2 and 3 respectively. 

Before taking the 'snapshot' above, I set the camera to Spot Metering mode, and fixed the shutter speed at 1/60 sec. I measured the brightness levels as:

Area 1 - the dark shadow beside the boat: f/4.5,

Area 2 - the side of the blue boat: f/10,

Area 3 - the well-lit white area: f/22.

At home, I then compared these figures to the table given within the course manual. That's when I hit problem one! My camera (a Nikon D300) uses fractions of f-stops, rather than just whole stops, therefore I couldn't just make a direct comparison to the printed figures and work out the range of the scene. Apparently, this is very common in DSLRs, which leads me to think that perhaps the course materials haven't been updated for quite a while.

I did some research, and found that the camera uses increments of 1/3 EV. I made my own table of figures and - if I'm calculating correctly - the number of f-stops between the darkest and lightest areas is 4⅔ (I'll have to find out if that is the correct way to write it!). This was about what I had expected, as it was very overcast, and contrast was low. I will repeat the exercise on a sunny day, to see if the range is greater. 

Later today, I'll write about my findings for the next task - 'Project 1: Dynamic Range.'