For this exercise, you were asked to find a scene with a high dynamic range. The best conditions for this are
- Bright Sunlight
- One bright reflecting surface
- An area of deep shadow with a dark surface
A suggestion was to use a A3 size piece of white paper as your highlight. Take the front of your house in the sunlight, and open the front door in order to case a black, dark shadow area. Pin the white paper somewhere near the door, or in the direct sunlight.
Make sure the ISO sensitivity is at its lowest, turn any noise reduction on your camera off. Set up the exposure and shoot so that there is just no highlight clipping of the white card, or white area.
Next, measure and make notes of the brightness of the white area and two or three of the darkest shadow areas. There are three ways of doing this.
- Set the metering mode to ‘Spot’ if that is available on your camera
- If you are using a zoom lens, set it at wide for the photograph, zoom into the maximum to measure the small areas
- Walk close to the areas you want measure so that they fill the frame
Make a note of the aperture/shutter speed combinations, and note exactly which area you measured.
Open the image in your processing software. Zoom into 100% magnification. Move to the white area. Using the software’s pixel value sampler ( It shows values from 0 to 255 in the three channels ), check that the value of the white is only a little less than 255 in each channel.
Now move to the shadows, and adjust the brightness until the details are visible. You should now look for an area in which the level of apparently real detail and noise are competing with each other, the shadow are in which you have difficulty telling which is which.
Now calculate the range between the two ends in F-stops. You will need to be familiar with the normal lens aperture notation (F-2, F-2.8, F-4, F-5.6, F-8) Etc. Marking One-stop differences.
For this exercise, I decided to go to a place called Snuff Mills. It is a large forest with a house situated towards the entrance area. I chose a really sunny day for this exercise as I wanted the white house to be ‘bright’. I knew that there would be dark shadow areas, especially in the trees behind the house, which would be perfect for this exercise.
I set the exposure so there was no highlight clipping on the white house, I also kept the ISO low. The settings I used were, ISO 100, F/6.3, 1/400. After I took the first photograph, I used the aperture priority setting which meant I could keep the ISO 100 and the F/6.3, but the shutter speed would change depending on where I zoomed into. I used the ‘Spot’ metering on my camera.
Below is a copy of the original image. I have noted the spots where I zoomed in, and what the shutter speed/aperture readings were. The darkest area was 1/15sec and the brightest area was 1/800sec.
I then had to calculate my camera’s dynamic range. I have to work out the number of F-stops between the darkest area and the lightest area. 1/15sec to 1/800sec. I may be wrong, but I calculate it to be 6 F-stops difference.
I must admit that I have struggled with this exercise. It took me several failed attempts to do this exercise, as I was getting all of the settings wrong on my camera, which obviously frustrated me, so therefore I stopped doing the exercise, but I knew I had to complete it. I did some more research and finally began to understand how to do the exercise, which then led me to going to Snuff Mills in order to complete it. However, when it came to ‘Measuring’ the dynamic range on my camera, I find this quite hard. I personally think I may have measured it wrong, as reading about dynamic ranges on camera’s, I think my measurement is quite low, especially when dynamic ranges on cameras should be roughly 9 stops. It may just be where I zoomed into and measured, I’m not sure. I am hoping that the next exercise will help me understand this more as I am still quite confused.