Pollution
Create a piece of light paper in order that it is similarly illuminated by simply indirect sun light. Choose a place where the light is dazzling. The most important point is that the conventional paper is illuminated evenly. Pick a time and place during which it is unlikely you will have any changes in how much mild is present.
Set up your digital camera in order that the white paper fills the complete field of view. The space from the camera to the paper is definitely not significant.
Put the camera in manual setting and make the following changes:
- Modify the focus in order that the camera is focused on the white piece of paper. Once you set major, do not change it out.
- Arranged the camera’s sensitivity to ISO 2 hundred.
- Collection the béance to f/2. 8.
- Set the image resolution into a low establishing.
- In case your camera has a self-timer characteristic, set it so that the camera shutter opens a few seconds when you take a picture. This reduces shake.
Given that your camera is focused within the paper, together with the settings adjusted correctly, take a series of images at several shutter rates of speed, changing with a factor of two. (I used: 30, 12-15, 8, four, 2, you, 1/2, .25, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, and 1/1, 500 sec shutter speeds. )
Repeat step four. This will provide you with two pieces of tuned photos. You will compare these types of later in this procedure.
Download all of the calibration photos onto your pc.
Make two data tables in your lab notebook computer to keep track of the pixel value for each calibration photo. One data table will be for the first set of calibration photos, the various other for the other.
Gauge the average pixel intensity of every photo employing ImageJ.
- Start ImageJ.
- Open the first photo using “File/Open” command.
- Click on “Analyze” and select “Histogram”.
- A histogram of the pixel values in the photo will wide open in its personal window. You can expect to use the histogram to gauge the average -pixel gray benefit in every single photo.
- Record the Mean, StDev, Min, Maximum, and Setting in your data tables. StDev is short for “standard deviation”. Minutes and Utmost are short for minimum and maximum, respectively. Imply is another identity for the regular. The suggest of this histogram is the typical pixel benefit.
- Click “File” and select “Open Next” to open the next file.
Do it again steps several. d. “3. f. right up until you have reviewed all photos in both equally sets of calibration photographs.
Generate a calibration curve simply by graphing the typical pixel worth (the mean of the histogram) on the x-axis and exposure time (in seconds) for the y-axis. The graph will have two data series, one particular for each set of calibration photos.
- This is a “semi-log” story.
Look at the graph and check the tuned curves by each set. Both the curves ought to cross or perhaps only be slightly apart. If there is a large amount of space between the two calibration figure or if some of the figure has a substantially different condition from the various other, you will need to repeat steps the whole process, being sure that the light conditions are exactly the same for equally sets.
