Saving Wild Cats

Photoshop Technique:
Image Analysis
Our common idea of photography is that our images tell a story, capture
moments and leave us with a lasting memory. From a scientific point of
view however, images can be used for a lot more and techniques in image
analysis to obtain data are becoming more and more common in research
methods.
Here we look at some simple image analysis techniques that can be
carried out using Photoshop. To get started open your image in Photoshop
and follow the steps below:
Measurements
Fig 39: A microscopic image
of a Stensor sp. taken at x10
magnification.
Inset - Fig 40: graticule bar
for reference measurements
also at x10 magnification.
Step 1: Ensure the measurement
log window is visible by selecting
‘Measurement Log’ from the ‘Window’
menu.
Step 2: Set a scale for your image by
selecting ‘Analysis’ followed by ‘Set
measurement scale’ from the ‘Image’ menu.
Select custom to bring up the window
below. The ruler tool is automatically
activated. Drag it along your reference
measurement to set pixel length.
Step 3: Enter the logical
length and logical units for
your measurment. In the
example shown, 431 pixels
is equal to the logical length
and units of 100µm.
Step 4: Select the ruler tool and drag it along the length of the area you would like
to measure. Press record measurements in the measurement log panel and repeat
the process for different ares of your image if required.
Hint: You can save your scale for future use by selecting ‘Save Preset’ and add a
scale bar to your image by selecting ‘Place Scale Marker’ under ‘Analysis’.
Recording Numbers
Fig 41: A flock of American flamingos (Phoenicopterus
ruber) that disappear amongst one another. The counting
tool is an easy way to mark each one without losing count.
Results
This image of flamingos is quite crowded and at times
it can be hard to differentiate one from another. The
counting tool allows us to mark each one as it is
counted and then record the results when finished. The
number of flamingos in the image is 30 as recorded
below. We can clear the counters on the image and
repeat to be sure our results are accurate and correct.
Step 1: Again, select ‘Measurement Log’ from the
‘Window menu.
Step 2: Select the ‘123 counting tool’ from the side
bar. Hint: Its grouped
together with the eye
dropper tool and ruler
tool.
Step 3: Click on your
image once for each
item you would like to
count. In the example image, I clicked once on each
flamingo.
Step 4: Click ‘Record Measurements’ in the
‘Measurment Log’ dialog box. You will then see your
data appear which you can export if you wish.
Data is exported as a txt file, which you can then
easily copy and paste into a spreadsheet for further
analysis if necessary.
By using our custom scale to measure the diameter of
one of the food vacuoles of the Stensor sp. our image
analysis results tell us that it is aproximmately 40µm in
length. We could go on to measure more of the food
vacuoles, comparing them to one another or analysing
their length in relation to another part of the Stensor sp.
Clicking here will record your
measurments below.
Above you can select, deselect,
export and delete records.