How to Photograph for Metron
Introduction
EponaTech’s
Metron software can be used with
any photographs, but if
the photos are taken following these guidelines, they will be particularly
well-suited for use with the software.
We
have a separate document about how to import radiographs into
Metron.
Things
to Consider when Taking Photographs
Place a “Scale Marker” in the Image
To be able to scale the image when you import it into Metron,
there must be an object of known size in the photograph.Actually,
you can use Metron even with unscaled images, but then some values
will be approximate, so its always best to use a scale marker
if you can.
For frontal and lateral photographs, a good way to include a
scale marker is to photograph the hoof on a block of wood, and
place a scale or an object of known size on the side of the block.
For the photograph of the sole of the foot, you want
to get a scale marker in thesame plane as the plane of the sole.We
have found it very handy to use a scale marker that
can be clipped onto a finger of the person holding the hoof, as
shown below
In the scale marker we use, we know that the distance between
the fiducial marks is exactly 2.0 inches.We also have room to
write the name or a code to indicate the identity of the horse,
which foot, and the date, using a dry-erase marker
Align the Camera Orthogonally to the Subject.
If you’re shooting a photograph of the sole, the
pointing direction of the camera should be at a right-angle (“orthogonal
to”) the plane of the bottom of the foot.
If you’re shooting a Frontal or Lateral hoof photo, try
to line up the camera so that its pointing direction is orthogonal
to the leg.For Frontal and Lateral photos, the camera should be
held so that it is at the level of the top of the block that the
horse is standing on – in the image the you shouldn’t
be able to see thetop surface of the board (see image below).
Use a Long Focal Length
If you have a choice, use a “long focal length”
to take the photos. For
example, if your camera has a zoom lens, then it is best to use
the zoom feature so that you can be as far away from the hoof as
possible, but still zoomed in so the hoof fills the field of view.
Such a technique will tend to remove “perspective effects”
from the image.
Make Sure the Subject Fills the Field of View
This is one of the simplest things, but also often
done wrong. When you take
the picture, make sure the hoof fills up the whole image as much
as possible without “cutting off” anything at an edge
of the image. We don’t want images with a lot of wasted space around the
outside of the hoof (later,
when digitized, this will cause a bigger image with lots of wasted
pixels, and the hoof will be represented with relatively fewer
pixels, possibly making it “grainy”).
Standard “Good Technique” for Taking Quality Photographs
Finally, the standard elements of taking good photographs
are, of course, important. For
example, good lighting – don’t take a picture of a hoof
when under a barn so the hoof is in shade when there is a bright
daylight background just behind the hoof.
How to get Photographs into Metron
Two Choices: Digital Camera or Conventional Camera and Scanner
There
are basically two ways: you can use either a conventional (film)
camera, or a digital camera. If you use a digital camera, things
are very fast and simple. If you use a conventional film camera, then
you either have to use a scanner to scan in the resulting photo,
or you have to use a developer that can return your pictures in
digital form – on a floppy disk or CD.
Almost all film developers now offer this (even the one
at your local grocery store)!
Getting
a Digital Image with the Correct Size and Format.
In
order to end up with a file that is suitable for use with Metron,
you need to
create a file with a "good" number of pixels (not too
many, not too few) and
it must be either a "JPEG" file or a "Bitmap"
file. It is best to try
to end
up with a "JPEG" file which will have the extension
".jpg". For example, the
filename might be "my_hoof.jpg".
The second choice is to use a "Bitmap" file
which
will have the extension ".bmp", for example "a_hoof.bmp".
Now,
getting a convenient size in terms of the number of "pixels"
is the other concern. A reasonable size for use with Metron is an image that is about
640x480
or perhaps 800x600 or maybe even 1024x770.
The number of pixels you
end up with depends on the resolution setting on your digital
camera, or the
resolution the developer used when returning your images on a
disk, or the "DPI"
(dots per inch) setting you choose on your scanner (with your
scanner's software). The total number of pixels also depends on the size of the image.
If
you use images with lots of pixels (like 1600 X 1200 pixels or
greater) things will
work (Metron can handle any size) but things will
be slower to deal with and
will take more disk space, and there really won’t be an advantage
to keeping all
those extra pixels. You may find that you’ll need to use a
magnification setting in Metron
(like 50%) in order to avoid having to use the scroll-bars all
the time to scroll around
your image. All in all, it’s best to try to get your
image of an appropriate size from
the start. Again, this would be somewhere from 640X480
up to 1024X770. If
you’re using a scanner: A lot of scanners you see advertise
that they can scan at 600
DPI or even 1200 DPI, but these settings will generate a file
that is way too big to be
practical for our purposes. All scanners can be configured to scan at lower
resolutions,
like 72 DPI, 100 DPI, or 150 DPI.
Image Orientation
All images in Metron need to be oriented with the “ground”
towards the bottom of your computer screen (for lateral and frontal views)
and with the “toe” towards the bottom of your computer screen for the view of the
sole. If your images are
oriented another way, Metron has image rotation abilities, which
you should be sure to use first, before going thru the “guided markup” procedure
in Metron.
Importing Images into Metron
When an image is imported into Metron,
a copy of the original is made and placed into a set of folders
where Metron maintains its image database.
Your original file will not be altered or deleted.
This means that after an import into Metron, you will actually
have two copies of your file on your disk (the original, and the
copy in the
Metron database).
If you wish, you could then delete your original and rely
on Metron for storage of your images.
There is an “Export Image” feature in Metron
that would allow you to create a copy from the Metron database
back out to any location you choose, should you need the image
file for another application.
If you are building a large, valuable database of images
in Metron, we suggest backing up the entire image database
from time to time. This
means saving a copy of the folder called “Databases”
which is in the folder that you installed Metron into.
The default location for this would be C:/Epona/Databases
.
