SIZE MEASUREMENT OF PARTICLES (THESIS DUE TOMORROW..PLEASE HELP!)

[Geology Guy]

Good Evening Everyone,
I need to measure the size of particles within the yellow boundaries in the image I attached. I learnt that size of objects or particles can be measured using either "Fit Ellipse" "Feret Diameter" or "Area". The purpose of my thesis is that I want to see if there is a relationship between the size of the particles within that yellow boundary and overall size of the space between them. I used "Area" in all the graphs I plotted but now my Professor is asking me why I did not use the Feret diameter instead. I used "Area" instead of "Feret Diameter" because someone on here told me that "Area" in Image J is a better estimate than "Feret Diameter" for the size of an object? Anyway I have no idea why the former is better than the latter and was wondering if someone can please clarify this.

My thesis is 10 hours from writing this message.

Thank you all for your help.

[Christian Goosmann-2]

Hi Geology Guy,
If I haven't misunderstood something, feret diameter is the smallest
diameter that you get when you rotate an object. Like the smallest gap
you could fit it through. First of all it is somehow connected to area
but it is in a different dimension because it is a length [µm] and not
an area [µm²]. For a perfect circle '(feret/2)² * pi' is the area, for a
square it is '(feret/2)²*4' so you see, the shape matters in how feret
relates to area. I would think that area is more precise when comparing
"sizes" but that depends on your experiment. If "sizes" means the
opening of gaps for other particles to pass through for instance, feret
diameters could make more sense measuring than areas which could belong
to irregular shapes. So if you ask how big is an object, if you want to
know volume, weight, or such, use area. If you ask how big must the gap
be where you can fit this object through, feret is not such a bad idea,
though beware, if you only have a cross section of a more irregular
object in three dimensional space to judge.
Hth
Christian

---
Christian Goosmann
Mikroskopie
Max-Planck-Institut für Infektionsbiologie
Campus Charité Mitte
Charitéplatz 1
10117 Berlin
Tel.: [phone]

Geology Guy wrote:

> <http://imagej.1557.x6.nabble.com/file/n5004387/Image_J_Picture.png>
> Good Evening Everyone,
> I need to measure the size of particles within the yellow boundaries in the
> image I attached. I learnt that size of objects or particles can be measured
> using either "Fit Ellipse" "Feret Diameter" or "Area". The purpose of my
> thesis is that I want to see if there is a relationship between the size of
> the particles within that yellow boundary and overall size of the space
> between them. I used "Area" in all the graphs I plotted but now my Professor
> is asking me why I did not use the Feret diameter instead. I used "Area"
> instead of "Feret Diameter" because someone on here told me that "Area" in
> Image J is a better estimate than "Feret Diameter" for the size of an
> object? Anyway I have no idea why the former is better than the latter and
> was wondering if someone can please clarify this.
>
> My thesis is 10 hours from writing this message.
>
> Thank you all for your help.
>
>
>
> --
> View this message in context: http://imagej.1557.x6.nabble.com/SIZE-MEASUREMENT-OF-PARTICLES-THESIS-DUE-TOMORROW-PLEASE-HELP-tp5004387.html
> Sent from the ImageJ mailing list archive at Nabble.com.
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html

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[gankaku]

Hi Geology Guy, hi Christian,

just a short comment on the last reply. The Feret's diameter is actually the longest straight distance inside an image object (not the shortest one!). ImageJ/Fiji also gives you the minimum feret, but this is also not the smallest distance inside a feature, since the determination method kind of ignores the (small) cavities in a particular object. Therefore, feret's diameter is very usefull for certain analyses but you need to handle it with care regarding specific data.

Even though, strongly depending on your experiment and interpretation (which might justify using e.g. feret's diameter), I would agree to Christian and rather take the area if I want to compare it to the overall area of the bigger feature (composed of the smaller ones). Because then, you compare area with area.

kind regards,
Jan

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[Adam Hughes]

Im assuming since you drew the boundary, then you know the total area of
the boundary. If so, then by summing all of the area of the particles, you
will have the area of the spaces just by subtraction. If your goal is to
measure the area of this space and correlate it to the total size of the
bounding curve, then it doesnt make much sense to me to do it any other way.
On Aug 12, 2013 6:50 AM, "Jan Brocher - BioVoxxel" <[hidden email]>
wrote:
>
> Hi Geology Guy, hi Christian,
>
> just a short comment on the last reply. The Feret's diameter is actually
the longest straight distance inside an image object (not the shortest
one!). ImageJ/Fiji also gives you the minimum feret, but this is also not
the smallest distance inside a feature, since the determination method kind
of ignores the (small) cavities in a particular object. Therefore, feret's
diameter is very usefull for certain analyses but you need to handle it
with care regarding specific data.
>
> Even though, strongly depending on your experiment and interpretation
(which might justify using e.g. feret's diameter), I would agree to
Christian and rather take the area if I want to compare it to the overall
area of the bigger feature (composed of the smaller ones). Because then,
you compare area with area.
>
> kind regards,
> Jan
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html

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