Photo analysis advice please!

[pattymiski]

I need to use photoshop to analyse some photo data for my degree in biological sciences, and I would like some advice on the best method for what I need to do, as I am totally new to Photoshop! I have version CS6 and a graphics tablet.

This might sound odd - I am studying the degradation of cow cung as part of a wider phd on dung beetles. Hence I have 1000 photos of dung (a sample is atatched). I won't be suprised if this makes you laugh, people always find it mad!

Each photo is of a circular metal trap on the ground, with a cowpat and an insect trap inside. The photos were taken in standard conditions and height, but I think the size/pixel count of the images vary and they are JPEGS. I need to work out what % of the trap is occupied by the dung (not including the area of the insect trap - just the soil area inside the trap). The traps are the same physical area, but vary slightly in shape (they were handmade!).

My main problem is that the dung and the soil are very similar colours, and it is hard to seperate them in some areas. I've tried using different tools, and the one that works best is the lasso and magnetic lasso tools, and using the histogram to note the pixel count of each selection. If I could make the dung and soil look more different from each other, it would help me to draw the shapes. I've tried manipulating contrast and brightness, but I don't know if there are any other things I could try? It doesn't matter what colour or whatever the image goes, as I am only interested in the pixel count.

Any advice on how best to manipulate the image and select the shapes would be wonderful!!
thanks!

 

[RTContent]

It depends on how accurate you want to be with your results. Doing it this way is bound to give you a fairly high percentage of error I'm guessing all your photos very in camera angles etc since you've already said they are different file sizes). Not very scientific if you ask me.

But if you are going to use Photoshop to measure and all your looking to do is draw a shape around a certain area, use the pen tool.

 

[Cory Wright]

As RTContent said, it depends on how accurate you want to be? Off the top of my head, why not create a measuring tool in another document. Create a circle with the circle shape tool, in the layer properties, create an outline and bring the fill down to 0 so all you see is the outline. Then, create more circles inside the circle (easiest would be to just duplicate layer and resize it), each occupying a percentage of the space of the first circle. Maybe create those with different color outlines, or a transparent fill color so you can see through. Until you have a measuring tool that shows you how much space something would be occupying.

Then, simple place the "graph" over each image, sizing it so the main circle is as big as the metal, and you should be able to visually see, based on your inside measurements, what percentage of space it occupies.

Not sure if that helps or is too much for what you are trying to do.

Cory