beetleman wrote:How do you come up with the length of your scale bar. Do you measure something on your specimen...easy in this case, and draw it in during processing? I know it is different for Micro.
Nope, no different at all -- you just get to use a bigger measuring stick for Macro.
The key trick is to shoot a picture of a physical ruler using the same lens settings -- including focus -- as you used with the subject. Then just use your favorite photo editing tool to transfer a measurement from the ruler image to the subject image.
The picture below illustrates one approach.
Using Photoshop, I added the image of the scale over the image of the beetle. I set the image of the scale to 25% opacity so I could see the beetle through it. Looking at the beetle and ruler together, I decided that a 5 mm bar would work well. Using the marquee tool, I selected a region a couple of pixels high and however wide it needed to be, to line up with 5 mm on the ruler. Then I filled with black in another layer, to draw the scale bar. The job was completed by removing the layer containing the image of the scale, and adding "5 mm" as a text layer.
I always do these things as layers so I can freely move them wherever they need to go to fit with the picture.
My smaller subjects sometimes need a scale bar less than a millimeter long. In those cases, I've traditionally used a slightly different approach involving some number-crunching to figure out how many pixels wide the scale bar needs to be. It's described
here.
--Rik
I love the wrap-around eyes on these large longhorn beetles and you are right, I never find carpet beetles in the carpet, always on the window 