Bokeh is typically a function of the relationship between 3 variables, aperture, Focal length, and distance to subject. To be more precise, these three variables have a large affect on depth of field which in turn will produce the out of focus region, aka bokeh. Its also important to note that these variables do not indicate the "quality" of the bokeh but more how much out of focus is the background. I.E. can you make out shapes and locations, or is it all a fine blur with no discernible features.
To get the fine blur you typically see with macro photography (this is what I am assuming you are referring to), you will typically use a macro lens at or near its shortest focusing distance (close to the subject) which will create a shallow depth of field and result in a very blurred type of bokeh. After setting your distance to subject, the depth of field can be controlled by stopping down the lens to achieve the desired result.
Keep in mind, the shorter the focal length, the closer to the subject you will need to be to obtain a 1:1 reproduction of your subject. This is one reason why many folks prefer the longer length macro lenses as they allow for a 1:1 reproduction ratio at greater distances. This is especially beneficial when photographing critters of any sort as it will help to not scare them off.
As point of note, a high shutter speed is required due to the shallow/thin depth of field when hand held. Any movement can cause the object to fall out of focus very quickly. You would be best to use a tripod to help avoid the motion blur entirely.
One of the other benefits of using the longer focal length lenses also have the added effect of increase background compression. Without getting to technical, the way the light enters the lens allows for the background to be "squished" ,if you will, causing it to appear more out of focus than the same subject framing at shorter focal lengths. To be honest this area is somewhere where I am lacking significant knowledge, so it may be best to ask professor Google for more information.
so in summary,
1. Use a macro lens or one that is "Macro or Close" focusing
2. Get close as close to your subject as you can, the closes to your lenses min focusing distance the better
3. Use your aperture to control depth of field. Note that even at small apertures the depth of field will still be very thin/shallow due to how close you are to your subject.
4. Use a longer focal length to compress the background and maintain a more comfortable distance from the subject
5. Use a high shutter speed (180th if you can)
6. Use a tripod.
If you are shooting where there is limited light, you may also what to consider a flash with a light modifier that will direct the light on the subject. Something like a snoot, or an old (but clean) cup taped to the flash will work fine.
I hope this helps. I am sure plenty of the folks here can add and or correct my advice as well. Have fun!
Last edited by W.j.christy; 05-11-2017 at 09:05 AM.