Hopefully this will be a series of articles on macro that will be of use to both beginner and experienced macro shooter. I will only be covering shooting macro with a DSLR setup and will add sections regularly Rather than clog this with replies and suggestions I will set up a separate comments/suggestions thread here http://photography-on-the.net ...php?p=9342080#post9342080.
The best all round lens for macro is a prime lens around 100mm focal length. I have yet to come across a bad macro lens made by a major manufacturer so canon 100mm, Tamron 90mm, Sigma 105mm, canon 60mm EF-S to name a few are all optically excellent. Longer focal length macro lenses not only cost a lot, they are harder to handle hand held, more difficult to get higher magnifications with and are in general slightly less sharp than their smaller cousins. I'd only recommend getting one if you really do have very nervous or dangerous subjects or you really do want the lovely background bokeh they can give.
Alternative (cheaper) macro lens setups
An alternative is to start off with a set of extension tubes (eg Kenko) and use them with a prime lens around 40mm to 85mm.Only major disadvantage is the loss of infinity focus.
An even cheaper alternative is to use lens reversing techniques.
You can reverse either a kit lens or say a 50mm lens directly onto the body using a reverse body coupler. This can give suprisingly good results but suffers from the problem of losing aperture control. You need to preset the aperture of an autofocus lens whilst the lens is mounted normally, set the aperture in Av mode, press the DOF preview button and remove the lens whilst keeping the DOF preview button depressed. This leaves the aperture set on the lens until the next time it is mounted normally but does result in a dimmer viewfinder. You can get round this problem by using a reversed older manual lens which has an aperture control ring.
Another reversing technique is to reverse lens onto the front of another lens. For this you need a male/male lens reversing coupler that has filter threads fitting both lenses. This has one advantage over the previous reversing method in that you retain aperture control of the main lens. This is normally done with a smaller focal length lens reversed onto a longer lens.
Achieving higher than 1:1 magnification
With a 1:1 macro lens of 150mm focal length or less you can get to 2:1 magnification or higher using a full set of extension tubes (68mm)
Another method is to reverse a smaller lens onto the front of the macro lens using a reverse male/male lens coupler. With a 50mm lens on the front of a 100mm macro lens you will get 3:1 magnification. Lens reversing like this is similar to adding diopter filters to the front of the lens although a 50mm lens is equivalent to a +20 diopter filter.
A body reversed 18-55mm kit lens will give a zoom macro lens going upto around 3:1 magnification.
The ultimate high magnification lens is the canon MPE-65 which goes from 1:1 to 5:1 magnification without additions.
You can go higher than 5:1 using bellows arrangements or even microscope objectives on a suitable tube and fixing. I'm currently playing with a 10X microscope objective mounted on a lens cap fixed to the end of 75mm of extension tubes.
Natural light is fine for macro shooting upto 1:1 magnification but past this becomes increasingly difficult. I tend to use natural light where I can for flowers and often larger bugs such as butterflies and dragonflies. I prefer shooting natural light on slightly cloudy days as this avoids the high contrast and ugly specular highlights you can get with full bright sun. Typical camera settings I would use for handheld work would be ISO200-1600, 1/200th, with the aperture around F6.3 to F11 adjusted using the ISO with the camera in TV mode. I normally dial in some negative Exposure compensation (around -.3 or -.6) to avoid blown highlights but this does vary with camera body. Obviously if you have a static subject and some form of stabilisation (eg tripod or bean bag) you can drop the shutter speed.
Flash has a number of advantages for macro work , you can always get enough light with small the aperture values that are often used to get reasonable DOFand it helps provide very high effective shutter speeds (the flash duration) which helps stop motion blur (either you or the subject). It becomes a necessity for most shooting above 1:1 simply because there is not normally enough light.
I use standard flashguns (430Ex) mounted on a bracket with a diffuser. You can obviously use macro flashes but I would avoid single flash tube ones and ones where you cannot move the flash heads which only really leaves the rather expensive MT-24Ex. Single tube macro flashes tend to give very flat looking shots and dual tube macroflashes are just rather hard to diffuse adequately.
Typical camera settings for full flash shots upto 1:1 magnification - camera in M mode, F11,1/200th, ISO 100/200. Above 1:1 you may need to start opening up the aperture more if you want to avoid diffraction softening, I tend end up around F5.6 at 5:1.
Flash in ETTL mode but the FEC (Flash Exposure Compensation) will need to be adjusted depending on the shot brightness. I have to adjust mine down to -.66 for dark backgrounds or no close background and upto + 1.66 for a white background from a normal setting of 0 FEC (note the normal setting for good exposure of a grey card may not be 0 FEC on some setups).
There are some situations where you may want to shoot mainly natural light but add some flash to light the subject a bit more- this often occurs if the subject is significantly backlit. Typical camera settings as for natural light shooting but with EC probably at -.66 and FEC set on the flash around - .66 to -1
Flash Brackets and Diffusers
I either use a DIY modded vidcam bracket which has a ballhead fitted on the top or a Manfotto 330B flash braclet with one arm removed and a Jessops medium ballhead fitted to it. The DIY bracket is similar to a Hakuba LH-1 ballhead bracket (EBAY) but again might need the supplied ballhead replaced with a larger cheap generic 1/4" male fitting ballhead. Obviously you also need a canon fit off-camera flash cord to use these brackets. I use coke-can diffusers on the front see http://www.flickr.com ...iscuss/72157594312315664/ but a similar diffuser like a lumiquest mini softbox would be fine.
5Dmk2 with modded vidcam bracket setup
40D with manfrotto 330B bracket setup
1.3 Supporting/stabilising the camera
I'm not saying anything about tripods or monopods as I do not use them.
I sometimes use a beanpole which I grip in my left hand along with a bit of camera.
I often rest the camera lens on something when I'm shooting such as a solid surface, or bits of me. One trick is to actually hold part of the plant or whatever near the subject and rest the camera lens on you hand or arm. Some people use beanbags especially for natural light shots of bugs.
1.4 Camera Body
The DSLR camera body used in macro is largely irrelevant as you tend to only use the simplest of functions on it. Most macro shooters shoot with manual focus by moving the camera to focus. The only debate you sometimes get is 1.6 crop vs full frame where 1.6 crop cameras obviously have an advantage of higher "print magnification". I can only say that I've found using an MPE-65 lens on a full frame 5D mk2 a delight and well worth the loss of print magnification (this can easily be regained by cropping).
The magnification maximum of most macro lenses is 1X or 1:1, this simply means that 1cm of subject produces 1cm of image on the sensor. The magnification is a property of the lens not the camera body/sensor size. Smaller sensor cameras produce higher "print magtnifications" simply because the image is enlarged more to produce a standard size print.
2.1 Measuring the lens magnification
The easiest way of finding out the lens magnification of a setup is to measure it. This can easily be done by photographing the mm scale of a ruler.
Then Lens magnification = sensor width (mm)/mm across pic
2.2 Calculating the lens magnification
The Maximum magnification of a lens reversed onto the front of another non macro lens is given by the formula
Magnification = focal length main lens(mm)/ focal length reversed lens
So a 50mm lens reversed on to 100mm lens will give 100/50 = 2:1
For a macro lens you simply add the intrinsic magnification of the lens
so for a 1:1 100mm macro lens with a reversed 50mm the magnification is 1+ 100/50 = 3:1
Magnification with extension tubes
For a non macro lens with extenson tubes the magnification is given by the formula
magnification = length of ext tubes (mm)/focal length of lens (mm).
So for a 50mm lens with a set of extension tubes totalling 68mm the max magnification = 68/50 = 1.36:1
For a macro lens again you simply add in the existing magnification, so for a 100mm macro lens with 68mm of extension tubes the max magnification should be 1+ 68/100 = 1.68 :1
However this is not what actually you get because at minimum focus the focal length of a macro lens shortens considerably from that at infinity. The focal length of a macro lens at minimum focus is given by the minimum focus distance/4 which for a 100mm macro lens works out to be around 75mm so the magnification you actually get is 1+ 68/75 = 1.9:1
In practice even this is a slight underestimate so I recommend you actually measure it with the ruler method.
Magnification of lenses reversed onto the camera body.
I have not come across a simple formula for working this out but from observation a reversed 50mm lens gives around 1:1 magnification and a reversed 28mm lens gives around 3:1 magnification.