Most of us photogs seem to think macro to be a realm which will need a lot of money/gadgetry. It sure is an amazing whole new world which holds the power to surprise and enthrall. While the price bit is true to an extent, one can achieve true macros with most lenses found in the (DSLR) kit.
All it takes is some patience and practice. Plus the easy availability of "tools" needed for these on Ebay does make these options viable.
I say that since almost all of these techniques come with an associated cost with increase in magnification
A) Reduced DoF, almost razor thin
B) Literally back breaking work
C) Extremely small working distances, can be very frustrating at times. But that's the trade-off!
Magnification is always a factor of the sensor size. A part of the reason why point and shoot cameras with their smaller sensor sizes will give better looking macros without using dedicated macro lenses.
Will use the Canon 40D's sensor size of 23mm as a reference in this post.
1:1 denotes a subject that fills the frame at life size, a 23mm subject will fill the frame. Most dedicated macro lenses reach this.
2:1 will mean only half the 23mm subject will be projected onto the sensor
The best way to check for the magnification one is shooting at is to shoot a MM scale and see how many MM markings one gets uncropped.
There are multiple ways of getting the lens to focus closer / gain further magnification -
1. Extension tubes (ETs) : Hollow tubes with no glass which push the lens rear element further away from the sensor, thus helping in projecting a larger/magnified image.
These also reduce the minimum focusing distance of the lens, and take away infinity focus on the other hand
The formula for calculating the magnification gained for ETs
Length of the extension tubes -> ET_FL
Length of the lens -> L_FL
Mag gained = ET_FL / L_FL
E.g. 60mm of ETs + 28mm lens
Mag gained = ~0.5x
There are "Auto" ETs that retain AF and aperture control capabilities, but these come at a price. The easiest/cheapest way is to find the fully manual ETs which only have basic two ends, one to mount the lens and the other to connect to the camera.
Head of a matchstick
Shooting a macro at 500mm, Sigma 150-500 mounted on 50mm of ETs
2. Lens reversal : Involves mounting the lens onto the camera using a "reversal ring" which fits one end to the front of the lens' filter thread and the other which fits the camera mount
Find the filter thread diameter for your lens and find a suitable reversal ring.
With techniques 1 and 2 one loses the capability to control the lens' aperture. Lenses which have a dedicated aperture control ring are preferable. Else one needs to resort to the followign technique
A) Move to Aperture priority or Manual mode with the lens mounted.
B) Dial in the intended aperture
C) Press the DoF preview button and while keeping it pressed unmount the lens
Note: This may not work with some Nikons since I've noticed a couple of models atleast which do not have the DoF preview button.
Some Nikon lenses I've noticed do not maintain the set aperture (since these have a separate movable latch which controls aperture)
The Canons seems to reset to Wide open, while the Nikons seems to close down to the max aperture! Do Nikons and Canons have to do do everything exactly the opposite of each other
Another very important point to note is that the viewfinder's going to be very dull/dim, needs external lighting to keep the subject visible at most times
Cameras keep the aperture open and close it down based on the aperture value only when taking the shot. In this case we'll be stopping the lens down and will result in lesser light coming through for composing the shot
To push things beyond lifesize, a combination of ETs + reversed lens could be used.
3. Lens coupling : Involved "coupling" two lenses face-to-face, generally with the one closer to the subject being of shorter FL
Here the male to male filter threads hold the two lenses together. The smaller FL lens in front acts like a diopter resulting in increased magnification.
Focal length of the lens mounted on the camera, generally a tele -> BL_FL
Focal length of the lens mounted face to face with the tele -> ML_FL
Mag gained = BL_FL / ML_FL
For example, reversing a 50 f1.8 onto a 55-250
@ 55mm, Mag gained = 55/50 -> ~1
@250mm, Mag gained = 250/50 -> 5
Be careful when ordering, one needs a "Coupler" and not a step-up/down filter
The 55-250 has a 58mm thread and the 50 f1.8 has a 52mm thread, so the coupler used was a "58mm to 52mm coupler"
Reversed the Soligor 28mm f2.8 (which Ashok very kindly passed on) onto the lens @ 250mm
The MM scale shows less than 2mm, which takes this to 10:1
@100mm the ridge of a Rs.5 coin
Reversing a 50 f1.8 onto a Tamron 90mm macro
Note: Both the lenses should have focus set to infinity as a starting point (atleast the lens in front). The lens in front should be open as wide as possible to prevent any corner vignetting.
Can result in less than sharp pictures due to diffraction since we're introducing glass in front of the base lens.
In all these techniques
1) The shorter the Focal length of the lens in front the greater the magnification one gets.
2) A good handholding/shooting technique is a must. A tripod/stable surface helps a great deal!
3) Off camera flash is almost mandatory, either through a wireless trigger or tethered using a TTL Cord
4) Doesn't necessarily imply spending large amounts of money ;)
And just to put the madness into on bundle :D
This one's a combination of technique 1 and 3
Canon 50mm f1.8 revered, 52-55mm coupler, Tamron 90mm f2.8 macro, Fotodiox Extension tubes (50mm)
YN-465 tethered to a simple flash bracket.
Hope this does entice you to try the world of macro, for not much ;)