I've often encountered people who would like to shoot macro images but give up because they can't afford a macro lens. They are always surprised when I inform them they can get into macro without a macro lens and in fact spending less than $100.00 if so desired.
A macro lens is always the most easy way to get into high magnification but certainly not the only way. For the purposes of this note I'll start from least expensive to most expensive macro lens alternatives.
1. Close up filters
Close up filters are magnifying lenses that can be threaded onto the front of a lens. They can also be held in front by hand in case of mismatched sizes or unthreaded lenses such as the lenses of most compact cameras. Close up filters are referred to by their magnifying strength in diopters. A +2 diopter is twice as strong as a +1 diopter. A +4 diopter is 4 times stronger than a +1, pretty easy. Inexpensive close up filters are often sold in sets of three containing +1,+2 and +4 diopters. All three can be stacked for even greater magnification. One of the pluses with close up filters is that while they allow you to focus closer to your subject and increase magnification of your subject they do so without contributing to any significant light loss. This means with close up filters you are not quite as bound to a tripod as you are with other means of achieving magnification. The downside (isn't there always a downside) is that close up filters are a big compromise on image quality giving softness out to the edge of the image area, this is not always displeasing but it is worth noting. The degradation of image quality can be minimized (never eliminated) by purchasing higher grade close up filters from manufacturers such as B+W. Even with the loss of quality its worth having close up filters in your camera bag for those times when a compromise shot is better than no shot at all.
2. Reversing rings
Reversing a lens, especially a prime (single focal length) lens will increase that lenses magnification ability. In the days of manual focus film cameras, reversing rings were common to take the standard 50mm lenses in use with most cameras and turn them into excellent macro performers. One of the great things about reversing lenses is that because of retrofocus lens designs being used in most wide angle lenses, reversing a wide angle lens typically yields very large magnifications and an increase in close focusing working distance (distance between the subject and the closest part of the lens to the subject) ability over other methods (see extension tubes bellow). Reversing rings have fallen out of use as lenses have become more and more electronic. Still it is possible on some of todays cameras such as Nikon DSLR's and all the mirrorless cameras on the market to adapt older manual focus lenses with reversing rings. You can even use an adapter to put a nikon reversing ring with an old nikon manual focus lens on a modern canon DSLR! Reversing rings themselves are very inexpensive costing less than $50.00 and picking up an old used lens that would work can cost very little indeed if shopping around. The biggest advantage to reversing a lens is that the quality of the lens' image is not degraded by the reversing. The only disadvantage with reversing a lens is that the light meter in camera may not read accurately particularly when using flash and some adjustments will be necessary.
3. Extension Tubes
Extension tubes are the most expensive alternatives to a macro lens in fact they often approach the cost of some used macro lenses. Extension tubes work by moving the optical center of the lens further from the imaging plane. This creates an oversized image circle that the sensor (or film) in the camera captures the central portion of this enlarges circle. The best analogy I use to visualize what's going on is to think of a slide or movie projector projecting an image exactly the same size as the projection screen. Now if you move that projector further away from the screen the picture gets larger and larger the further you go, much larger than the screen we are watching. Our screen stays the same size and what's on the screen is larger than it was before. In this analogy the projector was our lens, the screen was our image sensor or film and the distance the projector was moved by was our extension tubes. Extension tubes are often sold as sets of three and have their lengths printed on the barrel. The length of the tubes are printed there to give the end user an idea as to the magnification being obtained. For instance if you had 50mm of extension tube and a 50mm lens the magnification you would be getting is said to be lifesize (1:1) meaning the object in real life you are photographing is being projected onto your imaging plane at the same size as it is in real life. If you used 25mm of extension with a 50mm lens you would have half life size (1:2). In another example if we used 100mm of extension tube with a 50mm lens we would have double life size (2:1) meaning an object 5mm in real life will be projected onto our imaging plane as being 10mm in size. Extension tubes will work with most lenses but if the lens is too much of a wide angle problems will occur. As you increase the magnification (more tube length vs. focal length of lens used) the front working distance shrinks smaller and smaller. With wide angle lenses it is very easy to wind up with what is called a virtual point of focus where the actual point at which you would have a focused image has moved INSIDE the lens meaning that in reality you can no longer focus on anything. This can be remedied by using a reversing ring on the wide angle lens which will both increase magnification further AND because of the retrofocus design of most wide angles pushes the front working distance back out to a usable length. Extension tubes have no glass and therefore do not reduce image quality but because of the extension of the lens away from the camera they cause a loss of light. Extension tubes are almost impossible to use without a sturdy tripod.
This is just a quick primer on getting into macro photography without needing a macro lens. One of the nice things as well with the three methods mentioned above is that they can be combined with each other and with macro lenses to get even more magnification. So all the macro helpers I've mentioned here have a life beyond the days before you owned a macro lens.
