Thursday, 29 July 2010

What is a reversing ring and how do you use it?

Welcome to Macro Photography for beginners. Since the early days of writing this website you may have noticed that certain areas of macro photography and camera equipment have been neglected. There are several reasons for this, In most cases this is just because I've not got around to these ones yet, but mainly I have tried to concentrate on the equipment, software and techniques best suited to the absolute beginner to macro photography - from the point of view that this person may have very little experience of cameras or photography. Although macro photography can be difficult [or a bit of a challenge as we prefer to describe it!] it is a skill that is worthwhile learning. It is surprising how often close-up and macro photography can be useful during everyday life as well as dedicated work or projects. I once used macro photography to prove that a computer's optical CD drive scratched my disks in a legal dispute. If it was not for the digital images my case would have been very difficult to prove. In fact, I am convinced that without the photographs the dispute would not have been settled without going to court. I've also found macro photography useful for taking images of electrical circuits or components when wiring or soldering devices together. These are just a couple of recent examples but with some thought I'm sure I could think of several more. It is not accidental that I have neglected to write about reversing rings [also called reversing adapters, reversal rings and reversal mount amongst many other things] on this website in my previous macro photography posts. The fact is, I’m not really a big supporter of this type of device for beginners but accept that reversing rings and bellows should be covered in more detail to enlighten and inform beginners of the many benefits and pitfalls of their use in macro photography. I have therefore decided to write this post for those who are interested in some of the more obscure methods of macro photography. In this post we will look at the good old fashioned reversing ring and bellows whilst investigating some of the ways in which they can be used. At this point I would like to provide a big word warning and would advise readers to place their medication and a stealthy dictionary in a handy position.

Finding the right reversing ring for your camera
A reversing ring is an adapter that (as the name suggests) allows a camera lens to be attached to the camera in reverse i.e. the wrong way round. When the lens is reversed it can focus very closely. One of the main benefits of using a reversing ring is that you can connect any brand of lens to your camera provided that it has the correct size of filter thread. It is also an opportunity to use or recycle a lens that no longer works properly due to mechanical failure, for example if the electronic motor has developed a fault and will no longer auto-focus. This creates an opportunity to use a very high quality camera lens that would be otherwise gather dust in the junk drawer.

When selecting a revering ring or adapter you need to search by camera brand name, for example Canon, Nikon, Pentax, Sony, Konica, etc. In addition you will also have to determine the filter thread size of the lens to be reversed this is often displayed on the lens barrel. The most common thread sizes are 52mm 55mm, 62mm, 67mm and 72mm. Reversing rings are not the best selling photography products and stock levels will often be quite low. Problems of low stock are more prevalent with the most obscure filter thread sizes and with the lesser known camera brands. To further complicate matters it may be possible or necessary to use a reduction ring. This is an additional adapter ring used to reduce a large diameter filter thread to a smaller diameter filter thread. This can be incorporated if there is no reversal ring in the correct thread size for your particular choice of lens. A reduction ring can also be used to increase the distance between the lens elements and the cameras digital sensor. This allows the lens to focus closer to the subject and is effectively the same as using an extension tube.

Now, before we all get over-excited and decide that there is no need to spend good money on a proper macro lens, when we can just reverse a kit lens instead, for a fraction of the cost, there are (as always) some negative aspects to consider. The reversing ring is a device that worked better with old fashioned SLR film cameras than modern SLR digital cameras. The most obvious downside is that you lose auto-focus (obviously – because the lens contacts are facing outwards) and will need to set the aperture in advance, which is easier with older lenses that have an aperture ring. The lens contacts are vulnerable to being damaged whilst the lens is reversed and may need to be protected. This can be achieved by making a protective cover from a spare rear (screw-on) lens cover.

Although the low cost of buying a reversing may seem somewhat appealing to beginners of macro photography, they are of limited use on a digital SLR camera. In addition, it is worth considering that there may be further costs involved in getting the lens to work in reverse. It is widely accepted that not all lenses work in reverse [they were never designed to work this way]. Most camera lenses that can be reversed provide a fairly poor alternative to a high quality macro lens. There are plenty of rational reasons why a beginner to macro photography should avoid making or buying a lens reversing ring or adapter. If the main points above are not enough how about the fact that you could cause irreversible damage to the camera and/or lens. This can happen if the reversing ring breaks or too much weight is attached to the camera. In addition, this damage is classed as misuse and will not be covered by the manufacturer's warranty for the camera or the lens. In the unlikely event that you manage to successfully reverse a lens on a digital SLR and manage to get good results, you will be faced with further tribulations. The camera metering system relies on its ability to communicate with the lens. This is an important factor when setting the flash for macro photography.

The name bellows has been borrowed from those medieval devices once used to pump air into fires to intensify the level of heat. The same technology also filtered down into musical instruments such as organs, concertinas and accordions. So you may be forgiven if the term bellows conjures up strange medieval images of a smithy hammering a red hot horseshoe on an anvil. In photography the bellows obviously have the same corrugated appearance but their use is purely optical rather than pneumatic. In photography bellows is the term used to describe an expandable tube that allows the lens to be moved nearer or further away from the focal plane (digital sensor or film). Spend time reading macro photography books or internet forum posts and you will often find references to the strange and wondrous bellows. If you think digital macro photography is difficult spare some sympathetic thought for previous generations of dedicated macro photographers. There are still many photographers who use bellows and they can be used with digital cameras. The main benefit of using a bellows is that you can obtain very high levels of magnification. In addition, bellows are not expensive to buy in comparison to high quality macro lenses.

Reversing a lens on another lens by using a coupling ring
If you feel like throwing convention out of the window completely how about reversing one lens on the end of another lens? Although it initially sounds utterly preposterous, in principle it is not much different to using a set of bellows. This works by mounting the first lens (for example a 300mm telephoto lens) conventionally to the camera, then mount the second lens (for example a 28mm lens) using a coupling ring adapter. The coupling ring screws into the filter threads of both lenses.

Reversing the lens on the bellows
Using a lens with the bellows is likely to cause several types of image distortion. You may or may not have suffered from some of these photographic problems in the past. Lens errors are usually unwanted effects or distortions of the image. An aberration, according to the dictionary, is the failure of light rays to converge in one focus because of a defect in a lens. Now I'm going to use some words that are usually only reserved for camera lens reviews in glossy photography magazines. Common problems associated with using bellows include colour fringes (a type of image distortion known as chromatic aberration or achromatism). Coma aberration is the blurring of objects at the edge of the field of view. Vignetting is a reduction of brightness our saturation at the periphery (edges) in comparison to the centre of the image. Un-sharpness [which sometimes referred to as softness] and is the description of an image or part of it that is not in sharp focus.
So the problems of using these antiquated devices or a combination of them with digital technology will often outweigh any financial benefit. The main complaint against using bellows for macro photography is that they are often regarded as being too delicate. It is widely accepted that this type of photography is not best suited to nature photography. The over-fiddly set-up is one of the main reasons that bellows are ill-suited to active or moving subjects. To operate bellows successfully with a digital SLR camera it is likely that some additional components will be required. A remote switch (also known as a cable release) and a sturdy tripod are a useful combination for reducing camera shake. Configurations of equipment obviously vary depending on the brand & model of camera, lens and bellows used. However, it is highly likely that you will require some extension tubes to gain optimum results from the bellows. It is definitely surprising to learn that a bellows system method is still a very popular method of macro photography. This is most likely to be due to the high magnification involved. This is varies depending on the setup used but is often x3 to x18 [or above]. In many cases this can be achieved with very little financial outlay.

Macro Photography for Beginners
Firstly it’s good to be back writing about macro photography again, and I’ve enjoyed delving into the subject of reversing rings and bellows. It is my opinion that beginners to macro photography would be better suited to a digital SLR camera with dedicated macro lens. Most of the impressive digital macro photography that you see will be taken in this way. The easiest and most popular way of getting closer is to add a set of extension tubes. I’m not completely opposed to using bellows or reversing rings. I’ve seen some outstanding photography taken with this type of equipment. I just don’t think they are the best way for beginners to get involved in macro photography. Although there are always a few exceptions, perhaps if you are interested in learning about or experimenting with the Scheimpflug principle, bellows might be a better option.

If you take swift look at the popular Canon MP-E 65mm f2.8 1-5x Macro Lens, you can see by its shape, that it is designed on the principle of reversing a standard lens. It also has no auto-focus which makes it even more similar to a reversed lens. If reversing a lens on a digital SLR worked as efficiently as it did with film cameras and lenses with aperture rings, I would have been first in line to buy one when I first took up macro photography.

Marvin Africa

Writer and Macro Photographer