Posted by Alan Tunnicliffe
This article is not about how to take close ups, moreover it is about the accessories that are available to help us obtain the result without investing in a true expensive macro lens
Macro extension tubes and close-up lenses (filters) are attachments that add high magnification to virtually any camera lens. It is often unclear exactly how much magnification you will gain, in addition to whether one of the other macro options will provide a better solution for your needs, such as purchasing a dedicated macro lens.
An extension tube is simply a hollow cylinder that fits in between your camera and lens, causing the lens to move further from the sensor. This additional distance allows your lens to focus more closely, which in turn provides more magnification. Unlike most lens accessories, extension tubes don’t add any extra optics, and are therefore relatively inexpensive in comparison to a true macro lens.
An extension tube increases lens magnification by an amount equal to the extension distance divided by the lens focal length. For example, adding a 25 mm extension tube to a 50 mm lens will give a magnification gain of 0.5X. Therefore, if the lens original magnification was 0.15X, then the new magnification will be 0.15X+0.5X=0.65X. The closest focusing distance will also decrease to ~210 mm. Extension tubes provide minimal magnification when used with telephoto lenses — which is unfortunately their main weakness.
An extension tube is usually specified in terms of its extension length in millimetres. Most manufacturers provide a range of extensions from 8-35 mm, although multiple extension tubes can be stacked to increase the extension even further. Extension tubes can also include basic electronics to pass through signals between the lens and the camera body (such as for autofocus).
Important considerations. Image quality shouldn’t be a factor when deciding between different brands of extension tubes (all use the same. Build quality may be an important consideration — particularly if you plan on using it with a heavy telephoto lens. Additionally, older extension tubes don’t always work with newer lenses designed for cropped SLR sensors.
Pros and Cons of Extension Tubes
While extension tubes are an amazingly flexible solution, they may not always the best option for your type of photography. The best thing to do is to compare the pros and cons appropriately:
Extension Tube Advantages
- Much less expensive than purchasing a dedicated macro lens.
- Provides a flexible and upgradable increase in magnification with virtually any camera lens — even existing macro lenses.
- Does not place additional glass elements between your subject and your camera (minimising any potential loss in image quality).
- Provides consistent, predictable quality regardless of make / brand.
Extension Tube Disadvantages
- Provides only a minimal magnification gain with telephoto lenses.
- Causes your lens to lose the ability to focus on distant objects.
- F-stop set by your camera might not represent the effective f-stop from extension
- Causes your lens to focus more closely than it was designed. High magnification images will therefore usually have lower quality than with a dedicated macro lens.
- Requires that you remove your lens from the camera each time you wish to change the amount of extension.
- With zoom lenses, the image can go quickly out of focus as it zooms in or out.
If any of the above disadvantages has the potential to be a problem, it is worth considering using either a dedicated macro lens or a close-up filter (next section).
Close-up lenses are special lenses that screw onto the front of your lens like an ordinary filter. They are basically just a sophisticated magnifying glass that is placed between your lens and the subject. It is for this reason that they are also often called “close-up filters.”
A close-up filter works by decreasing the effective focal length of whatever lens they are used on. This decrease in focal length means that the extension has to increase correspondingly — which ends up magnifying the image similar to using an extension tube.
A close-up filter is usually specified in terms of “dioptres,” which is a measure of their magnifying power. Higher numbers give more relative magnification on a given lens, but image quality also tends to decrease correspondingly. Typical values range from +2 to +5 dioptres, although multiple close-up lenses can be combined to increase this further.
Close-up filters increase magnification much more when used with longer focal length lenses. For example, a 50 mm lens requires +10 dioptres to achieve a magnification gain of just 0.5X, whereas a 200 mm lens requires only +2.5 dioptres. Conversely, a given close-up lens might be too powerful (and decrease image quality too much) when used on a 200 mm telephoto lens, but might be just right on an 80 mm lens.
Pros and Cons of Close-up Lenses
As with extension tubes, it is important to compare the pros and cons of adding a close-up lens to gain magnification:
Close-up Lens Advantages
- Provides more magnification than extension tubes when used with telephoto lenses:
|12 mm||25 mm||+2 Dioptres||+4 Dioptres|
- Retains more light at a given f-stop setting when compared to extension tubes (since the effective aperture no longer increases).
- Does not require removing the lens from the camera body.
Close-up Lens Disadvantages
- Inconvenience. A different close-up lens is required for each filter size.
- Provides a minimal magnification gain when used with focal lengths less than ~80 mm.
- Decreases the working distance for a given amount of magnification
(the distance between the subject and the front of your lens)
- Places additional glass between your camera and subject, which may decrease image quality.
- Often more expensive than extension tubes (but less than a dedicated macro lens).
- May prevent your lens from being able to use other filters.
Other Macro Objects
While extension tubes and close-up lenses are the two most common ways to increase magnification, other options exist. Popular alternatives include the following
Teleconverters. Even though these are typically used to increase the focal length of a lens, they are also a popular way to increase magnification. A 2X teleconverter doubles the maximum magnification. Disadvantages include (i) a loss in image quality and (ii) an increase in the minimum f-stop (max aperture), which may prevent a camera from being able to autofocus.
Bellows. These are basically adjustable length extension tubes. They are much more expensive than normal extension tubes, but also often enable your lens to make tilt/shift movements to reposition the depth of field. Bellows are quite cumbersome, so a tripod is a requirement.
Reversing Rings. These allow your lens to be mounted in the reverse direction. They attach to your camera where you would normally mount the lens. Your lens front filter mount then screws onto the reversing ring, causing the inner part of your lens to face outward. Shorter focal length lenses will allow for closer focusing distances and higher magnification. The main disadvantage of reverse rings is that they result in an extremely narrow range of distances which can be in focus. Other complications potentially include the loss of aperture control and autofocus.
Cropping. You can enhance the size of a subject in a print by simply cropping the image. This is an easy and powerful option if you have some extra resolution to spare.
Lighting the Subject
Having looked at the accessories we can use for taking close ups, now let us look at how we can light the subject……..
Daylight. This type of lighting is normally outdoors unless you are using natural light through a window indoors. Daylight is the most natural source of lighting, however, as with most single light sources, reflectors may be needed to put light into shadow areas.
On camera flash. Using the cameras pop up flash is another alternative, however this produces harch shadows which can be helped slightly with a diffuser. It may also cast a shadow from the lens depending on length of lens and distance to subject.
Off camera flash. Using your portable flash(s) with an extension cable or slave unit allows more flexibility to light the subject evenly, using either a single flash or multiple flashes preferably diffused. Check this you tube link which is very informative.
|Ring flash. This is a circular flash that fits around the camera lens for a more even type of lighting and is fired by a controller fitted onto the cameras hot shoe. Many can be used as either flash or a constant light source and the more expensive models can control each half of the ring, setting the brightness differently on each half.|
|O ring flash. This is an accessory that utilises your own portable flash. It fits over the flash head and around the lens to give an even illumination the ring flash does. The output power is dictated by the power of your portable flash.|
|Macro lights. These lights are more expensive than ring flashes or O rings but they enable superb close-up lighting control with exceptional flexibility.|
I have not mentioned studio flash set ups because this article is more about types of portable equipment which is easy to carry, set up and use ‘in the field’.