Tuesday, 30 October 2012
Monday, 29 October 2012
Reversed-lens
Macro photography reveals a new world that is normally unseen and can turn the ordinary into the extraordinary. Macro lenses may be expensive, but there do exist more budget friendly alternatives. This tutorial is about using a reverse mounted lens to take macro photographs.
A lens to reverse mount, it need not be from the same manufacturer as your camera because the lens will be mounted by its filter threads and not the mount as is normally done. A good candidate here is the 50mm f/1.8 due to its low cost. The lens ideally needs to have a manual aperture ring, old manual focus lenses work well here regardless of make. Lenses without an aperture ring such as Nikon G-series and Canon EF lenses can still be used if you keep the lever on the lens' mount that controls the aperture open by hand, though this is far from ideal.
You lose the ability to focus when reverse mounting a lens. A plane a fixed distance away from the lens will be in focus and you will need to move either the subject or the camera to place the subject in this plane. The depth of field is extremely shallow even when the lens is stopped down so you may find it challenging at first to get the subject in focus.
A reversing ring which has a mount for your camera on the one side and filter thread on the other. The revsersing ring that I bought has 52mm filter thread which exactly matches the threads of the Nikon 50mm f/1.8 lens. If your lens and reversing ring threads don't match you will need to use a step-up or step-down ring.
Lighting
The problem of sufficiently and evenly lighting the subject can be difficult to overcome. Some cameras can focus on subjects so close that they touch the front of the lens. It is difficult to place a light between the camera and a subject that close, making extreme close-up photography impractical. A normal-focal-length macro lens (50 mm on a 35 mm camera) can focus so close that lighting remains difficult. To avoid this problem, many photographers use telephoto macro lenses, typically with focal lengths from about 100 to 200 mm. These are popular as they permit sufficient distance for lighting between the camera and the subject.
Ring flashes, with flash tubes arranged in a circle around the front of the lens, can be helpful in lighting at close distances.Ring lights have emerged, using white LEDs to provide a continuous light source for macro photography, however they are not as bright as a ring flash and the white balance is very cool.
Good results can also be obtained by using a flash diffuser. Homemade flash diffusers made out of white Styrofoam or plastic attached to a camera's built-in flash can also yield surprisingly good results by diffusing and softening the light, eliminating specular reflections and providing more even lighting.
Ring flashes, with flash tubes arranged in a circle around the front of the lens, can be helpful in lighting at close distances.Ring lights have emerged, using white LEDs to provide a continuous light source for macro photography, however they are not as bright as a ring flash and the white balance is very cool.
Good results can also be obtained by using a flash diffuser. Homemade flash diffusers made out of white Styrofoam or plastic attached to a camera's built-in flash can also yield surprisingly good results by diffusing and softening the light, eliminating specular reflections and providing more even lighting.
Macro Ring Flash
Macro Twin Flash
DIY Macro Flash Diffuser
Teleconverter
A teleconverter (sometimes called tele extender) is a secondary lens which is mounted between the camera and a photographic lens. Its job is to enlarge the central part of an image obtained by the objective lens. For example, a 2× teleconverter for a 35 mm camera enlarges the central 12×18 mm part of an image to the size of 24×36 mm in the standard 35 mm film format. Teleconverters are typically made in 1.4×, 1.7×, 2× and 3× models, of which 1.4× and 2× are most common. The use of a 2× teleconverter gives the effect of using a lens with twice the focal length. It also decreases the intensity of the light reaching the film by a factor of 4 (an equivalent of doubling the focal ratio) as well as the resolution (by a factor of 2).
When used with somewhat slow lenses they may reduce the effective aperture enough that the camera's autofocus system will no longer work; depending on the camera system, this may range from f/5.6 to f/8.
Dedicated teleconverters only work with a limited number of lenses, usually telephoto lenses made by the same manufacturer, or by a third party manufacturer to a matching standard.
Using a teleconverter with an existing lens is usually less expensive than acquiring a separate, longer telephoto lens, but as the teleconverter is magnifying the existing image circle, it also magnifies any aberrations.
Fucntion
A teleconverter works similarly to a telephoto group of a proper telephoto lens. It consists of a group of lenses which together act as a single diverging lens. The location of a teleconverter is such that the image produced by the objective is located behind the teleconverter in a distance smaller than its focal length. This image is a virtual object of the teleconverter which is then focused further away and thus enlarged. For example when a single negative lens is placed so that the image formed by the objective is located in the midpoint between the lens and its focal point the lens produces the image in its focal point enlarging it two times thus acting as a 2× teleconverter.When used with somewhat slow lenses they may reduce the effective aperture enough that the camera's autofocus system will no longer work; depending on the camera system, this may range from f/5.6 to f/8.
Dedicated teleconverters only work with a limited number of lenses, usually telephoto lenses made by the same manufacturer, or by a third party manufacturer to a matching standard.
Using a teleconverter with an existing lens is usually less expensive than acquiring a separate, longer telephoto lens, but as the teleconverter is magnifying the existing image circle, it also magnifies any aberrations.
Close-up Filter
In photography, a close-up filter, close-up lens or macro filter is a simple secondary lens used to enable macro photography without requiring a specialised primary lens. They work identically to reading glasses, allowing any primary lens to focus more closely.
Close-up lenses typically mount on the filter thread of the primary lens, and are manufactured and sold by suppliers of photographic filters. Some manufacturers refer to their close-up lenses as diopters, after the unit of measurement of their optical power.
While some single-element close-up lenses produce images with severe aberrations, there are also high-quality close-up lenses composed as achromatic doublets which are capable of producing excellent images, with fairly low loss of sharpness.
Close-up lenses are usually specified by their optical power, the reciprocal of the focal length in meters. Several close-up lenses may be used in combination; the optical power of the combination is the sum of the optical powers of the component lenses; a set of lenses of +1, +2, and +4 diopterscan be combined to provide a range from +1 to +7 in steps of 1. A split diopter has just a semicircular half of a close-up lens in a normal filter holder. It can be used to photograph a close object and a much more distant background, with everything in sharp focus; with any non-split lens the depth of field would be far too shallow.
Extension Tube
An extension tube - also called extension ring - is used with interchangeable lenses to focus closer, useful in macro photography.
The tube contains no optical elements; its sole purpose is to move the lens farther from the image plane. The farther away the lens is, the closer the focus, the greater the magnification, and also the greater the loss of light (requiring a longer exposure time). Lenses classically focus closer than infinity by moving all optical elements farther from the film or sensor; an extension tube simply imposes this movement.
Extension tubes without electrical contacts will not allow an electronic automatic camera to control the lens, thus disabling autofocus and in some cases forcing a user to shoot wide open unless the lens offers manual aperture control. More expensive extension tubes contain electrical contacts allowing the user to use autofocus and electronically control the aperture of the attached lens.An advantage to the non-electrical tubes is their lower price.
Other items like lens adapters may unintentionally have an effect similar to an extension tube. A lens designed for a small flange focal distance may not be able to focus to infinity when a lens adapter places the sensor too far away.
Working Distance and Focal Length
The working distance of a macro lens describes the distance between the front of your lens and the subject. This is different from the closest focusing distance, which is instead (usually) measured from the camera's sensor to the subject.
The working distance is a useful indicator of how much your subject is likely to be disturbed. While a close working distance may be fine for photographs of flowers and other stationary objects, it can disturb insects and other small creatures (such as causing a bee to fly off of a flower). In addition, a subject in grass or other foliage may make closer working distances unrealistic or impractical. Close working distances also have the potential to block ambient light and create a shadow on your subject.
At a given magnification, the working distance generally increases with focal length. This is often the most important consideration when choosing between macro lenses of different focal lengths. For example, Canon's 100 mm f/2.8 macro lens has a working distance of just ~150 mm (6") at 1:1 magnification, whereas Canon's 180 mm f/3.5L macro lens has a more comfortable working distance of ~300 mm (12") at the same magnification. This can often can make the difference between being able to photograph a subject and scaring them away.
However, another consideration is that shorter focal lengths often provide a more three-dimensional and immersive photograph. This is especially true with macro lenses, because the greater effective focal length will tend to flatten perspective. Using the shortest focal length available will help offset this effect and provide a greater sense of depth.
Depth of Field
The defining characteristic of macro photography is of course that subjects are shot at close distances. While this close camera-to-subject proximity can lead to visually arresting images captured from an intimate perspective, this sort of photography presents unique technical challenges as well.
In this article I'll address one of the most significant of these challenges - controlling depth of field (DOF). The term depth of field refers to the area in front of and behind the point on which focus is set that can be rendered in sharp focus. As we'll explore throughout this article, DOF control plays a very prominent role in macro photography.
The cute creature in the image below is a cicada nymph, by definition the larval or sub-adult stage of an insect with partial metamorphosis. For me, this image is a failure. Why? Almost all the interesting parts and features of the nymph are are out of focus - its abdomen, wing buds, legs, even the front of its head.
Why are so many of the image elements blurred? It's not due to poor focusing technique. If you look carefully, you’ll see that I placed focus on the cicada's eye, always a good choice whether photographing people or insects. The lack of sharp detail results from insufficient DOF. That is, the range of objects in front of and behind my point of focus that can be simultaneously rendered in sharp focus is extremely shallow. The result? We see sharp detail in just a tiny portion of the whole image.
Understanding depth-of-field
Before we can begin to figure out how to better control DOF, we must first understand the factors that make it so problematic in macro photography. Depth of field is dependent upon three factors: aperture value, focal length and subject distance. When each of the other two variables are fixed, setting a larger F-stop number (which actually means a smaller aperture opening) will result in a larger DOF. Using a longer focal length will result in a smaller DOF. And shooting at a closer subject distance means a smaller DOF.In macro photography, however, DOF depends primarily on just two factors: aperture value and magnification. At any given aperture value, the higher the magnification ratio, the smaller the DOF. And this explains why DOF is so shallow in macro; the magnifications are simply much larger than in any other type of photography.
With this in mind, let's go back to the cicada image that began this discussion. When photographers see such a shallow DOF, they instinctively think the aperture was set very wide (a small F-stop number). But this shot was made at f/9.0 which, outside of macro photography, is considered to be a narrow aperture. That leaves magnification as the main contributor to shallow DOF. This nymph is only 2 or 3mm in length, and since I wanted to photograph it filling a large portion of the frame, I had to use an extreme magnification ratio – in this case, of 5:1, meaning that the cicada's projection on the sensor was 5 times its actual size! Extreme indeed, and so DOF is extremely shallow, at only a fraction of a millimeter.
Since DOF is affected by aperture and magnification, let's see what happens when we alter them. First - aperture value. The robber fly below was shot using a very small aperture: f/16. In fact, this aperture is so small that is causes a significant loss of sharpness due to diffraction. And it still doesn’t help this image much; the DOF is too shallow with most of the subject out of focus.
The second thing that can be done is to lessen the magnification by stepping back from the subject and making it take up less space in the frame. This most certainly works to increase DOF. Yet I have two major problems with this 'solution'. Having the subject fill a smaller part of the frame than intended forces you to crop the image in post processing. And while a large crop may make the subject appear as if you shot it at closer range, you end up with less detail, eliminating one of the most appealing aspects of macro photography.
Furthermore, as a wildlife photographer I always wish to capture my scene in as close a state as possible to the final image. Using a small magnification and then making a significant crop collides with this ideal and personally I avoid this unless there is simply no other choice.
(Taken from www.dpreview.com)
Composition
It's hard to overstate the importance of composition. For all of the emphasis we as photographers tend to place on which camera, lens or other gear to use, there's nothing that contributes more to a pleasing image than careful attention to the framing of your subject. In this article I'm going to discuss some of the compositional techniques most applicable to macro photography. I'll illustrate these with a lot of images, as these concepts are often much easier both to understand and apply with visual examples in mind.
I have already mentioned POV (point of view) in an earlier article as a critical aspect of composition in macro photography. Shooting from the same vantage point as the subject creates a feeling of intimacy which is so important in wildlife imagery.
Lead Room
The concept of 'lead room' is important in macro as well as other wildlife photography. The idea is that the frame should contain extra space in the direction in which the animal's eyes are looking. Indeed, having a subject looking at the nearest edge of the frame can be unappealing. The use of appropriate lead room contributes greatly to a sense of balance in the image. Consider the examples below.
Lead room doesn't have to be overly drastic to be effective. I'm not suggesting you shove your subjects all the way into one corner or the other. You want just enough additional space in the direction to which the eyes are looking to give the image room to 'breathe'.
This basic understanding of lead room can be augmented for an even more appropriate application to macro. For creatures whose eyes are not prominent features, the amount of lead room should be based instead on the subject's shape and body structure. In macro, many of our subjects have very long and narrow abdomens.Rule of Thirds
The rule of thirds offers another guideline for maintaining balance. Most of my images are either centered or follow the rule of thirds - this usually depends of whether the subject is looking straight at the camera or to either side.
(Taken from www.dpreview.com)
Of course there are many situations in which it does make sense to center the subject in the frame, as you can see in the example below.
Magnification
How to calculate macro magnification? Some photographers add on close-up filters , extension tube or teleconverter to maximize the macro magnification and wonder what magnification ratio they are shooting at. It is very simple, you only need a ruler.
Magnification = sensor width / # of mm captured
= 22.2/22
= 1X (approx)
Magnification = sensor width / # of mm captured
= 22.2/11
= 2X (approx)
Magnification = sensor width / # of mm captured
= 22.2/7
= 3X (approx)
Add the native 1X from the macro lens and you get 1.68X. However, the actual measurement tells us you can get up to 2:1 magnification. It is even more surprising to hear that you can get up to 2:1 too on the 150mm.
Life Size (1:1)
It's all depend on your camera's sensor size, please refer to your camera specification to check the sensor size, or you can check your specification on www.dpreview.com .
For example, an APS-C DSLR, Canon EOS 60D's sensor size is 22.3mm x 14.9mm (from dpreview). A 22.3mm long subject fully fills up the width of the 22.3mm sensor, then it's life size magnification (1:1).
By looking at the ruler above, you see approximately 22mm there, therefore it's 1:1 (life size).
Magnification = sensor width / # of mm captured
= 22.2/22
= 1X (approx)
Magnification = sensor width / # of mm captured
= 22.2/11
= 2X (approx)
Magnification = sensor width / # of mm captured
= 22.2/7
= 3X (approx)
(Taken from http://orionmystery.blospot.com)
Illustration above shows you the different magnifications when you shoot a real life subject at different magnification and also with a FF (Full Frame) camera. Let us assume the soldier fly image was shot with a 60D (crop sensor) at 1:1. The yellow, red and blue frames are what they would look at at 2X, 3X (crop sensor) and 1X (FF) respectively.
Based on the input from a few forum members, you can get up to 2:1 by adding a full set of 68mm of Kenko Extension Tubes to a 90mm, 100mm, and 150mm macro lens.
Theoretically, the calculation goes like this:
Magnification gained = # of mm of tubes used / focal length
so if you used all 68mm of tubes on say a 100mm, you should gain an additional 68/100 = 0.68X
Okay, I know you magnification junkies out there won't be happy with 2:1, you want more. You can still add a 1.4X Teleconverter to your setup and get up to about 2.5X. Actual macro magnification may vary so again, go shoot a ruler. So the best way to calculate/measure macro magnification is to shoot a ruler.
