CLOSE-­‐UP AND MACRO PHOTOGRAPHY INTRODUCTION Close-­‐up and macro photography is a form of photography that opens up a whole new world and is something that can be done almost anywhere. You do not need to spend huge amounts on travel to find fantastic scenery and interesting or unusual subjects. Many subjects are possible and common examples are flowers and insects but almost anything can be of interest when photographed in close-­‐up or macro. On a cold or rainy day we may look to objects closer to home such as cutlery, household ornaments, jewellery or the household pet. Often, when travelling, a close-­‐
up shot of a logo, sign, ornamental lock or an adornment on a uniform may form part of the travel journal. They can add interest to the photographic story. This type of photography usually involves getting close to the subject and producing an image that is magnified at the camera sensor. A long focal length lens or close cropping of an image can, however, have similar effect. The work of certain specialist photographers in this area is worth viewing: -­‐ Shikhei Goh who lives on an Indonesian island near Singapore -­‐ Yousef Al-­‐Habshi of Abu Dhabi, UAE -­‐ Jimmy Kong a Malaysian photographer -­‐ Maneesh Kaul an Indian photographer from Kashmir -­‐ Joel Sartore who is a National Geographic photographer from Nebraska MAGNIFICATION Magnification = image size / object size (or m = i/o) So if the object is 10 mm long and at the sensor the image is 10 mm long we have a life size image and magnification is 1 True macro photography is where the image size is the same or greater than the object size (it is in fact where the magnification falls between 1 and 50) DEFINITIONS The different types of photography are defined by the magnification used. General photography x1/10 and smaller Close-­‐up photography x1/20 to x3 Extreme close-­‐up x1/5 to x5 Photomacrography (macro) x1 to x50 Photomicrography (where a microscope is used) x25 to x2000 Notice that there is an overlap between these, as the definitions vary greatly and are very loosely applied. Mike Hewitt Page 1 of 8 OPTICS o v u i m = i = v o u mmax = maximum magnification possible mmax = 1 umin = minimum focussing distance (umin/f) -­‐ 1 f = focal length of lens The closer we get to an object the larger the image The focal length of a lens is the distance from the optical centre of the lens to the sensor when focussed at infinity. Lenses are able to focus down to a nominated minimum focussing distance. At an object distance of 2f the magnification is 1 (object size ‘o’ and image size ‘i’ are the same and the back-­‐focus distance is 2f or twice the focal length) f o i 2f 2f At an object distance between 2f and f the magnification is greater than 1 f o i f At an object distance of f the magnification is infinity (in fact no image is formed) f o Mike Hewitt f Parallel rays – image infinitely large and at infinity Page 2 of 8 EXPOSURE Theoretically, a lens truly focussed at infinity would create a point image at its shortest back-­‐focus distance f (the “image” would have no dimensions). At its minimum focussing distance a lens is racked out to its fullest extent. As you rack it out you are changing the required exposure but this will not exceed about quarter of a stop when the lens is being used in this normal fashion. When a lens is moved even further away from the camera and its sensor the greater exposure that is required becomes significant. OPTICAL EQUIPMENT • At a magnification of 1:1 a normal lens is a poor performer. • Although macro lenses are specifically designed for 1:1 or greater they can still focus at infinity and do make good portrait lenses. • A macro lens is a flat field lens and works best at around m=1 • Macro lenses are generally quite expensive. A flat field lens compensates for the curved focussing plane that occurs with a normal lens. A normal lens will be in focus at the centre of an image and will have softer edges where it focuses forward of the sensor. Having a flat field is important in macro photography due to the narrow depth of field involved. Other options are available: 1. Long focal length lenses with a macro setting (these are not true macro lenses but are lenses with a closer than normal focussing capability). 2. Supplementary lenses (close-­‐up filters or dioptres), which are magnifying elements screwed onto the front of a lens. By reducing the focal length they enable closer focussing than is possible with the prime lens alone. They are rated in dioptre power and the magnification produced by a combination of a prime lens focussed at the infinity setting and a supplementary lens is; m = fD/1000 where f is the prime lens focal length and D is the dioptre power of the supplementary lens (available up to at least +10) -­‐ They reduce both the maximum and minimum focussing distances. -­‐ Although resulting in reduced quality, dioptres may be stacked. -­‐ Dioptres are available in single and double element. The double element type is of better quality. -­‐ They must be stacked in order with the strongest closest to the lens. -­‐ Their power is additive (D1 + D2 = D) -­‐ They do not reduce the amount of light reaching the sensor -­‐ Use a mid-­‐range aperture or they will vignette -­‐ They suffer spherical aberration (the further the rays are from the optical axis the closer to the lens they focus) Mike Hewitt Page 3 of 8 3.
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Rear converters (teleconverters) – these fit between the camera body and lens. They are an optical device and are specified in terms of converter power (a times 2 converter will double the focal length). They do not alter the minimum focussing distance for the prime lens alone, which means they are good for close-­‐up work f-­‐number = focal length/physical aperture size Because the rear converter increases the focal length the f -­‐number increases for the same physical aperture size. Light levels at the sensor are reduced so greater exposure is required. Extension rings and tubes (these are fixed, have matt black interiors and can be purchased in various lengths – it is possible to make your own but take care with how you attach your lens). The extension length = focal length x magnification (E=fm) If you extend any lens by the same as its focal length it will be 1:1 or life size and will need two stops more exposure (inverse square law). Modern units allow in-­‐camera metering to automatically change exposure. Extension bellows (these are adjustable) 6.
Reversing rings (can use to improve image quality for a standard lens at close-­‐up distances), which allow a standard lens to be reversed. A standard lens used normally has large object distance and short image distance. 7.
Enlarger lenses. These are flat field lenses and designed for short object distance and long image distance. They are of good quality but do not have internal focussing and a bellows is required. Other equipment that is useful with close-­‐up and macro photography: Stable tripod In some situations, where lighting is suitable, it may be possible to take close-­‐up images hand held. It is preferable, however, to use a solid tripod that supports the camera without vibration. Vibration is more noticeable at large magnification and tripod damping may be needed (by hanging weights from the centre column). Horizontal support arms for camera These allow the camera to be positioned on the end of a counterweighted arm that is extended out from the tripod (useful for photographing subject from directly above or for avoiding tripod legs getting in the way). Cable release or remote trigger This is necessary where a tripod is being used and avoids camera movement on activating the shutter. The mirror lock up function should also be used for SLR cameras (not an issue with SLT – single lens translucent -­‐ cameras). Mike Hewitt Page 4 of 8 Subject support Some form of support may be required for the subject (e.g. clamps, stands, tables, makeshift hangers or wire). Lighting equipment The subject will be too close for the use of on-­‐camera flash and other techniques can be used as follows: -­‐ Specialised ring lights are available but can be costly. -­‐ Separate key and fill flashes. -­‐ Reflectors and diffusers can be used on their own or in conjunction with the key and fill flashes. -­‐ A light tent is easy to set up using, for example, an old bed sheet. This provides good diffuse lighting and by positioning the setup near an external window the lighting ratio can be controlled. -­‐ A lens hood is required to minimise flare. Grey card for checking exposure Although exposure may be determined by using the in-­‐camera meter an accurate reading may be taken by using a grey card held at the subject position. This is a good method when photographing a flat subject such as an image that requires retouching or text on a printed page. LIGHTING CONSIDERATIONS There are four basic types of lighting Brightfield -­‐ Subject is dark relative to the field (light source behind the subject). -­‐ Used for translucent subjects and will emphasise fibre or hair protrusions. -­‐ Maximises flare (lowers contrast) so use low power lighting. -­‐ Need to use masks to prevent flare. -­‐ Can use a light-­‐box with an acrylic or translucent top diffuser, and possibly side diffusers (lights may be built in or placed external to the box but it is important that they provide even illumination and not be so close as to burn the diffuser or the subject). Lens Field of view Mask Light-­‐box Lights For delicate biological samples (larvae, eggs in water) flash illumination may be necessary (avoids heat and poached eggs) Mike Hewitt Page 5 of 8 Darkfield -­‐ Subject is light relative to the field (background), as the light source is above the subject. -­‐ Used for opaque subjects. -­‐ Must have enough space below the subject to avoid illumination of the background Where the subject is a mix of translucent and opaque materials a mix of top and bottom lighting may be used. Lens Collimated light source Field of view Glass support Must have enough space Box with matt black interior Natural Representation -­‐ Truly natural lighting may be used in the field, however these notes are intended to demonstrate how to simulate this natural appearance. -­‐ As in normal portraiture, use a key and possibly a fill light. -­‐ The key light should be placed to light the important side of the subject. -­‐ The key light should be higher than the subject (like the sun). -­‐ For best effect light sources should be large relative to the subject, and soft. -­‐ Reflectors may be used where necessary. Lens Key light Field of view Fill light Optical inversion can occur where lighting comes from an inappropriate angle. This is where dips are interpreted as raised areas ( is interpreted as ). It is due to us viewing the shadows and perceiving the light as coming from above even when it is not. Mike Hewitt Page 6 of 8 Shadowless -­‐ Evenly illuminated, very soft and shadowless lighting. -­‐ May use a parabolic reflector, or white reflectors around the subject. -­‐ Can set up a light tent using, for example, an old bed sheet. Lens Field of view Parabolic reflector Mask Lights Light-­‐box Lens Supports (e.g. chairs) Field of view Low-­‐level table White bed sheet It is always important to consider the subject and the lighting direction for the best image. With live subjects the heat from lighting and their reaction to disturbance may cause them to be more motile. This would be a problem at the small apertures and long exposure times that are necessary in macro photography. Flash exposures will freeze motion, however, diffusers may be necessary to soften the lighting effect. DEPTH OF FIELD In macro photography image magnification is higher than normal. The increased image size means that greater exposure is necessary and this can only be achieved with longer exposure times and/or increased ISO values. Increasing the aperture size (smaller f numbers) is not an option here due to the impact that this would have on depth of field. Depth of field is narrowest at large apertures and when the subject is close. Mike Hewitt Page 7 of 8 The standard method of calculating depth of field is based on the hyperfocal distance (distance to closest point that is acceptably sharp when camera focussed on infinity). This varies with the lens focal length, the aperture used and the acceptable size of the circles of confusion in the finished print. The standard method is not suitable for calculating depth of field with close-­‐up or macro photography. Where the image magnification exceeds 0.1 errors in the standard method become significant. D = depth of field For magnification >0.1 C = acceptable circle of confusion size (0.33mm) N = camera f number D = 2CN(m+1) E = enlargement value (to enlarge from sensor 2
Em size up to the print size) m =
magnification Note: -­‐ A constant value is used here for C, as m has much greater significance. -­‐ The enlargement value E for a full frame camera (sensor 36mm x 24mm) and an intended 10 x 8 print is 8.5 (for the side with the greatest enlargement) -­‐ For an APSC camera (cropped sensor) the sensor size varies depending on the camera make but typically the crop factor is about 1.6 (the E value for a 10 x 8 print would be 8.5 x 1.6 or 13.6) -­‐ As an example, for a cropped sensor camera, at f11 and a magnification of 0.5 the depth of field is 3.2 mm. At a magnification of 1 it is 1.07 mm Clearly depth of field is very limited and camera stability and focussing accuracy are critical. It is best to focus manually and focus peaking (in viewfinder illumination of in-­‐focus edges) if available, can be extremely useful. Alternatively, select a focus point and adjust the focus ring until the green AF light appears in the viewfinder. Using small apertures will increase depth of field but diffraction effects can become noticeable, particularly at high magnifications. The optimum f NO where depth of field is acceptable and diffraction is not noticeable may be calculated as follows: Nopt = 15.6 (21-­‐E) E (m+1) OTHER CONSIDERATIONS Aspects such as composition, background and the visual weight of different parts of the image should be taken into account in the same manner as for any photograph. The point of focus, however, is critical due to the narrow depth of field (it is best to photograph the subject such that it is parallel to the image plane). Live subjects are best photographed early in the day when it is cooler, as they are then less active. Taking multiple images and focus stacking in Photoshop may be possible. An interesting exercise at home is to restrict yourself to an area of say 3 meters by 3 metres in the garden, or to one room within the house. Then endeavour to find and take as many interesting close-­‐up or macro images as you possibly can within that area. You will be surprised by what you discover. Mike Hewitt Page 8 of 8