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Unlike the M8 or the R8/R9+DMR, the new Digilux 3 was not constructed with reference to 35mm. The camera is based upon the digital FourThirds system. Why then would the Digilux 3 require a crop factor, when the focal lengths of lenses from the M8 and R8/R9+DMR system are multiplied by factors 1.33 and 1.37 respectively?
There is no rule saying that a focal length of a lens has to be multiplied with a crop factor. Every lens has a specified focal length (or a focal length range, if it’s a zoom lens), defined by the physical distance between the lens and the focal point. However, the angle of view generated by the camera and lens is not only the product of the focal length but also the size of the sensor or film. The lens projects a circular picture with declining brightness towards the edges. A rectangular crop within that circle represents what reaches the film or sensor. The smaller that crop is, the smaller the angle of view and field of vision; and the greater the enlargement. Since Leica’s M and R systems were built around 35mm cameras, the 35mm format is still considered standard – here, certain focal lengths are expected to deliver certain angles of view. For example, the 50mm lens is commonly referred to as ‘the standard lens’, delivering the standard angle of view; but since the sensors of the M8 or R9+DMR are 25 to 32 per cent smaller than the 35mm format, these cameras require a 35mm lens in order to arrive at a comparable angle of view. The multiplication of the focal length by crop factors 1.33 (M8) or 1.37 (R9+DMR) simply illustrates the angles of view and enlargements that 35mm photographer can expect from their lenses – a faithful 50mm standard will mutate into a humble telephoto, a 35mm in turn into a standard focal length.
As mentioned above, the Digilux 3 is the product of the FourThirds system. It was designed as a digital camera. The corresponding Leica, Olympus and Sigma lenses are also designed specifically for the FourThirds standard, and not for 35mm format. Hence, when a four-thirds focal length is converted into 35mm terminology using the related 2.0 crop factor, what you get is of course fictional – but the same applies for the M8 and R9: the multiplication merely serves to help 35mm photographers refer back to what they’ve learned from the 35mm medium. In other words, when a 35mm photographer mounts a D-Vario-Elmarit 14–50mm Asph on the Digilux 3 and imagines it as a 28–100mm lens, he will be able to visualise just how much of a telephoto the zoom lens is.
While the conversion is helpful, it applies only to the angle of view and the enlargement. The depth of field, on the other hand, will be greater than what one has come to expect from certain focal lengths (while still smaller than the physical focal length may suggest). The aperture size of an aperture value depends entirely upon the physical focal length, meaning that the optimum aperture will be a little bigger than that of a 35mm camera; diffraction-induced blur begins to show a little earlier due to the shorter focal length.
Why do digital camera sensors require band elimination filters for infrared light when the sensor cells already have filters for red, green and blue light? Is it because the infrared may overheat the sensor? If there wasn’t such a filter, we could also use the camera for infrared photography.
CCD-Sensors are more sensitive to the wavelengths of the near infrared, starting from 700 nanometres, than to visible light; but near infrared has nothing to do with heat radiation (far infrared), where wavelengths are substantially longer. The individual sensor cells are covered with colour filters to the Bryce E. Bayer standard, enabling the camera to reconstruct colours in addition to brightness information; unfortunately, as to which wavelengths are allowed to pass and which not is a little more complicated. For example: the red colour filters block green and blue but permit infrared to pass nearly unimpeded. Surprisingly, this is also true for the blue filter, despite the blue wavelength-band being far away from the near infrared. The green filter in turn blocks a sizeable percentage of infrared light.
The sensor’s red, blue and – to lesser extent – green-sensitive cells would therefore also register infrared light, a distortion that cannot be undone by simply altering the camera’s white balance. Different materials reflect infrared differently. Rarely can this be predicted, and colour has very little to do with the phenomenon. Green foliage reflects a lot of infrared, causing the photographic reproduction to be particularly bright; this is because the plant cells reflect the infrared in the same way that soap bubbles reflect visible light. In other cases, green objects may just as easily turn out black in the infrared exposure. Two similarly coloured fabrics can have completely different reactions to IR light if they consist of different material or have been processed differently. Without an effective IR band elimination filter the resultant colour shifts are unpredictable and hard to correct.
The second problem that comes with the sensor’s susceptibility to infrared light is sharpness falloff. Depending on their wavelength, rays of light are refracted by different degrees of force. The consequence is the so-called chromatic aberration, which has to be corrected for the colours of visible light in order to prevent the contours in the periphery of a photo from dispersing and leaving colour fringes. Infrared light is refracted even weaker than the red light, and this deviance remains uncorrected. Older lenses feature a red marking opposite the range scale, indicating to which extent the focal plane shifts in infrared photography. If the infrared percentage of light is not filtered out, then a blurred, slightly larger IR picture will overlay the sharp picture formed by the visible light.
How can we prevent dust from getting onto the sensor – especially with regard to pictures taken with small apertures, when we start to notice diffuse, dark smudges in the picture?
If you were to never change the lenses of an SLR or rangefinder camera, the abrasion of the camera’s moveable components would still shed microscopic particles; these inevitably find their way behind the shutter curtain and onto the sensor. What’s more, dust is likely to enter the camera no matter what the moment you change lenses. In the case of 35mm cameras, the film transport prevents dust and other particles from pestering the reproduction permanently; however, these particles feel all the more at home behind the focal plane shutter of a digital camera, multiplying with each new supply of dust.
Hence, before a lens is changed the camera is best switched off to prevent electric charge from attracting flakes of dust. However, it doesn’t guarantee that the sensor will be spared entirely from dust. Tip: every once a while, photograph an unstructured surface such as a blue sky or sheet of paper using a small aperture setting. Check the reproduction for potential spots and smudges.
Another good idea is to make a habit out of cleaning the camera interior using a lens blower, as provided for this purpose by camera stores; alternatively you can use an enema syringe, which will be available at the local pharmacy. Dust particles are hygroscopic; they tend to attract the humidity of the environment and stick to the sensor. If used in time, the blower tool will blow away any loose particles in the camera or on the sensor. Cleaning the R9 and R8 is especially easy, as the digital module can be removed and the sensor cleaned either with the blower or, in more difficult cases, with an optical cloth. In the case of the M8, the sensor has to be made accessible by activating ‘sensor cleaning’ in the menu, which opens the shutter. Both cameras benefit from Leica’s solid sensor coating, making mechanical damage highly unlikely.The lens blower is a gentle approach, and sometimes you will need to try something else. However, brushes will often only introduce additional dust into the camera, while compressed air from spray cans or carbon dioxide bottles can damage camera components through pressure and cold. You can make a simple tool yourself by twisting a sheet of lens paper to a point, holding it with a pair of tweezers and using the paper tip to pick particles off the sensor. Alternatively you can draw upon tools such as ‘SpeckGrabber’ (www.kinetronics-europe.de) or ‘Sensor Swab’ (www.photosol.com/swabproduct.htm).
The Digilux 3’s sensor is protected by a special dust filter. When the camera powers up, the filter vibrates with a 30khz ultrasound frequency, shaking off potential dust particles which are fixed eventually by adhesive strips inside the camera. If this fails, the camera can be set to LiveView mode, which flaps the mirror to the side and reveals the shutter. Then the filter can be cleaned as described above.
