False myths on Resolution
Errors not surprise me that even today continue reading (and hearing) a lot of people is the resolution of a picture . For starters, there is much confusion about what we mean by this term. Well, simply refers to the total number of pixels that has the photo. For example, a 12 Mega Pixels camera generates a file of, say, 4,000 pixels x 3,000 pixels = 12,000,000 pixels. The resolution of that photo (or more precisely, the file) is 12 million pixels.
Resolution
But often you’ll hear someone who has asked you a picture (even an advertising agency!) Say that “I better with 72 points per inch . ” This information is useless. What we have to say is how many pixels you want to take the photo. For example: 1,500 pixels wide or 800 pixels high. This data perfectly defines the resolution of the file that you send. As an example, these pictures have a resolution of 900 x 600 pixels, a size suitable for the Internet.
And the dots per inch?
The question then is, what resolution do I need? Depends on what it is going to use the photographs : for viewing on the monitor or to print ? And here come into play dots per inch (also called dpi or ppi).
The Eye vs Camera
The maximum and minimum focal ratio of the eye is more limited than a normal lens (f3.3 – f15 versus f1.8 – f22) but this is more than offset by a broad ISO range (1-800 ISO versus 100 ISO 3200 in a typical digital SLR). In addition, the dynamic range of the eye is infinitely superior: 1:10.000.
Instead, the shutter speed of the eye is single (1 / 100 sec.) which has an evolutionary point of view is perfectly adequate, but the camera clearly has more options (such as very fast shutter speeds, which allow you to freeze movement, something the eye can not do, or the opposite extreme, long exposures required to build light and see what is invisible to the eye).
And what about the sensor ? Well that’s where the difference is enormous: it is quite large (like a digital back CCD) and has pixels of similar sizes, but has a resolution equivalent of several hundreds of mega pixels, although this parameter is not exactly comparable: a point, the eye only processes a fraction of the total visible area, the rest remains out of focus black and white!
Let’s see a possible example: The human eye, on a sunny beach, with a shutter speed of 1 / 100 sec. to f11 and an ISO of 12 (and a resolution of, say, 350 Mpix.). The exposure equivalent of a digital SLR camera (of say 12 Mpix.) would be: f16, 1 / 500 sec. and ISO 100. This of course is only a theoretical calculation since all these parameters are not exactly comparable in reality or equivalent …
The Human Eye and Digital Camera (2)
Now let’s see how it compares with a digital camera from a quantitative standpoint.
Before, we relate the different parts of both: the goal is the combination of the lens and the cornea (which in turn serves as a UV filter as well). The diaphragm is constituted by the combination iris / pupil (which expands or contracts to change the opening), and the sensor is the retina. Finally, the image processor is the brain.
The Human Eye in Figures
There is some controversy regarding the focal length of the human eye: some authors speak of 16 -18 mm although it seems that consensus is another figure: 22-24 mm , whose value depends on several factors such as distance from the eye to the subject, age and health of the individual.
The Diaphragm
The maximum diameter of the pupil depends on the age (this is well know amateur Astronomy and Astro !) in young people come to dilate the pupil to 7 mm, a figure that is reduced from 5-6 mm of 40-45 years. In contrast, the minimum diameter of the pupil is 1.5 mm. With these figures we can calculate the focal ratio (f) of the human eye, from f3.3 (of 4.6 for adults over 45 years) to f16 at its opening minimal, ie, a relatively short range compared with a normal lens ( for example 50 mm f1.8 – f22).
The Human Eye and Digital Camera (1)
Eye are accustomed to reading about the rapid progress of digital cameras, with more and more mega pixels, anti-vibration systems, technologies, more accurate auto focus and a host of increasingly sophisticated technologies, we can have the feeling that they are prodigious machines. However, the camera perfect sophisticated and still the eye . And let’s see why.
The Human Eye: An Incredible Machine
First, it should be noted that the functioning of the human eye rests on the most sophisticated and powerful computer that exists on our planet: the brain . What we see is the result of what has caught the eye with what the brain has processed. The analogy in digital photography-relatively speaking-would capture raw (RAW file or data captured by the CCD) and processed image (in Photoshop or JPG file that the camera has been generated from data raw).
Example of this teamwork of the eye and the brain is the fact that the human eye actually sees the world upside down and reversed as in a mirror (like a camera optical bench). It is the brain that is responsible for correcting the image in the two axes. In fact, babies see the world uncorrected (this the the reason why they often look in the opposite direction to the movement trying to follow).
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Lighting in Food Photography
Light in the Food Photography is essentially the task of defining the volume of the dish or food to portray. In the post above mentioned the main objective of food photography is not one that show the product in a palatable , eat like giving. That is a task shared with the / The Home Economist (or stylist), which deals with the preparation and placement of the product and the photographer who has the task of lighting and framing the product.
Food Photography: The Volumes
Not the same light a steak dish a soup. What is the differentiating factor? The volume . In the first case, usually it’s volume is interesting to note, including the texture of the meat and juicy appearance. In contrast, in the case of soup, raw plate geometry and surface aspet it. Therefore in the first case we use a low angle, usually 45 ° to the horizontal, and if we use a soup encuandre zenith (orthogonal to the plane which supports the plate).
Lighting
Use a framing overhead and side lighting contrasted to highlight surface textures . We also use another flash at 45 °, diffused light (for example, a window of light from at least three or four times the diameter of the dish) which is responsible for lighting smoothly the rest of the dish . This flash is placed between 90 ° and 180 ° to above. In this way, we managed to light up the whole plate at the same time enhances the texture of the cream. Try to imagine how this dish would be if we used a frame at 45 degrees and you will notice the difference.
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Food Photography
Food Photography pursues the same objective that Advertising Photography in general show an object in the most attractive and appealing as possible in order to eventually induce purchase. Translated to the world of Food Photography we seek to present the food so tasty . The cotton test to see the picture, is to ask if it seems appetizing and if we want to eat what we see in the picture. If yes, then mission accomplished!
Food Photography: A Question of Photogenic
But how do we get what looks appetizing photograph? First, like everything in photography, there are foods (products or prepared meals) that are photogenic and others not. Therefore, this factor plays in favor or against us. For example, foods like an orange, a strawberry, a salad, etc.. are inherently photogenic (attractive colors and textures are regular and interesting). Instead dishes such as soups, cooked dish, a stew of meat in gravy, etc.. are nothing photogenic and therefore difficult to photograph well.
Food Photography with Perfect Perfect
Second, we need to get the food that we are photographing perfect (or almost). Not worth a strawberry or orange anyone either. They have to be perfect. There are two ways to do this: go to a regular supermarket and buy several kilos of this product and pray to display a perfect piece, or-more-attend recommended certain grocery stores that are dedicated to this and you can get parts you apply with excellent quality. Obviously this service has a price-and not cheap.
Filters in Digital Photography
One of the issues on which there is some confusion when it comes to digital photography is about what filters are recommended to use a digital camera. There is a perception that everything can be done in Photoshop , but this is not true. There are two types of filters that are difficult to replicate in post-production effects (unless fitting techniques are used in several shots). These are the Neutral Gradient Filter and Lens Hood .
Gradient Filter Neutral
Curiously enough is a filter unknown (and underutilized) among fans of photography. The most commonly used format is the Cokin , rectangular in shape. At the top has a neutral gray gradient and the bottom is clear. There are different gradient densities (as neutral gray filters) depending on the amount of light you want to block. There is a little-used variant that has a reverse gradient, ie, the gray area in the center of the filter and the gradient occurs both above and below.
Polarizer Filter
The Polarizer filter is another essential for Digital Photography . Light behaves as a wave form that propagates in a straight line and consists of two components: an electric and a magnetic traveling at 90 degrees relative to each other. In certain circumstances (as when the light hits water or glass, or in the upper atmosphere) one of the two components is eliminated in the process. We then say that the light is polarized (one axis or another). Polarizer filter is precisely what makes the other remaining component filter, completely eliminating polarized light.
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Aerial Photography from Kites
Aerial Photography is a photographic discipline itself, since it is characterized primarily by the position from where the picture is taken: from the air . Thus, a photograph taken from a skyscraper would not be an aerial photograph, but from a helicopter flying over the same area could get the same framing and perspective. Aerial photography has traditionally from helicopters, airplanes and balloons. Today, thanks to digital photography have developed other methods are simpler and cheaper.
Aerial Photography from kites (KAP): Introduction
Aerial photography from kites (known in the Anglo world as KAP – Kite Aerial Photography) is performed primarily by hanging a camera from a kite-flying stably, and closing the shutter from the ground using radio control (RC), or by a intervalometer connected to the camera (in this case is usually called self KAP). Therefore we can define two different teams depending on whether land is controlled by RC, or automatically triggered by an intervalometer (auto KAP).
The basic equipment of KAP is as follows:
• A kite . It is not worth anyone. Has to be stable in flight and have sufficient strength to lift the camera equipment. There are two kinds of kites for KAP, with structure and unstructured. They differ among themselves, besides the presence or absence of structure-flight by the angle of each type of characteristic that is committed and the range of wind speeds in which it is able to fly (there is light wind kites and kite High Wind-there is a kite that can fly in winds of 5 km / h in 40 km / h for instance).
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What I can deep-sky objects photographed?
One of the aspects of deep-sky astrophotography that produces more confusion is to understand the apparent size that each object, not visible to the naked eye, as are some planets or the moon.
So I put an example which we hope will come to understand this: the relative apparent size of the moon and the great Andromeda Galaxy (also known as M31). The Moon has an angular size of about 31 arc minutes. M31 has an angular size of about 180×60 arc minutes.
In the picture, you can see a photo montage of the two in which you can see the apparent size relative . That is, if M31 had the same luminosity as the moon would look like in heaven. Impression is not it?
This object is immense and that despite its remoteness – 2.5 million light-years its apparent size is huge (in fact, twice the size of the Milky Way).
Implications From a photographic point of view
Deep Sky Photography – Implications From a photographic point of view
(A) In the case of emission and reflection nebulae, many of the best known, and photography have a very large angular size, so focus telescopes are used short to medium (between 200 mm and 1,000 mm overall ). In this case, the aperture (the diameter of the front lens) is very important due to the low luminosity of the object.
(B) The low luminosity of the object involves long exposures (about 3-5 minutes to 30-40 minutes) which has important implications for further processing (noise control) and the equipment used (it takes a ultra precise tracking sidereal to prevent the stars and the object exit calendar – trailing in English).
(C) light pollution (CL) is very important: it determines the contrast between the sky background and the object. The more CL, lower contrast and the worse the quality of the picture. The atmosphere on the other hand – these focus-has very little impact on the quality of the picture.
(D) In the case of objects of smaller apparent size, such as planetary nebulae and most of the galaxies, the approach changes: longer focal lengths are needed (not as much as Planet), the order of 1,500 mm to 3,000 mm. The opening is still very important (more open = more light = shorter exposure time). However, long exposures are kept, and the processing is similar to the large emission nebula.