Amp Glow And Hot Pixels

Amp Glow And Hot Pixels


When you take a picture with a digital camera, as more fully explained in more depth articles, it “captures” the picture set before the lens (which we define as “analog”) and is converted to digital and then the It saves on memory.

The transition from analog to digital has made great strides and cameras of the latest generation they are able to reproduce reality with a very high detail, almost perfect. In fact, almost. And this is because the conversion from analog to digital will never be perfect, there being problems, the limits that can not be exceeded. Obviously we are talking about very small phenomena, often imperceptible to the eye also attentive phenomena but in some cases come to the fore doing fine show in the images captured by us.
Several times in other articles I have talked about the thermal noise introduced by the photo sensor and how to deal with the problem (noise: tips to reduce it and the noise reduction in digital images), but in addition to the noise you have to remember that there are two problems that can manifest itself : the so-called Hotpixel and Amp glow (the glow of amplification, if translated), using the term that identifies it.

Amp Glow

The amplifier Glow is a phenomenon of electroluminescence. The read amplifier continuously generates heat (IR), the heat which in turn generates electrons on the pixel array of the CCD sensor (CMOS sensor is less affected by this problem). These electrons are going to add up the electrons that come from outside the photosites, distorting the real value.
Normally this phenomenon is seen in long exposure photographs (precisely because the amplifier is on for quite some time) and tends to be concentrated in a well defined area of ??the sensor (in the area closest to the amplifier). In the picture above, originally dark area in the upper left is very clear: the clear halo is precisely the amp glow (the photo should be uniform).

The only way to eliminate this defect is to turn off the read amplifier, which can not easily be done … and often can not be done and that’s it.
The amplifier, however, is not the only component of the circuitry to generate this phenomenon: it must also consider the camera battery (when supply current heats) and the protection circuit (or rather, the diode). If the first problem is related as is often mounted in a position far from the sensor, one can not say the same for the protective diode, often positioned in the vicinity of the sensor itself. These, like the amplifier, it can create a halo, making it even worse our image. In the picture below we can see the double halo, generated precisely as a buffer and protection diode. Again you can not do much to solve the problem, if not buy a camera “better” or that it was built taking into consideration the amp glow.

Bulb Mode When To Use It

Bulb Mode When To Use It

The bulb mode is one of the ways most appreciated by owners of SLR as it allows to drastically expand the use of a camera, the photo of the “classic”, it is a portrait or a landscape.
The Bulb mode simply allows the photographer to capture an image until the shutter is pressed, in practice the shutter remains open until it is the photographer to decide on the closure by pressing the shutter button. E ‘can use the bulb mode by choosing the manual mode or shutter priority: once in this mode, the scroll wheel of the times in the direction of the increase of the same until, after probably 30 “, there appear the words” bulb “,” bulb “,” b “or something similar. In this mode, remember, the shutter is opened the first press of the shutter button and closes the second pressure.

The Bulb mode is used mainly for long exposures night. The main advantage is that it allows the photographer to achieve shutter speeds longer than 30 seconds, limit “automatic” than most cameras
Obviously, the bulb mode is always used in combination with a repeater by shooting in remote or wire that is: that we would create vibrations in the press a second time the shutter button are too high and the photos would be irretrievably moves.

the bulb mode can be used to take some very special as those described below.

The Lightning. The Bulb mode is perfect for capturing lightning because it allows the photographer to stop the exposure when needed. After identifying an area that could be affected by lightning, shot in bulb and wait. As soon as the lightning strikes, close the shutter. This prevents to let more light once the lightning downloaded.

Stars. Another classic use of the Bulb mode is a photograph of the wake of the stars. To capture a trace bright image, you must wait at least twenty minutes, which is only possible with this photography mode.

Drawing with light. Painting Light means asking, in dark environment, before the lens and draw something with a light (flashlight, for example). Once a finished design you can close the shutter preventing further light enters the lens design to “finished”.

Fireworks. just like lightning, with fireworks you can decide when to stop recording. In addition, thanks to this mode, you can capture the same image multiple fires exploded in sequence, closing the shutter only when the resulting image (in our imagination!) Satisfies us.

Accessories – The Close-Up Lens

Accessories – The Close-Up Lens
The lenses are close up of the interesting tools that can transform, of course with some exceptions, a traditional lens in a lens with strong magnification and reduced minimum focusing distance For these two reasons, the close-up lenses are often used in macro photography when you have no desire to spend a lot of money to buy a specific target for macro photography.

The lenses have a close up magnifying power or better approach defined in diopters +1, +2, +4, +10. As the number of diopters, is approaching the point of focus.

Diopters above are calculated as the ratio

f being the focal length of the basic lens (expressed in millimeters). Using a lens with focal length of 250mm is equivalent to having a number of diopters equal to 1000250 = + 4.

Of course you can combine multiple lenses close up to each other in order to increase this factor always remembering to screw the lens in descending order the highest close to the lens and the lower outward. The overall effect will be equal to the sum of the diopters mounting a lens with +2 and +1 with a get the equivalent of a +3.

Obviously there are serious disadvantages in using these lenses the first is the presence of spherical aberrations This results in the difficulty to focus the peripheral part of the image. With low-diopter lens we will see a general softening, increasing however diopters one exceeds blurred. A second disadvantage is the brightness a lens reduces the brightness of a stop.

Last but not least eye on the quality of the lens economic solutions will give financial results getting worse and not just the final picture.

The lenses have a close up cost, a set of 5 pieces can be easily found around 3050 €. Less, forget it! If you look for quality, then look for the lens close up based doublets glued achromatic.

The first are mere pieces of plasica (cost very little) but turn the lens in full manual. The seconds instead transfer the electrical connections allowing the lens to function automatically (exposure and focus for example) as if it were connected directly to the machine.

As mentioned before, the extension tubes, inserted between the camera body and the true objective and just, allow to increase the magnification ratio and to decrease the minimum focusing distance. All this is due to a very simple physical principle the lens away from the sensor. Eye to blur zoom in means to make the goal very sensitive to camera shake, so a stand is an inseparable companion.