Newsmeldung von slashCAM: Basic Video Production: Video Production Basics: Aperture of rudi - 31 Dec 2009 06:55:00
Antwort von ruessel:
Who needs it more precisely: http://www.sprut.de/misc/digifoto/belichtung/belichtung.htm
For example, synonymous important:
How much light now comes from the outside world to the film / chip depends on the lens diameter and the distance between the lens from the film / chip. A great Lens in a small distance ensures good lighting, a small lens at a great distance to the dim light in the camera. The lens diameter d and the lens distance f (focal is accurate enough) k are the aperture summarized:
k = f / d
Amount of light and sensor size
On the basis of the above aperture value formula has a standard lens (f = 50mm) with a lens diameter of d = 18mm a very good aperture value of k = 2.8. A camera phone with 5 mm focal needed for the same aperture a lens diameter of only 1.8 mm. As the lens surface of the Normalobjektivs but is 100 times larger, they can capture synonymous 100 times more light than the camera phone. If the cell phone photo sensor is only 1 / 10 of the Height and Width of the normal lens has sensor () film, both cameras are from the same Full Resolution Sample, the phone has only 1 / 100 of the light available. The result is a high picture noise.
Antwort von domain:
The last sentence can only underline:
"However, it is better to make one of the top s.für good illumination of the scene and used only in emergencies, to electronic amplification." Apparently so is (professional) cameras synonymous even in normal mode, ie without prior Gainzuschaltung a certain gain, the recordings could not otherwise turn on for example, -3 dB gain-noise yet.
For consumer cameras, but at least it usually means always turn auto Gainkontrolle too. Only when the illumination of a scene is so good that it is synonymous properly without gain arises exposed normal contrast and brightness of the colors synonymous.
The addiction to extreme Lowlightfähigkeit a camcorder can be assessed only once, therefore, first without and gain zweitetens I think it is a bit oversold and marketing argument.
For about one must always be aware of: with very low light shots are never really good, synonymous if the camera is still so bright.
Average Gainverstärkung is really only for pure night shots, or if anything too little light is available, but then the images synonymous look accordingly.
You have only to time the 12 lux test shots here to look. Regardless of the camera, sometimes dark times brighter color or with more or less noise, but they always look very relatively modest.
Antwort von deti:
The dB gain information on're synonymous only relative numbers and each 6dB doubles the voltage level. But there is no definition, what an absolute value at a certain brightness for example, is to be achieved at 0dB. Thus, each sensor or camera manufacturers can, of course synonymous fix arbitrary values, whereby the different impressions could be explained by the bright image at low light. Probably it would be better to normalize the reference images, so that a similar picture impression corresponding to the SNR gets measurable value.
http://en.wikipedia.org/wiki/Decibel#Video_and_digital_imaging
Deti
Antwort von ruessel:
Question: Is the share Gainverstärkung with the ISO setting on a digital camera like?
Antwort von deti:
Question: Is the share Gainverstärkung with the ISO setting on a digital camera like? The ISO setting on digital cameras is identical with the gain in video cameras. For historical reasons, photographers and videographers to use just different terminology. The ISO value was originally defined by the nature of the footage and the ISO setting s.der Camera has merely adapted to the automatic exposure control s.The different film properties. But since digital sensors are not interchangeable, the effect of a different ISO value to be achieved using electronic means. There are different approaches:
- The strengthening of the analog electrical signals of the image intensifier is changed before the A / D converter.
- The range of values for the A / D converter is changed (eg by gamma curves and a wider dynamic range windowing for example 14bit vs. 8bit JPEG).
- The spatial Resolutionwird sensor side or in the DSP in favor of a higher light sensitivity reduces.
In addition, still a lot of signal processing in the game, so that you can rarely say exactly which parts of the signal chain of impact that a gain / ISO change.
Deti
Antwort von ruessel:
Well ..... Why then see strong images of a DSLR in Gainverstärkte Comparison of a video camera is light years better? Only because of the larger chip but unlikely?
Antwort von rolli46:
On the subject of Aperture you should synonymous depending on the aperture different focus (attention) not only depth of field. To this end, there is an interesting blog entry with trunk (www.fxsupport.de).
