Sony HDV HVR-A1E

[vdo-30]

Merci Eric des précisions données j'attends donc voir les prochains modéles hdv.

[STEF]

Les conseils de la BBC pour HC1 ou AE1 :
http://www.bbc.co.uk/rd/pubs/whp/whp034-add19.shtml

[Eric D.]

c'est assez simple en fait il suffit d'imprimer l'un des fichiers joints en taille standars (pas de mise a l'échellebien sur)

puis de coller ce minuscule indicateur en regard de l'échelle de diaph du camescope



et voila un systéme précis d'aide a l'exposition ...

fichier PDF

fichier EPS



HC1 Exposure Settings

The exposure control on the Sony HDR-HC1 is a really handy adjustment available as a dedicated control on the left side of the camera. When enabled, you have 24 different "notches" that can be chosen in order to alter the aperture and processing being done. I recorded a sample piece of footage cycling through these 24 options, and then played it back with Sony's "Data Code" setting on to see the results. With this you can determine with certainty what aperture and gain settings were chosen by the system. Notches 1 through 5 and 14 through 24 showed unique values for the aperture and gain. But in the middle range from notch 6 through 13 the settings are the same, always f4 and 0dB gain. How can this possibly be? It is quite obvious that when using this range of settings, the picture is changing in intensity. There is an explanation. With the broad dynamic range of the CMOS sensor there is another parameter the camera can tweak to regulate exposure!

Unlike CCD sensors, the CMOS sensor can give meaningful data back across a wider range of light intensity, or in other words it has a much wider dynamic range. This translates into many more possible values being sent into the image processing section of the camera. The actual electronics responsible for creating the digital values is an analog to digital converter, or ADC. Sony has apparently leveraged the extra information available to offer additional variation to the exposure control.

In Sony's literature it is explained that the EIP processor is dealing with 14 bits of range, which comes from the CMOS sensor itself out of its ADC. The exposure control is then apparently narrowing in on different specific ranges of bits to provide a kind of "sliding window" across the broad range of values coming from those 14 source bits. This is not always the same number of bits wide. I expect it ranges from 5 bits in dim scenes recorded with 18db of gain to 12 bits wide for really brightly-lit scenes.

First examining bright sunlit scenes, the values coming out of the sensor are kept quite high, near the uppermost values that the sensor can possibly report. But as well significant detail in the shadow is available. In HC1 footage it appears that around 12 bits are used to represent the red, green, and blue brightness values under that kind of lighting. This gives the broad dynamic range many people rave about in daylight HC1 clips.

When the scene is darker, the camera still provides a linear response, but with lower values coming in it is forced into using fewer bits altogether. When the response of the sensor drops really low, even lower than what HDV's 8 bits would normally record, gain is applied by multiplying the signal to bring it up to fill the 8 bits. This is the same kind of gain that we've been accustomed to using all along in CCD cameras, and is represented as an amount in decibels (dB). For each 6dB of gain the signal is doubled. And the signal is shifted up by one bit. This effectively throws out half of the possible values, or one bit of information. For instance, with an 8 bit signal such as HDV then if you have 18dB of gain it means the signal has been doubled three times since each 6dB shift means it got doubled once. Doubling three times is the same as being multiplied by 8, and would then mean that three bits of data are lost. In this circumstance the bottom three bits hold no meaningful values, effectively resulting in a signal with only 5 bits of variation. This is what gives the horrible patchy grain we've seen under high gain.

Here is a chart with the aperture and gain settings used in the camera, and a third column of what I expect could be the sliding bit ranges used by the camera out of the available 14 bits. That third column is total speculation on my part, based on the video appearing to have about 12 bits of range when the image is really bright, shifting gradually down to around 8 bits of range with indoor lighting, and finally about 5 bits in the dimmest of settings:



It is possible that on each of the color channels the bit ranges are set differently. Or even possible that the output from the EIP stage is always only 7 bits, even though the MPEG compression in HDV calculates things based on 8 bits. So the bit ranges are known only by Sony at the moment. All I know for sure is that some table of sliding ranges like this exists in the camera to manage the broad dynamic range coming out of the sensor.
-Lorin


A+

[Alrick]

Une petite question a eric.d

je pars cet été en tournage sur documentaire aux etats-unis dans le dakota du sud et je m'interroge encore sur le choix du materiel.
la petit sony HVR-A1E me parraissait idéal par rapport a mon utilisation ( beaucoup en exterieur, interview,grand espaces...)
connaissez-vous les prix aux etats unis, le materiel subit t'il une taxe au retour en france, sinon me conseillez-vous une autre cameraa qualité professionel.

[soad]

oups desolé j'ai posé ma question sur bar marine):



salut à tous,
je suis cameraman professionnel dans l'événementiel,
je suis intéressé par la HVR-A1E, elle est dans mon budget 2000 à 2300 €

quels sont les avantages & inconvénients si on utilise la sd?
car je travail seulement avec dv )

est ce qu'elle correspond pour des salles peu éclairée?

si vous connaissez un modèle en particulier car je tourne beaucoup pour les mariages.

Merci pour vos expériences.

[Eric D.]

Avantages Aucuns en dehors du format 16.9 et de la HD par rapport a une VX 2100 inconvéniants l'ergonomie pour un travail Pro.

pour ce qui est de la basse lumière c'est pas vraiment sa tasse de thé.

apres c'est plus dans le budget malheureusement

A+

A+

[soad]

Eric,
ya t' il un support SDHC pour catre mémoire ,
je rêve d'avoir cette camera car je suis cameraman pour mariages, reportages, etc...

si j'économise, je préfère celle ci mais j'ai trouvé la Panasonic AG-HMC71
à 1490 euros au lieu de 2790

merci pour tes précieux conseils avant que je me lance

[Eric D.]

Oui en CF mais en liaison cable avec le HVR-MRC1

http://www.cameravideo.net/forum/new...pd170-etc.html

A+