If you have ever tried to designate yourvideo cameraat yourTV setor yourcomputer monitorto record the range you see , you get it on that it does not ferment – instead of the unchanging mental image that youreyessee , there is either unbelievable spark or a black rolling bar . This short video recording fileshows you what happens when you try it . The video express two dissimilar frequence for the monitor : 70 Hz and then 60 Hz .
Theflickeris due to two things :
If you have study the HowStuffWorks articleHow Television whole shebang , then you know how a standard CRT show work . A individual electron beam scan horizontal lines of pixels across the filmdom , lighting up each picture element when the beam hit it . The pixels are made of individual phosphor dots that glow when the beam bump off them . To our eyes , the dots burn for about 1/30th of a 2d , so we see a steady image . For a video tv camera , however , the dots do not appear to burn nearly as long – the television camera is much less sensitive topersistencethan our eyes .
When you watchthe picture , the second shot has a monitor refreshing every 60th of a 2d and a camera taking a inning every 60th of a instant . The wideblack barthat you see show you a collection of pixels that have faded by the prison term the television camera prove to image them . The bar rolls because the photographic camera and admonisher are not exactly synchronise . TV stations use exceptional monitors and cameras that are capable to synchronise with one another , so the camera ’s CAT scan follow the reminder ’s scan .
Some camcorders use 30 frame per second ( fps ) and do not have the problem if you’re able to get the monitor to review at a pace of 60 fpsprogressive . They may also work on television ( seeHow HDTV Worksfor a description of reformist vs. interlaced scanning ) . Some camcorder use a 1/100th of a secondshutter speed(causing trilled black barroom ) unless you turn the " unfaltering shot " mode off to get it back to 1/60th or 1/30th of a second shutter speed .
To record a computer monitor image , you take to try out with differentrefresh ratesin the varan preferences or in the host computing gadget software package . There are display calling card forpersonal computerswhose video drivers allow you to pick the refresh rate . This charge per unit setting may take some experimentation to get it to match your camera setting . If your television camera apply 24 Federal Protective Service , use a multiple of 24 – practice a refresh charge per unit of 48 Hz or 72 Hz to get disembarrass of the vexing scrolling bars . habituate 640 x 480 mode on the reminder to help lessen the job . Television set with the usual cathode beam pic tube do not have an adjustable screen refresh charge per unit . They will either work with your camera or they wo n’t .
For a person trying to take a screen shot using a TV camera , the well-fixed solvent is to shoot off anLCD panelon aportable computer . bland - screenLCDsdo not have this problem .
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