The Perfect Sunrise

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When I like to take photo a television at the program running, the picture is not clear. The Black block continually affect photo. Mobile Camera or Digital Camera also not take a clear picture,.

But I saw a lot of photos in advertising has photo of television with running program. How they took that. Below is sample,. its little bit clear, and no black color blocks are there.

enter image description here

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I swear we had this question already but I can't find it.... –  mattdm Jan 31 '12 at 12:45
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@mattdm I think it was about video and got migrated to avp. –  drewbenn Jan 31 '12 at 16:23
    
If you look carefully, many advertisements for TVs contain fine-print about a "simulated picture" –  slead Feb 2 '12 at 22:04
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3 Answers

The reason that you get a black band across the screen is that you are using a shutter speed that is too short.

The image on the screen is refreshed at a specific rate. This rate differs depending on where you live but it's either 50 or 60 Hz. There are also televison sets that refresh the image at double the rate; 100 or 120 Hz.

The screen is refreshed from the top to the bottom, and when the refresh reaches the bottom, the top has faded to black in time for the next refresh. Thus, some part of the screen is always black at any given moment.

To avoid the black band in the pictures, you need to have a shutter speed that is long enough to capture several frames. On the other hand, any movement in the TV image will of course be blurred if you capture too many frames.

You can try a shutter speed like 1/10 second, which would give you 5-6 frames.

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1+ Thanks Guffa. –  Sagotharan Jan 31 '12 at 11:15
    
+1 I have taken pictures of broadcasting tv successfully at 1/60. In my country TV is NTSC, which has a refresh rate of 60 Hz, i.e. 60 times per second. In this case it was a CRT tv. Is my guess that being the shutter opened for the same time as a complete refresh cycle should last, it captures the band of lit "pixels" that draws the image as it travels the screen up-down. I think this allows to capture one frame, or most probably part of one frame and part of the next, being this the fastest shutter for NTSC TV –  Jahaziel Jan 31 '12 at 20:30
    
@Jahaziel: It's not part of one frame and part of the next, as then you would see the black band between them. If you managed to capture a good image of a single frame, you were lucky enough to start the exposure in the vertical blank. If you have a digital camera you could just shoot away and hope for that luck, and perhaps one in twenty is a keeper. –  Guffa Feb 2 '12 at 0:52
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A lot of television pictures used in advertising are digitally added to the television so what you are seeing is not the actual camera output. I worked alongside designers producing consumer electronics catalogues and this was fairly standard practice.

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In the days before computer effects, they actually synchronized the television scan rate to the camera shutter. Basically, there were systems that would take a video camera sync signal, and play something like a video cassette back with the timing precisely synchronized so each film exposure contained one CRT scan. –  Fake Name Feb 1 '12 at 6:12
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I have never attempted to photograph a television so I am somewhat speculating here but I would imagine that this is down to the selected camera shutter speed.

The TV you are photographing will have a particular refresh rate maybe 50/60/100/200Hz or higher in some cases (the faster the refresh rate the faster the shutter speed you should be able to get away with).

In order to capture an image that doesn't have the refresh lines it should just be a case of lengthening/shortening the shutter speed to match (or rather, be slightly slower than) the refresh rate of the TV. You could try starting at 1/25 second initially using trial and error from there. You will want a shutter speed that is slow enough to capture a screen correctly but not so slow that the action on the screen becomes blurry due to movement. If blurring becomes a problem you could always pause the TV which should make capturing the shot easier for you.

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1+ thanks Mark J P . –  Sagotharan Jan 31 '12 at 11:13
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