Miguel Bunster Posted June 25, 2004 Share Posted June 25, 2004 One more question, whats the equivalent in ASA for a camera like Sony PD-150 or XL1? I read somewhere that for HD it was 320. Many thanks in advance! Miguel Link to comment Share on other sites More sharing options...
Premium Member Kevin Zanit Posted June 25, 2004 Premium Member Share Posted June 25, 2004 I rate most video cameras at about 320 - 400 ISO. You can find out for your self by pointing the camera at a gray scale chip chart, and connecting the camera to a waveform monitor. Adjust the cameras exposure until it reads correct on the waveform. Then take an incident reading in the same light as the chart. Adjust your meters ISO until the exposure it gives you matches the one set on your camera. Kevin Zanit Link to comment Share on other sites More sharing options...
Miguel Bunster Posted June 26, 2004 Author Share Posted June 26, 2004 Kevin, I get the idea but when in IRE units is the exposure correct? And in the spot meter Should I look for a Stop equal to the one used in video camera? Thanks Miguel Link to comment Share on other sites More sharing options...
Premium Member Kevin Zanit Posted June 26, 2004 Premium Member Share Posted June 26, 2004 The white chip should read as 100 and the black one zero (or 7.5 depending on set-up). These figures are roughly what you should, some slight variance is fine. They should look like steps. Another way to do it is use a gray card and let the camera auto-expose for the card, then match your meter to the stop. Don't use a spot meter, as I said use an incident meter, and then adjust your ISO until the meter displays an F-STOP that matches your camera's. Link to comment Share on other sites More sharing options...
Premium Member Phil Rhodes Posted June 26, 2004 Premium Member Share Posted June 26, 2004 Hi, I question this. I've found that video cameras are able to produce perfectly good images in levels of light several times lower than the sensitivities implied by this commonly-reccomended test would suggest. Recent experience shooting 1600ASA stills against a video camera implied that the video was at least a stop faster. Phil Link to comment Share on other sites More sharing options...
Sam Wells Posted June 26, 2004 Share Posted June 26, 2004 Hi, I question this. I've found that video cameras are able to produce perfectly good images in levels of light several times lower than the sensitivities implied by this commonly-reccomended test would suggest. Recent experience shooting 1600ASA stills against a video camera implied that the video was at least a stop faster. Phil It depends on the signal/noise ratio you are willing to accept, the format, and the path in post production, how you finish. -Sam Link to comment Share on other sites More sharing options...
Premium Member Phil Rhodes Posted June 26, 2004 Premium Member Share Posted June 26, 2004 Hi, I hasten to add that I wasn't in any kind of gain for this. I suspect that video cameras may vary by typically a stop to a stop and a half - the gain/speed situation with Panasonic hi-def cameras is well-known. Phil Link to comment Share on other sites More sharing options...
Sam Wells Posted June 26, 2004 Share Posted June 26, 2004 Yes but even at zero gain, I think noise floor dicates how far you can take it -sam Link to comment Share on other sites More sharing options...
Premium Member David Mullen ASC Posted June 26, 2004 Premium Member Share Posted June 26, 2004 What shutter speed you are using is also a factor. The F900 is like 320-400 ASA at 0 db with a 1/48th shutter but you can turn off the shutter and gain another stop. And the Varicam is supposedly a stop faster than the F900 but also noisier at 0 db, so some people are shooting at -3 or -6 db on it and ending up at roughly the same speed as the F900. I find I tend to treat the F900 more as a 500 ASA camera in night scenes than in day scenes, but that's because I prefer the highlights being less hot in night scenes so I am essentially slightly underexposing. My brief experience with the PD-150 was that at 0 db, it was in the 320-500 ASA range at 60i with a 1/60th shutter (i.e. no shutter.) Link to comment Share on other sites More sharing options...
Miguel Bunster Posted June 26, 2004 Author Share Posted June 26, 2004 Great! thanks for the info! Miguel Link to comment Share on other sites More sharing options...
Premium Member Laurent Andrieux Posted June 30, 2004 Premium Member Share Posted June 30, 2004 Another way to do it is use a gray card and let the camera auto-expose for the card, then match your meter to the stop. I'm sorry Mr. Zanit, it doesn't work because the automatic iris level is not set for average value by default. (it's generally set half the way beetween "peak value" (100 IRE) and average value. If you use the waveform monitor, it's best to set on 100 IRE for the white but the 18 % grey can be set at 50 IRE as well. One thing I didn't see here is the fact that if video camera builders don't give any ASA/ISO spec (that would have no sense) they give you a lux necessary rating for a certain T stop. Then you can : - calculate it from this formula : T²/t = (E.Siso)/250 ; T : T stop, t : exposure time (1/60 s...) E : lumination in lux. - use a lux meter : set the secified illumination, take a meter and see what sensitivity will diplay for the specified T stop. I can give you this advice : CCD Had are given 2000 lx f 5.6 thats about 200 iso Hyper Had are given 2000 lx f 8 : 400 iso Power Had are given 2000 lx f 10 (11-1/3) 640 iso most recent CMOS are given 2000 lx f 11 : 800 iso Link to comment Share on other sites More sharing options...
Miguel Bunster Posted June 30, 2004 Author Share Posted June 30, 2004 Thanks! Miguel Link to comment Share on other sites More sharing options...
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