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Old April 28th, 2010, 05:38 AM   #1
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HM700 spot meter range, can it be extended?

The spot meter function on the HM700 shows when an image has an area with a maximum exposure indicated as 300%. I take from that that the dynamic range is 300:1. Is there a way of extending that so that in very high contrast lighting situations the highlights can be held but the darker areas can also show detail without going completely black. I have tried the Black Stretch but that gives the overall image a much flatter contrast. I notice on a very bright sunny day (which we've had a few of here recently) when I add ND filter to hold the highlights, too much of the darker area goes to black. If I open for the shadows I loose the highlights. Similarly with a stage show that I shot on the HM700 without ND I couldnít keep any detail in shadow areas yet when Iíve previously shot in the same theatre under the same lighting conditions using DV, I donít recall having such a noticeable problem.
Can anyone point me towards a solution or is it a characteristic or the camera and or the format.
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Old April 28th, 2010, 04:07 PM   #2
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Hi George

The black stretch (a.k.a. "Toe") controls shadows but the Knee controls the highlight compression. Using both at the same time will lower the overall contrast and in effect render a wider dynamic range.
The shapes of the different gamma curves in the camera also effect the overall dynamic range with better results from the cinema curve. I will usually choose the cinema curve and lower its value which shifts the whole curve down leaving more headroom. I will then bring the knee down as low as it will go, increase the toe and expose for the highlights. This technique works best when capturing the 4:2:2 output with a high bit rate directly from the camera (with a Nano for example) but has the potential to render acceptable results with 35mbps 4:2:0 as well. It really requires testing by the DP before your shoot to see how much you can pull from the shadow areas and how much is actually desired.
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Old April 30th, 2010, 02:12 AM   #3
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Thank you Tim, that's very helpful. I'll do a bit of experimenting now.
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