HM700 spot meter range, can it be extended? at DVinfo.net

George Kilroy · April 28th, 2010, 04:38 AM

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 couldn’t keep any detail in shadow areas yet when I’ve previously shot in the same theatre under the same lighting conditions using DV, I don’t 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.

Tim Dashwood · April 28th, 2010, 03:07 PM

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.

George Kilroy · April 30th, 2010, 01:12 AM

Thank you Tim, that's very helpful. I'll do a bit of experimenting now.

April 28th, 2010, 04:38 AM	#1
George Kilroy Major Player Join Date: Mar 2010 Location: Midlands UK Posts: 699	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 couldn’t keep any detail in shadow areas yet when I’ve previously shot in the same theatre under the same lighting conditions using DV, I don’t 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.

April 28th, 2010, 03:07 PM	#2
Tim Dashwood Wrangler Join Date: Aug 2005 Location: Toronto, ON, Canada Posts: 3,637	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. __________________ Tim Dashwood

April 30th, 2010, 01:12 AM	#3
George Kilroy Major Player Join Date: Mar 2010 Location: Midlands UK Posts: 699	Thank you Tim, that's very helpful. I'll do a bit of experimenting now.