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Subject: Re: raw 3.1 professional custom profiles for highend digital cameras



Again what you are missing is the linear nature of digital and the fact that SO MUCH CRITICAL data is recorded in that brightest stop. Yes, you can meter for the highlights and then open up, but how much? 3-4 stops is simply too imprecise. Is it 3 stops or 4 stops for your sensor to record a textured highlight? If is 4 and you only open 3 stops then you've lost a full 1/2 of all the levels your sensor can capture.

The Minolta spot meter allows you to measure a spot and assign it as highlight then meter a shadow and assign it as a shadow reading. The meter then reads out the different and will tell you what the scene luminance range is. It is this information that a regular meter can't do easily.

When Bruce indicates the importance of determining the true ISO of the sensor, it is this information that will help tell you whether you need to compensate up or down to get an accurate exposure. If the scene is less than the dynamic range of the sensor, then you expose to the right.

If the scene is beyond the range of the sensor then you must;

Decide whether the shadows or the highlights are the most critical for your scene and expose accotdingly or,

Bracket to get a range of exposures that might be combined by multiple exposure or in HDR or,

Pick another scene to shoot :-)

A 1/3 or 1/2 or 1 stop reduction in exposure will have an impact on the quality of the resulting image. In the old days of digital capture, there was a need to pull exposures because of video chip blooming-a result of extreme highlights effecting areas around bright highlights. Often this video blooming meant you HAD to reduct exposure to save not only the highlights but surrounding areas. . .these days the sensors are far better at containing blooming and the need to artificially reduce exposure to fix the blooming isn't really required.

The whole point of this exchange is to highlight the fact that digital exposure _IS_ different than film exposure and needs to be treated differently. Yes, exposuing digital is somewhat like exposing chrome reversal film except for the fact that film does NOT have the ability to capture nearly the amount of usable detail near total white. Digital does. That brighest stop contains a TON of data that can be used and manipulated with curves. . .film doesn't.

Yes, overexposure with either digital or film will result in no detail in blown highlights-it's just that digital has a lot more data just before getting blown out. And looking at an sRGB luminance histogram with highlight warnings that are 1 stop conservative doesn't help. Knowing the exact point where detail is maintained and where highlights will blow is more important.

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