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Subject: Re: ACR Calibration



Mike,

I think we’re all in agreement on the fundamentals. So this discussion is more for enlightenment and not to prove anyone right or wrong. In that spirit:

The CC image is designed for calibration, not aesthetics. It has a very low dynamic range. In my own tests I get consistent calibration results with bracketed exposures. I do not get the same consistency when I vary the ACR exposure tab by the same amounts.

When shooting nature and wildlife I do pay attention to the histograms and previews. But I don’t let the “expose to the right” paradigm overrule common sense. Sometimes blown highlights are perfectly acceptable. Obviously, not in the studio. And they are not desirable in most landscapes.

Some examples: I was shooting a daytime indoor event at a sports stadium. The speaker was in front of a large glass window that overlooked a soccer field. There was a large silver trophy next to him. I used flash to expose the subjects correctly. Still, the window was totally blown highlights. This is exactly what the audience saw as well. The resulting image captured the subjects clearly and the ambiance of the room.

I shoot a lot of evening soccer games in incredibly poor lighting. I will frequently underexpose these and shoot raw, just to maintain useful ISO and adequate shutter speeds for the action. Even so, there will sometimes be blown highlights from the score boards and metal reflections in the sidelines.

I recently saw a very good explanation. An on coming automobile headlight in daylight is barely noticeable. But the same light at night is blinding. The amount of light did not change, only the reference to the rest of the scene. Similarly, sunlight reflecting off a side view mirror can make it difficult to see the car in front clearly. Our eyes also adapt to middle tones, daylight, nighttime, and dawn/dusk. They took millions of years of evolution to calibrate.

Using only the histogram as a micrometer for exposure, then making adjustments with a chain saw is not very intelligent in some cases.

I still believe very strongly that calibration should be based on a photographically correct exposure. Once I got the ACR brightness tab set for my cameras, my exposures do track my cameras and hand held metering.

The best thing about digital is that there are so many options available to us. Some can be pretty extreme but very effective.

Cheers, Rags ;-)

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