making exposure.

Latitude is broad if your subject has little contrast and if you will edit the image before use.

Latitude is the amount by which your camera's dynamic range exceeds the range of the subject, if and only if you have the opportunity to edit the image before final use.

There is very little latitude if you're using a digital file or transparency as-is. Digital files need to be within 1/3 of a stop if you use them as-is! Luckily most cameras are this good today.

Latitude slims as subject contrast increases. Latitude evaporates when your subject has too much contrast. When this happens there is no correct exposure. It looks bad no matter how you set the exposure. This stumps many beginners. Many times we encounter subjects with too much contrast to be captured without modifying the light.

If there is so little to no latitude today, why do people still discuss it as if it was helpful? Black and white negatives were 99% of photography for the first 150 years of photography. Color only went mainstream in the mid 1970s and digital has only been popular for the past 48 months. B/W negatives have always had broader range than almost any subject. You could overexpose five or ten full stops and get great prints, if you were willing to expose the paper long enough. Old timers take latitude for granted. Digital has no tolerance for overexposure, although, unlike film, it takes a couple of stops of underexposure easily.

Subject Contrast and Lighting Ratio

If the subject's contrast exceeds the brightness range of your digital camera or film, there is less than no latitude and there is no correct exposure! These images look awful no matter how you set the exposure.

An example is photographing indoors and expecting to see both the room's interior and the view out the window.

This confuses beginners. Beginners waste time with hocus-pocus get-rich-quick Photoshop schemes like HDR (High Dynamic Range) compositing to attempt to turn crappy light into a good photograph.

Good photographers modify the lighting to make the subject photographable. Add light to the dark parts with fill flash or other lighting or reflectors, dim the bright sections, or both. Bright windows are dimmed by putting gels (sheets of gray plastic filter material bought at stage and movie lighting supply houses) over windows. Scrims (black mesh cloth mounted in frames) are used to dim the light falling on something outdoors.

This is why you'll see all the things you do on a movie set. That's the lighting and rigging required to make a scene photograph naturally. Shooting in available daylight looks horrible and amateur: shadows in people's eye sockets look completely black on film and make people's heads look like skulls while sun shining off foreheads make everyone look bald. Fill the shadows with fill flash or a white reflector and dim the direct light with a scrim held above and out of the picture for pro results.

© 2007 KenRockwell.com

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