January 14, 2010

Big waves on the coast

click photo for full-size image
photo by Donald Kinney

Tuesday evening the local weather lady was advertising 20 foot waves on the coast.   My mouth started to water...

click photo for full-size image
photo by Donald Kinney

O.k. folks...   Time for another Histogram lesson.

This is for the benefit of a couple of my photo buddies who tend to blow out their whites on occasion -- if I told them directly I'm pretty sure I'd hurt their feelings.

It all boils down to getting some detail into the high-values -- not just letting the highs bunch up in a big mess at on the right side of the scale.   Many times the range of tones in a brightly lit scene exceeds the capability of what the sensor can record.

About the only thing the digital photographer can do to prevent blown-out whites in Aperture-Priority or Shutter-Piority modes is a bit of Exposure Compensation -- reducing the amount of exposure. --Out-smarting the meter, so to speak...   Just keep in mind that it is better to under-expose a shot, rather than bunch up the whites on the right side of the scale with over-exposure.   It's usually a process just guessing at the amount of Exposure Compensation, unless you want to check the Histogram that some cameras will display immediately after taking the shot.

Initially, after my in-field Exposure Compensation, the high-values didn't quite reach the right end of the scale, so while I was in CameraRAW I forced those tones right up to the end of the scale (pure white), then I brought the low-values on the left side of the scale down just a bit to achieve slightly more contrast.

But notice how the graph doesn't extend all the way to the left edge of the Histogram? -- this shows that there aren't any pure blacks anywhere in the image.   The darkest tone is sort of a dark-medium gray, which is pretty much what the actual scene looked like.   Normally, you would want a full range of tones, with the graph extending from end to end of the scale, without large bunches of tones piled up on either end.

The bottom line is that except for specular highlights and dead black blacks you want detail in both your high values and your low values.   That's how Ansel Adams and Minor White made such stunning photographs with such a wide range of beautiful grays.   Of course, they were using film and had some additional tricks for getting their tones to land in the correct spot.   They would go to the trouble of measuring individual light values in a scene with a "spot meter", then see how those tones were going to fit on a scale of ten stops -- from pure black to pure white, and if the range was too wide (((or not wide enough))) for the dynamic range of their film they would determine if they should under-expose or over-expose the shot, and calculate exactly how much they should either under-develop or over-develop their negatives.   They called it the Zone System.

For the person developing his own black and white film, it all boils down to -- if you need to reduce contrast you over-expose and under-develop, and if you need to increase contrast you under-expose and over-develop.   The same sort of thing can be emulated, as I have described above, in the digital darkroom -- Photoshop or many of the other image processing programs.

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photowannabe said...

Great lesson today, but my brain seems to be on vacation or something. I will have to come back and digest this again.
Love this time of year and the Maverick waves. Beautiful.

Jo's-D-Eyes said...

Hi Don,

Its has been a while ago, but being busy... you know,with all the festivities and frineds/family etc. Happy new year wishes & lots of creative Pho's for you and your Kitty, your blog has & is as always an inspiration for me, I love those waves in photography but in reality its not my favo. Glad its on pho's., great stills. Love them the way you show them.

see my Ice cold skate fun pics,

Greetings from JoAnn/Holland

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