Shoreline #1

At Alameda's Shoreline Park.

Fruitvale Bridge #3

This was taken with a Nikon D-7000.   A cloudy morning but some foreground light recovered via HDR.

On the Importance of Raw

  All high end cameras and some consumer cameras offer to give you your pictures in either Raw or Jpeg format (or sometimes both).    Raw format is simply the data off the sensor whereas jpeg format is the result of transforming that data into a image and compressing it in a lossy way.

  The conversion from Raw to Jpeg is not trivial.  A digital pictures is a rectangular grid of pixels, each pixel being an intensity value for Red, Green and Blue.

• The camera's sensor only records the intensity of one color at each pixel location.   The intensity of the other two colors must be determined from neighboring pixels.    
• The camera must determine the color of the light that illuminated the scene and then transform all the color values so that white objects appear white in the Jpeg and other objects appear their correct color.
• The image must be sharpened. 

 The camera's computer does all this computation very quickly.  Usually it takes less than a second to create a Jpeg from the sensor values.   The alternative way to create a Jpeg is to take the Raw file from the camera and run it through software provided by the camera manufacturer.   For my D7000 it takes about 30 seconds to convert a Raw file to a Jpeg file.  That is 30 seconds running on a very fast cpu that's many times more powerful than a camera's computer.

The question is often raised: should I shoot Jpeg or Raw? 

Well, the in-camera Jpeg is produced in one second on a weak processor, and the Jpeg from the Raw will take 30 seconds to create on a very powerful machine.

 Put that way which Jpeg do you think is better?

Alameda Theatre

 The recently revived Alameda Theatre.   It had shut down while a crummy duplex theatre existed at the shopping center.  Now it's back in almost its former glory (it was turned into a multiplex as single screen theatres just can't make it these days).

Harbor Bay Ferry

The Harbor Bay ferry crossing the bay for San Francisco.

AT&T and T-Mobile merger

  Much has been written about proposed AT&T and T-Mobile merger.  The bad part is that it will reduce competition and that means the customer will have fewer choices and the choices will not be as good.   At least Verizon will remain a strong competitor.

  I'm hoping for one good thing from this merger -- AT&T will finally allow SIM-unlocks for the iPhone as they do for all other phones they sell.    When travelling internationally the big advantage of a GSM phone is being able to purchase a SIM card from the country where you're visiting.   That gives you a local number in that country so you can make much cheaper calls (as international roaming charges are a complete ripoff).   Also a local number means that local people can call you without having to dial a long distance number.

 I assume that the reason that the iPhone was singled out for special treatment as regards unlocking was that AT&T felt it would lose money if  a subscriber bought a subsidized phone from AT&T and then immediately quit and left AT&T.  Now the early termination fee is very high and the iPhone is sold worldwide so it doesn't make financial sense to buy it from AT&T if you plan on terminating early.

Tree and Storm

At the Harbor Bay Ferry terminal.  Another HDR photo.

Fruitvale Bridge #2

Another HDR photo of the Frutivale bridge.   This was shot with a Nikon D-100, Nikon's first prosumer grade DSLR.

Raw material for an HDR photo

These are the three images that combined together to create the photo shown below.   The numbers denote the difference in F stops between what the camera computed as the ideal exposure and the exposure used.

Mashup Masterpiece

An amazing mashup of videos to create a masterpiece.

Palm Trees

We were between storms and I stopped by the Grand Street marina.   I was trying to get some HDR shots of the boats but it was just a little too dark to shoot the -2 stop underexposed shot without a tripod.   So I took a three shot sequence of the palm trees.  It turned out to be a good looking HDR photo.

Fruitvale Bridge #1

This is one of my first HDR images.   This is the Fruitvale Bridge, a combination auto and railroad drawbridge.  The auto drawbridge is down and the railroad drawbridge is up.

By using HDR I was able to capture the sky and reflections in the water and made them look to have the same brightness.

What is HDR and why is it important?

   Imagine you go to the park on sunny day with a few puffy clouds in the sky.
 The grass is a rich green and the sky a deep blue with brilliant white clouds.  Sitting in the shade of a tree you see someone reading a magazine.

  It's a typical scene and you can see all aspects of it at once.  You take out your digital camera to make a record of this and you end up frustrated.  You can take a picture of the green grass but then the sky is a washed out blue and it's hard to see who is sitting in the shade of the tree.  You can photograph the sky but then the grass turns out dark and you can't even see the person in the shade of the tree.  Or you can photograph the person but when the green grass looks mostly white and the sky itself is all white like a bulb.

  The problem is that digital cameras can take pictures over a range of light intensities that's far less than our eyes and brain can perceive.  So you have to chose which of the three parts of the beautiful park scene you want to record and that's just frustrating.

 This is where High Dynamic Range photography comes in.   With HDR you take a sequence of pictures with the exposure set to capture three different ranges of light intensities.  You keep the camera still - you just change the exposure settings (generally just the shutter speed since aperture changes can change the focus).    Then you use special software to combine the three pictures into one, using the properly exposed parts from each picture.

 In our park example you might take one picture at the normal exposure determined by the camera to be suitable for this scene.  Then you would overexpose the next shot by two F stops and underexpose the next shot by two F stops.

 The preceding picture of the view of San Francisco from the beach was done that way.  That allowed the grass near to camera to be exposed for properly as well as the sky which was much brighter than the ground, even on this cloudy day.

  In subsequent posts we'll got through some examples and discuss the software.

 

A view of San Francisco taken from an Alameda beach.

This is an example of a High Dynamic Range (HDR) photograph.  It's a composition of three photographs taken in sequence, each with a different exposure.    I'll have more to say about HDR in a later post.



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