And You Thought the Previous Post was Long and Tedious

The following is basically an argument for turning off the flash and turning up the ISO for indoor photography.  Unless you are really bored, you should take that advice for what it's worth, quit reading this post and resume doing the important things in your life.

Grumpy, thanks for providing me with a realistic image with which to work. If I didn't acknowledge the realities of indoor flash-photography, my readers might rightly accuse me of oversimplifying the challenges of color correction.

This is absolutely NOT a criticism of your photography skills. I have succumbed to the use of flash photography on many occasions. Often one is not in the mood to tinker with camera settings and disabling the flash is often one of the more inconvenient or impossible settings to achieve in a camera. 

Instead, this post is about raising awareness about the control one can exert on the color of the lighting in a photograph. It's about the idea that a high ISO setting in indoor environments, and spending some time using Picasa can help people easily reduce noticeably "off-white" lighting in their photography.

Now I'm 'bout to get Henry Higgins on you. Only my pedantic tirade will be about lighting, not speech.

Last warning: the following is boring. Leave now or risk falling asleep on your keyboard.

No sooner had I pressed "publish" on my previous articulation on the ease of color-correction in Picasa, than the Grumpy one publishes an array of photographs that appear designed to disprove my thesis.

Case in point:

Here we see a photograph with no fewer than three distinct light sources. Areas where the light sources blend are present as well, and pretty much rule out the possibility of whole-picture color-correction.

I will diagram it:

I have highlighted three different color regions by surrounding them with a different colored line.

The fourth color region is the orange-colored background, which I felt was too large to draw a border around.

Through tinkering, I have reached the conclusion that the reason for the pink hue in this photo is that the camera was white balanced to sunlight (true white light), and the camera's flash is slightly to the pink side of white. Thus every picture where the flash is the dominant light source will have a pink tint. (I'm sure that Grumpy's fancy new camera has the smarts to know when the flash is on and automatically white-balance for that. Now he just needs to remember to bring it along. ;) I kid.)

• In the foreground, which I've circled with a bluish line is the area where the flash dominates. 
  
• The near background has some flash-influence, especially on lighter colored items. I've circled these with a mint-colored line.
  
• Far in the upper right background, circled in yellow is a window to the outside. Using Picasa's Neutral Color Picker in this region yields no change in the tint of the picture. This is how I reached the conclusion that the camera's white-balance was configured for sunlight.
  
• The rest of the background is distinctly orange-colored, which is clearly the result of incandescent lighting in the room.

So, now we understand the competing light-sources in the picture and it should be obvious why we couldn't just use Picasa's Neutral Color Picker to balance the color for the whole photo. Picasa assumes that only one light source is at play in the entire picture. 

Perhaps someday an algorithm will be created to white-balance automatically by region, but that's a fairly complex problem, so for now color-conscious photographers have to make everyone go outside for a portrait, or they turn off their flash. In this way, a single source of light can be achieved and subsequently "corrected" if the camera's white-balance setting was incorrect for the type of light in the portrait.

In the above picture, the color can be corrected for the foreground by using the Neutral Color Picker on the tablecloth near the bottom left corner of the photo. 

Better yet, you can choose to use Picasa's Auto Color button and it will do almost the same thing, but a little better.

In general, the Auto Color feature does a better job of finding a neutral color to correct by than I do. 

Generally, what it appears to do is line up the red, green and blue in the histogram so that they overlap as much as possible. Picasa doesn't give you the ability to slide the colors around manually, which is entirely sensible considering the difficulty involved in that.

Nonetheless, as a photography geek, I think it would be nice to have a tool for tinkering with the color levels.

I have had that before, and Paint.NET has that ability. But for whatever reason (training perhaps?) I am only marginally successful at using those tools.