Thursday, January 22, 2009

G9: Portrait Distance

It seems to me that actual height for a tightly composed head shot is about two feet. How far away from the subject should the camera be to capture this two foot high subject? I suppose the distance can be calculated but frankly it is just easier to tape a yardstick to the wall and take a few shots.

For my G9, these are the camera-to-subject distances for various focal lengths.

The focal lengths in the chart are the same as the focal lengths from the previous posting which gave the maximum aperture for various focal lengths.

The depth of field can be calculated from distance, focal length and aperture. Taking some liberties in rounding off, depth of field for a portrait setting with the G9 is about one foot – give or take a few inches.

This little experiment would seem to indicate that a blurred background would be easily obtained with the Canon G9; however, the opposite is true. In fact, blurred backgrounds are difficult to obtain and extreme blur for portraits and larger scenes is nearly impossible to achieve with the G9. The apparent discrepancy is because the depth of field calculation is intended to predict the onset of blur and not the extreme.

Next: an example of typical G9 background blur for portrait setting

Monday, January 5, 2009

G9: Focus Vertically or Horizontally?

Although I’ve made several postings about focusing the G9 (sort of cross referenced here), a few days ago I began to think that my G9 was focusing much better when held horizontally (landscape) than when held vertically (portrait). In fact, sometimes it would not focus when turned vertically. Was my G9 broken?

On further review, I’ve come to realize that the small Flexizone frame works best on vertical lines when held horizontally and on horizontal lines when held vertically. Said another way, when shooting in landscape orientation (the “normal” shot), look for a vertical line on which to focus. When shooting a portrait, look for a horizontal line and focus on it.

My problem – when I feared my G9 was broken – was that I was shooting in portrait orientation and the subject lines were vertical. The G9 just would not focus on those vertical lines with the small Flexizone frame. But turning the camera to landscape orientation, it focused immediately.

In much the same way, when using the small Flexizone frame, the G9 struggles to focus on simple horizontal lines when the camera is in landscape orientation. Turned vertically, focusing is routine on those same horizontal lines.

The AiAF matrix of focus points does not have this problem – probably because one of the focus points usually finds an appropriate contrast pattern.

I still prefer the small Flexizone frame but now have a better understanding of those missed focuses. Strange, but true.