Monday, April 29, 2013

Good Bokeh and Bad Bokeh

Bokeh is a buzz word that describes the out of focus portions of an image.  If you want to impress your peers, point to a photo with a lot of out of focus areas and say "Wow, the bokeh in that photo is amazing."  Most likely, your peers will nod in agreement.

The definition of bokeh is subjective.  To a large degree, you know good bokeh when  you see it.  I describe bad bokeh as an image where the out of focus areas are distracting.  Instead of a smooth and gradual move to blur, the bad bokeh image creates patterns in the blurred area.

Look at the image of the Northern Flicker and Harris Sparrow above.  The Flicker is in focus.  The nearby Sparrow isn't.   The creamy green out of focus area behind the Flicker is good bokeh.

A super telephoto lens has an extremely shallow depth of focus.  It is so shallow that I often have to decide what portion of my subject should be in focus because I can't make the whole  subject sharp.  In this photo of a female Red-winged Blackbird,  I used the shallow depth of field to highlight the bird and to create a mood.  There were so many plants in front of the Blackbird, that it would not have been recognizable with a normal lens.  With a shallow depth of focus, the stem in from create a blur that lowers the overall contrast.  

This photo of a Swamp Sparrow illustrates bad bokeh.  The sparrow is sharp and crisp in spite of the tangle of branches around it.  The background is out of focus.  Portions of the left side of the background have a weird pattern.  When you look at a large version of this image, the background patterns are a flaw.  Bokeh so bad that there is a name for it - nisen bokeh.   This is when an out of focus line is broken into several light and dark out of focus lines. 

Good and bad bokeh is usually considered to be an attribute of the lens.  Canon uses extra blades in the iris of some of  their lens to make the aperature more circular.  This prevents the pattern of the blades from showing up in the out of focus highlights.  In this case, the same lens produced good and bad bokeh on the same day.

What went wrong?  I'm not an expert but at least two factors contributed.  First, the bad bokeh on the left side of the image is out of focus branches between me and the sparrow.  Just like aperture blades, they imprinted their shape on the out of focus highlights. Second, heat waves in the air caused distortion of the highlights.  Look at the out of focus specular highlight a little above the sparrows tail.  If you enlarge it, you will notice that it isn't a smooth blur but there is extra detail in it.

I could have reduced or even prevented the bad bokeh in the sparrow image by moving my camera to a place without branches beteween the camera and sparrow.  That works in theroy but the reality was that the sparrow wasn't posing - I had to follow it.  I do try to do most of my nature photography in the early morning before the heat waves become a problem.

Friday, April 26, 2013

Help From a Birder

I check NEBIRDS occasionally to see if any birders in the Omaha area have seen anything interesting.  Fontenelle Forest is a popular spot so occasionally a birder will report on the same day that I photographed there.  If I returned with photos of a dozen birds, the birder will report seeing at least 50 different kinds.  I have room to improve.  

Canadian Geese are common in Fontenelle Forest wetlands.  This one was resting next to the stream.

I continued  walking down the trail without any special images in my camera, when Phil Swanson walks up.  Phil is one of the best birders in the state.  Apparently the birds flock to him because he always sees more birds in one visit than I do in a dozen. 

I mentioned that I had seen a White-throated Sparrow.  Phil mentioned that he had already seen at least half a dozen different kinds of sparrows.

Phil's magic worked well today.  While we were talking, a Lesser Yellowlegs decided to pose for us on a mound of grass. 

I think some of Phil's magic rubbed off on me today.  I have never seen a Northern Bob White in Fontenelle Forest.  I enjoyed meeting this one a few hundred yards from the spot that I talked to Phil.

Thursday, April 25, 2013

Spring Has Finally Arrived

Last year Nebraska had the earliest spring on record.  This year it is extremely late.  Now that we've had several days in a row without snow, I'm confident that  spring has finally arrived.  

I thought I was ready for the warblers to arrive.   Apparently not!  My ability to spot and focus on warblers before they move on is rusty.  I thought I saw a warbler but it was long gone I had a photograph.  

I spent some time photographing a pair of Lesser Yellowlegs.

This Swamp Sparrow was singing on a branch near the water.  The branch still is partially covered with mud from the 2011 flood.

There were several kinds of duck in the water.  Several wood ducks flew out of a tree before they in camera range.  The image above is an American Coot coming in for a landing.  

A Harris Sparrow was searching for food among the newly sprouted plants.