Photo Jottings

This page will attempt to explain what “Bokeh” is by showing you some samples taken with various lenses, at different apertures, focus points, and areas of the image.

Bokeh is a Japanese word used to describe “fuzziness,” or in our case, the characteristics of out-of-focus points of light in our images, either foreground or background.  Most of us shoot with the foreground sharp, and the background blurred, this looks natural and most people associate “Bokeh” with background blur, but you can also have foreground blur,which looks weird to me, and other people too.  Just because a background is out-of-focus and all blurred out doesn’t mean it’s going to be smooth and pretty; often it can be harsh and distracting, and most of this is a result of the lens design.  In this article, we’ll stick to the artistic points of Bokeh, and not worry about lens design constraints and other technical issues that affect Bokeh, and can’t be user changed anyways.

Three bokeh examples.

This is a shot from the Sony 70-200mm F/2.8 G lens, taken at F/4, 70mm.  It’s neutral to slightly smooth, and looks good to me.  It shows a smooth, even disk, slightly soft with no noticeable outlined edges.  This is a fairly typical bokeh rendition of a more expensive fast lens.

Here is an example of a super smooth bokeh.  It’s from the wonderful Sony (Minolta designed) 135mm F/2.8 STF lens which is probably the best lens produced today for wiping out backgrounds.  Sony uses a fancy lens element and extra 10 blade stepless aperture to produce this effect.  Notice how everything is soft and diffused, and almost is a nice picture in itself!  It’s the same basic scene as the other two images above.

General samples below.

When the out-of-focus highlights are in front or behind the subject, the bokeh can be rendered differently.  The crop on the left shows a harsh background bokeh, the same lens on the right crop shows a smooth foreground bokeh.  Some lenses do this, some don’t.  Common accepted wisdom on this subject is;  if the lens displays poor bokeh for the background, it will show smooth bokeh for the foreground.  I don’t always see this.  The lens used for the crops is theMinolta AF 100-200mm F/4.5.

Above samples are indicative of bokeh from (usually) less expensive medium zoom lenses offered by Minolta and Sony.  The single dot in the middle look (left) isn’t noticeable in newer lenses.

The left crop shows the bokeh in the center of the image, which looks pretty good.  The right crop shows what happens at the edges of the image, where the highlights have a partial, semi-circle edge.  This is common performance when using the largest aperture.  The same area was chosen for each shot for easy comparison, and both were taken at F/5.6, 300mm using the Sony 70-300mm F/4.5-5.6 G lens.

In this crop we see the aperture shape show up, see the heptagons, or seven sided polygons?  I used the Sony 50mm F/1.4 lens, at F/4.  This lens has a circular aperture, but has seven blades, which don’t really form a good circle at smaller apertures, a nine bladed aperture would be more round at F/4.  Just because the lens has a circular aperture doesn’t mean it will have a circular shape in the highlights when stopped down.

Here’s a fascinating tidbit not really related to bokeh.  When the foreground is blurred, you’ll get red outlined highlights, with the background blurred, you’ll get green outlined highlights, this is called spherochromatism, and usually goes away as you stop down, and is mostly noticeable on fast lenses when used wide open.  Crops from the Sony 50mm F/1.4 lens, @F/1.4.

Swirling bokeh explained.

The left crop above is what’s known as “swirling bokeh.”  It looks like the background is spinning.  When you stop down the aperture, it goes away.  Many people have never seen this, because it only shows (usually) at full wide open aperture, and when the whole frame has the same type of detail, like the bush displayed here.  Crops from the Sony 50mm F/1.4 lens.

The top right crop shows the cause of the swirling or spinning bokeh, and both top crops use the same background spot for comparison.  The top left crop from the center of the image shows a nice circle.  The top right crop from the corner has lentil or flattened semi-circles along the entire image periphery, (though extending close to the center area), and this elongated orientation creates the spinning illusion around the center of the image.  The different lower corner crops show the highlights going from lentil shape to circular by closing the aperture one stop, which eliminates the swirling or spinning look.  The above images were taken with the Sony A700, and Sony 50mm F/1.4 lens.

Bokeh, not blur.

This is how bokeh is rendered on the Sony 500mm F/8 reflex lens.  This lens uses a small mirror up front to redirect light back down into the camera, and partially covers the front element, that’s why you get the ugly donut shaped highlights.  In this image, the subject is close to the background.

This is the same lens, but focused up close, with a far off smooth background.  Some people look at their images and decide their lens bokeh is smooth like this, but you’re not seeing the character of out-of-focus highlights, which is what this page is about.  Any lens will show a smooth background given the right conditions.

Points to ponder

Lenses may show a different bokeh at different apertures, at different focal lengths (for zooms) and at different focal points, like foreground or background.

Bokeh can look different around the image periphery than it does in the center, especially when the lens is used wide open.

Aperture shape has little to do with the look of out-of-focus points of light.  Also, just because a lens has a circular aperture doesn’t mean it will produce a round point of light when stopped down.

Any lens can show a smooth background depending on distance, scene make-up, and how far out of focus it is.  Remember, bokeh is how out-of-focus points of light are rendered, meaning the character of the point of light, not how far out of focus a background scene is.

A wide open aperture will not always produce the best bokeh, in fact, my experience in reviewing dozens of lenses (over 110 now) points to a more common one-stop-down from maximum aperture as the smoothest bokeh, especially for fast lenses, telephoto zooms generally look good wide open at the long end.

I hope this article helps you understand what “Bokeh” is, and more importantly, explains the differences in actual shooting.