Review - Bokeh lens simulator Photoshop plug-in


Provides: The ability to simulate short depth of field on your images
Developer: Alien Skin Software
Minimum Requirements: PowerPC or Intel Mac, Mac OS X v10.4.1, Photoshop CS3 or greater, Photoshop Elements 4.1 or greater, or Fireworks CS4.
Retail Price for Bokeh: $199.00
Availability: Out now

The art of the blur. That's what we are talking about here: blurring images. We see this blurring all the time in movies when the camera shifts its focus from one protagonist to another so that person A is in focus at one point and person B is in focus at another. The quality of that "out-of-focus" is Bokeh, and if you didn't properly get that blur in your camera, the Photoshop plug-in, Bokeh, will do a great job of giving you a second chance for great bokeh in your computer.

Bokeh is a Japanese word which can mean blur or haze, but comes from the word "boke" which means mental haze or senility (go figure). However, when it comes to photography, Bokeh refers to how beautiful the part of the image is that is out of focus, or outside the depth-of-range range of what's in focus in the image.

Forgive me, but let me digress a bit here for those who need a bit of "the physics of photography." If you already know about depth-of-fields and f-stops and all that, go ahead and skip down a few paragraphs. If not, then please read the following so the rest of this review may make more sense.

Camera lenses have a diaphragm that varies how much light can get past the lens and the diaphragm is composed of a collection of blades. The number of blades varies from lens to lens. Think of this diaphragm as a door. If the door is only open a tiny bit, than very little light gets through, if the door is open all the way, a lot of light gets through. The darker your available light, the more you want the door open all the way and if the thing you are photographing is in a lot of light, you may want to close the door so that your film or sensor are not overwhelmed with light. The nomenclature for how big the door is is called the Aperture of the lens and is referred to as an "f-stop." Interestingly, large f-stops let in very little light while small f-stops let in large amounts of light. Large f-stops, like 18, 22, or larger have very deep depth-of-field while small f-stops like 1.2 or 2.4 have extremely short depth of field and are preferred for creating good Bokeh. [The depth-of-field is the distance in front of and behind the specific item you have in focus.]

A short depth-of-field means that you can photograph one item and everything in the foreground and background will be out of focus. The reason you may want this is so that the viewer of your image will be forced to look at the subject of the image. As you go through this review you will see examples of this and the reasons will become self-evident.

Unfortunately, to get really good Bokeh, you need a very fast lens. A fast lens is one that lets a LOT of light through and has a small f-stop number. There is no doubt that you will get the best Bokeh using your camera. But there's a catch:

  • You might take a photo and it isn't until you get back to your computer when you realize that your depth-of-field wasn't short enough.
  • Or the thing that you didn't notice in the background is very noticeable now.
  • Or the your lens isn't fast enough to provide the level of bokeh you want/need for that photo.
  • Or you didn't have a chance to properly set up your camera to obtain the best bokeh for the shot as you were just trying to get the shot.

The possible reasons for why you need bokeh, or more bokeh, are vast.

Users of Photoshop have always been able to resort to creating a Gausian Blur in regions they wanted out of focus, but the truth is that the blurring created by using Gausian Blur are not the same as those for bokeh and the difference can be a bit subtle or quite pronounced. There's a reason for this and it has to do with the physical construction of the blades in the diaphragm If you look at the image below, I've drawn a crude representation of the "blades" in the shutter that slide over each other to increase or decrease the size of the aperture. While the number of blades in each lens can vary, the larger the aperture is open, the longer parts of the blades are displayed. It's those longer sections that play with the light and effect the character of the blurring.

shutter blades

Below is an image of a street lamp and some buildings in the background. Photographically the image is centerless. There's nothing to focus on. In general, the eye will be driven to items that are brighter or in focus. Here, nothing is bright and everything is in focus.

original street lamp image

Below is the same image but a Gausian Blur has been cast upon the background

gausian blur on parts of the image

Finally, this image has been processed with Bokeh. One of the things to point out are the horizontal rounded window ledges. Note that there is almost a double-ghost image as opposed to the Gausian Blur shown above. An out-of-focus camera lens is not just blurry, but will typically have some sort of optical aberration as described above. This is an easy example of where Bokeh "gets it." Simply, a Gausian Blur is good, but Bokeh is better, and better simulates how a camera lens bokehs. So, while this is certainly not the best photo in the world, it is miles better than it was. Now it has focus that was created by blurring things that shouldn't be in focus. Interesting, huh?

a true bokeh image

There are two ways to "bokeh" an image in Bokeh, and your options are completely forced upon you by the dynamics of your image. In the image above, I had to make two sets of selections. First, I selected the most distant items and gave them a strong Bokeh. Then I selected the parts of the image that were closer and gave them a partial Bokeh. The rest, I left alone. Simply put, some of the time with Bokeh you may need to make selections and place items on separate layers. Fortunately, there are a number of tools right within Photoshop to assist the user to obtain good to great selections.

When you look at the controls for Bokeh, there are three options: Settings, Bokeh, and Vignette. The Settings is a collection of pre-made bokehs using different "famous" bokeh lenses and some stylizing options I'll get back to. The Bokeh tab is a chance for you to customize the appearance and how it's done. Above I was using the "None" for the focus region so that anything that's in the layer is effected.

bokeh controls

The Radial is when you want (for example) a face in focus (protected) and everything else in bokeh. You do have the ability to vary the radial from circle to a very sharp oval and the range of the "feathering" of the bokeh. Another example where Radial is advantages is when you need to focus part of the image to be in focus as shown below.

radial bokeh

An example of the Planar bokeh is shown below with the right side the original photo and the left side with bokeh. In the application of this approach you have a line with two ends that you can vary the vertical/horizontal aspect by dragging and you can very how long the bokeh transition is by simply dragging the line longer or shorter.

bokeh in depth

Bokeh can also do vignettes as shown below. Simply, this is just one more approach to force the eye to focus on part of the image. Without the vignette, the image is open and the eye is forced to the pelican on the pole, but by adding the vignette there is structure around the bird and it's not left drifting on the page.


The controls for vignetting also provide for color (of the vignette), intensity, and the amount of feathering. In a bit of confusing user interface, there is a tight integration between the intensity control inside Vignette and the rest of the application. One would assume that if you were working in the Bokeh tab, you'd not be seeing the effect of any vignetting. That is not the case and you have to manually bring the intensity down to zero. Meanwhile you have no control on where the focal center of the vignetting is located: it's always in the middle of the image. The only way to change this is to crop after processing the image.

Likewise, if you have the radial or line control from the Bokeh tab, you will see them when you go into the Vignette tab. So that you do not see them, you have to go back to the Bokeh tab and click on the "None" focus region radio button. I found this crossover of tool interaction confusing and unnecessary.

One dynamic that I found "not-for-me" is that you can alter the shape of the bokeh aberrations. Earlier I discussed how the number of the blades in a len's diaphragm will effect the shape of the bokeh. Since the aberrations in Bokeh are all software generated, Bokeh provides shape aberrations for either circles or hearts. Thus you can have heart-shaped aberrations around a wedding photo. There's obviously a calling for things like that but I'm not asking. Fortunately one does not HAVE to have these and there's lots left in Bokeh for curmudgeons like myself.

One other thing I really appreciate about Bokeh, is that when you click the OK button, a new layer is created in your image with the Bokeh alterations so that your original image remains untouched. Cool.

In short, Bokeh is not an inexpensive plugin. At $200, it's not for everyone. On the other hand, the results are vastly superior than what you can get from what people have been using (the Gausian Blur). Anyone who has a good photo but in need of better focus by blurring would be missing out some great options by passing on Bokeh.

My one strong wish would be an ability to create multi-sided objects for bokeh protection. The radial and planar controls are good, a multi-sided one would be better. Similarly, I'd like to see some control on the location of the vignetting foci. Lastly, I'd like to not have the cross-over of tools so that when I go into the Vignette tab, I do not see the controls from the Bokeh tab and when I'm in the Bokeh tab I do see the effects of the Vignette (unless I want both (e.g., an optional checkbox please)).

Even with these wishes and small limitations, I'm giving Bokeh a full 5 "A" rating because it does what it says it does and it does it well.

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___________ Gary Coyne has been a scientific glassblower for over 30 years. He's been using Macs since 1985 (his first was a fat Mac) and has been writing reviews of Mac software and hardware since 1995.

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