Using your lens’ bokeh as a design element

In previous articles we could see how a fast 85mm can be used for shallow depth-of-field to shoot nearly anywhere by melting away the background. There’s another aspect to this – the bokeh of the lens. The bokeh is a reference to how the quality of the background blur is rendered by a lens. It can be smooth, or have “jittery” patterns to the edges of objects, and the highlights.

Do note though that bokeh and shallow depth-of-field are not quite the same thing. While the DoF / choice of aperture does affect the appearance of the bokeh of a lens, the shallow depth-of-field look isn’t “bokeh”. Similarly, you can’t do something like “add more bokeh”. Bokeh is the quality of that background blur. It’s mostly an aspect of the lens design.

Now, very often, when a fast prime lens is used wide open, there’s a kind of swirly feel to the background blur – and if you’re aware of this, and find an appropriate background, it can really accentuate the portrait.

The image at the top of Jen & Corby, was shot at f/1.4 and you can see how the background behind them has a distinctive circular swirl to the out of focus high-lights.

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aperture and depth of field

A question that came up in the forum recently was whether an 70-200mm f4 zoom would give you the same kind of look that an f2.8 zoom would.

For me, the f2.8 aperture is essential, especially with a telephoto zoom. For the same scenario, it gives me a higher shutter speed than the f4 zoom. Or I can use a lower ISO. More importantly, since I often bounce flash in large areas, the f2.8 aperture gives me more chance of successfully bouncing my flash than an f4 aperture would.

But what does the change in depth-of-field look like?

Keeping in mind that the how much the background appears to be blurred, depends on a few things:
– the chosen aperture. The wider the aperture, the shallower the depth-of-field will be, giving a more blurry the background. (This is the main factor that affects how much the background will be blurred.)
– how far your subject is from the background,
– your chosen focal length.
– The bokeh of the lens will also affect whether the background appears more blurred, or less. (Note that bokeh and shallow depth-of-field are not the same thing.)

The change in depth-of-field is incremental. If you had to look at a photograph showing amazingly thin depth-of-field, you wouldn’t be able to tell just from the photograph alone, whether f2 was used or f2.8 … but a side-by-side comparison will reveal the answer. An individual image won’t. However, it will be obvious when an image was shot at f 8 or f11 (on a 200mm lens for example), compared to either f2 or f2.8 … we should be able to recognize that a shallow depth-of-field was not used on the f8 or f11 image.

There are hordes of examples of how depth-of-field changes with aperture. But I thought it might be interesting to see with an overlay of images, just how much the depth-of-field appears to change …

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creating a background with narrow depth-of-field & great bokeh

I met up with my favorite model Anelisa yesterday in New York, specifically to shoot images for a more extensive review of the Nikon 85mm f1.4G AF-S lens. And then it struck me how pointless it is in a way. This is truly a superb lens. It improves on the legendary Nikon 85mm f1.4 AF-D lens in some key areas. (For me the updated lens was an immediate upgrade.)

But ultimately, you could get similarly beautiful images with any short portrait lens that gives you a very narrow depth-of-field AND has great bokeh. (Just to reinforce that again .. narrow DoF and bokeh are not the same thing. But I digress.) So, whether you’re shooting with a Nikon 85mm f1.4 lens (B&H), or the Canon 85mm f1.2 (B&H), or Canon 85mm f1.8 (B&H) … these images are easily attainable. It is more about the technique and thought-process and approach, than any specific piece of equipment. However, you do need photo equipment that enables you to achieve what you want to, technically and stylistically.

So walking around with Anelisa, looking for great backgrounds I saw this fantastic Art Deco styled exterior of a diner. And I knew that with the various colors and shadings in the late afternoon, it would give beautifully colored reflections at various angles. Here is the pull-back shot …

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bokeh – a few notes

October 26, 2010

bokeh – quality of lens blur

The way that a specific lens renders the out-of-focus areas in the background (ie, the bokeh of the lens), is always an interesting aspect of any lens’ behavior. If the out of focus areas show hard edges, or highlights with a kind of double edge, then the bokeh can appear intrusive. Then it is called harsh bokeh. If the out of focus areas are smooth without the edges being defined, then the bokeh is described as being pleasant. And then on occasion, you get bokeh that is … well, let’s just call it ‘interesting’.

I noticed that the Nikon 105mm f2.8 VR macro (B&H) can at times show a weird circular swirl in the background. It is especially noticeable if there are bright out of focus highlights. The photo at the top shows this clearly, even with a background that should appear smooth. In comparison, we can see how the famed Zeiss Makro-Planar T* 100mm f/2 ZF (B&H), renders the highlights. Smooth. Just as you’d expect from a lens with such a reputation.  (Both images were shot at f2.8 although the Zeiss is capable of f2 which is exceptional for a 100mm macro lens!)

Just for interest here, I thought of showing how a few other lenses compare in how they render the background …

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shallow DoF / depth-of-field is not the same thing as great bokeh

The first thing you might notice in this image is our super-cute model, Johannie.

Next you will probably notice either:
- the strange background pattern, (due to this lens’ bokeh),
- or the wafer-thin depth-of-field of the Nikon 50mm f/1.4D used wide open
- or the lighting on her, (a reflector),

These are all inter-related in some way for this photo …

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