I've been meaning to make this post for a while, but finally got around to it. This is intended to address a personal pet peeve.
A word that gets thrown around a lot in photography is "Bokeh". It's a word that's often used to simply refer to a photo with shallow depth of field where the subject is in focus and the background is out of focus.
That's actually not a correct use, however. Bokeh is derived from a Japanese word that means "blur", however it is a term that refers to what the out of focus area looks like.
Bokeh is a characteristic of a particular lens, and there are a lot of very subjective terms that get thrown around like "creamy" or "smooth" or "busy" to describe it.
In general, though, the smoother the rendering of things like points of light in the background, the more aesthetically pleasing the bokeh is often considered to be. There are a few general rules that may give you some idea of what makes for "good" or "bad" bokeh, although this is by no means absolute. Subjectively "good" bokeh is often the result of residual uncorrected abberation in a lens(particularly spherical abberation). Here are a few I can think of:
1. Generally, the larger the aperture, the more potential a lens has to produce pleasing OOF areas
2. Telephoto lenses tend to universally be good, often for their relatively simple optical design
3. Along with that, often times simple lenses are good for good bokeh, although again this isn't hard and fast.
4. Going with my point about uncorrected spherical abberation, lenses that use things like aspherical elements(which are designed to correct speherical abberation in large aperture lenses) can end up with busier bokeh.
I took several photos this afternoon with varying lenses with different properties to try and illustrate this. Since it was cold outside today, you get to see a boring photo of Kentucky's finest soft drink, Ale-8-1, sitting on the windowsill with my back yard in the background.
In any case, here's a sort of classic example. This is a manual focus Nikon 105mm f/2.5 lens, a staple of the line-up for years. As a minor point, there are two different optical formulas for this lens. This is the older formula, which is in a "chrome nose" body-I slightly prefer its rendering, although in these examples I couldn't see a difference so you're only getting one
With that said, there are areas where it could be called a bit "busy" so let's go to something different that might render a bit smoother-this is my 70-200mm f/2.8 AF-S VR, a fairly complicated lens but one that still retains really smooth bokeh thanks to its large aperture and long focal length. Notice how the background essentially melts into just a smooth, even rendering of the grass and a very blury transition to the shed outback.
To go the other way, though, let's look at a couple of other modern f/2.8 zooms-the 24-70mm f/2.8 AF-S, and the 14-24mm f/2.8. Often, wide angle lenses in particular are not as pleasing
Even wider primes aren't immune to "busier" bokeh. Here is another Nikon legend, the 35mm AI-s f/1.4. This lens has a large aperture and loads of uncorrected spherical abberation, but it's still not particularly great. I suspect that some of Nikon's advanced tricks-in particular the floating element("close range correction") play into that somewhat.
Although the background is nicely out of focus, the bokeh of this lens has one fatal flaw. Notice that OOF highlights are rendered as bright "rings"-often the opposite is desired where the light has a more Gaussian type distribution toward the center of the disk. This can make the bokeh of this lens somewhat distracting.
I don't have any truly terrible lenses easily accessible. One of the worst designs for this is the reflex(or mirror) lens, which use to be common because it's a cheap way to get a really light and small telephoto(500mm is common) but they tend to render points of light as "donuts."
I'll wrap this up though with an example of a lens that has what some might call distracting but I call interesting Bokeh. This is a Lensbaby Twist 60, which uses one of the oldest computed(rather than trial and error) lens formulas called the Petzval. When these lenses first came on the market in the ~1890s, they had some of the best center sharpness around, but not a particularly flat field. What's more of note, though, is that they tend to render what's often called "Swirly" bokeh-I think you can see it clearly in this photo. This is something of a signature of Petzval lenses(although I've also seen it in a few other more advanced formulas, like the Auto-NIKKOR-S 5,8cm f/1.4) although there are other designs with their own signature bokeh.
A word that gets thrown around a lot in photography is "Bokeh". It's a word that's often used to simply refer to a photo with shallow depth of field where the subject is in focus and the background is out of focus.
That's actually not a correct use, however. Bokeh is derived from a Japanese word that means "blur", however it is a term that refers to what the out of focus area looks like.
Bokeh is a characteristic of a particular lens, and there are a lot of very subjective terms that get thrown around like "creamy" or "smooth" or "busy" to describe it.
In general, though, the smoother the rendering of things like points of light in the background, the more aesthetically pleasing the bokeh is often considered to be. There are a few general rules that may give you some idea of what makes for "good" or "bad" bokeh, although this is by no means absolute. Subjectively "good" bokeh is often the result of residual uncorrected abberation in a lens(particularly spherical abberation). Here are a few I can think of:
1. Generally, the larger the aperture, the more potential a lens has to produce pleasing OOF areas
2. Telephoto lenses tend to universally be good, often for their relatively simple optical design
3. Along with that, often times simple lenses are good for good bokeh, although again this isn't hard and fast.
4. Going with my point about uncorrected spherical abberation, lenses that use things like aspherical elements(which are designed to correct speherical abberation in large aperture lenses) can end up with busier bokeh.
I took several photos this afternoon with varying lenses with different properties to try and illustrate this. Since it was cold outside today, you get to see a boring photo of Kentucky's finest soft drink, Ale-8-1, sitting on the windowsill with my back yard in the background.
In any case, here's a sort of classic example. This is a manual focus Nikon 105mm f/2.5 lens, a staple of the line-up for years. As a minor point, there are two different optical formulas for this lens. This is the older formula, which is in a "chrome nose" body-I slightly prefer its rendering, although in these examples I couldn't see a difference so you're only getting one
With that said, there are areas where it could be called a bit "busy" so let's go to something different that might render a bit smoother-this is my 70-200mm f/2.8 AF-S VR, a fairly complicated lens but one that still retains really smooth bokeh thanks to its large aperture and long focal length. Notice how the background essentially melts into just a smooth, even rendering of the grass and a very blury transition to the shed outback.
To go the other way, though, let's look at a couple of other modern f/2.8 zooms-the 24-70mm f/2.8 AF-S, and the 14-24mm f/2.8. Often, wide angle lenses in particular are not as pleasing
Even wider primes aren't immune to "busier" bokeh. Here is another Nikon legend, the 35mm AI-s f/1.4. This lens has a large aperture and loads of uncorrected spherical abberation, but it's still not particularly great. I suspect that some of Nikon's advanced tricks-in particular the floating element("close range correction") play into that somewhat.
Although the background is nicely out of focus, the bokeh of this lens has one fatal flaw. Notice that OOF highlights are rendered as bright "rings"-often the opposite is desired where the light has a more Gaussian type distribution toward the center of the disk. This can make the bokeh of this lens somewhat distracting.
I don't have any truly terrible lenses easily accessible. One of the worst designs for this is the reflex(or mirror) lens, which use to be common because it's a cheap way to get a really light and small telephoto(500mm is common) but they tend to render points of light as "donuts."
I'll wrap this up though with an example of a lens that has what some might call distracting but I call interesting Bokeh. This is a Lensbaby Twist 60, which uses one of the oldest computed(rather than trial and error) lens formulas called the Petzval. When these lenses first came on the market in the ~1890s, they had some of the best center sharpness around, but not a particularly flat field. What's more of note, though, is that they tend to render what's often called "Swirly" bokeh-I think you can see it clearly in this photo. This is something of a signature of Petzval lenses(although I've also seen it in a few other more advanced formulas, like the Auto-NIKKOR-S 5,8cm f/1.4) although there are other designs with their own signature bokeh.
