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Background Blur (Bokeh)—NOCT-Nikkor vs Canon 85/1.2L

Last updated August 01, 2005 - Send Feedback

Minimizing depth of field in order to produce a silky-smooth background is an excellent tool for isolating a subject and making it “pop”.  Depth of field is reduced with increasing magnification (focusing closer), increasing focal length (100mm vs 50mm), and wider aperture (f1.2 vs f2.8).

Magnification is not a choice; instead, one composes for the subject matter; the magnification is whatever it happens to be.  The aperture used is a choice, but a lens can only be “opened up” to its maximum aperture, which is no faster than f1.2 for any commercially available lens for Nikon or Canon.

The choice of focal length is related to sensor size, in that a particular field of view at a specified distance requires a specific focal length which depends on the sensor size. This is the so-called “focal length multiplier”, a misleading term, but one which reflects the fact that shooting a 2/3-frame camera like the Nikon D2X requires a shorter focal length lens to achieve the same field of view as on a full-frame camera like the Canon EOS 1Ds Mark II.

A consumer digicam, with its tiny sensor, has a focal length range something like 5.8-17mm. Its maximum aperture is rarely larger than f2.8.  Thus, it suffers from both a very short focal length and “slow” maximum aperture, both of which maximize depth of field; no pleasing background blur can be achieved.

Excerpt

This page is an excerpt from the D2X vs EOS review now part of DAP.

The full review includes a full version of this page, with the following aperture series as 1024-pixel-wide images (and maximal-quality JPEG compression):

D2X+NOCT-Nikkor:  1.2, 1.4, 2, 2.8, 4, 5.6, 8, 11
Canon EOS 1Ds Mark II + 85mm/f1.2L:   1.2, 1.4, 1.6, 1.8, 2, 2.8, 4, 5.6, 8, 11

The NOCT-Nikkor and the Canon 85mm/f1.2L

How pleasing is the out-of-focus background on the 2/3-frame sensor of the Nikon D2X using the 58mm/f1.2 NOCT-Nikkor compared with the full-frame sensor Canon EOS 1Ds Mark II using Canon’s 85mm/f1.2L? (the 85mm/f1.2L “II” USM is the current model, this article used the original version).

The 58mm and 85mm provide a nearly-identical field of view when used on their brands' respective sensors (58 * 1.51 = 88mm), and both are f1.2, the fastest aperture available for Nikon or Canon today.  Thus, these two lenses are an ideal match for answering this question.  They were also chosen because they offer nearly ideal focal lengths for portraiture.

When considering background blur, the comparison should take into account both the amount of blur and its bokeh, or the smoothness and pleasantness of the out-of-focus areas. Bokeh is a subjective quality that is highly valued by some photographers.

The NOCT-Nikkor may be found used on ebay (from $1200 to $2400 US, depending on condition), and is a manual-focus lens.  The 85mm/f1.2L may still be purchased new for about $1500. [Canon offered a 50mm/f1.0L for a period of time, but it is no longer available, and never had a reputation for sharpness].

It should be noted that the NOCT-Nikkor displays very strong curvature of field, even at infinity focus, a property which may be used to advantage in further isolating the subject, but which makes the lens a poor choice when planar (flat) subjects are photographed.

The test scene

Exposure for the shots on this page was identical for both cameras; the different contrast and color characteristics are evident, though this is influenced by the raw processing software (Nikon Capture and Digital Photo Professional).  White balance was set using the partially-obscured white patch on the Macbeth Color Checker card.

I found an agreeable fellow who stayed put long enough to shoot a full aperture series on each camera.  The background was chosen to include distracting elements, including the wicker basket, some color objects, some vertical poles, and some bright spots.

It might seem silly to stop down an f1.2 lens very far, there being smaller, lighter and cheaper f1.4/f1.8/f2 optics available. However, a 1/8000 second shutter speed might not be fast enough under some daylight or studio conditions.  Also, f8 or f11 might be desirable and there is no reason to eliminate either of these lenses from consideration simply because they have an f1.2 maximum aperture.  Also, with some lenses, the out-of-focus image rendition can be very pleasing at wider apertures, but less pleasant when stopped down (though this excerpt shows only f1.2 and f1.4).

Aperture series

Show below are results at f1.2 and f1.4.  The full aperture series, with 1024-pixel-wide originals, is part of the diglloyd D2X vs EOS review in DAP.


f1.2
TOP: 1Ds Mark II with 85mm/f1.2L
Bottom: Nikon D2X with 58mm/f1.2 NOCT-Nikkor

The longer focal length of the 85mm/f1.2L show more background blur.  Background objects have become large diffuse circles.  However, the NOCT-Nikkor is producing an equally pleasing, if not more pleasing effect, producing out-of-focus background elements which have smoother transitions from light to dark, whereas the 85mm/f1.2L shows outer rings of brighter tone.  My preference at f1.2 is the NOCT-Nikkor.



f1.4
TOP: 1Ds Mark II with 85mm/f1.2L
Bottom: Nikon D2X with 58mm/f1.2 NOCT-Nikkor

While the 85mm/f1.2L clearly has more background blur, some of the out-of-focus highlights again have more defined edges than those of the NOCT-Nikkor.  Though the 85mm/f1.2L image has greater blur, it does not have the same creamy-smooth rendition that the NOCT-Nikkor is showing.  However, the NOCT-Nikkor does show one bright ring in the upper right, and its increased depth of field counteracts the effect.

Conclusions

A larger sensor offers increased background blur, due to the use of a longer focal-length lens to achieve the same field of view. 

However, background blur is only one element of the “look” of the out-of-focus areas.  This look is called bokeh and is one factor that distinguishes a lens that is merely sharp from one that is sharp and lovely.  The bokeh of the 85mm/f1.2L is not quite as pleasing as the NOCT-Nikkor.  The latter produces creamy-smooth rendition, whereas the 85mm/f1.2L produces harsher transitions. 

I favor the NOCT-Nikkor for its smoother transitions on out-of-focus highlights, but when shooting EOS bodies both the NOCT-Nikkor and the 85mm/f1.2L may be employed (using an adapter for the NOCT-Nikkor).  Unfortunately, Nikon users cannot use Canon lenses due to an incompatible flange to focal length distance.

If your photographs involve selective focus such as head or torso shots of people with a pleasantly blurred background, the Canon 85/f1.2L is a very good choice, and autofocus is a huge plus. Canon’s 35mm/f1.4L has excellent bokeh, and may be another option for Canon  shooters when a short focal length is appropriate. The 135mm/f2L is also a good choice.

Nikon shooters who are willing to use manual focus may want to obtain a used 58mm/f1.2 NOCT-Nikkor. Comparisons of the NOCT-Nikkor to the Nikon 50mm/f1.4D show that the NOCT-Nikkor produces more pleasing image rendition.

My experience on the Nikon D2X shows that in spite of the increased depth of field produced by the use of shorter focal length lenses, very pleasing background blur may be achieved.  Suitable lenses with pleasing bokeh include the 35mm/f1.4 AIS, the 70-200/f2.8VR, the 85/f1.4, the 200VR and others.  In short, pleasing bokeh does not require the use of a full-frame camera.

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