On my previous post, we listed the best portrait lenses to own. But what exactly does one look for when comparing portrait lenses?
We looked at the 50mm, 85mm and 135mm. We explained that the 50mm is considered the standard lens since this has the same field of view that the human eye sees. So like the human eye, you can also see a lot more of your subject including the background.
Longer focal lengths (FL) like the 85mm and 135mm produce tighter fields of view and will tend to compress the background and foreground to make it appear that the background is closer than it actually is. It also makes objects farther in the background appear larger. This all becomes more apparent in location shoots where you have to work with a scene.
So depending on your type of work you can choose the best FL that suits your style of shooting.
Aside from the focal length differences, what other characteristics should one look at?
the visual quality of the out-of-focus areas of a photographic image, especially as
rendered by a particular lens.
The word comes from the Japanese language which means "blur".
In these set of photos I took of my motorcycle, I placed the focus point over the Triumph sticker. So this area should remain sharp as well as any surface that is in the same plane as this sticker. Surfaces outside of this plane will be out of focus (i.e. anything before or after the sticker and the windscreen will be out of focus).
Notice the circular blobs or out of focus areas on the left side. Some people would call this bokeh pleasing to the eyes while others may consider it too busy. It's really very subjective.
This image was taken with a Nikon D750 and the 50mm lens at it's widest aperture of f1.4
The next image below was taken with an 85mm f1.4G also at it's widest aperture of f1.4. Now compare the bokeh of the image below to the one above.
Which one is more pleasing? This is a very subjective question. But I think we can all agree that the out of focus (OOF) areas or bokeh from the 85mm 1.4G is more blurry (blurrier?) than the one from the 50mm. For me the 85mm 1.4G bokeh is more pleasing than the 50mm 1.4D bokeh. Also notice that the features in the background of the 50mm lens appear to be bigger in the 85mm lens. This is just an effect of the telephoto lens.
But the drawback is the need for critical focus when shooting with the 85mm. Longer focal lengths tend to magnify movement or camera shake compared to shorter focal lengths. Add to this variability is when shooting people and the subject's movements causes more blur. Just something to consider.
These last set of photos were all taken with the newcomer- the 135mm F2 DC lens. As mentioned in the previous post, this lens has the ability to adjust the front or rear out of focus areas.
In these set of photos, I made adjustments to the rear defocus control. First setting is at the center point.
Second image is with R2 setting.
Third image with R2.8 settings.
For most people, these settings don't really mean much. The bokeh is pretty good in all the images and the differences in the defocus control settings are almost negligible.
However, between the 85mm F1.4 and the 135mm F2, it appears that the bokeh of the 135mm F2 is smoother than the 85mm. Again it's a subjective opinion, but I've worked with the 85mm long enough and the quality of the images produced by the 135mm is just different.
The 135mm F2 DC lens is a very specialized lens with a feature added in for those who are very picky about their backgrounds. So for serious portrait shooters who do a lot of location work, this will be a good lens to have.
Not going to talk about sharpness that much since almost all lenses even kit lenses are sharp when properly used. It all boils down to technique and how you acquire focus - do you do focus and recompose, do you have your focus dot always on the subject's face, are you always shooting at the widest aperture, etc. Sharpness for me is a matter or technique, so it's always best to test your lens before you do any shoots. It's also possible a lens may be back or front focusing, in which case this adjustment needs to be made in the camera.
The glory of 70mm is the sharpness of the image it offers - K. Branagh
So for me, the quality of the out of focus areas is a better characteristic to review on a lens than it's sharpness.
In summary, the 50mm lens is the most versatile, easiest to use and offers the best value for portrait lenses. But in terms of bokeh quality, the 85mm and 135mm lenses are still the kings and offers portrait photographers an excellent creative tool to work with.