THE PRIME PORTRAIT: THE DIFFERENCE BETWEEN F/2.8 AND F/1.4

My lens assortment has grown and evolved throughout my career. I started
with all prime lenses, as they were optically superior during that time. But
zoom quality improved, and I started using two main lenses: 24–70mm and
70–200mm, both f/2.8. Optically, they were sharp, and the convenience
of zooming through the focal lengths was terrific. Every five years or so, a
sharper, quicker auto-focus version would come out, and I’d be first in line to
upgrade. With these two lenses, I was good to go.

But reviewing images after assignments and travel workshops,
I realized I was missing something. I longed for
the silky, soft bokeh that only a fast prime could produce.
Wouldn’t my f/2.8 zoom lenses produce about the same
quality of bokeh as f/1.4? Would using a fast prime lens
for my portrait create a better shot?
Obviously, there are a lot of differences beside maximum
aperture between zooms and primes. Size, weight, cost,
sharpness, and focal range all come into play when deciding
which lens to use. But one simple fact remained: Most of my
prime lenses were two full stops faster than my zooms, and
this would affect background quality and image separation;
but by how much.
Scenario One: I really wanted to focus on bokeh quality
at different apertures for this shoot. With that in mind,
I decided to use a selection of prime lenses at f/5.6–f/1.4.
I also wanted to see what other advantages or disadvantages
might crop up between apertures. I chose an alleyway
with lots of depth to best illustrate bokeh differences.
We were shooting in mid-morning light with bright sun
overhead. Every photographer knows that bright sun isn’t
ideal for portraits, so to deal with the harsh light, we broke
out one of my favorite lighting accessories, the Sun-Swatter
(made by California Sunbounce Pro). The Sun-Swatter is a

4×6′ overhead diffusion panel that can be held easily and maneuvered by one
person. Even in windy conditions, this scrim is terrific for producing beautiful
soft, diffused light. We placed our model, Katrina, in the middle of the alley
with rows of flowers and light posts behind her for the first image.
I started shooting at f/1.4 using my 85mm. This lens is one of my favorite
prime portrait lenses, and looking at the LCD, I was elated to see the painterly
quality of the background shooting at f/1.4. I was using my Nikon D500 in
aperture priority mode for the images. I started to change aperture settings,
shooting at f/2.8, f/4, and f/5.6.
Hands-down, the mood, quality, and separation of f/1.4 were preferable
to f/5.6. But when comparing f/1.4 to f/2.8, there was less difference. The
f/2.8 version had a little more detail, but what I really noticed was the bokeh
quality. The f/1.4 image looked softer and a better choice for a flattering portrait.
Since I was shooting in available light using the Sun-Swatter, changing
exposures was easily accomplished by simply changing the aperture setting in
aperture mode. But my shutter speeds were around 1/3200. Shooting flash
was going to require some special techniques.

Scenario Two: One reason I drifted away from shooting
portraits at f/1.4 outdoors was the challenge of using flash.
Speedlights could work at 1/3200 in High-Speed Sync
(HSS) mode, but power output was greatly reduced. Two
things changed that made shooting HSS portraits with
speedlights much easier. First, softboxes started accommodating
multiple speedlights to overcome the reduced
power output in HSS mode. And second, wireless flash

using a radio signal became standard, allowing hassle-free
flash triggering in bright sunny conditions.
To further explore the prime lens question, I decided to
photograph Katrina using a 30″ FourSquare softbox and
a 50mm f/1.8 prime. The FourSquare box allows up to four
speedlights to be used; I used three Nikon SB-5000s with
dome caps attached inside the softbox. The dome diffusers
spread the light throughout the softbox for clean, even
lighting when the flash exits the softbox. I attached my
WR-R10 radio transmitter to my D500. Using this radio
transmitter, I didn’t have to worry about line of sight to my
flashes, or interference from the sun.
Using a variety of apertures with the softbox, once again
I discovered shooting at f/1.8 was preferably to shooting at
f/2.8. Even though there was just over a one-stop difference,
the background looked better wide open. But is this enough
to justify paying big bucks for a prime? I wanted to try one
more scenario before I made my decision.

Scenario Three: Speedlights have approximately 60 watts of power, so
using three SB-5000s roughly equates to 180 watts of power. I wanted
more power so I could use a larger softbox and underexpose the ambient
light for better separation. For this task, I set up my Elinchrom ELB 400
(using a Quadra HS head), specifically designed for Hi-Sync photography.
Unlike HSS, which uses a strobic flash mode, Elinchrom Hi-Sync retimes
the shutter and flash pop to ensure flash at very fast shutter speeds. I’ve
found that by using this setup, I can shoot at 1/4000 with beautiful light
on my subject. I attached a 39″ Elinchrom Rotalux Octa softbox to the
HS head, and used the Elinchrom EL-Skyport Plus HS transmitter to trigger
the strobe. I switched up lenses again, this time using a 35mm, f/1.4 prime
lens. We moved locations to another alley with gritty brick walls to illustrate
changes in bokeh.
Once more I photographed Katrina using apertures from f/1.4–f/5.6.
One difference for this shot was that I underexposed the background by
one stop, which further emphasized the separation shooting at different
apertures. I made an interesting discovery using a wide-angle prime at
f/1.4: Shooting wide open made a bigger difference when compared to the
other prime lenses in my testing. Why? Because more of the background

was visible behind the subject, and
changes in depth of field and bokeh
were more obvious. In other words,
the background made up more of
the image using a wide-angle lens.
I liked the f/1.4 images much more
than I did the f/5.6 shots when
shooting with a wide-angle prime
lens. Combined with the softer
quality of light using the larger softbox,
these images were my favorite
from the shoot.
Another point became very
obvious during this shoot: Photographing
at f/1.4 requires perfect
focus technique. I needed to put my
focus point right on my model’s eye;
otherwise, I would have soft images.
If she wasn’t facing the camera, I knew one eye would be
slightly softer than the other. Shooting tight with an 85mm,
my subject’s eyes were sharp while her nose and ears were
slightly blurred due to the extreme shallow depth of field.

Time to Prime?
Do you really need that f/1.4 prime lens for the best portrait?
The answer is, “It depends.” Based on my testing, I
found I really preferred the bokeh using my 35mm wideangle
prime at f/1.4 compared to f/5.6. Using my 85mm
prime at f/1.4 vs. f/5.6, there was also bokeh difference; but
with less background visible at 85mm with tight head shots,
I’d probably be just fine using my trusty 70–200mm shooting
at f/2.8. Yes, I like the bokeh better at f/1.4 using my
85mm, but investing in this prime lens if you already owned
a 70–200mm f/2.8 might make you pause. On the other
hand, if you like shooting environmental portraits, I really
preferred the bokeh at f/1.4 using the 35mm prime, and
purchasing this lens was an easier choice for me.
Another point worth mentioning is that f/1.8 primes
are almost $1,000 cheaper than their f/1.4 counterparts.
There’s only a 2/3-stop difference, which means there
won’t be much difference in depth of field. But not all
bokeh is equal, and individual lenses produce different
qualities of bokeh.
As photographers know, depth of field and bokeh are
just one part of getting a great portrait. Cameras, lenses,
and flash are tools that help bring our vision to reality. Subject,
location, rapport, and emotion are also critical aspects
of good portraiture. But now that I own a couple of prime
lenses, I can’t blame my equipment for a bad shot. It’s up to
me to create the evocative portrait of my subject

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