Portraits: Biggest Blur for the Buck

Nikon D600 + Nikon 85 1.8G.  f/1.8, 1/800, ISO 100

This question was posted on DPReview and I thought it is a useful question: "What is the greatest amount of blur you can get in the most compact package for portraits?"

Update: thanks to readers' suggestions, I added Fuji 56 1.2, Samsung 85 1.4, and Nikon 135 f/2.

Better Point-and-Shoot Shots with an External Flash

Last weekend, one of our friends celebrated their daughter's birthday party.  On this kind of occasion, I don't usually bring a DSLR anymore - I feel it is a little too much when we're not the celebrants.  Instead, I brought our trusty Lumix LX5 (reviewed here).  However, to get the best image quality out of the LX5, I paired it with an external flash, the Yongnuo YN-560EX (reviewed here).

Yes, the 560EX is a manual not TTL flash.  (I don't have a dedicated TTL flash for the Lumix LX5.)  However, using a manual flash while shooting run-and-gun is actually easier than it sounds.  (See: Therapy for TTL Addiction: How to Use Manual Flash).

In this post, I'll discuss my thought process in setting the flash and ambient exposures.

Panning Action Shots - Two Approaches

This weekend, we attended a fun birthday party where kids got to ride a zipline.  It would have been easy to freeze the action using flash, however I felt that a shot that captured the motion would more effectively convey the kids' excitement.  I used two approaches to do this. 

First Approach: Panning

The first approach is a more conventional approach, namely panning the shot.  Panning the shot means to use a slow shutter speed, then moving the camera in the direction of the subject's motion while taking the shot.  The effect is to keep the subject relatively sharp, while the background is blurred with motion.  Here's what it looks like:

The shot at the beginning is also an example of panning.  For both shots I used a shutter speed of 1/15.  Panning is quite challenging and sometimes, all you get is blur, like this:

To me, it's still more emotional than a sharp but completely static shot, but that's just my opinion.

Second Approach: Flash Blur + Panning

Another approach I used is to combine panning with flash blur.  Flash blur also uses a slow shutter speed to create blur, but keeps the subject sharp with the burst of flash.  More info on flash blur here.  Here's a sample shot:

For the flash blur effect to work as I intended, I underexposed the ambient, while keeping the flash on the subject normally exposed. If ambient is not underexposed, then the shot looks similar to regular panning.  I used shutter priority and selected a slow shutter speed of around 1/15.  I used exposure compensation to underexpose by about 1EV.  In Nikon, flash exposure takes exposure compensation into account, therefore I offset the underexposure with around +1 FEC.  Manual exposure would have worked as well: I would have selected 1/15 for shutter speed, then adjusted aperture until the light meter shows underexposure of 1 stop.  No offsetting FEC adjustments would have been needed.

With this flash blur approach, I got a much higher rate of acceptable shots.  The tradeoff compared to regular panning is that the background blur is less noticeable.

More samples of flash blur:

Sidenote: rear sync vs. front curtain sync
Usually, when using flash at slow shutter speed to show movement, using rear curtain produces a more natural result because the motion trail comes behind the subject.  I used rear curtain sync for the flash blur shots.  If you look at the background, you'll see that it's frozen, with the motion trail flowing to the right.  In this situation, because I was panning, I think front curtain sync would have looked ok too, though I didn't get to try it.

Flash Blur (Basic)

The shot above is an illustration of flash blur, where part of the subject is relatively sharp, but the subject's movement appears as a trail/blur.  It can be good or bad, depending on your intent.  The upside is that it definitely creates a feeling of movement.  The downside is the blurriness of the subject.

Whether you want to avoid flash blur or intentionally cause it, here's how it happens:
1. Exposure is set for normal exposure (not underexposure) of ambient light.
2. Shutter speed has to be slow.
3.  Flash is activated and the flash exposure is also normal.
4. Subject and/or camera have to be moving.

The flash freezes the subject's image either at the beginning of the exposure (front curtain sync) or at the end of the exposure (rear curtain sync).  In either case, the subject's movement becomes visible in the image from the slow shutter speed.  If the ambient is sufficiently underexposed, flash blur becomes imperceptible.

Here's another sample of flash blur:


Extreme case of flash blur (and not appropriate in this case):

Swing into focus (Basic)

Getting sharply focused images is a challenge for toddler photos. I want to capture shots of our toddler in all his joy and it is at those times when his movements are least predictable.  I tried out a few techniques to help improve focus.

Method 1: focus priority + hold down the shutter
I normally use the focus and recompose technique (select the focus point closest to the point of interest, half-press the shutter to acquire focus, recompose, then press the shutter all the way).  The problem with the focus and recompose technique is that there is an interval between the acquisition of focus and the release of the shutter.  When our toddler moves, as he frequently does, the focus is lost. 

Steps:

1. Switch to AF-S / activate focus priority. Some cameras like the D200 have a setting called "focus priority" (don't release the shutter unless and until the image is in focus). My D80 doesn't have such a custom setting but behaves as if it's on focus priority when I switch to AF-S (autofocus single).

2. Intentionally focus somewhere else first.  It seems the D80 has a threshold of acceptable focus that is not high enough for me.  In other words, sometimes it will consider the image in focus when I don't consider the image to be sufficiently focused. To avoid getting a shot that's not sufficiently focused, I intentionally put the image out of focus first by focusing somewhere else.

3. Put the focus point on the target and hold down the shutter. With the focus point over the now-blurred target, I hold down the shutter.  The shutter doesn't release immediately because it's on focus priority. However, as soon as the image is in focus, the shutter releases.

Method 2: AF-ON
The logic for this one is similar to the previous method but somehow, it seems I get better results with this method. I first customize the AF-L/AE-L button to AF-ON.  This means that pressing the AF-L/AE-L button will acquire focus. Pressing the shutter half-way no longer causes the camera to focus.

Steps:

1. Switch to AF-S / activate focus priority.

2. Intentionally focus somewhere else first.

3. Put the focus point on the target and hold down the shutter.

4. While holding down the shutter, hold down the AF-L/AE-L button. As soon as the image is in focus, the shutter releases.

Method 3: trap focus (aka focus trap)
Our toddler was playing with a swing and I used trap focus (which I read about at other sites) with some success to get shots of him on the swing. This one also requires customizing the AF-L/AE-L button to AF-ON.

Steps:

1. Switch to AF-S / activate focus priority.

2. Put the subject at the target distance and focus. In my case, I grabbed the swing with my free hand, held it in the position I wanted for the shot, then focused using the AF-L/AF-E button.

3. Allow the subject to move.  The subject comes out of focus.

4. Keep aiming the focus point at the same target you chose in #2. In my case, the eyes.
5. Hold down the shutter.  The shutter doesn't release immediately because it's on focus priority.

6. Wait for the subject to come into focus.  As soon as the subject moves into the distance where it comes into focus, the shutter releases.