As human being we often fall prey to being creatures of habit. I’ve certainly found this to be the case when I’ve gone out to photograph birds in flight. I invariably set my Nikon 1 V2 to the typical settings I use, which includes using AF-C at 15 fps. Until recently I never really thought about the interrelationship between the rhythmic motion of a subject and frame rate.
I don’t know why this was not apparent to me earlier (old age perhaps?), but when I was selecting images for my recent terns hovering article it became glaringly obvious that the wing positions of the tern repeated about every fifth frame of my AF-C run.
NOTE: Click on images to enlarge.
Shooting at 15 fps was certainly helpful in terms of getting images of the subject bird positioned correctly in the frame, but that speed did not necessarily generate as many unique wing positions as may have been expected. This all comes down to how the speeds of the natural rhythmic motion of the tern’s wings when it is hovering and the frame rate I used with my Nikon 1 V2, intersect in terms of image capture.
When shooting larger birds like pelicans flying, a 15 fps frame rate yields a higher number of unique wing positions since the rhythmic motion of the pelican’s wings is much slower.
Some of these types of images can certainly be captured as single frames if a photographer times their shots well.
As readers who have been following some of my recent articles will know, I’ve been experimenting with shooting moving birds at 60 fps. When using my Nikon 1 V2 at this frame rate, or at 30 fps, AF-C is not possible. At these higher frame rates the first frame locks focus for the balance of the run of images. Through some experimentation I’ve found that since the action happens so quickly having the first frame locking the focus isn’t an issue at all for certain types of images, especially when shooting at 60fps.
For example, capturing a run of images of a bird landing or leaving a static position, like the gull launching out of the water in the following three images, is an ideal use of a 60 fps frame rate.
Since the 40 image buffer on my Nikon 1 V2 fills in 2/3 of a second when shooting at 60 fps the bird typically has not moved far enough to cause it to go out of focus even it if is approaching the camera. The timing of your image run is critical when shooting at 60 fps, and it does take some additional concentration.
Locking focus based on the first frame is also a non-issue when a subject is moving at right angles to your camera. In these situations using a fast frame rate like 60 fps with a Nikon 1 V2 can yield a good range of differing images as you can see in the four frames below.
The four images above were captured at 60 fps. It is interesting to note that if I would have shot this same cormorant taking off from the surface of the water at 15 fps in AF-C (which would have been my typical setting) I would have missed 3 of the 4 images shown above.
Let’s look at six consecutive images of a tern hovering. These were captured at 60 fps.
As noted earlier, when I captured terns hovering using a frame rate of 15 fps, the resulting images had recurring wing positions about every fifth frame. When shooting that same tern behaviour at 60 fps the burst yielded recurring images every fifteenth frame. This obviously gives a photographer a much broader selection of subject composition options in the resulting stream of images. And, since the tern was not physically moving closer to the camera while it was hovering having focus locked by the first frame was not an issue at all.
Using a mirror-less camera like a Nikon 1 V2 can provide photographers with more frame rate options than would be the case with a typical DSLR. With a V2 these include single frame, AF-C at 5 fps, AF-C at 15 fps, 30 fps and 60 fps.
Selecting different frame rates depending on the objective of the photographer can have a large impact on the variety of images that can be captured, and may also yield images that were not possible (other than through luck) when shooting at slower frame rates.
On a personal basis I will be shooting my Nikon 1 V2 at 60 fps on a regular basis when shooting birds in flight. I’ll also be using single frame and 15 fps AF-C settings depending on the subject, its speed and direction, and my image objectives.
My intent is to keep this photography blog advertising free. If you enjoyed this article and/or my website and would like to make a modest $10 donation through PayPal to support my work it would be most appreciated. You can use the Donate button below. Larger donations can be made to firstname.lastname@example.org through PayPal.
Article and all images are Copyright Thomas Stirr. All rights reserved. No use, duplication or adaptation of any kind is allowed without written consent. If you see this article reproduced anywhere else it is an unauthorized and illegal use.
One thought on “Rhythmic Motion and Frame Rate”