Timing A Photograph; Shutter Lag; EVF Lag; What Do These Mean For The Fuji X-T2?

We hear about shutter lag.  We hear about electronic viewfinder (EVF) lag.  We hear about autofocus lag.  We hear about all kinds of electronic, mechanical as well as human factors that can cause our images to be made, not the split second when we really want them to be made, but a fraction of a second later.  In most photography, these problematic lags won't make a bit of difference, but if you are trying to capture the "peak" of action, learning about and understanding your camera can make a difference between capturing that peak moment and missing it.

In the case of a moving object, I wanted to understand for myself if there is a lag in what I see, and where I see it, in the EVF of my Fuji X-T2 and what and where that object may be in reality.  In the past, EVFs have been notorious for providing the photographer a view that has already passed.  In other words, when looking through your EVF you might see a runner at one particular spot, when in reality the runner has passed that spot because the lag in the transmission of the image onto your EVF lags for a short time.  The other type of EVF lag occurs when making several exposures in quick sequence.  The EVF can blackout and/or produce a time lag and you cannot accurately track your subject. You almost have to guess where your subject is if you are panning along with it. 

Additionally, I wanted to know how much shutter lag there may be with my X-T2.  Along with those two issues, I wanted to know if autofocus, with shutter button pressed halfway as I would anticipating an image, is causing any delay when actuating my shutter.  How do I find out of that stream of potential problems are real or not?  Test them.

Granted, these are rudimentary in nature and have minimal validity to real life.  But the tests are within my capabilities as I am without scientific measuring devices.  But still, I wanted to understand how shutter lag and any lag in seeing my moving subject while looking through the electronic viewfinder (EVF) affected the timing of a photograph I may want to take.  If I learn the intricacies of my gear, I can compensate.

Thinking about this I set up an easy test and a real life test.  The easy tests would consist of photographing the smoothly moving second hand in a clock app on my iPad (not the type of second hand that moves/stops for a second/moves/stops for a second, etc.) trying to press the shutter at the exact time I saw the second hand reach a line beneath one of the numbers on the clock face.  That would give me an idea of how long of a lag there is between the time I saw the second hand reach the line and when the shutter exposes the image.  I decided to do this two ways, both with the shutter button pressed half-way as I would typically have it when anticipating a moving object, one with autofocus engaged and the other with manual focus to ascertain if there was any difference in timing when the AF mechanism is in the chain of events.

The other test would be to go out and try to capture a moving subject at a specified point to find out if any shutter/EVF lag I encountered in the first test really affected a real life subject.  

One variable that I can't measure is my reaction time.  It varies slightly, I'm sure so I took 20 images for each test to determine an average or "typical" result.  I thought a sample of 20 should be sufficient.

Here are the tests I conducted:

a) First test is to press shutter as I see (through the EVF) the second hand hit the mark           below the number
b) Again, looking through the EVF, the second test is to press the shutter in anticipation of     when the second hand will be on the mark (trying to time it)
c) Autofocus engaged but shutter button pressed halfway as I would do in the field
d) Manual focus but shutter button halfway as I would do in the field
e) Same tests but looking at the clock directly, not through the EVF, to ascertain if there is     a slight difference in what I would see directly from what I see through the EVF
f) Same tests utilizing the electronic shutter versus the mechanical shutter

I placed my Fuji X-T2, booster grip attached with all settings set for maximum performance, on a copy stand, parallel and about 20" from the subject, an iPad displaying a digital clock. The ISO to auto, shutter speed at 1/250th second to eliminate slow shutter effect.  I set the Fuji 35mm f/2 lens (one of the latest generation and fastest focusing lenses) wide open at f/2 to eliminate any time it takes to stop down the lens before the shutter fires.  I would watch the second hand sweep around the clock face and press the shutter at the appropriate time as described above.  Also, I decided to conduct the test by manually pressing the shutter button instead of using a cable release as this would be typical if I were in the field and photographing a moving subject.

Note:  I am not timing autofocus time.  As I press the shutter halfway, the lens autofocuses as I time my exposure.  This is how I would do it in the field if I were anticipating photographing a moving object when it was in a specific place.  That is another test entirely and would be lens specific.

Here is how I set up each test followed by my conclusions.

Test 1  Mechanical shutter, autofocus with shutter button pressed halfway, looking through the EVF and fully pressing the shutter when I actually see the second hand hit the line below a number on the clock  This test is to ascertain how far the second hand is past the line when the image is made, i.e., lag time, which includes my reaction time.  In each test I'm showing the typical result from twenty exposures.

Test 2  Same as test 1 but with electronic shutter.

Test 3  Mechanical shutter, autofocus with shutter pressed button halfway, looking through the EVF and fully pressing the shutter when I anticipate the second hand will hit the line below the number.  This test is to ascertain if I can time my press to hit the mark.

Test 4 Same as test 3 but with electronic shutter.

Test 5 Mechanical shutter, manually pre-focused and shutter button pressed halfway, looking through the EVF and fully pressing the shutter when I actually see the second hand hit the line below a number on the clock This test is to ascertain how far the second hand is past the line when the image is made, i.e., lag time, which includes my reaction time as well if there is a difference in lag between autofocus and manual focus.

Test 6 Same as test 5 but with electronic shutter.

Test 7 Mechanical shutter, manually pre-focused and shutter button pressed halfway, looking through the EVF and fully pressing the shutter when I anticipate the second hand will hit the line below the number.  This test is to ascertain if I can time my press to hit the mark as well if there is a difference in lag between autofocus and manual focus.

Test 8 Same as test 7 but with electronic shutter.

Test 9  Mechanical shutter, autofocus with shutter pressed button halfway, looking directly at the clock, NOT through the EVF, and fully pressing the shutter button when I actually see the second hand hit the line below a number on the clock  This test is to ascertain a) how far the second hand is past the line when the image is made and b), if there is a difference between looking through the EVF and looking at my subject directly. 

Test 10  Same as test 9 but with electronic shutter.

Test 11  Mechanical shutter, autofocus with shutter pressed button halfway, looking directly at the clock, NOT through the EVF, and fully pressing the shutter when I anticipate the second hand will hit the line below the number.  This test is to ascertain if I can time my press to hit the mark when looking directly at my subject, not through the EVF and if there is a difference between looking through the EVF and directly observing my subject.

Test 12 Same as test 11 but with electronic shutter.

Test 13 Mechanical shutter, manually pre-focused with shutter button pressed halfway, looking directly at the clock, NOT through the EVF, and fully pressing the shutter when I actually see the second hand hit the line below a number on the clock.  This test is to ascertain a) how far the second hand is past the line when the image is made and b), if there is a difference between looking through the EVF and looking at my subject directly.

Test 14 Same as test 13 but with electronic shutter.

Test 15 Mechanical shutter, manually pre-focused with shutter button pressed halfway, looking directly at the clock, NOT through the EVF, and fully pressing the shutter when I anticipate the second hand will hit the line below the number.   This test is to ascertain if I can time my press to hit the mark when looking directly at my subject, not through the EVF and if there is a difference between looking through the EVF and directly observing my subject.

Test 16 Same as test 15 but with electronic shutter.

Test 17 and 18 To further test my ability to anticipate and fire the shutter at just the right moment, I conducted two short tests with autofocus on (prefocused and shutter pressed halfway) as well as manual focus with shutter pressed halfway using a digital stopwatch.  I tried to anticipate and hit the even number second (5, 10, 15, 20, etc.) exactly.

Here is the average human + shutter + EVF lag with autofocus.  It works out that I was off the mark on average of 0.050 seconds.

Here is the average human + shutter + EVF lag with manual focus.  It works out that I was off the mark on average of 0.066 seconds.

Here are a few real world images.  The first, of the Amtrak engine, I was trying to anticipate when the front of the train would visually merge with the edge of the small silver structure.  As you can see, my timing was pretty good.  The train was moving at an estimated 40 mph (64 kph).

(click to enlarge)

The following images represent my trying to time when the front edge of each rail car of the same train would merge with the front edge of the silver structure.  This did not go so well.  Me or the camera?  Probably more me than the camera since my prior tests show almost not shutter or EVF lag.

(click to enlarge)

(click to enlarge)

(click to enlarge)

(click to enlarge)

(click to enlarge)

It seems I missed the desired capture point consistently by about 5 ft. at approximately 40 mph.

Conclusions:

My first conclusion is that there was no way for me to take out the "human" factor of my personal reaction times, anticipation times, etc.  Sometimes I was early pushing the shutter and sometimes late.  I tried to nail each exposure as explained in each test.  But, as in real life out in the environment, human reaction times have an impact as well.  We have no machines to actuate our shutter at an exact time out in the field, so "human" variation plays a role.

Secondly, the differences I found in see and actuating the shutter were rather minimal, with the exception for the very fast moving subjects (train).  Then the differences become more pronounced.  A clock is a pretty slow moving subject but a fast moving train makes a difference.

In my opinion EVF lag is minimal, possibly non-existent, in the X-T2. When a potential EVF lag is combined with a potential shutter lag, my shutter actuation times were less than 1/5 of a second consistently.  I saw no difference in shutter actuation times when looking through the EVF versus looking directly at my subject and actuating my shutter.  

I found no difference when the camera was in autofocus or manually pre-focused.  I didn't see any impact of the AF mechanism on shutter release times.

Finally, I saw no difference in using the mechanical shutter versus the electronic shutter. The timing of both were identical, as far as I could ascertain.

Not shown here, but also tested in the field, I found that setting my shutter actuation for 5 frames per second allowed me to easily track and pan with a high speed subject.  In this case, with an Amtrak engine approaching at 79 mph.  EVF blackout was minimal and did not impact my ability to see exactly where my subject was and successfully track it.

So what does this all mean.  The greatest factor in keeping you from getting the exact image you want to make with a moving subject is YOU!  Your reaction time, your ability to time, your ability to pan with your subject, etc., in my opinion, has more impact on the final image than the electronic chain of events present in the Fuji X-T2.

Disclaimer:  I'm certainly not perfect.  Just ask my wife!  LOL.  I may have made errors but I tried to logically think my way through this whole testing procedure to remove any unknowns and tightly control variables.  If you see an obvious mistake I made, please leave a comment and advise.  My goal is to provide meaningful information, not only for my own benefit, but for yours as well.

Thanks for looking. Enjoy! 

Dennis A. Mook 

All content on this blog is © 2013-2017 Dennis A. Mook. All Rights Reserved. Feel free to point to this blog from your website with full attribution. Permission may be granted for commercial use. Please contact Mr. Mook to discuss permission to reproduce the blog posts and/or images.