A Quick “Train” Subject Detect Autofocus Test With The X-H2S

Amtrak Train #94 westbound through Wakefield, Virginia. (click to enlarge)
Fujifilm X-H2S; 16-55mm f/2.8 lens @ 22mm; 1/2000th sec. @ f/6.4; -1.6 Exp. Comp.; ISO 320

Recently, I drove to a nearby very small town that has the Norfolk Southern Railroad mainline running through it.  My intent was to photograph the Amtrak passenger train that originates in Norfolk, Virginia at 9 a.m. each morning.  I planned to use ‘Train’ subject detect autofocus as another in a series of AF tests with the X-H2S.  

The problem I always encounter when trying to photograph Amtrak trains on this portion of the mainline is the trains run due NW and the sun is due SE at the only times the trains pass through.  A directly backlit sky.  One of the hardest kinds of AF targets.  But this day the sky was kind of amazing with with both upper and lower level clouds and the sun occasionally provided some shade on a very hot, humid morning so I thought I would give the "Train" detect AF setting a test.  This was a much nicer sky than the normal fully overcast or fully blue with no clouds.

My subject would be backlit, very high contrast, very fast moving and the dynamic range would test the sensor, especially in the deep shadows near the locomotive's undercarriage.  Hmm.  What to do?

I set the X-H2S for shutter priority, 1/2000th second, Back-Button AF-C, single AF point, auto ISO, auto WB, 15 fps and the exposure compensation for -1.6 stops to try to keep the very bright clouds from blowing out.  The 'blinkies' feature in the EVF is a nice warning that all detail would be lost in those highlights that blink black/white.  Would there be enough dynamic range to capture the detail in the locomotive's undercarriage and trucks (wheel sets)?  Knowing and extensively using several other Fujifilm cameras, I felt confident it would have the dynamic range necessary.

After about a thirty minute wait, I saw the train's headlight in the distance so I took my preplanned position to get the composition I desired.  As the train approached, I placed the focus point over its nose and when at a reasonable distance I pressed the shutter button.  As the train drew closer and larger in my EVF, I panned to the left to keep it in the center of my frame.  As I did this I watched the single point focus square lock on to the front of the train (turned green) and and then the square tuned into a white rectangle letting me know the AF system was now tracking the train. The train roared past me at about 79mph (127kmh), its speed limit.  I made a total of 28 frames.  Just under 2 seconds worth.

Since this was the first time I had tried 'Train' subject tracking, I had no idea of how far or when the AF system would start tracking the oncoming train.  I think it was about half way through the series of 28 exposures that the camera switched from keeping the locomotive in focus by regular AF-C to 'train tracking' mode.  I would estimate that the switch came about the time the locomotive's front reached the road crossing.  

Two quick observations from this little test, which is only a single data point.  First, the normal AF-C kept the train in focus as it approached in the distance and second, when it the AF switched to the 'train' mode, it continued to keep it in focus even when the locomotive was virtually next to me.  I was a bit surprised it kept the locomotive in focus that close and going that fast.  Normally, in my experience, when a very fast moving object gets very close, most camera's AF systems lose the ability to keep it in focus because the AF system just isn't fast enough to do so.  I think this is another example of where the speed of the stacked, BSI sensor in this camera can do things previous cameras cannot.

One other aspect of the experience was welcomed.  While panning and making the exposures, there was no EVF blackout.  This camera is a first for me in having no EVF blackout.

By the way, all 28 images were in sharp focus.  I'm sure I'll conduct more 'Train' AF tests as trains are one of my pet subjects.  For this test, I’ll give the camera an A+.

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Thanks for looking. Enjoy!  

Dennis A. Mook  

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