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My AF testing target. This target is 8.5" X 16.5" (216mm x 419mm) (click to enlarge) |
In December, I made my annual long weekend journey to photograph wildlife on Assateague Island, home of the Chincoteague National Wildlife Refuge located on the Eastern Shore of Virginia. In this post, I lamented that I largely felt the trip was a failure as I had issues getting sharp focus on several stationary large birds with my Fujifilm X-T2 coupled to the Fujifilm XF 100-400mm f/4.5-5.6 lens, with and without its matched 1.4x tele-converter. Was the problem me or my gear? I surmised it was probably me.
Not leaving well enough alone, I have been thinking about why I was having issues getting accurate focus, it seems, only with wildlife. I examined my camera settings, technique, etc., to try to determine why I wasn't getting 100% sharp images with these two excellent pieces of gear. And I must say the two make, indeed, an excellent combination. I needed to engage the scientific method to change one variable at a time to eliminate one potential cause at a time.
Last week, I was slowing cruising through the Yorktown Battlefield of the Colonial National Historical Park. Yorktown is where the last battle of the American Revolutionary War was fought. As I slowly made my way, I spotted an adult white-tailed doe peeking out from the woods just to the left of the road. I stopped in the roadway and just waited (there was no one else around). Evidently, being used to human presence, she walked across the road into one of the cut fields that once served as a battlefield. To my surprise, 6 additional white-tailed deer of various ages followed her across. They stopped and started grazing about 100 ft. from the roadway. I slowly pulled forward so as not to startle them and get myself into a position to possibly make some images of these 7 glorious animals. I creeped forward and stopped my vehicle in a position that wasn't too close. I had my Fujifilm XF 100-400mm lens with the 1.4x tele-converter already mounted to my X-T2. I rolled down the front passenger's window of my vehicle, checked my exposure settings and ISO and made some images of all of them as well as zooming in to record just a few of them. Every once in a while one would raise her head and look my way to check for danger. However, most of the time I had a great view of their white tails! Why do animals always seem to stand with their rumps toward us photographers? Lol.
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Off-white wall with no texture. AF would not focus on this wall. Uneven lighting was not a factor. (click to enlarge) |
When I returned home, I uploaded the images into Lightroom to examine them and, much to my dismay, many were just not in sharp focus. In fact, using the grass in which the deer were standing as a reference, it appeared that many were focused slightly behind my target.
Again, frustration in not getting what I thought I was getting and still not figuring out why. After the last experience, I went into my camera and changed the AF tracking settings hoping that re-examining those settings may help. It didn't.
This new failure lead me to two potential causes. Let me first say that my shutter speeds, apertures and ISO was sufficient to stop motion. Also, being that in every image there was something in sharp focus told me that settings were not the issue. Back to the two potential causes.
First, I asked myself if the marked focusing rectangles shown in the EVF reflect the actual positions of the AF points on the sensor itself? I know in digital cameras I have owned in the past, as well as in reviews testing autofocus in cameras, some cameras' viewfinders don't necessarily represent the actual position of the AF points. Were mine accurate? I didn't know.
Second, is the camera/lens combination actually focusing accurately on a consistent basis? In some of the images I made focus was dead on. In this instance I generally was focusing on the broadside torso of an adult white-tailed deer instead of trying to focus at such a distance on just the head/eyes. Depth of field, I figured, would take care of the eyes being in focus. In other images, the focus seemed to be slightly behind my large target. As I said, looking at the grass in which the deer were grazing as well as some of the other deer in close proximity, it appeared my camera/lens combination was back-focusing. How could that be? Aren't mirrorless cameras supposed to focus right off the front of the sensor? Additionally, I have my camera set (when using S-AF) to not fire unless the subject is in focus. In every exposure the green focusing square in the EVF was showing indicating the subject was in focus.
Now, let's look at the first point to see if we can eliminate or establish misrepresentation of where the actual focusing points are as a cause.
My next step was to design some sort of simple test to examine the position of the AF rectangles as shown in the EVF to ascertain if they are, indeed, aligned with the AF points on the sensor. I set up a test with my camera pointed at a blank off-white white with no detail and no contrast. In other words, the camera would not autofocus at all on the surface.
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Example of bring AF target closer and closer to the AF point from the left. Pardon me for the poor quality image as I just shot a photo of the LCD screen on the back of the X-T2. (click to enlarge) |
I then conducted the same test with all 5 sing AF point sizes. All were perfect. Then I moved to multi-point Zone Focusing. Same thing. The AF points in my camera perfectly matched the AF points on the sensor. I now have a high level of confidence the focusing points as shown in the EVF exactly correlate to where they are on the sensor.
This leads me to conclude that I can eliminate the position of the autofocus points as a cause of mis-focusing in my images. They are all exactly as marked.
The AF points now eliminated as a potential cause of not focusing where I think I'm focusing, it is time to move to the next step.
My next step may be sending my camera body along with the 100-400mm lens and 1.4x tele-converter to Fujifilm repair to have them check to ensure the lens is functioning properly with my camera.
However, before I do that, I want to check one more time that image stabilization is not a cause. I've used the lens with IS on and IS off. However, I want to definitively say that IS is not a cause and I don't feel with the tests I've done so far that I can say that for sure. If I eliminate that entirely, I will send the camera/lens combination off for Fujifilm to check them as a unit.
I just had two thoughts about all of this. First, earlier that same day as I wandered around, I photographed an Amtrak train in the Williamsburg, Virginia station unloading passengers. I was using the same camera/lens combination. Also, this tree (below) I used as an illustration in a previous post was also photographed after the deer images were made with the same combination. Every one of those images, in both instances, are dead on sharply focused. However, when I photographed the deer, I had issues. And, what started all of this, when I was in the Chincoteague NWR, I had the same experience. Now, I'm not talking about birds, animals, etc., moving, but pretty much stationary and images made only after the green AF square alights in my viewfinder.
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Made earlier the same day with the same camera/lens combination. (click to enlarge) |
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This image of this tree was made with the same combination just after the deer images were made. (click to enlarge) |
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Another almost 100% crop. No issues with focus or sharpness. Issues only seem to occur with animals and birds. Doesn't make sense to me either! All of these images were handheld. (click to enlarge) |
Another thought. What is different between the birds/animals and the other subjects I photographed may be the amount of contrast. Focusing on the side of a deer, in reality, is not very contrasty as is focusing on a solid color bird. That may be another worthwhile avenue to pursue before sending my gear off to Fujifilm to be checked and calibrated.
Stay with me and I'll eventually figure this out. When I do, I'll let you know so you have the benefit of my testing and conclusions. After all, we all want success in our photography and if you can benefit from my experience, I'm happy to share them with you.
Thanks for looking. Enjoy!
Dennis A. Mook
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