How to nail focus with Peak Highlight on FujiFilm X-Series cameras?

Remember, this is focus assist, not focus magic. The trick with both of these aids is to remember that it's really the same as getting sharpness right on the screen: as you turn the focus ring, you're moving the plane of focus back and forth, and you want to place it so it coincides with your subject.

If you are shooting at wide apertures and want focus to be just so, and you click as soon as the focus lines appear, you probably won't nail it. Instead, you need to do what a contrast-detection autofocus system would do: get it close, and then keep going slowly until the highlight fades or moves to something too near (or too far, if you're going that way), and then turn back the other way. Go back and forth increasingly carefully as you refine the focus and find the exact perfect spot where the object you want in focus is right on the center line.

Of course, this may be difficult with subjects that aren't still, but the basic principle is the same. You just might not have the time to get it right, and might need to accept a little bit of missed focus — or use a smaller aperture in these situations to give yourself a little more depth of field to cover up focus inaccuracy.

You may find it helpful to play with the options: I find the "low" setting for focus peaking is easier than the bigger-effect "high" option. And I find red or blue easier to see but more distracting for composition (so I keep it at white).

The settings to choose for the focus assist will depend a lot on the scene and photography conditions, as well as personal preferences, to be not too distracting but still easy enough to see where the focus is. I have found cyan to be most suitable for me most of the time, with no clear preference over high/low.

In most conditions the focus plane is obviously visible (it further helps to move the focus back and forth a bit to give it motion), and zooming in to the desired subject to fine-tune the focus, it's easy to achieve the desired focus. However, in dark conditions the focus becomes increasingly hard, which fools the focus peaking, as there is micro contrast everywhere from the sensor noise.

One issue I have with native Fuji lenses is fly-by-wire focus -- making tiny adjustments is very hard, the jump in focus is just too much with a large aperture (like 56/1.2 wide open), which is painfully obvious with focus peaking as the plane will jump past your desired point. Mechanical legacy lenses are much easier to focus manually.

Focus peak highlight enhances areas of high contrast with blue, red, or white. The intensity of the enhancement is associated with the amount of contrast. Low requires higher contrast to enhance. High requires less contrast to enhance. To obtain critically sharp images, use the Low setting along with a color that contrasts with the scene. Red has worked well for me in most situations.

Focus peeking works on the image as it is displayed. Film simulations that enhance contrast may make low-contrast lenses easier to focus. However, they may also produce too much contrast, making it difficult to determine when focus has been achieved. In these cases, a less intense simulation may be used. Film simulation preview may also be disabled.

Many scenes are easier to focus in monochrome, since the color highlight stands out against gray, but the only way to do this is to switch to a monochrome film simulation. This causes JPEGs to be saved in monochrome, but RAWs can still be processed to color if desired.

With manual focus lenses used with stop-down metering, the depth of field makes it difficult to focus exactly. Don't worry too much about it. The focusing procedure is the same, and the depth of field will ensure focus. However, if you are concerned or otherwise having difficulty focusing, it is fine to open the aperture while focusing. Then stop down as desired before exposure. Don't worry about micro changes in distance to the subject. Depth of field will cause focus to be retained. Some adapters have a ring dedicated to control the aperture without changing the aperture setting on the lens.

1. Move the focus area over the desired focus point.

2. Enable focus assist, usually by pressing the back wheel. Magnification can be changed by scrolling the back wheel. I usually use the high magnification setting because it's easier to see.

3. Start with large and fast ring movements. Gradually move the ring slower and more carefully as you turn it back and forth.

   • Rapidly turn the focus ring. You will see the contrast enhancement appear, then fade away.

   • Reverse the direction of the ring. Turn more slowly. Contrast enhancement will again increase, then decrease.

   • Carefully, reverse direction when it just begins to disappear.

   • Stop turning just after the point of maximum enhancement.

   • Return the ring to the point of maximum highlight enhancement, usually the midpoint of the last two reversals.

4. The image should be in focus. You may notice a "shimmer" among fine details, such as fabric textures. In some cases, the shimmer may be used to refine focus.

5. Hold the camera steady while taking a few shots. Don't forget to double check composition.

I am still experimenting with all this, but I have found setting the widest aperture,focussing with care and precision, then stopping down appears to work best. Focussing at, say f5.6 the highlight area isn’t as clearly defined as it is at f2. I agree with other comments here - it is an assist, not an outright solution. Taking the shot a few times and refocussing each time does help your chances of getting it right.