When it comes to on-site machine vision diagramming, many people's first reaction is:

The image isn't clear? Adjust the lens first.

A bit to the left, a bit to the right.

It feels clearer now, yet it still seems a bit lacking.

After hours of tweaking, it still wasn't stable.

Often, the problem isn't with the camera.

Instead, the focus sequence was incorrect.

Focusing isn't about randomly turning the dial based on feel.

The correct order actually makes it faster.

Don't rush to focus yet – keep the aperture set.

Before focusing, set the aperture to the appropriate position.

Then fix it in place; do not make any back-and-forth adjustments.

When the aperture changes, both the image brightness and the depth of field will adjust accordingly.

At this point, it's easy to misinterpret whether something is clear or not.

Next, zoom in on the real-time image.

Find a location with a clear contrast between light and shadow and well-defined edges.

For example, product edges, character edges, or hole edges.

This is the easiest spot to determine whether the focus is correct.

in simple terms:

Don't just look at the entire image – focus on the edges.

Now that everything's clear, don't rush to stop.

Many photographers stop adjusting the focus as soon as they think the image looks clear enough.

Actually, it's best to take one more step.

Continue adjusting the setting gradually in one direction until the image begins to blur.

Then adjust it in the opposite direction; again, locate the position where the image began to appear blurry.

The area between these two positions is usually the most suitable focal zone.

Don't fix your gaze solely on a single "most obvious point."

Identifying the blurred boundaries on both sides makes it easier to determine the exact position.

A gentle forward and backward scan is more reliable than stopping based on intuition.

The brightest does not necessarily mean the clearest.

This issue is very common in real-world scenarios.

As the screen lights up, many people think:

"It seems clearer now."

Not necessarily.

Exposure, gain, and aperture all affect brightness.

However, brighter light does not necessarily mean more precise focus.

When focusing, what really matters is whether the edges are sharp enough.

When the focal point is not properly aligned, the edges will appear blurred.

Once the focal point is properly positioned, the edges will appear significantly sharper.

So, remember this:

Focus on the edges rather than just the brightness.

Do not modify the parameters randomly.

During machine vision system debugging, factors such as aperture, working distance, exposure, and gain all affect the image quality.

The biggest fear is having to adjust everything together.

Move the focus.

Adjust the exposure again.

The aperture moves again.

Although the final scene has changed, it's unclear who exactly caused it.

A more reliable approach is:

First, fix the baseline conditions; then adjust each one individually.

When such changes occur, it becomes easier to identify the cause.

On-site debugging is often not due to difficult parameter tuning.

Instead, the variable is being updated too frequently.

Common pitfalls when focusing

The aperture hasn't even been set yet, yet we've already started focusing.

The image is not enlarged; simply observe the overall appearance.

Focus solely on whether the light is visible, not on whether the edges are sharp.

When these issues arise, focusing can easily become unstable or fluctuate repeatedly.

In fact, the correct order is quite simple:

Set the aperture first.

Zoom in again to view the high-contrast edges.

Finally, perform a small-step focusing operation both before and after.

By fixing the sequence, the speed can actually increase.

Don't always rely on your touch when focusing.

If each adjustment yields a different result, it indicates that the outcome is not yet sufficiently stable.

True excellent autofocus isn't just about the image looking clear this particular time.

Instead, applying the same method again will yield a similar result.

Therefore, when it comes to machine vision focusing, the most important factor is not whether the focus is precise or not.

Rather:

Is there a repeatable method?

First, fix the conditions.

Now, let's look at the edges.

Finally, perform a small-step focus adjustment.

Don't just twist it around haphazardly at the start.

Many seemingly complicated autofocus issues can be resolved simply by changing the sequence of operations.