When working in industrial vision, have you ever encountered this situation?

Photographing metal parts:

In the bright areas, everything is white; in the dark areas, everything is a black mass.

Lower the exposure, and the highlights finally come into focus, but the shadows remain completely black.

Increase the exposure—details in the shadows become visible, but the highlights are overexposed.

At this point, what you might be encountering isn’t a focusing issue, but rather:

The contrast between light and dark in the scene is too extreme for the camera to capture in a single shot.

01｜What is dynamic range?

Simply put:

Dynamic range is the camera’s ability to capture both bright and dark areas simultaneously.

For example, when photographing a metal part:

The surface is highly reflective, while the interior of the groove remains very dark.

Normal shooting may capture the highlights but fail to reveal the shadows.

Cameras with a wider dynamic range have the potential to preserve details on both ends simultaneously.

02｜How does HDR work?

HDR, known in Chinese as High Dynamic Range.

A common practice is:

Use a short exposure for bright areas, a long exposure for dark areas, and then combine the valid information.

For example:

Short exposure reveals the reflective areas, but the grooves are too dark.

With a long exposure, the grooves are clearly visible, but the reflective areas appear completely white.

By combining the two images, you can simultaneously discern details in both areas.

However, HDR is not limited to the multi-frame synthesis approach; some industrial sensors also support capturing varying exposure levels within a single frame.

03So, does that mean I can just buy an HDR camera?

Don’t rush yet.

Although HDR is very useful, it does come at a cost.

In particular, when using a multi image compositing approach, if the product is moving at high speed, ghosting may occur or the acquisition rate may be compromised.

Basler Product Documentation+1

Moreover, HDR is not a universal glare eliminator.

If the issue is simply that the light is shining directly into the lens, it’s often worth trying a different lighting angle, adding diffused light, or adjusting the polarizer first.

04｜How do you determine on-site whether HDR is needed?

It’s very simple—let’s do a quick test:

First, lower the exposure to see if you can bring out the details in the highlights.

Then increase the exposure further and see if you can bring out the details in the shadows.

If, under both exposures, the highlights and shadows are both clearly visible but you still can’t capture a single shot that gets both right, then an HDR solution is worth considering.

If, no matter how you adjust the exposure, the defect remains invisible, you should prioritize re examining the lighting setup.