Introduction
We photographers often face the problem that the differences in brightness in a scene exceed the dynamic range of our camera. Especially in landscape photography, for example with sunsets or motifs with a bright sky and dark foreground, this leads to blown-out highlights or blocked-up shadows. There are two established methods for compensating for these contrasts: the graduated neutral density filter (GND filter) and HDR (high dynamic range) technology. Both approaches have their strengths and weaknesses.
Gradient filter – compensation already during shooting
A graduated neutral density filter is an optical filter that is dark in the upper half of the image and becomes transparent towards the bottom. This primarily darkens the bright areas (e.g., the sky) while leaving the foreground unaffected.
Advantages:
- Natural results straight from the camera: little or no post-processing required.
- Fast operation: ideal for situations where the light changes quickly.
- Long exposures possible: particularly important for flowing water, passing clouds, or light trails, where multiple exposures would be problematic.
Drawbacks:
- Fixed transitions: The filter's progression does not always match the horizon line or irregular edges of subjects (e.g., mountains, trees) exactly.
- Additional equipment: Filters, mounts, and adapters (if necessary) must be transported and used.
- Limited flexibility: Subsequent corrections are virtually impossible once the exposure has been set in the field.
HDR – More dynamic range through exposure bracketing
HDR (High Dynamic Range) is based on combining multiple shots with different exposures. These individual images are used to calculate an image that has a higher dynamic range than a single sensor could capture.
Advantages:
- Maximum flexibility: Exposure range can be precisely adjusted to the scene.
- Perfect adaptation to complex lighting conditions: Even with irregular structures or rich details in the foreground.
- Powerful post-processing options: Tone mapping allows creative adjustments to brightness and contrast.
Drawbacks:
- Complex in practice: Usually requires a tripod, exposure bracketing, and post-processing on a computer.
- Movement in the image: People, water, or leaves blowing in the wind can lead to ghosting.
- Unnatural results possible: HDR is often exaggerated and then looks artificial.
- Tone value breaks: If the light values are too high, tone value breaks can occur.
- Losses: Not all image data is available in HDR until the finished image is output. This often limits the editing options.
Comparison in practice
- Speed and simplicity: Gray gradient filters are ideal when you want immediate, presentable results.
- Maximum image control: HDR is superior when the scene is very complex and there is no clear dividing line between light and dark.
- Creative effect: Gradient filters usually produce a more natural image, whereas HDR can have a very dramatic effect.
Conclusion
Whether a gray gradient filter or HDR is more suitable depends on the subject, working method, and personal preference.
- If you value natural results and spontaneous photography, gray gradient filters are a good choice.
- If you are willing to invest time in post-processing and want to exploit the maximum dynamic range, HDR is the way to go.
In many situations, both methods even complement each other: a gray gradient filter can reduce the contrast range during shooting and subsequently facilitate HDR processing. Both techniques offer the advantage of allowing you to take photos at times when others put their cameras away.
Another technique for exposure compensation is the UDI (Ultra Deep Image) technique, which, however, requires much more processing effort. This will be discussed separately.
