Understanding Image Quality Image Quality Factors

Image Quality Factors

The quality of a digitised aerial photograph depends on much more than scanning resolution. The format of the physical photograph, the context of its production and its current condition can all influence the final result.

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What Determines Image Quality?

Aerial photographs scanned at exactly the same resolution can display very different levels of detail.

The quality of the resulting digital image can be influenced by a range of factors, including:

  • The quality of the original photography
  • Whether the source material is film or print
  • Atmospheric conditions at the time of capture
  • Motion blur from the aircraft
  • Camera focus and lens performance
  • The condition of the original archive material
  • Image processing methods

For this reason, image quality cannot be determined by scanning resolution alone.

For more information on image scale and flying height, visit our Scale & Flying Height page.

Original Film vs Photographic Prints

Whenever possible, NCAP scans directly from the original film negative or transparency.

However, in some collections, particularly historic military collections, original film may no longer survive or may be unsuitable for scanning. In these circumstances, the only surviving source material may be a photographic print.

Why does this matter?

A photographic print is a later-generation copy created from the aerial film. Each generation of copying introduces a small loss of detail.

As a result:

  • Scans from original film generally provide the highest image quality.
  • Scans from photographic prints may appear softer or less sharp.
  • Enlarging or scanning a print at a higher resolution cannot recover detail that is no longer present.

NCAP will always digitise the best available resource.

Processing & Image Enhancement

All imagery supplied by NCAP is scanned using professionally calibrated equipment and established quality-control procedures.

Because NCAP processes large quantities of aerial imagery, images are balanced using automated workflows. This provides:

  • Consistent presentation across collections
  • Faster processing and delivery
  • Reliable large-scale image production

Images are not normally manually balanced on an individual basis.

Similarly, enhancement techniques such as edge sharpening, local contrast enhancement and selective tonal correction are not routinely applied to imagery supplied through NCAP services.

While these techniques can improve visual appearance, they do not create additional image information.

In Summary

When assessing the quality of an aerial photograph, it is important to consider:

Source Material

Original film negatives generally provide higher-quality results than photographic prints.

Original Photography

Flying conditions, camera systems and image scale all influence the level of detail captured.

Digitisation

Scanning captures the information present within the source material, but cannot recreate detail that has been lost or was never recorded.

Image Quality = Source Material + Original Photography + Digitisation

If you are unsure whether a particular collection or image is suitable for your project, please contact the NCAP Sales Team at ncap@hes.scot.

IN THIS SECTION

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Discover how aircraft flying height and photograph scale influence the level of detail visible within an image. Understanding these relationships will help you assess what information can realistically be identified and interpreted.

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Learn why aerial photography coverage varies between locations, periods and collections, and how this can influence the imagery available for your project.