What is ISP tuning?

Image Signal Processor (ISP) tuning involves optimizing the performance of image sensors by adjusting the processor and converting RAW images from image sensors into high-quality images.

To attain the best image quality, various ISP parameters (demosaicing, auto exposure, auto focus and auto white balance, lens shading correction sharpness and denoising, color correction, and so on) are optimized in a tuning procedure. This procedure can take up to months.

Benefits of ISP tuning in imaging solutions

Camera with better ISP tuning shows increased performance in terms of image quality in a variety of lighting conditions. ISP tuning benefits include:

Higher sharpness:

Better saturation:

Color shading correction:

Better HDR:

and so on.

Better ISP tuning deals with various measurement conditions to attain better quality images

How to perform image quality tuning

A step-by-step process is adopted in ISP tuning to avoid unnecessary iterations. For best image qualities, each ISP block is fine-tuned to respond appropriately to different lighting conditions. The steps are very critical in that, if one ISP block is not tuned correctly, the following blocks suffer and result to unwanted image quality. The tuning process is explained below:

3A tuning

This involves setting the 3A Algorithms (auto exposure, auto balance and autofocus) to control the camera exposure, white balance and focus. 3A tuning helps in enhancing images in real time and under various conditions.

Objective image quality tuning

The objective measurements in ISP tuning process involve different camera parameters including dark current, noise model, distortion model, AWB reference values etc.). Standard test charts taken under controlled lighting conditions are used as reference while calculating theses camera parameters, ISP tuning deals with various Measurement criteria like MTF, △C, △E, auto white balance error, Brightness, SNR, color shading or luma shading to attain the quality images.

A lab setup with a uniform light source, test charts and measuring equipments like lux meters is a key requirement while capturing these images.

Subjective evaluation

After correctly setting the initial tuning, most of the objective requirements are typically met.  To achieve the preferred results, afurther fine-tune (a subjective evaluation) is done by:

Capturing and analyzing real-life scenes to realize gaps in quality expectations.

Modifying the ISP parameters by accommodating preferences or adding calibrations

Image quality evaluation

During this ISP tuning step, the image quality testing is carried out to decide ISP parameter optimization extent. This task involves two phases

Objective testing

After 3A tuning, objective image quality testing is done where KPIs are measured in line with standard test charts like, ISO, the image is then taken in different imaging lab lighting conditions. The test cases and image quality pass/fail criteria are matched with the camera’s applications. 

Subjective testing

Subjective testing deals with exposure to various scenarios like indoor, landscape, outdoor, times of the day, etc. Some of the factors are analyzed for, noise level, brightness, sharpness and resolution, texture details, natural colorfulness.

Image quality Benchmark Test

This process involves comparing both objective and subjective image quality of a tuned device under tests with other standard consumer devices.

Conclusion

Due to daily demands on improved camera performance, ShenZhen CK Vision Technology Co., Ltd with over 11 years of experience, specializes in R&D, ISP tuning camera. We have a professional optical lab that tests the objective and subjective performances of various camera models like Sony, Samsungpixel plus, etc.

Visit our page for more info.