1200mm: Digital Teleconverter

Started 8 months ago | Discussions thread
Eric Nepean
Eric Nepean Veteran Member • Posts: 5,655
Not Interpolation Re: 1200mm: Digital Teleconverter

Note that the Digital Teleconverter function is only for JPEG files, it is not available for RAW files.

There is a reason for that.

Typical JPEG processing discards well over half the image detail.

Building a really good interpolater is an expensive and tricky job. Hard to do and hard to maintain.

It would be downright crazy to throw out much of the image data, and then develop an expensive and tricky interpolation function to bring it back.

IMO what Panasonic and Olympus have done is selected the center portion of the image, and tweaked the JPEG engine to keep much more of the detail.

JPEG typically averages color values are typically average over at least 4 adjacent pixels, simply not averaging will provide the required detail.

In the Luma channel, much of the detailed information is discarded by normalising  the DFT results with the quantisation matrix and rounding. Changing the quantization matrix is a straightforward way to keep a lot more detail.

This explains why the DTC is not available in RAW.

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