1200mm: Digital Teleconverter

Started 8 months ago | Discussions thread
OutsideTheMatrix Senior Member • Posts: 7,471
Re: Not Interpolation Re: 1200mm: Digital Teleconverter

Eric Nepean wrote:

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.

But it is only throwing away data that is outside the area of interest and which may not be of any interest to the photographer. I shoot RAW+JPG now (only the JPG file part shows the DTC), why doesn't Oly make the x2 DTC filter available in Work Space so people can apply it to their RAWs? It should work the same way! Also, I sometimes use M size 5 MP for x2 DTC to get a nearly non interpolated result (5 MP vs 4 MP not much different) to get a much faster burst shooting rate, especially with the fully electronic shutter on my EM10Mk2.

But when using x2 DTC at the full 16 MP I do see more crater detail on the moon than I see without the DTC.

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