What your lens actually produces at 24mm (Part 2)

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Digital Nigel Forum Pro • Posts: 10,472
What your lens actually produces at 24mm (Part 2)
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The previous thread got rather long and moved on to other topics, while I've continued to do more research, so I thought I'd start a new thread with the findings so far:

  1. All lenses that I've tested, even high quality primes, seem to have some distortion that's corrected by default in the camera or when processing RAW images.
  2. The distortion is worse with zoom lenses than primes.
  3. The distortion is usually worse at the wide end of zoom lenses.
  4. The distortion is significantly worse with compact zooms.
  5. In the worst cases, the image circle doesn't cover the sensor, so you get black (vignetted) corners in the uncorrected images.
  6. In cameras that do this, the manufacturers don't want you to know, and hide it in the OOC JPEGs and via the lens correction hints they embed in RAW files. Adobe slavishly follows those hints, but some others don't.
  7. Fixing the distortion means applying an equivalent opposite distortion, then cropping to the desired aspect ration. The in-camera crops are sometimes more severe than if you do it manually while processing the RAWs. This is because they allow for decentered lenses, and don't want to risk asymmetrical vignetted corners being visible in OOC JPEGs.
  8. Applying lens correction reduces image sharpness and can increase noise, particularly near the edges. It's needed to keep straight lines straight, but many natural scenes don't have straight lines. So, if you want the sharpest possible landscape, bird and animal photos, you might gain from reducing lens correction, or even turning it off altogether.
  9. Most cameras offer the option of 16:9 crops. In most cases, these could take advantage of more of the sensor's width than 3:2 crops, but manufacturers don't do this. However, if you process from RAW and apply your own lens correction, you can.
  10. The corrected, cropped image will generally be smaller than the original sensor size. To hide this, the OOC JPEGs are upscaled to the original size, which is a form of CIZ. So, every OOC JPEG has had a form of  CIZ applied!

I've now uploaded lots of images to Flickr:

https://www.flickr.com/photos/recliner/albums/72157713211816491

Here's one example:

I've also calculated what percentage of the sensor's pixels get used in an OOC JPEG at the widest angle.

Only about 88% of the RX100M6's sensor's pixels contribute to the OOC JPEG at 24mm. In effect, the sensor size is reduced to about 17.6mp.

Here's a summary of the other lenses:

 Digital Nigel's gear list:Digital Nigel's gear list
Panasonic FZ1000 Canon PowerShot G7 X Nikon Coolpix P900 Panasonic ZS100 Sony RX10 III +18 more
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