Originally posted by photogerald By the way, these images courtesy of Gerry Winterbourne from the other forum nicely illustrate the improvement in LV between the K20D and K-7:
Gerald, impressive comparison.
If you're really curious to know what's going on in LV, I recommend doing one of my standard tests.
- Print my zone plate test chart (A4 B&W is ok), downloadable here:
(make sure to download in original size -- please don't delete the (c) mark) - Zoom onto the large plate hanging at some distance, getting you an image like attachment #2 (K-7 in 10x)
- Actually take a photo and crop to 100%, getting you an image like attachment #1 (K-7 100% crop)
Discussion: 1. 100% crop:
The printed zone plate has all rings printed correctly, with only minimal printing Moiré pattern. All Moiré you see in the 100% crop is from the demosaicing process. BTW, this would look more ugly for a camera w/o AA filter. The K-7 only produces neglegible Color Moiré near the Nyquist frequency.
At about half the Nyquist frequency, you see 4 pseudo rings (i.e., they are not on the printed chart!) which you can use to determine the exact pitch of the Bayer pattern (2x the pixel pitch). As you can see, the demosaicing manages to resolve beyond the Bayer pattern pitch almost up to the Nyquist freqency (LR2).
2. 10X Live View zoom:
The LV image shows 2 pseudo rings. It turns out they are at the same location as in the 100% crop, i.e., at 50% Nyquist frequency. One sees too that in the vertical direction, the resolving limit is at about half that which is 25% Nyquist frequency, in horizontal direction, it is better and it resolves up to 25% Nyquist frequency w/o the pseudo ring.
This means that in vertical direction, 10X LV uses line skipping (only every 2nd Bayer cell is read out -- pseudo rings are a sampling artifact) and in horizontal direction, every Bayer cell is read out and converted into a single rgb value. Proper demosaicing is skipped because some neighbors are missing.
Overall, this means that the
effective K-7 LV resolution in 10X is 2336x776 or 1.8MP.
Some last note: The K-7 LV resolution improves at the 8x and 10x scale. Up to 6x, it uses line skipping
and row skipping.
A similiar analysis for the K-5 would be interesting indeed.