Resolution of M43 lenses

Started Mar 31, 2013 | Discussions thread
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Detail Man
Detail Man Forum Pro • Posts: 16,420
Re: Demonstration of Differences in DxO Geometric Corrections

Anders W wrote:

Detail Man wrote:

Anders W wrote:

Sure. DxO crops the image to a rectangular shape. If you ask LR kindly, I think it will do the same. Or if you ask DxO kindly, it might abstain from the cropping, which from a diagnostic point of view might be even better. If additionally, you make sure that the amount of correction applied by the two converters is exactly the same, it might be an interesting comparison.

OK, magister, I have now cropped the Adoobie image down to the girlie-man size of a mere 3499x2624 pixels (seemingly all that it could handle), and gratiously lowered the DxO Optiques Prose image size to a similar puny dimension. Once again, download the Original images and display them in an image-viewer at 20% size (collapsing 5x5 pixel arrays into single, centered pixels).

Lightroom 3.6:

Note the pattern that appears to imply a single centrally placed optical correction reference point.


DxO Optics Pro 7.23:

Note the four circular patterns that appear to imply four separate correction reference points.

I anxiously await your refutations showing that Adobe is the embodiment of crystalline perfection.

Note: The DPReview post-display system appears to be malfunctioning. This is my 2nd and final possible edit. If images do not display, click on the Gallery Page links to download the Originals.

DM ...

I see all kinds of interesting moiré patterns depending on the magnification of the image itself as well as display magnification. But I wouldn't want to make anything out of that.

I grant you that reasonable uncertainty (of the appearance of patterns, even in the case of decimation ratios of 5, where we know that 5x5 pixel-arrays collapse into a single display pixel).

Now if you really want to test this DM, one way of actually getting somewhere without a whole lot of work would be the following: Take your test image, distort it using the one RAW converter, output it, and then try to undistort it using the other RAW converter. If the algorithm is essentially the same, you should be able to come back to square one, i.e., the pure, straight, column-row pattern that you started out with (though perhaps a bit degenerated in ways that are for present purposes a bit irrelevant). If not, then you shouldn't. For safety's sake, you might want to approach the matter from both ends, distorting with LR and undistorting with DxO, distorting with DxO and undistorting with LR.

That procedure would work in the case that both processors are known and understood to accomplish all geometric corrections only after de-mosaicing (such that TIF manipulation is representative). Maybe, maybe not. It (may) depend on an individual processors' architecture.

My guess is that when you just use the main distortion slider of the respective RAW converter, they will for all practical purposes do the same job. When working on the basis of lens profiles, however, things may well stand differently. In that case, both may make use of more than a single parameter to correct more complex forms of distortion, and the parameters they use may be different.

Have posted a number of Originals that demonstrate the geometric differences that can (as far as I am concerned) be easily seen by (at least my own) eyes (of DxO geometric corrections relative to large numbers of OOC JPGs, as well as some RAW Therapee, Lightroom, and Silkypix corrections).

You seem to perceive such differences as minor, relegating them to the realm of the virtually unmeasurable, the insignificant, the subjective. However, you have not spent the time that I have looking carefully, and your perceptual processes may simply not be cognizant and/or interested in the visible differences. That's OK - but I do not see that as a basis for your speculation.

One would have to assume that DxO Labs goes to the trouble of characterizing individual lens-systems, then abandons that information in favor of corrections that have more "artistic appeal" to their customers than technical accuracy comporting with what they have measured.

Or, one would have to assume that DxO Labs is merely "obsessing" in implementing their optical corrections to levels of accuracy that you personally may find unecessary because your own eyes do not happen to object to what (to my eyes) appears to be somewhat simpler and (personally perceived by me to also be less effective) implementations of geometric corrections.

The issue of primary concern in your mind appears to be whether your particular tool of choice is adequate for your own perceptual purposes, preferences, and tastes. And, it seems that it is.

Note: I don't know how you create the synthetic RW2 that you are playing with. But it should obviously not be such that either RAW converter tries to apply any distortion correction by default. Any distorting or undistorting should be done by you via the sliders.

It is true that the Panasonic image-file meta-data for a LGV 14-140mm at 25mm FL exists in the RW2 test file, and Lightroom (unlike DxO Optics Pro and RAW Therapee) unfortunately does not allow the user to defeat its application in silent geometric corrections. It may be that Lightroom's manual adjustments multiply together with (as opposed to simply add to in the control-chain) such pre-applied and non-defeatable "silent" geometric corrections. The result of such a multiplicative process (may) result in composite effects that cannot later be separated.

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