Interesting, thanks!
The 12-32mm looks more wide-angle then the 12-50mm to me? But the
distortion of the 12-32mm @12mm looks bigger to me too?
Curious: how do you use PTLens for these m43 lenses in your workflow if you
don't want ACR to correct them? I like to keep as much wide-angle as
possible. So far I use PTLens in LR only with legacy glass...
2016-09-02 1:51 GMT+02:00 Moose <olymoose@xxxxxxxxx>:
> On 8/31/2016 2:06 PM, Mike Gordon via olympus wrote:
>
>> I assume you realize that you only see the distortion because you are
>> using a RAW converter that does not use the lens provided data to correct
>> distortion as part of the conversion.
>>
>> Yes, I still find it irritating that if use ACR one is stuck with the
>> corrections as designed into the metadata.
>> Sometimes one might like higher res in corners and less corrected
>> geometric distortion. Should be the photog choice, no?
>>
>
> This is a complicated subject. First illustration covers a lot of ground,
> which may, I hope, become clear as you follow along. <
> http://www.moosemystic.net/Gallery/tech/DXO/Dist_Corr.htm>
>
> First, look at it from the camera manufacturers' point of view. My sensor
> is 4592 x 3448* pixels in size. If I output different sizes from my Raw
> converter, it's going to cause confusion - and raise questions I'm not sure
> I want to address. Also, I want my JPEG and Raw outputs to look the same.
> Many of the lenses I make, and many of those of the other µ4/3 maker who
> codes lens distortion correction info into its Raw files, require little or
> no correction, and so are correct at the sensor size.
>
> BUT, BUT, linear distortion correction must change relative sizes of parts
> of the image.
>
> I can correct working from outside to center, but then the central part is
> reduced in size, I have arcs of black on the edges - AND - as all digital
> re-sampling reduces resolution, I make a prime spec worse. People forgive
> some edge decline in resolution, since that's been going on forever. So,
> that's not an attractive solution.
>
> Or, I can correct working out from center. But with barrel distortion,
> that actually makes the image larger, in effect uncompressing what the lens
> has compressed away from the middle. So what do I do? I don't want to
> output larger images, as above. And I don't particularly want to throw away
> image data I've captured. But I know, though hardly any users do, that my
> nominally xx mm lenses really vary ±5% for 95% of production, with a few
> even further from nominal value. So if I shave a little off the edges, and
> a bit more off the corners, nobody is likely to notice. As a bonus, I get
> to chop off the lenses' optical aberrations in the farthest corners.
>
> For my lenses with moderate optical distortion, I'll correct 100%. For my
> higher distortion lenses/focal lengths, I'll compromise, under-correcting a
> little, and throwing away less image. Most of this and that last paragraph
> are plausible fictions, but do agree quite well with my experience.
>
> The Panny 12-32 mm lens has lots of distortion, optically, and their JPEGs
> and their version of SilkyPix Raw conversion all slightly undercorrect the
> distortion, but look pretty good. Oly takes a slightly different approach
> with the 12-50 mm zoom; they've even more optical distortion @ 12 mm than
> the little Panny, but they correct it more. (This leaves the odd situation
> where most tests will show the larger Oly to have less distortion than the
> Panny. That makes sense to us, as we assume it's part of the price for such
> a diminutive lens - but in fact, the Panny is optically the better lens, at
> least in that one characteristic, at that focal length.
>
> Why Adobe chooses to go right along with Panny and Oly, I don't know for
> sure. Perhaps the price of receiving access to proprietary info that allows
> exact reproduction of the distortion correction of the manufacturers?
>
> DxO, on the other hand, is creating their own profiles, without a need for
> compromise. So they take the simple way, outputting larger pixel size
> converted images.
>
> If you roll over carefully, you will also see that there's still a little
> "bulginess", and a slight curve in the just above center straight line, in
> the Silky/ACR conversions, while DxO and PTLens correct completely.
>
> PTLens is even trickier. If applied to the uncorrected image, it stays
> within the pixel bounds, but both corrects more thoroughly AND retains more
> of the original image. HUH??? If you pay close attention to the roll-overs,
> you will see that the Panny/Oly/Adobe correction works from the center out;
> the very center doesn't change in size at all, and the corrected image gets
> progressively larger as you go out.
>
> The PTL correction works both ends, from some middle distance from center.
> The very center gets smaller, so that the farther areas don't have to be
> enlarged as much. It also works with the size of the image it's given. If I
> feed it the uncorrected original, surrounded by blank space to make the
> size of the DxO corrected version, PTL uses all that space to create
> something very much like the DxO correction, although with little arcs of
> black along the edges.
>
> DXO allows one to back off and doesn't use the metadata corrections but
>> their own, for good or for bad.
>>
>
> I like that DxO option of partial correction, in theory, although I don't
> think I've ever used it. OTOH, PTL offers the most flexibility. I can get
> more of the image captured, corrected, in the original pixel size, or give
> it more room and get something almost identical to DxO correction, and then
> have the option of filling in the black arcs using PS Content Aware Fill,
> or crop slightly.
>
> PTL also, at least with this lens, corrects the corners a tiny better than
> DxO and with the Oly 12-50, a lot better. <http://www.moosemystic.net/Ga
> llery/tech/DXO/LensCorrect.htm>
>
> And here's another comparison, with Oly Viewer 3 and RawTherapee this
> time, showing clearly the advantage of DxO and PTL for retaining that WA
> that you spend those $ for, rather than throwing it away in software. <
> http://www.moosemystic.net/Gallery/tech/DXO/_A001643_dist_corr.htm>
>
> Distorted by choice, Mike
>>
>
> Larger, Straighter Moose
>
> * That's Panny; Oly 16 MP sensor is 4608 x 3456.
>
> --
> What if the Hokey Pokey *IS* what it's all about?
> --
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