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Software correction of lens aberrations

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sabesh

sabesh

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I read here that the Panasonic GH1 corrects lens aberrations via s/w (at least with the 14-140). Is this a m4/3 standard? I'd love it if my E-P2 did this as well :) Thx.
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Sabesh
http://www.flickr.com/photos/sabesh/
 
sabesh said:
I read here that the Panasonic GH1 corrects lens aberrations via s/w (at least with the 14-140). Is this a m4/3 standard? I'd love it if my E-P2 did this as well :) Thx.
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All micro 4/3 cameras correct distortion with any lens that provides the necessary data (all micro 4/3 lenses provide this) and additionally Panasonic also corrects lateral CA in its lenses.

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John Bean [GMT]
 
Keep in mind that the camera only does it for JPEGs.

If you shoot raw, your image editor needs to be aware of the distortion parameters (stored within the raw file) and make appropriate adjustments. Both Lightroom 3 and SilkyPix do make these adjustments automatically.
 
rhombus said:
Keep in mind that the camera only does it for JPEGs.

If you shoot raw, your image editor needs to be aware of the distortion parameters (stored within the raw file) and make appropriate adjustments. Both Lightroom 3 and SilkyPix do make these adjustments automatically.
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As does Adobe Camera Raw in Photoshop CS4 and Elements.

Bob
 
What the soft correction do is to correct for :

1. CA
2. Distortion
3. Vignette

which is only part of the result of lens abbe. there are several others that are not ( and likely not able to for now ) be corrected including the like of Stigmitism, Longitudinal Chromatic Aberrations ( LoCA ), Coma , Ghosting, Flare etc ....

Between Olympus and Panasonic there is some difference how they applied the correction it seems but not much difference. One thing though soft correction, just as any Post processing routine goes, is a destructive process, and decrease image quality. Some see it OK, but I would say M4/3 need to deliver another line up of lens that natively deliver proper optical performance instead of relying on soft correction to work. Just different need for different people.

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  • Franka -
 
And Lightroom 2.6
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How long does it take a vegetable to start loosing its freshness? This happens in the amount of time it takes it to go from its victory party to its congressional office!
 
Franka T.L. said:
... One thing though soft correction, just as any Post processing routine goes, is a destructive process, and decrease image quality. ...
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The generalization "software correction is a destructive process which decreases image quality" is incorrect.

When image processing is said to be destructive , it is a technical statement. Destructive in this context means explicitly that data is "irrevocably changed" ... that is, the original data is lost and replaced with new data ... not that it 'destroys' or 'degrades' the data. Good image processing does not degrade the image quality, even if it changes it irrevocably. If this were not the case, NO work with Photoshop or any other image editor, or raw converter, could be used, and we can all see how rendering work with Photoshop improves the image quality even though its operations are "destructive". The lens correction metadata and the routines which apply it are indeed improving the quality of the images made by these lenses.

As example, I have the Summilux-D 25mm f/1.4 ASPH. This lens is a superb performer on my E-1 and L1 bodies, which do not support any automated lens correction metadata. It exhibits a very small amount of residual chromatic aberration when I process the raw files from these cameras, easily removed in the raw conversion using any good raw converter.

Panasonic equipped the Summilux 25 with lens correction metadata to the Micro-FourThirds standard, however, and I can use the lens on the G1 as well with the DMW-MA1 mount adapter. When I do, suitably (correctly) implemented raw converters (like Camera Raw 5.6, Lightroom 2.6 and 3PB, Silkypix, etc) use the lens correction metadata to eliminate the residual chromatic aberration entirely. Rendered to a TIFF file, this is indeed a destructive process (as all raw conversion is) but the image quality is unarguably improved in doing so.

Removing chromatic aberration and geometric distortion, and any other form is image aberration, as well as adjusting tonal scale, color balance, cropping, etc, are indeed all destructive editing processes ... They're done to improve the image quality .

--
Godfrey
http://godfreydigiorgi.posterous.com
 
Franka T.L. said:
One thing though soft correction, just as any Post processing routine goes, is a destructive process, and decrease image quality. Some see it OK, but I would say M4/3 need to deliver another line up of lens that naively deliver proper optical performance instead of relying on soft correction to work.
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Agreed - all things being equal proper optical formula is preferable over soft corrections. But things are never equal. There's I believe a myth that m4/3 lens are relatively small, light and cheap (not always) solely because of format geometry. Certainly it's mostly true but if Oly and Pana didn't allow themselves to heavily compromise on optical formula when it comes to distortions and CA we most probably would see much bigger, heavier and/or slower and pricier m4/3 lens.

Btw, here's how 14-45 image looks uncorrected wide open at 14mm. This kind of distortion would never fly with cheapest APS-C 18-55 kit zoom of any brand (ok, maybe if Yugo were doing lens) despite Pana lens costing 3x more.





--
http://pbase.com/klopus
 
Franka T.L. said:
Between Olympus and Panasonic there is some difference how they applied the correction it seems but not much difference. One thing though soft correction, just as any Post processing routine goes, is a destructive process, and decrease image quality. Some see it OK, but I would say M4/3 need to deliver another line up of lens that natively deliver proper optical performance instead of relying on soft correction to work. Just different need for different people.
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Are you sure you understand what you're asking for? I found this attitude (don't give me any inferior lenses that have to be 'fixed' with software) fairly common among people who don't grasp the tradeoffs. Sure, the lens could be designed with an element or three to try to correct these traits.

But... The corrections may not be as effective (easier to do in software in some cases, especially C/A.) The lens becomes larger and heavier, and more likely to have defects (more elements to misalign.) The correcting elements may add inperfections of their own. More elements will mean more flare and lower contrast, even though the modern nanocoatings have reduced this impact somewhat.

Ever wonder why fast 50s are so popular, and uniformly one of the best lenses in a 35mm system? The geometry allows a simple lens design that is well corrected. :)

On the whole, I'm satisfied with the way Panasonic and Olympus have taken advantage of the new freedoms in lens designs. There isn't a single dog in the system, and most are far up on the excellant side.
Walter
 
saghost said:
I found this attitude (don't give me any inferior lenses that have to be 'fixed' with software) fairly common among people who don't grasp the tradeoffs.
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[...]
saghost said:
On the whole, I'm satisfied with the way Panasonic and Olympus have taken advantage of the new freedoms in lens designs. There isn't a single dog in the system, and most are far up on the excellant side.
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Well said. The cost (both financial and in size and weight) of achieving this performance level purely optically is generally underestimated. The freedom to design hybrid optical+digital correction of new lens designs has resulted in considerable reduction of size and weight with little or no loss of final image quality compared with a similarly performing conventional lens.

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John Bean [GMT]
 
The situation here is not what it seems to be. In truth, one can do better and less costly corrections to distortion and aberations in software than by adding extra elements, bulk and cost. Indeed whenever a lens is designed by raytracing, what comes out is a set of distortion parameters to various orders. It is difficult to design that next modification to null these out exactly. It would require more tweaks more elements etc. ad infinitum. With today's fast processors, you can quicklly carry out the necessary calculations for correction to any order you wish. Ask your self, how on earth(or off) does the Hubble telescope work so well? And recall that time when the Astronauts made a repair visit to install new software tweaks.

That image above showing barrel distortion is irrelevant since it never sees the light of day. It's like showing an image from a lens after one of it's elements has been removed.
 
saghost said:
On the whole, I'm satisfied with the way Panasonic and Olympus have taken advantage of the new freedoms in lens designs. There isn't a single dog in the system, and most are far up on the excellant side.
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The 17/2.8 and oly 14-42 are widely accepted as POS; the 14-42 being inferior to the regular 43 counterpart. The best lens of the bunch, the 20/1.7 is great if you compare with other m43 lenses.. once you start comparing with 50/1.4 from other brands, then its a CA dog as well.
saghost said:
Walter
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Good post saghost and johnblue.

BTW I'm disappointed that photozone says it cannot provide a rating on m43 lenses as they are software corrected. I think it's an excuse, as really they could just let the converter do the auto-correction and then do all their measurements like nothing has happened.
 
ogremage said:
Good post saghost and johnblue.

BTW I'm disappointed that photozone says it cannot provide a rating on m43 lenses as they are software corrected. I think it's an excuse, as really they could just let the converter do the auto-correction and then do all their measurements like nothing has happened.
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I think their view is that once you do software corrections, you're no longer assessing the optical quality of the lens, and that this is not fair, because if you introduced similar corrections for lenses from other manufacturers (Canon, Nikon, etc.) then those software-corrected lens results would be better as well. DxO Optics Pro has what they call "Lens Softness" control, which selectively sharpens the image as you get near the edges and corners, the exact pattern of sharpening based on the known characteristics of the lens and the f-stop being used. It works well, although some people say that if you look closely at 100% some artifacts of this process may be visible.

Bob
 
Robert Deutsch said:
ogremage said:
Good post saghost and johnblue.

BTW I'm disappointed that photozone says it cannot provide a rating on m43 lenses as they are software corrected. I think it's an excuse, as really they could just let the converter do the auto-correction and then do all their measurements like nothing has happened.
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I think their view is that once you do software corrections, you're no longer assessing the optical quality of the lens, and that this is not fair, because if you introduced similar corrections for lenses from other manufacturers (Canon, Nikon, etc.) then those software-corrected lens results would be better as well.
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That sounds reasonable at first glance but doesn't really stand close scrutiny. The micro 4/3 lenses are designed to be digitally corrected and all the necessary parameters are integral with the lens and supplied to the camera and any other downstream software for this explicit purpose. Note that the corrections are applied automatically and are those intended by the lens designer, not necessarily "perfect". This is not at all the same as applying adjustments later without regard for the designer's intent.

With this in mind it's completely reasonable to compare the automatically produced images from these hybrid lenses directly with the automatically produced images from their optic-only counterparts, although Luddites are free to disagree of course :-)

--
John Bean [GMT]
 
Godfrey said:
Godfrey said:
... although some people say that if you look closely at 100% some artifacts of this process may be visible.
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IMO, if you're looking that closely at a photo, there isn't really all that much to see in the photo. ;-)
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Yes, a digital image instance of "can't see the wood for the trees".

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John Bean [GMT]
 
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