"Repairing" an out-of- focus picture
in [DSP]
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From: Jerry Avins on 31 May 2010 23:07 On 5/31/2010 4:42 PM, JimAtQuarktet wrote: > On May 28, 11:52 pm, "Nitram"<morris.vian(a)n_o_s_p_a_m.gmail.com> > wrote: >> Hi, >> >> My question might be simplistic as neither optics nor image processing is >> my field. >> >> Firstly, I was wondering if it is possible to compensate for a picture >> taken by an out-of-focus digital camera by doing a 2D deconvolution on it >> (MMSE filtering or something like that), in order to recover the in-focus >> picture >> >> Secondly, can the optical transfer function between a properly focused >> picture and an out of focus picture be parameterized in such a way that a >> user could recover the image by gradually varying that parameter until the >> image is in focus? If this is indeed possible, what is that transfer >> function? (any references to existing literature would be welcome). >> >> Thank you for your help. > > I am sorry I was late for this discussion. The answer to this is yes, > and the answer to the second is yes. With a technique designated > SeDDaRA, the blurred image is compared to a reference image after > application of an FFT and the transfer function is derived. The > function is converted into a point spread function via an Inverse > FFT. Any deconvolution technique can then be used to deblur the > image. The process is fast compared to iterative tecniques, and at > least as effective. Examples can be found on our website at > http://www.quarktet.com/Gallery1.html as well more info about > SeDDaRA. Our software program Tria (free-to-try) enables easy > application of the method. Where do you get the reference image? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: Jerry Avins on 31 May 2010 23:14 On 5/31/2010 4:42 PM, JimAtQuarktet wrote: > On May 28, 11:52 pm, "Nitram"<morris.vian(a)n_o_s_p_a_m.gmail.com> > wrote: >> Hi, >> >> My question might be simplistic as neither optics nor image processing is >> my field. >> >> Firstly, I was wondering if it is possible to compensate for a picture >> taken by an out-of-focus digital camera by doing a 2D deconvolution on it >> (MMSE filtering or something like that), in order to recover the in-focus >> picture >> >> Secondly, can the optical transfer function between a properly focused >> picture and an out of focus picture be parameterized in such a way that a >> user could recover the image by gradually varying that parameter until the >> image is in focus? If this is indeed possible, what is that transfer >> function? (any references to existing literature would be welcome). >> >> Thank you for your help. > > I am sorry I was late for this discussion. The answer to this is yes, > and the answer to the second is yes. With a technique designated > SeDDaRA, the blurred image is compared to a reference image after > application of an FFT and the transfer function is derived. The > function is converted into a point spread function via an Inverse > FFT. Any deconvolution technique can then be used to deblur the > image. The process is fast compared to iterative tecniques, and at > least as effective. Examples can be found on our website at > http://www.quarktet.com/Gallery1.html as well more info about > SeDDaRA. Our software program Tria (free-to-try) enables easy > application of the method. Pictures on the web site are better far defined after processing, but colors are altered even in areas of solid color where I would expect no change. In other pictures, the contrast is increased beyond what sharper focus alone would achieve. What postprocessing has been applied? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: Clay on 1 Jun 2010 12:31 On May 28, 11:52 pm, "Nitram" <morris.vian(a)n_o_s_p_a_m.gmail.com> wrote: > Hi, > > My question might be simplistic as neither optics nor image processing is > my field. > > Firstly, I was wondering if it is possible to compensate for a picture > taken by an out-of-focus digital camera by doing a 2D deconvolution on it > (MMSE filtering or something like that), in order to recover the in-focus > picture > > Secondly, can the optical transfer function between a properly focused > picture and an out of focus picture be parameterized in such a way that a > user could recover the image by gradually varying that parameter until the > image is in focus? If this is indeed possible, what is that transfer > function? (any references to existing literature would be welcome). > > Thank you for your help. Yes to some extent it is possible, if you lookback to the 1980s when Kodak introduced the Disc camera. Its trick was the point spread function (optical equivalent of a 2-d impuse response) was know by Kodak so when they processed the disc film (it was only 16mm), a computer would deconvolve out the point spread function effectively sharpening the image. Since this was only available for this camera, the disc film had a market advantage. But soon this technology was incorporated into 35mm film printers (even with an unknown point spread function) to provide for image sharpening. Some of the early stuff was over sharpened and the holoes in the images were a bit distracting. Today, one buys software with lens correction details for a library of lens and a picturer's EXIF info is used to select the corrections. The following is one of the leaders in this field now: http://www.dxo.com/intl/photo Clay Clay
From: glen herrmannsfeldt on 1 Jun 2010 13:59 Clay <clay(a)claysturner.com> wrote: (snip) > Yes to some extent it is possible, if you lookback to the 1980s when > Kodak introduced the Disc camera. Its trick was the point spread > function (optical equivalent of a 2-d impuse response) was know by > Kodak so when they processed the disc film (it was only 16mm), a If I remember it right, 8mmx10mm. Also, that the disc cameras were the first mass production cameras with a non-spherical lens. It seems not so hard to do with molded plastic, as with individually ground glass. > computer would deconvolve out the point spread function effectively > sharpening the image. Since this was only available for this camera, > the disc film had a market advantage. But soon this technology was > incorporated into 35mm film printers (even with an unknown point > spread function) to provide for image sharpening. Some of the early > stuff was over sharpened and the holoes in the images were a bit > distracting. -- glen
From: Clay on 1 Jun 2010 14:14
On Jun 1, 1:59 pm, glen herrmannsfeldt <g...(a)ugcs.caltech.edu> wrote: > Clay <c...(a)claysturner.com> wrote: > > (snip) > > > Yes to some extent it is possible, if you lookback to the 1980s when > > Kodak introduced the Disc camera. Its trick was the point spread > > function (optical equivalent of a 2-d impuse response) was know by > > Kodak so when they processed the disc film (it was only 16mm), a > > If I remember it right, 8mmx10mm. I know it was small. Also this is when they announced the Extar emulsion which quickly replaced Kodacolor II as their C-41 film for use in 35mm. > > Also, that the disc cameras were the first mass production cameras > with a non-spherical lens. It seems not so hard to do with molded > plastic, as with individually ground glass. > Nowadays, molded aspherics are becoming common. My 17-35mm nikkor zoom has a highly aspheric front element. Its shape reveals itself by simply reflecting a light off of the front of the lens as you tilt it. Its central region is concave whereas it is convex on the outer region! Clay |