Luminous Landscape Forum
Equipment & Techniques => Cameras, Lenses and Shooting gear => Topic started by: Ray on July 27, 2006, 02:06:51 am
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My first digital camera was the D60 with a pixel pitch close to that of the current 1Ds2. Shortly after the D60 was released, we had the 1Ds with a larger number of pixels and a larger sensor.
I always though it curious that 1Ds owners would emphatically declare, on this site and elsewhere, that their camera was 'ruthless' with inferior quality lenses and that to get the best from the camera you needed really good lenses. In other words, lenses are the weak link.
I found it curious because my common sense (nous) told me that all cameras perform better with better lenses. The 1Ds or 1Ds2 is no exception.
Now that I'm an owner of a 5D, I can test this 'common sense' theory of mine.
I first carried out tests with a rather average zoom, the 100-400L IS, with and without 1.4x extender, and demonstrated some surprising results.
Suspecting the results might be a bit inconclusive because of the inferiority of the lens (which was actually described as crap by a person whose name I shall not mention), I decided to repeat the test with a better quality lens at a close distance to a test chart of lines and textures, which I constructed myself for the purpose.
My sharpest lens is the humble Canon 50/1.8, which I used for the test. The next sharpest would be the much more expensive TS-E 90mm.
The following images are a bit large (around 2MB after download) but they demonstrate clearly that even at f22, the 20D delivers more detail than the 5D, after cropping the 5D image to the same size as the 20D image then interpolating.
There's always an issue of sharpening. Should one sharpen the interpolated 5D image and not the uninterpolated 20D image? Should one sharpen both images, but the interpolated 5D image more?
I've chosen the latter option as a compromise with concerns of Bill Janes, althought it's clear to me that sharpening does not alter the outcome. The 5D images are sharpened more than the 20D images in the following examples.
For the benifit of those who don't want to bother downloading the test images, the results are unambiguous. The 20D produces more image detail and better contrast at both f22 and f8, than the 5D after cropping.
This is good news for those who are expecting a 22mp 5D or 1Ds2 successor.
The first image is an overview of my test chart which consists of Norman Koren line charts, fluffy twine and various grades of sandpaper pasted to a plywood base with wood grain. After viewing a TV documantary on Andy Warwhol (have I spelt that correctly?) it did occur to me for a brief fraction of a second that perhaps I should urinate on my carefully constructed test chart to create some subtle gradients. I decided against it on the grounds of hygiene.
[attachment=842:attachment]
The following 3 images are really self explanatory.
[attachment=841:attachment] [attachment=843:attachment] [attachment=844:attachment]
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After viewing a TV documantary on Andy Warwhol (have I spelt that correctly?) it did occur to me for a brief fraction of a second that perhaps I should urinate on my carefully constructed test chart to create some subtle gradients. I decided against it on the grounds of hygiene.
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That was probably the right decision.
Those guys complaining about how demanding the 1ds was on their lenses were probably speaking about the corners... and your test kind of supports their statement since you reached the conclusion that the lenses you tested had no problem dealing with the extra detail prodived by the 20D as a result of the higher pixel density [in the APS- sized center section of the image circle].
I am not sure that your conclusion about a 22MP 1ds3 is a logical deduction of your test results, since you are overlooking how poorly images would look in the corners of images taken with current wide angle lenses with such high pixel count FF sensors...
Cheers,
Bernard
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...
After viewing a TV documantary on Andy Warwhol (have I spelt that correctly?) it did occur to me for a brief fraction of a second that perhaps I should urinate on my carefully constructed test chart to create some subtle gradients. I decided against it on the grounds of hygiene
...
Ray,
Your 5D is NOT weather-sealed!
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My first digital camera was the D60 with a pixel pitch close to that of the current 1Ds2. Shortly after the D60 was released, we had the 1Ds with a larger number of pixels and a larger sensor.
I always though it curious that 1Ds owners would emphatically declare, on this site and elsewhere, that their camera was 'ruthless' with inferior quality lenses and that to get the best from the camera you needed really good lenses. In other words, lenses are the weak link.
I found it curious because my common sense (nous) told me that all cameras perform better with better lenses. The 1Ds or 1Ds2 is no exception.
Now that I'm an owner of a 5D, I can test this 'common sense' theory of mine.
I first carried out tests with a rather average zoom, the 100-400L IS, with and without 1.4x extender, and demonstrated some surprising results.
Suspecting the results might be a bit inconclusive because of the inferiority of the lens (which was actually described as crap by a person whose name I shall not mention), I decided to repeat the test with a better quality lens at a close distance to a test chart of lines and textures, which I constructed myself for the purpose.
My sharpest lens is the humble Canon 50/1.8, which I used for the test. The next sharpest would be the much more expensive TS-E 90mm.
The following images are a bit large (around 2MB after download) but they demonstrate clearly that even at f22, the 20D delivers more detail than the 5D, after cropping the 5D image to the same size as the 20D image then interpolating.
There's always an issue of sharpening. Should one sharpen the interpolated 5D image and not the uninterpolated 20D image? Should one sharpen both images, but the interpolated 5D image more?
I've chosen the latter option as a compromise with concerns of Bill Janes, althought it's clear to me that sharpening does not alter the outcome. The 5D images are sharpened more than the 20D images in the following examples.
For the benifit of those who don't want to bother downloading the test images, the results are unambiguous. The 20D produces more image detail and better contrast at both f22 and f8, than the 5D after cropping.
This is good news for those who are expecting a 22mp 5D or 1Ds2 successor.
The first image is an overview of my test chart which consists of Norman Koren line charts, fluffy twine and various grades of sandpaper pasted to a plywood base with wood grain. After viewing a TV documantary on Andy Warwhol (have I spelt that correctly?) it did occur to me for a brief fraction of a second that perhaps I should urinate on my carefully constructed test chart to create some subtle gradients. I decided against it on the grounds of hygiene.
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Ray,
Your tests are interesting and demonstrate a fundamental point about MTF. Photographers who say that the camera outresolves the lens are speaking rather simplistically, and appear to be assuming that the imaging chain is no stronger than its weakest link.
In a test such as yours, the system MTF is being tested and this includes the lens, camera sensor, and raw conversion or in camera software. However, MTFs multiply. To determine the MTF of the final output, one multiplies the MTF of the lens by that of sensor and software. This is discussed in simple terms on this site in section 3.2:
[a href=\"http://www.edmundoptics.com/techSupport/DisplayArticle.cfm?articleid=289]http://www.edmundoptics.com/techSupport/Di...m?articleid=289[/url]
Now even if your lens does not have the best MTF at a given frequency, a camera with a higher MTF will always give a better system MTF since this is the product of the lens MTF (which remains the same) and the camera MTF (which increases with the D20 because of its finer pixel pitch).
Norman Koren goes into more detail on his site
http://www.normankoren.com/Tutorials/MTF.html (http://www.normankoren.com/Tutorials/MTF.html)
The classical formula for system MTF is 1/r = 1/r1 + 1/r2 + ... + 1/rn, where r is the system MTF and r1, r2, etc are the MTFs of the lens, sensor and other components. This works only for low MTFs (around 10% such as used in USAF resolution charts). For higher frequencies, one must separate the frequency components with a Fourier transform, perform the multiplications, and then recombine the results with a cumbersome convolution process. This is beyond the capabilities of most of us, but the principle is understandable.
Another consequence of the multiplicative properties of MTFs is that the system MTF is lower than might be expected, since we are multiplying factors that are all less than unity. For example if the individual MTFs are 50% and there are three links in the chain, the overall MTF would be 12.5%
Bill
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Ray, what are the pixel dimensions of the photos from the 5D vs the 20D?
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Ray, what are the pixel dimensions of the photos from the 5D vs the 20D?
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The 5D images are cropped to the same dimensions as the 20D images then interpolated to the same file size of 46.8MB. Essentially it's a comparison between 4.8m big pixels and 8m small pixels.
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Another consequence of the multiplicative properties of MTFs is that the system MTF is lower than might be expected, since we are multiplying factors that are all less than unity. For example if the individual MTFs are 50% and there are three links in the chain, the overall MTF would be 12.5%
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Bill,
How does this explain the fact that detail (texture, high contrast fine B&W lines, low contrast broad lines etc) are hardly worse at f22? There should be a significant fall-off in MTF at all frequencies at f22 compared with f8, shouldn't there?
The following crops compare maximum line resolution for both cameras at f8 and f22. The number 100 on the chart is irrelevant. I didn't calculate a precise distance to the target that would enable me to derive an lp/mm rating, but if I were counting lines, I don't see the result would be much different at f22 or f8.
[attachment=846:attachment] [attachment=847:attachment]
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Bill,
How does this explain the fact that detail (texture, high contrast fine B&W lines, low contrast broad lines etc) are hardly worse at f22? There should be a significant fall-off in MTF at all frequencies at f22 compared with f8, shouldn't there?
The following crops compare maximum line resolution for both cameras at f8 and f22. The number 100 on the chart is irrelevant. I didn't calculate a precise distance to the target that would enable me to derive an lp/mm rating, but if I were counting lines, I don't see the result would be much different at f22 or f8.
[attachment=846:attachment] [attachment=847:attachment]
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Ray,
The 5d image is difficult to interpret because of aliasing and moire, so I will concentrate on the 20D image at f/8 and f/22. Actually, the MTF is much higher at f/8 as revealed by Norman Koren's quantitative methods using image J
[a href=\"http://www.normankoren.com/Tutorials/MTF5.html]http://www.normankoren.com/Tutorials/MTF5.html[/url]
Here is the 20D image at f/8 with readings taken from the top of the resolution chart. The maximum value is about 251 and the minimum value is 7. Calculating C(f) yields a value of 0.95 (C(f) = (Vmax-Vmin)/(Vmax+Vmin))
[attachment=848:attachment]
And here is the image at f/22. As you can see, the contrast is much lower, but the perceived resolution is about the same. The eye needs only a MTF of about 10% to resolve the lines:
[attachment=849:attachment]
C(f) is now 0.36.
To figure MTF I would need C0, and this is left to the reader.
Bill
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Ray, I’ve read more times than I can count about the superiority of the 20D pixel pitch, i.e. the 20D is capable of capturing more resolution than the 5D or 1Ds because of the 20D’s smaller pixel pitch. Moreover, I’ve yet to see anyone dispute this proposition. So, I’ll go out on a limb and dispute the rationale of this proposition. (I don’t own a DSLR so I can’t speak from actual experience, but I don’t believe that I need actual experience to poke holes in this proposition.)
Ray, I postulate that your test only shows that, for a given sensor area and pixels of nearly equal quality, more pixels resolve more detail than fewer pixels. I don’t think your test shows that a smaller pixel pitch is superior.
Lets do a very simplified though experiment. Assume we have a sensor size X with 100 pixels with a pixel pitch of Y. We also have a sensor size ½X with 100 pixels and a pixel pitch of ½Y. Everything else is constant, i.e., the pixels and lenses over the entire sensor areas are of equal quality. In this case, I postulate that pixel pitch Y will resolve the same detail as pixel pitch ½Y. The smaller sensor needs the smaller pixel pitch to equal the resolution of the larger sensor because the image details on the smaller sensor are also smaller.
In the real world, of course, pixels and lenses are rarely equal, especially when different sensor areas are involved. Therefore, I won’t speculate whether in actual use a 20D is capable of resolving more detail than a 5D or 1Ds.
Ray, I expect and hope that you and the other more technically inclined participants in this forum will let me know whether I’ve totally missed the boat on this one or if my reasoning is sound.
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Ray,
In a test such as yours, the system MTF is being tested and this includes the lens, camera sensor, and raw conversion or in camera software. However, MTFs multiply. To determine the MTF of the final output, one multiplies the MTF of the lens by that of sensor and software. This is discussed in simple terms on this site in section 3.2:
http://www.edmundoptics.com/techSupport/Di...m?articleid=289 (http://www.edmundoptics.com/techSupport/DisplayArticle.cfm?articleid=289)
[a href=\"index.php?act=findpost&pid=71852\"][{POST_SNAPBACK}][/a]
I looked at the website quoted and....shuddered....
Every component within a system has an associated MTF and, as a result, contributes to the overall MTF of the system. This includes the imaging lens, sensor, capture boards, and cables, for instance.
(my emphasis)
Anyone who has even a passing interest in hi-fi will be fully aware of the claims, counterclaims, warfare and and total BS that surrounds so-called 'audiophile' cables.
Are we really heading that way....please God, No...
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The smaller sensor needs the smaller pixel pitch to equal the resolution of the larger sensor because the image details on the smaller sensor are also smaller.
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Are they?
As has been recently postulated on a couple of threads (one of mine included), the image that hits the sensor is not smaller - the image projected by the lens is the same size in FF and cropped-frame cameras. It is just that the sensor, being physically smaller, covers a smaller part of the image projected by the lens.
So there is the theoretical possibility of greater resolution is the pixel pitch is smaller. I think the greater issue is that the smaller pixel pitch leads to greater electronic noise and so requires more in-camera processing.
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Spidermike, I don’t see the logic in your analysis. Using your logic, one could say that the image projected by a lens on a 35mm film camera is not smaller than the image projected on an 8x10 view camera. You may be correct if you are prepared to only use a 35mm size crop from the 8x10, but isn’t that approach a little bizarre?
Perhaps I should have made it clear that I assumed that the full sensor area would be used in each case.
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Ray, I postulate that your test only shows that, for a given sensor area and pixels of nearly equal quality, more pixels resolve more detail than fewer pixels. I don’t think your test shows that a smaller pixel pitch is superior.
Dmerger, I'm using the word superior here to describe an attribute which allows one camera (the 20D) to do something another camera (the 5D) cannot. There are other attributes of the 5D which could be described as superior to the 20D.
As a thought experiment, if you were stuck in a room with the 20D and 5D and had just one lens, which camera would allow you to capture the most information about the scene through the window?
The reason these tests are of interest to me is that ever since the introduction of the 1Ds we have had numerous claims that greater pixel density than that of the 1Ds will serve little purpose because lenses are simply not good enough.
In fact certain people have even implied that the performance of a lens at f22 is hardly better than that of a Coke bottle. Well, here's the proof of the pudding. Even at a Coke bottle aperture of f22, greater pixel density than that of the 1Ds and 5D can serve a purpose with ordinary, current 35mm lenses.
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And here is the image at f/22. As you can see, the contrast is much lower, but the perceived resolution is about the same. The eye needs only a MTF of about 10% to resolve the lines:
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Bill,
I think that is the explanation. We're now back to a previous discussion about the extent to which the lower over all MTF at f22 can be augmented with contrast enhancement and sharpening techniques.
Both images below, comparing f8 with f22 on the 20D, have been sharpened, but the f22 image sharpened more and local contrast enhancement applied. I've overdone the f22 contrast a bit, but the images are surprisingly close, to my eyes, considering these are 300% enlargements.
There's no doubt though that the f8 image is slightly better, cleaner. The f22 image shows a break-up of the finer lines sooner.
BTW, the irregularity of the contrast and width of these lines is due to imperfect printing, but I'm not sure if this is caused by inappropriate gamma, dot gain or simply that I didn't use the 2880 dpi setting. In these examples, it doesn't really matter because the irregularity is a detail feature in itself and shows up at both f8 and f22.
[attachment=850:attachment]
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Ray, it depends. If you are at the window with an unobstructed view, and “most information” means capturing as much of the exterior scene as possible, then the 5D wins hands down. If you are far from the window and a large part of the 5D frame is of the interior, then the 20D may capture a little more resolution of the exterior. In the first example, however, the 20D captures ZERO information outside its field of view. In the second example, the 5D captures the same field of view of the exterior but with a little less resolution. So, without more information, I’d say that the 5D would capture the most information, no contest.
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Ray, it depends.
[a href=\"index.php?act=findpost&pid=71931\"][{POST_SNAPBACK}][/a]
You're stuck, whether close to the window or not. You need to capture as much information as possible about enemy troop positions in the distance. You can take as many shots as your flash card allows. You have one lens only. Which camera do you use?
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You're stuck, whether close to the window or not. You need to capture as much information as possible about enemy troop positions in the distance. You can take as many shots as your flash card allows. You have one lens only. Which camera do you use?
[a href=\"index.php?act=findpost&pid=71932\"][{POST_SNAPBACK}][/a]
The way people respond to these types of comparisons really shows what kind of photography they do. Anyone who has ever done much wildlife photography knows that the longest telephotos become feeble when the subject is either small or distant, and people with this kind of experience know what its like to have a large frame of nothing.
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Neither, I run like hell!
Ray, I see your point, but I don't see what it proves. We can create a lot of scenarios where a 5D would be better and others where a 20D would be better, e.g. whether a wide field of view is desired or you don’t have a long enough lens and want a close-up. In your scenario, the 20D would be best, but I don’t think it has any bearing on the “superiority of the 20D pixel pitch”.
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Neither, I run like hell!
Ray, I see your point, but I don't see what it proves. We can create a lot of scenarios where a 5D would be better and others where a 20D would be better, e.g. whether a wide field of view is desired or you don’t have a long enough lens and want a close-up. In your scenario, the 20D would be best, but I don’t think it has any bearing on the “superiority of the 20D pixel pitch”.
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I
It has no bearing on the superiority of one camera in ralation to another in general terms, but it does have a bearing in specific terms. As the saying goes, best tool for the job.
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Don't forget that the 5D and 20D have much stronger AA filters.
1Ds produces VERY sharp single-pixels.
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Don't forget that the 5D and 20D have much stronger AA filters.
1Ds produces VERY sharp single-pixels.
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Then you'd expect to see more moire with the 1Ds . I've seen very nice images from the 1Ds, but I [a href=\"http://www.geocities.com/andyandmichele/index.htm]found[/url] a while back, that even the 10D captured finer details due to its finer pixel pitch (but obviously fewer total details), leading me to conclude that the "Strength" of the AA filter in both was similar. (A bit better definition of the enemy troops on the horizon!)
I'd love to see a good methodology for comparison of AA "strengths" so we'd really know how they stack up.
Andy
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The way people respond to these types of comparisons really shows what kind of photography they do. Anyone who has ever done much wildlife photography knows that the longest telephotos become feeble when the subject is either small or distant, and people with this kind of experience know what its like to have a large frame of nothing.
[a href=\"index.php?act=findpost&pid=71938\"][{POST_SNAPBACK}][/a]
John,
Of course, if you start adding conditions then the thought experiment will be expanded and the choice maybe different. If you had just one shot left, on the basis that all the other shots on the card contained essential information and could not be deleted, and, if the angle of view of the lens was such that the FoV with both cameras (from your stuck position) was not cropped by the window frame and the interior of the room, then the larger format camera would provide more general information and any loss of specific information might not be relevant.
However, as you can see in some of the charts I've posted, the difference between the 20D and the 5D can mean that the name 'Norman Koren' is either legible or illegible, or in the case of the thought experiment, the type and model of a tank partially obscured by foliage, certain or uncertain.
However, the reason I did these experiments was not just to confirm that the higher pixel density 20D could resolve more detail with the same lens from the same distance, but to confirm that it could so so even at f22.
Having recently come across the following chart at Roger Clark's site, which relates diffraction spot size to f stop number, it would seem to me that resolution at f22 with a small pixel camera such as the 20D should be very poor.
Unfortunately, since I don't have any in-depth knowledge about much at all, I'm at a loss to explain how a whopping big Airy Disk 28.5 microns in diameter can permit a camera with a pixel pitch of around 6.4 microns to do so well at f22.
[attachment=855:attachment]
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However, the reason I did these experiments was not just to confirm that the higher pixel density 20D could resolve more detail with the same lens from the same distance, but to confirm that it could so so even at f22.
Having recently come across the following chart at Roger Clark's site, which relates diffraction spot size to f stop number, it would seem to me that resolution at f22 with a small pixel camera such as the 20D should be very poor.
Unfortunately, since I don't have any in-depth knowledge about much at all, I'm at a loss to explain how a whopping big Airy Disk 28.5 microns in diameter can permit a camera with a pixel pitch of around 6.4 microns to do so well at f22.
[attachment=855:attachment]
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Maybe most of the area of the disk only represents a small percentage of light intensity.
My opinion is that this whole idea of "diffraction limits" is ill-conceived or ill-applied.
I don't believe an arbitrary application because there is some correct arithmetic associated with it!
It is very apparent from my experience that this stuff does not apply, unmodified, to digital photography. An airy disk does not pixelate - it only reduces pixel-to-pixel contrast, effectively raising the exposure index of high-frequency detail, but sharpening restores it.
It is also apparent that images from WA lenses get softer from diffraction at much lower f-stops than longer lenses. I see my 10-22 zoom getting softer above f/7.1 but my telephotos don't start getting soft until much higher.
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However, the reason I did these experiments was not just to confirm that the higher pixel density 20D could resolve more detail with the same lens from the same distance, but to confirm that it could so so even at f22.
Having recently come across the following chart at Roger Clark's site, which relates diffraction spot size to f stop number, it would seem to me that resolution at f22 with a small pixel camera such as the 20D should be very poor.
Unfortunately, since I don't have any in-depth knowledge about much at all, I'm at a loss to explain how a whopping big Airy Disk 28.5 microns in diameter can permit a camera with a pixel pitch of around 6.4 microns to do so well at f22.
[attachment=855:attachment]
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Ray and John,
Another table from Roger Clark's site adds some useful information. As John mentions, as the aperture decreases, the diffraction spot becomes larger and contrast is lost. However, resolution at low contrast still is present. The Rayleigh resolution criterion is MTF at around 10% and contrast can be restored by sharpening, as Ray demonstrated in his comparisons at f/8 and f/22. However, I find it difficult to believe that it would not be better to have good contrast in the first place, and it would be best to evaluate the entire image before coming to conclusions about the success of the sharpening approach.
[attachment=856:attachment]
Another approach to image restoration is with the Richardson-Lucy deconvolution algorithm. As you may remember, this method was used to rescue images from the Hubble telescope before the optics could be fixed. As I recall, the problem was spherical abberation. Unfortunately, this algorithm is not available (to the best of my knowledge) as a plugin for Photoshop.
[a href=\"http://www.clarkvision.com/imagedetail/image-restoration1/index.html]http://www.clarkvision.com/imagedetail/ima...ion1/index.html[/url]
Here is an interesting thread on the subject:
http://www.howtofixcomputers.com/bb/ftopic...05-0-asc-0.html (http://www.howtofixcomputers.com/bb/ftopic164305-0-asc-0.html)
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Maybe most of the area of the disk only represents a small percentage of light intensity.
Considering that absolute resolution at f22 is only a few lines less than at f8, it seems a surprisingly large percentage to me. However, in principle that sounds like a good explanation to me.
It is also apparent that images from WA lenses get softer from diffraction at much lower f-stops than longer lenses. I see my 10-22 zoom getting softer above f/7.1 but my telephotos don't start getting soft until much higher.
I've always thought the Canon 10-22 was a rather soft lens. I had to test 3 of them before finding one that was almost as sharp at 15mm and f8 as my Sigma 15-30. Maybe I should compare these 2 lenses at a wider aperture. The Sigma seems to behave, between f8 and f16, pretty much as other lenses do, ie. no significant fall-off in resolution.
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However, resolution at low contrast still is present. The Rayleigh resolution criterion is MTF at around 10% and contrast can be restored by sharpening, as Ray demonstrated in his comparisons at f/8 and f/22. However, I find it difficult to believe that it would not be better to have good contrast in the first place, and it would be best to evaluate the entire image before coming to conclusions about the success of the sharpening approach.
I wouldn't argue with that, Bill . What I think is happening here is that the diffraction spot sizes in Roger's tables are for ideal lenses fully diffraction limited at the f stops quoted. He probably mentions that somewhere. As one stops up from f22, the diffraction spot size decreases, but not in inverse proportion to the MTF. Other aberrations detract from the improvement. A lens's sweet spot, whether it is at f4, f5.6 or f8, usually delivers only very marginally greater MTF than at the next stop down, but it's enough to get some people excited.