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Old Feb 5, 2005, 3:38 AM   #21
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What plugin is that? I might want to try it too.

I, too have found that the photos coming out of the 20D, in general do seem very soft compared to what I'm used to from my P&S cameras. But, as has been mentioned, the P&S cameras are probably using pretty aggressive sharpening internally, and may not have any sort of anti-aliasing filter.

The anti-aliasing filter effectively blurs the image before it gets to the image sensor in order to prevent (not surprisingly) aliasing. For those of you with a background in electronics and/or sampling theory or digital audio, you'll note that the effect is the same as a low-pass filter ahead of an A-D converter. The idea is that you absolutely *must* cut off any signals higher than 1/2 the sampling frequency before you do the conversion or you'll end up with aliases (birdies for you radio folks).

Those aliases, in the case of digitized audio for example, show up as sounds at frequencies which were not in the original signal. That's just not acceptable so you need a very steep anti-aliasing filter to cut off the freqencies at just below 1/2 the sampling frequency. (Do a google for Nyquist Theorem).

For digital audio, the problem is achieving this perfect analog filter to use ahead of the A-D converter. Much of the "harsh" or "gritty" sound that CDs have compared to analog recordings is due to the horrible phase shifts introduced by these anti-aliasing filters which have the difficult chore of passing signals up to 20KHz but absolutely blocking anything above 22.35KHz. If you can come up with an analog filter that can do this, and not show any phase shift at 20KHz, then the world is awaiting your magic design.

This problem has been helped by going to higher sampling rates such as the 96KHz sampling used by some new digital recording equipment.

For the optical "signal" being applied to the image sensor in the camera, this means that you must blur the image just before the image sensor so that you don't have any details which would be smaller than 1/2 the sensor site "frequency". Or at least that's what I imagine the AA filter in the camera to need to do. I wonder if achieving an optical AA filter is as difficult as achieving the perfect analog audio filter. If so, then some of the softness we're all seeing may be simply an unavoidable byproduct of trying to do things right, oddly.

Doing this AA filtering eliminates the optical equivalent of these "birdies" and is necessary for good digitization of the image without the spurious visual manifestations of aliasing.

So one probably shouldn't despair if their fancy digital SLR seems to produce slightly softer images than their Point & Shoot units. As has been mentioned before, it's much better that the camera has the AA filter, and if you want extra sharpness, you can apply some post processing to achieve this. On the other hand, if you take out the AA filter, and you end up with aliasing (which you will), you will not find it easy or possible in most cases to remove it later with post processing.

At least that's the theory. But I still must say I was a bit shocked to see how much less sharp the shots from my 20D are than the ones from my Kodak DX7630. But I'm getting used to it. And I do understand the reasoning behind it all.

Now I need to play more with the various post processing programs and plug-ins and the like and try to become better at the art of the digital darkroom. But at least I don't think the new camera is broken, and I'm somewhat heartened to see that other people have also noticed this seeming softness.

Now what was the plugin that I should try?

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Old Feb 5, 2005, 10:42 AM   #22
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Sigmo, loved the discussion you posted about AA filters. Now, I wonder if that is really how it works...

I think the plugin people were talking about was this one:

http://www.fredmiranda.com/shopping/20DCSpro
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Old Feb 5, 2005, 3:09 PM   #23
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I have previously posted in the 'newbies' group about my nervousness in buying a 20D because I had read on the net that people had returned cameras because of lack of sharpness of image. Today on a shopping expidition in the UK I asked the manager or the leading chain of specialist photo stores whether any 20D's had been returned to him. Apparently yes, and to such an extent that Canon had recalled all his stock. He assured me that the customers replacement cameras had not suffered from lack of sharpness and that his new replacement stock seems OK. So, for people struggling with lack of sharpness it might be worth you returning your camera for a check up while still under guarantee. Two doors down there was an other camera shop, an independant - he said that he had sold loads and had no returns - but I could see that he was lying. A local manager of another shop told me over the phone that he had also had returns of the 20D because of lack of sharpness but put it down to operative inexperience. I think there is a problem, or at least there has been a problen, which Canon have been aware of and have been trying to rectify. I will put off bying my 20D until I feel that everything has settled down.
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Old Feb 5, 2005, 5:21 PM   #24
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geoffs wrote:
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Sigmo, loved the discussion you posted about AA filters. Now, I wonder if that is really how it works...
That's exactly how it works: http://www.wfu.edu/~matthews/misc/DigPhotog/alias/
... and some really understanding folks too!
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Old Feb 5, 2005, 6:14 PM   #25
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Quote:
That's exactly how it works: http://www.wfu.edu/~matthews/misc/DigPhotog/alias/
... and some really understanding folks too!
Hey. That's a good, clear, simple explanation of it. I'm glad I don't have the camera that they show which has no AA filter! I guess my intuition about this was fairly accurate.

I did download that plugin and have played with it a bit. Boy, that does seem to work well. Now I'll have to take more time and really explore its use.

With a tool like that, I'm no longer concerned that the 20D has any problem with lack of sharpness. I really believe that my P&S cameras are just employing a lot more sharpening internally so that the images just look sharper to begin with. As has been mentioned, this might not be the best way to go because it can't be undone very easily if you don't like the effect. I guess I'm pretty happy with the 20D for now. I believe they made the right decisions despite probably losing some sales due to the initial reaction that it creates.

It's sort of like the way headphone manufacturers used to make headphones which attempted to achieve flat frequency response. But now, for most consumer-grade 'phones, the manufacturers purposely set the 'phones up with exaggerated (read inaccurate) response to make them stand out from the crowd so that they'll sound better to you than the pair next to them at the department store when you just listen for a few seconds or minutes. You end up getting lousy frequency response, but they sell better for the impulse buyer and that's the bottom line. So too with the digital cameras, I suppose. If you can make the photos appear sharper, even at the expense of accuracy, then you may sell more cameras. You also see this done where the out-of-the-box settings on some cameras push the saturation up really high to make the photos seem "snappier". It may not be accurate, but it probably does sell cameras.

Now I'm off to play with that new plugin more.

Thanks everyone.

Sigmo

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Old Feb 5, 2005, 8:30 PM   #26
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sigmo wrote:
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... I suppose. If you can make the photos appear sharper, even at the expense of accuracy, then you may sell more cameras. You also see this done where the out-of-the-box settings on some cameras push the saturation up really high to make the photos seem "snappier". It may not be accurate, but it probably does sell cameras.
They do this to big screen and TV monitors too... accuracy doesn't sell - Highly saturated and oversharpen pictures with loud bass do, just check any Best Buy and Circuit City!
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Old Feb 6, 2005, 2:04 PM   #27
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Folks, just got my 1Dmk2 back from Canon for CCD cleaning. I also sent my three L lenses for calibration with the body. I got a note back from them: pretty interesting one at that. And after reading it, it makes sense.

They are claiming the P&S cameras have SHARPNESS tweaked way up there. Along with contrast and colorsaturation, to make VIVID , SNAPPY photos the norm.

The 10D/20D models have moderate amounts of sharpness dialed in, and a bit higher than normal saturation.

The 1Dmk2 has NO sharpness dialed in, and it set for "optimum" color saturation and contrast. This is done with the expectation the photographer will tweak all this in software (in the lab, as they say).

What's curious, is that they then say the 1DsmkII has some sharpness dialed in, and also tweaks the saturation a bit.

To get P&S sharpness, Canon says to set the 1DmkII to SHARPNESS=5, plus a few color tweaks in the camera. To get 1Ds effects, add SHARPNESS=2... etc.

If there is interest, send me a mail and I'll scan and forward the Canon info (its in printed presentation format).

--

I also have a D60... and have always loved it's detail. Here's a table of true pixel size versus camera. Now consider that lenses have finite sharpness, it becomes a real morass as to which camera should be sharper. But the smaller the pixel, the better it can be. Add an anti-alias (low pass) filter, it fuzzes the lines a bit. But all things equal, smaller should be better.

The LP filter, there to spread color and brightness across multiple pixels so that the image quality can be maintained due to RYRYRY GYGYGY BYBYBY nature of CCD's, does soften the image... but not much more than the lens itself already does. The IR filter is also handy. It removes color fringing that most of us have complained about with our earlier point and shoots. Pro's know about these effects (or should), thus don't complain because they know the goodness of these "features" outweighs the "badness". The pixel size below is in microns.

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Old Feb 6, 2005, 6:33 PM   #28
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Read page 26 of the pdf file at the following link which has the same info Canon Service provided to you.

http://www.photoworkshop.com/canon/EOS_Digital.pdf



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