1Ds MKIII and Optical Low Pass filtering

[Jonathan Wienke]

I'm fine! It's the Universe that's f***ed up!

[djgarcia]

Do serious photographers still bother with UV filters? I thought it had been established that modern lens coatings are so hard there's really no need for an additional piece of protective glass.

Call me old fashioned - B+W UVs on all my Zeiss & Leica glass ... just in case

[BernardLanguillier]

The way I read Michael's post is "don't expect a significant resolution difference compared to the 1ds2", and he is not even talking about wide lenses.
[a href=\"index.php?act=findpost&pid=147132\"][{POST_SNAPBACK}][/a]

It seems that this was just a bad dream, the updated version of Michael's review doesn't seem to contain these comments anymore. I guess that we'll know more after his return from Africa.

Cheers,
Bernard

[Graeme Nattress]

Yes, it will be interesting to find out what Michael found out. Aliasing and optical low pass filtering is a very interesting topic of discussion, and certainly rouses debate. But that's what I like about photography - it's a nice mix of the technical and artistic!

Graeme

[djgarcia]

But that's what I like about photography - it's a nice mix of the technical and artistic!

Right on, Brother!

[MarkKay]

I read the review within a day of posting and I never saw anything about a comparison in resolution to the 1DsmkII.  

It seems that this was just a bad dream, the updated version of Michael's review doesn't seem to contain these comments anymore. I guess that we'll know more after his return from Africa.

Cheers,
Bernard
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[BernardLanguillier]

I read the review within a day of posting and I never saw anything about a comparison in resolution to the 1DsmkII.
[a href=\"index.php?act=findpost&pid=147710\"][{POST_SNAPBACK}][/a]

You are correct, it wasn't there in the first review. My point was not about the comparison with the 1ds2, but on the effects of AA filters.

In the initial review, there was a long section on AA filters, their values and downsides, and clear comments that the 1ds3 appears to have a stronger AA filter than the 1ds2, which requested more sharpening to have pleasing results in print. There were also some comments on the result of the comparison with the P45+ focusing on the difference in per pixel sharpness.

Besides, the introduction was starting with Michael saying that he would once more write his impressions as is, and that some people would not like them. This introduction being followed by a detailed discussion on AA filters clearly gave the impression that Michael was not too impressed with the resolution of the 1ds3. Most of his positive comments have not been touched.

Unless I am mistaken, these sections appear to have been removed from the current version of the article.

The only comment left is that the prints are "sharp".

Cheers,
Bernard

[DarkPenguin]

At the end of the review this comment is found ...

In a version of this review which was online for a few hours on Oct 18-19, there was a discussion of antialiasing filters and how I felt that there would be advantages to the 1Ds MKIII not having one, for a variety of reasons. Due to a mix-up, an early version which was not intended for publication because of mistakes in my initial analysis, found its way online in error.

I regret any confusion that this may have caused.

[MarkKay]

Well the problem is that when all these comparisons are made, many feel that after RAW conversion no alterations should be made to the image when comparing different image parameters.  The problem of course is that of course the CCD MF back images captured with no AA filter are going to look greatly different. In my experience the CCD  MF images do not take as much sharpening (and they do not need it) as the canon images.  So there is going to be a subjective component when applying sharpening.  In the end, I am very interested in seeing a RAW comparison between the canon 1DsmkIII and the MF backs after the "optimized" workflow.

The 40D images are soft but take agressive USM --  but sometimes depending on the image, I feel like there are some observed artifacts to get the image to where I would like it to be.  

At the end of the review this comment is found ...
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[marcmccalmont]

Well the problem is that when all these comparisons are made, many feel that after RAW conversion no alterations should be made to the image when comparing different image parameters.  The problem of course is that of course the CCD MF back images captured with no AA filter are going to look greatly different. In my experience the CCD  MF images do not take as much sharpening (and they do not need it) as the canon images.  So there is going to be a subjective component when applying sharpening.  In the end, I am very interested in seeing a RAW comparison between the canon 1DsmkIII and the MF backs after the "optimized" workflow.

The 40D images are soft but take agressive USM --  but sometimes depending on the image, I feel like there are some observed artifacts to get the image to where I would like it to be.
[a href=\"index.php?act=findpost&pid=147739\"][{POST_SNAPBACK}][/a]

Having worked with the same camera with and without the AA filter I prefer the images (in general) without the AA filter and much less software sharpening to the stock camera with the AA filter and twice as much (or more) software sharpening. The difference (subjective) is subtle but nevertheless there. The final prints both optimized need to be compared.
Marc

[John Sheehy]

Having worked with the same camera with and without the AA filter I prefer the images (in general) without the AA filter and much less software sharpening to the stock camera with the AA filter and twice as much (or more) software sharpening. The difference (subjective) is subtle but nevertheless there. The final prints both optimized need to be compared.
[a href=\"index.php?act=findpost&pid=147752\"][{POST_SNAPBACK}][/a]

To me, the biggest problem with AA filters is that they are there even when you don't need them.  They are needed when the optics are very sharp, and they serve no purpose (and cause no significant losses, either) when they are very soft, but in that range where the optics are just a little soft (which is true of most Canon wide-angle lenses), then they add an extra level of softness, perhaps unnecessarily.

What is needed is something like a vibrating sensor, which replaces the functionality of the AA filter with mechanical motion, sweeping the sensor in small circles at least fast enough to do a full circle at the fastest shutter speed or practical flash duration, and the firmware in the camera could have information about what diameter of circle (if any) is needed for each lens at each f-stop.  A user preference could scale the diameter even further.

[Graeme Nattress]

Indeed, the OLPF is there if you need it or not. However, I think it wouldn't be easy to make a vibrating sensor produce the nice gaussian distribution that the OLPF proveds and could provide for artifacts of it's own if it's distribution was more regular and less smooth.

Graeme

[Ray]

Whilst searching the internet for software solutions to aliasing artifacts, I came across this interesting patent by Kodak which addresses (I think) the problem of the lower frequency artifacts below the Nyquist limit.

Here's an extract from the full text.

...... the invention comprises a system for reducing sub-Nyquist aliasing artifacts in an image below a visually perceptible level, where the system includes: a source of image data having sub-Nyquist aliasing artifacts; a visual perception stage utilizing a visual perception algorithm to identify the location and characteristics of the sub-Nyquist aliasing artifacts, thereby generating artifact coordinates and parameters; and an artifact removal stage for processing the sub-Nyquist aliasing artifacts by reference to the artifact coordinates and parameters to reduce their visibility, thereby providing an artifact corrected image.

 While the aliasing is not always totally removed, the advantage of the method according to the present invention is that aliasing is rendered less visible in situations where it might otherwise be visible, all the while using a minimal amount of processing. This provides a feed forward method of minimizing certain aliasing artifacts while not imposing a heavy computational load on the image processing system.

The process seems to involve scaling the source image to a reduced resolution image, then back up again to full resolution, then comparing the upscaled image to both the downscaled image and the original image using a lot of fancy algorithms.

..another extract from http://www.freepatentsonline.com/EP1471728.html

(e) scaling the high resolution source image to reduce the pixel resolution of the high resolution source image to a display resolution, thereby generating a reduced resolution image; and
(f) predicting the visual perception difference between the high resolution source image and the reduced resolution image, thereby identifying the artifacts in the reduced resolution image.
(g) scaling the reduced resolution image back up to the resolution of the high resolution source image, thereby producing an upscaled image;
(h) differencing the high resolution source image and the upscaled image and providing difference components; and
(i) using the difference components and the high resolution source image, the scaled image and the upscaled image to determine parameters of the artifacts, said parameters including artifact type, artifact location, and other parameters such as artifact frequency and phase.

[danm628]

What is needed is something like a vibrating sensor, which replaces the functionality of the AA filter with mechanical motion, sweeping the sensor in small circles at least fast enough to do a full circle at the fastest shutter speed or practical flash duration, and the firmware in the camera could have information about what diameter of circle (if any) is needed for each lens at each f-stop.  A user preference could scale the diameter even further.
[a href=\"index.php?act=findpost&pid=147832\"][{POST_SNAPBACK}][/a]

Move a lens element.  Which is already being done for IS.   Then you can move it much faster than you could move the relatively heavy sensor.  (I foresee hacked IS FW to do this on cameras with the AA filter removed.)

In practice I think you would need more than one full circle to deal with Nyquist.  Hmm...  I'm not used to thinking of signal fade in cameras but it could be an issue with a flash setup.  How constant is the output vs. time?  Should I consider the optical input a Rayleigh faded signal?  

Ack -- I'm mixing work with hobby.  This is bad.  Very bad.  Need to go take pictures and not think about this anymore.

 - Dan

[John Sheehy]

Move a lens element.  Which is already being done for IS.   Then you can move it much faster than you could move the relatively heavy sensor.  (I foresee hacked IS FW to do this on cameras with the AA filter removed.)

In practice I think you would need more than one full circle to deal with Nyquist.  Hmm...  I'm not used to thinking of signal fade in cameras but it could be an issue with a flash setup.  How constant is the output vs. time?  Should I consider the optical input a Rayleigh faded signal? 
[a href=\"index.php?act=findpost&pid=147993\"][{POST_SNAPBACK}][/a]

Increase the speed, then (optical element or sensor).

Well, the best solution is to oversample the optics and omit the AA filter, but that requires reading out many more pixels and introduces storage/tranmission issues.

[Jonathan Wienke]

Move a lens element.  Which is already being done for IS.   Then you can move it much faster than you could move the relatively heavy sensor.

A full-frame sensor is smaller and lighter than most lens elements, and moving the sensor would work with all lenses.

[Ray]

A full-frame sensor is smaller and lighter than most lens elements, and moving the sensor would work with all lenses.
[a href=\"index.php?act=findpost&pid=148031\"][{POST_SNAPBACK}][/a]

We're already moving the sensor or lens for image stabilisation purposes, depending on design. Are we suggesting here a sacrificing of IS so we can dispense with AA filters?

[John Sheehy]

We're already moving the sensor or lens for image stabilisation purposes, depending on design. Are we suggesting here a sacrificing of IS so we can dispense with AA filters?
[a href=\"index.php?act=findpost&pid=148036\"][{POST_SNAPBACK}][/a]

Why would you need to sacrifice sensor-based IS?  You just superimpose the two needed motions.  For lens-based IS, there is no conflict.

[danm628]

A full-frame sensor is smaller and lighter than most lens elements, and moving the sensor would work with all lenses.
[a href=\"index.php?act=findpost&pid=148031\"][{POST_SNAPBACK}][/a]

The IS lens element is small and relatively light.  Without taking apart my lenses and 5D I can't say whether the IS element is lighter than the sensor and sensor packaging.  Though on principal I will accept that the sensor is lighter, so it's really a question about the packaging around the sensor (how much mass do we need to wiggle).  

Summing the IS and AA motions into a single lens is simple, at least in theory.  Of doing it this way means that you only get the AA advantage with some lenses.  Moving the sensor works with all lenses on that body.  Of course as mentioned in another reply you do need faster reads from the sensor which causes other problems.  

  - Dan

[Ray]

Why would you need to sacrifice sensor-based IS?  You just superimpose the two needed motions.  For lens-based IS, there is no conflict.
[a href=\"index.php?act=findpost&pid=148225\"][{POST_SNAPBACK}][/a]

Okay! I'll defer to your superior knowledge on such matters. In my simple-minded way I just assumed if I reach out to catch a cricket ball and then attempt to catch something else at the same time, I might miss the cricket ball. Generally I believe I can only do one thing at precisiely one time. However, I can walk and chew gum at the same time because I don't use my legs for chewing.