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Author Topic: Michael's Tests of EOS-1Ds  (Read 17433 times)
jwarthman
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« Reply #80 on: October 02, 2002, 11:42:09 AM »
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[font color=\'#000000\']Jim mentioned downsampling a 33MB 1Ds file to 9MB to put it on the same footing as the D30 and then upsampling both files to search for differences. I'm not sure if such an experiment is going to be at all useful. One would expect any differences, if any, to be very subtle. But if you did see any differences, with a magnifying glass, how would you know they were not differences in the lenses used?[/font]
[font color=\'#000000\']Ray,
In the steps I described, the same image would be printed twice - once using full resolution of the 1Ds, and once after downsampling (to emulate a D30) then interpolated to make the second print the same size as the first print. The differences cannot result from the effects of different lenses because it starts with a single image!

Like you, I expect the differences to be subtle. Recently I printed two copies of a 12 x 18 print on my Epson 1270. One was printed by setting the Epson driver to 720 PPI, the other using 1440 PPI. Both prints were quite good. But placing them next to each other, and viewing from a few feet distance, the one printed at 1440 was somehow deeper and richer. Upon close examination (without a loupe), the differences were hard to pinpoint.

Perhaps printing an 8 x 10 from the D30 and from the 1Ds will produce a similar difference - we'll see!

Enjoy!

-- Jim[/font]
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mtomalty
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« Reply #81 on: September 28, 2002, 09:47:03 PM »
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[font color=\'#CC9900\']Michael

Thanks for the early and thorough info on the 1Ds.
In you first report,on the subject of moire,you mentioned that since
a large proportion of your work is wildlife and scenic in nature you
didn't expect moire to be an issue for you.
As a former 1d owner (I had one for 2 weeks before getting an
inside tip that the 1Ds was to be announced and fortunately deal
with an understanding supplier) I ran into moire quite a few times in
my short stint with the camera-specifically in  birds feathers,some
animal fur,sand dunes,and the occasional brick wall.
Before you have to return the camera to Canon and if the opportunity
presents itself could you shoot some bird images.
I'd be curious to see if the higher pixel count will help alleviate this
problem.

Thanks
Mark Tomalty[/font]
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jackmac
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« Reply #82 on: October 02, 2002, 07:27:30 PM »
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[font color=\'#000000\']Thank Michael for his work by buying his Video Mag.
Michael, I reupped in anticipation of you getting Canon to get you the 1Ds in record time. After you sold me on the D-30 in a timely way, I figure I have saved $4,000 in film. So another extension of my subscription for $99 seems a more than fair exchange.
Ressing Up. I could get some 13x19 prints off some subjects with the D30. I am assuming that posters 20x30 are now in reach. But with what printer?
By the way, regarding the question someone had of going to 20meg chips seems useless for 35 size since this site has discussed that at 11 we are maxing out the resolving power of Canon lenses, true? From here on out the increase in dynamic range to negative film levels would be more useful.

Additionally, Michael's suggestion that we talk to the camera to make it change control is interesting, I'm already talking to my camera, but it isn't responding.[/font]
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Dale Cotton
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« Reply #83 on: October 04, 2002, 09:47:45 AM »
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[font color=\'#000000\']JacMac asks:

"By the way, regarding the question someone had of going to 20meg chips seems useless for 35 size since this site has discussed that at 11 we are maxing out the resolving power of Canon lenses, true?"

Reading the www.imaging-resource.com 4/3rds project report I came across the following:

"...According to Olympus, most current lenses for 35mm SLRs resolve down to about 10 microns, and top-end lenses to around 6 microns."

From dpreview's 1Ds report we can see that the 1Ds' pixel size will be 8.8 microns. Looks like the answer is "getting darned close".

Since the 1Ds fits 11.4 million pixels in a 35.8 x 23.8 mm imager and the 14n will fit 13.89 in the same area, that suggests the 14n's pixel pitch will be 7.2 microns. Working backward (and presuming my math is correct), 16.72 million pixels, each at 6 microns, would meet the ceiling imposed by lens resolving power.

This is not to suggest that even a 16.72 megapixel camera would provide the ultimate resolution for 35mm format. I think Foveon has taught us that. I want a full-frame, 17 megapixel X3 dSLR for XMas.[/font]
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halftone
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« Reply #84 on: October 07, 2002, 05:02:20 AM »
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[font color=\'#000000\']A couple of points which hopefully add a little on aliasing/tonal smoothness, and dynamic range. My biggest concern with the review and conclusions is how the #### I am ever going to afford a 1DS...

Quote
Of course there will now be a chorus of those who say, "Ya, but a drum scan would have really shown a bigger difference in favour of film." Humm. Maybe. But here are my thoughts on this recurring topic. I have had drum scans made from my 35mm and medium format film on several occasions. Yes, an 8000 ppi scan is impressive, and can make bigger prints. But, I'm also convinced that while they give me more pixels, I don't get a whole lot more real data. There simply isn't that much more information on film than about 4,000 PPI. Above that we get bigger files, but not much more information. Maybe, 20% more than the 3200 PPI scans that my Imacon Flextight Photo scanner is capable of, but not 2 or 3 times as some inexperienced people presume from the numbers.

I agree with Michael's 4,000ppi  'diminishing returns' assessment as far as image detail is concerned, but it isn't enough to reach conclusions regarding tonal smoothness.

Film grain is irregular both in size, distribution and topology, and all of these attributes interact with the fixed geometry of pixel size and distribution. What many people believe is grain in their scanned images is often aliasing, which produces an exaggerated grain-like structure comprising false colour/false luminance pixels.

Avoiding this in low-pixel-count scanners is only possible by using a low-pass optical system (soft lens or antialiasing filter) which hurts image detail as well.

Grain aliasing can be so extreme as to render a scan unusable, especially with grainy, fast B&W silver-based films, but generally it is acceptable with scanners  >=4,000ppi.

When it happens, the result is far more 'texture' than the film image exhibits when viewed or printed by analogue techniques.

Having seen comparative drum scans of an ISO100 tranny done at 4,000, 8,000, and 12,000 ppi, there isn't much gain in resolution of image detail above 4,000ppi, which accords with what Michael says in his review. By 8,000 ppi the scan has virtually all of it. Yet 12,000ppi shows a significant increase in grain detail over 8,000ppi, with better rendition of individual grain shapes. A lot of people say this doesn't matter, grain detail is not image information we want...

However, if we don't capture precise grain information, what we get through the conversion to pixels is aliasing, and a characteristically false and 'noisy' rendition of the film image. An Imacon scan at 3,200ppi necessarily adds an unknown  extra dimension of aliasing noise.

How much, and how destructive depends on the anti-aliasing filter and CCD properties, even the lightsource, but it is important to recognise that any comparison with scanned film is not a comparison with film itself.

Pedantically, I think it would be worth doing a comparison involving a 12,000ppi drum scan, to get a more absolute measure of the differences between the film images and the EOS1DS. Not for the sake of resolution per sebut to judge relative tonal smoothness more accurately.

Having said all that, I am sure digital will still win, but the existing methodology probably makes film look rather worse than it is in this respect (and JPEG'ing of an image full of aliasing products compounds the issue, to film's disadvantage).

Michael's observation of moire and the artefacting of the red-shed boarding are more of the same. Aliasing is inherent with pixel-based systems, though the Foveon sensor will avoid  colour aliasing and only alias luminance.

For me, the only obvious remaining advantage of film (apart from avoiding divorce and bankruptcy) is dynamic range.

My main interest and use of scanning is so I can use colour negative and B&W chromagenic films, exactly because they have a mad dynamic range : what you can see with adaptive eyes, you can photograph, pretty much.

I have tested and found 12+ stops with these materials. 10 stops of this is completely usable, there is severe compression in the rest, but it is still there. This is absolutely liberating compared to tranny, and gives me the control I only had in the wet darkroom with B&W, and more.

Alongside this, the D1S is, as reported, distinctly poor at 6 stops.

What's more, it is almost certainly an engineered inhibition. CCD sensors can now achieve 14 stops range, and do so completely linearly. I don't know any reason why CMOS should be worse, so it sounds like Canon have knobbled the range.

I hope this will prove to be something that applies only to JPEGS, and the RAW files will contain far more range.

There is a very good reason why Canon may have done so : wide range images look absolutely awful on-screen, impossibly flat, low contrast. You have to work with them, as raw material, and you wouldn't want to have to cope with the consequences of JPEG, it has to be clean, raw, high-bit data.

So the JPEG format is probably assumed to be for rapid onward transmission as a production file, with levels set, and only 8bit/ch available. To do anything else would frighten the desk editor who receives the file, and involve them in making judgements which are best left to photographers...

Fingers crossed, anyhow.

Regards
Tony Sleep (sometime filmscanner reviewer - suddenly retired

Tony Sleep Photography ::[/font]
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samirkharusi
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« Reply #85 on: October 20, 2002, 01:47:01 AM »
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[font color=\'#000000\']Perhaps the following is useful and easy to remember:
1. Nyquist theory says that you need two pixels to resolve a line pair. Yes, I actually verified this with a D30. Not 4 pixels.
2. Despite Foveon's claims, the Bayer array does NOT destroy the resolving power of a sensor all that much. In my tests with a D30, you lose 15% on the horizontal and vertical axes and almost nothing on the diagonal. Yes, I also verified this.
3. The "diffraction limit" is not a hard cutoff. It depends on definitions used. If you start with black & white bars and accept very low contrast in the output, lenses can deliver absurdly (and uselessly) high lp/mm. This is the primary source of those 100+ lp/mm claims that you used to see in decades past. Photodo has a lengthy expose on this on their MTF explanations. You need a definition that delivers a usefully high contrast level. Astronomers tend to use FWHM (Full Width at Half Maximum of the Airy disc) since this is what they use to match pixel sizes to telescope configurations, seeing conditions, and the Nyquist criterion (two pixels per line-pair). With this definition the theoretical diffraction limit of a lens in lp/mm = 1000/f-no for a wavelength of 4900 Angstroms (yellow light). Ie a theoretically perfect lens delivers 125 lp/mm at f-8. It would be more lousy in deep red light (< 90 lp/mm) and a lot better in deep blue (> 160 lp/mm). Ie real world lenses are unlikely to do better than, say, 80 lp/mm in white light at f-8 using the FWHM criterion. This also means that it is not particularly useful to use pixels that are smaller than around 6.5 microns if your lenses are optimised for f8 (like most 35mm lenses). Using all the above, a D30 is certainly good enough for lenses that deliver 45 lp/mm, a D60 around 60 lp/mm and a 1Ds between the two. I tested 3 Canon primes and NONE deliver, at a usefully high contrast level, anywhere near 45 lp/mm outside f5.6 to f11. Mass produced lenses are indeed that bad. Again, from my own testing with a D30, I would extrapolate that with a good Canon prime at f8 you can expect 2300 lines per picture height from a 1Ds (Lines per Picture Height is used in the digicam testcharts, just to confuse matters!). Depending on the printing resolution you desire (240dpi (9.6" high), 180dpi (12.8"), or whatever) you can determine what your own cutoff print size will be when compared to larger formats. Normal, unaided human vision considers 240dpi as pretty razor-sharp and should not be able to distinguish (resolution-wise) as to whether the source was a 1Ds sensor or an 8x12" negative. 180dpi satisfies many people too, especially when printer-related imperfections also come into play. Remember, a lot of people were and still are satisfied with D30 prints at 8x12". But this gets into subject matter/context arguments...[/font]
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