Re: Nikon Super CoolScan 4000 ED - some questions

On Fri, 16 Sep 2005 05:42:24 +0100, Kennedy McEwen
<rkm@xxxxxxxxxxxxxxxxxx> wrote:

>It is worth noting that this interpretation of resolution, whilst not
>unique to yourself, is incorrect. Two forms of resolution take place in
>scanners - sampling resolution (which I prefer to call sampling density
>to avoid confusion) and optical resolution. Sampling resolution or
>density is the headline number that the manufacturers hit you with and
>is basically the number of pixels that the scanner samples per inch. It
>doesn't say anything about the actual performance of the scanner or how
>distinct any pixel is from adjacent pixels. That comes down to optical
>resolution and, as I am sure you have guessed, manufacturers are less
>than vociferous in making customers, let alone potential customers,
>aware of that. There are good reasons for this - people are stupid and
>will buy a scanner from a manufacturer that claims 4,000ppi resolution
>than one who offers only 1500cy/in resolution.

Kennedy,

yes, I'm fully aware of this. That's why I reduced my scan
resolution from 4,000 ppi first to 2,400 ppi, then to 2,000 ppi.
Of course I lose some information that way, I'm fully aware of
that too, but not enough to warrant the much larger files.

>The autofocus works on the film
>grain, not on the image itself. The only time it should fail is if
>there is no film grain at the autofocus position, eg. a completely
>transparent emulsion. Even then, minor dust and scratches on the
>emulsion surface should be enough to focus on. This suggests that the
>optical system is not focussing well enough at its optimum position for
>the grain to be resolved very well at all - which confirms your
>complaint.

Interesting! I guess I will have to have the scanner cleaned and
checked. However, perhaps the errors happened because the
scanner focussed on the glass surface, rather than on the film.
I use GePe anti-Newton glass frames.

>BTW - are you aware than the autofocus point can be moved to any point
>in the image? This is particularly useful once you resolve your focus
>problem and only have to deal with film flatness - it lets you get the
>optimum focus on the part of the frame you think needs it, not just in
>the middle.

Yes, I used that function in a few cases. Do you happen to know
under which circumstances the scanner puts the autofocus point
back in the center? I'd like it back when I scan the next
picture, but I couldn't find out, so I always moved it back by
hand, which may be unnecessary.

>Not what it means. Photon noise is just the random variation on the
>arrival of photons at the sensor. [...]

>So the fact that the photon noise is quite so low is a consequence of
>the limitation of the CCD, not an indication that you are close to the
>limits of what is achievable. Basically, it means that the CCD can only
>detect and store the signal from a limited number of photons before it
>saturates - around 100,000. If you could get a better CCD with more
>storage capacity in each cell then you could expose for a longer time,
>detect more photons and get better signal to noise. Since you are stuck
>with whatever Nikon felt gave them the best trade-off between
>performance and cost, the best you can do is to simulate a bigger
>capacity CCD. That is all that multiscanning does.

Thanks for the very good explanation! I'm learning.

> From the discussion above, I hope you now realise that this is not only
>unfulfilled, but unrealistic in your terms, but I doubt there is much
>more information actually on the film in the first place.

Oh, but there is! When I look at the photo, from which I took
the two samples, through a magnifying glass, the text on the bus
is absolutely black and sharp, incomparably better than the
light grey fuzzy stuff in the scans. I can only surmise that the
optical quality of the scanner optics is way below that of the
camera lens through which I took the photo.

>Fuji Velvia, for example, goes out to 160lp/mm if the original contrast
>is about 1000:1 - but even then, the contrast on the film will only be
>about 15% - lower contrast detail will be lost. 160lp/mm is equivalent
>to a little over 8000ppi. At a more typical 1.6:1 contrast, Velvia can
>only resolve 4000ppi, again reproducing around 15% contrast on the film
>(1.15:1). There are marginally higher resolution colour films around,
>but not generally available, but this is just the film - the camera lens
>and any defocus or shake during exposure will limit the image resolution
>further.
>
>So, unless your images often contain very fine detail at a very high
>contrast and you shot them with top of the range lenses at their optimum
>aperture and used a tripod for everything then it is unlikely there is
>much more than 4000ppi on the film itself.

Wish I could send you the original slide! This was Ektachrome
100 shot through a good Canon lens. Too bad I have no way of
scanning through a microscope to show you what's actually on the
slide.

But assuming the film contains good 4,000 ppi information, but
the scanner's optics are obviously way below that, the
phenomenon is already explained.

>In article <l33ji118l0n73b8379v1jso381hnna5fo1@xxxxxxx>, Hans-Georg
>Michna <hans-georgNoEmailPlease@xxxxxxxxxx> writes

>>I'm still under the impression that this scanner produces
>>reasonably sharp pictures at 2,000 dpi. Of course raising the
>>resolution always adds some information to the result, but
>>raising it to the native 4,000 dpi yields rather little. Egdes,
>>for example, don't become any sharper.

>They may not look like it to you, but if you run some measurements, they
>certainly are.

Of course the 4,000 ppi scans contain more information than the
2,000 ppi scans, but the difference appears small to me,
particularly when compared to the roughly 4 times larger file
size.

>>Let me post an example. Please have a look at
>>
>>http://www.michna.com/temp/images/india0203_detail_2000dpi.png
>>http://www.michna.com/temp/images/india0203_detail_4000dpi.png

>Also, what scanner settings did you use for these because both show
>rather a lot of posterisation and, given the format, I don't think that
>is a compression artefact.

The 2,000 ppi scan was stored in JPEG format at the highest
quality setting. The 4,000 ppi scan was never compressed, only
converted from TIFF to PNG, so it does not contain any
compression artefacts. I converted both to PNG to avoid losing
quality again after cropping.

I guess that there are much better scanners that can easily
resolve 4,000 ppi to the pixel. I'd guess they'd be advertised
as 8,000 ppi at least, probably even 16,000 ppi. Do you happen
to know such scanners? What do they cost?

Hans-Georg

--
No mail, please.
.

Relevant Pages

  • Re: The logistics of film scanning
    ... I would not consider a film scanner without this feature. ... Yes, scan in TIFF, or with Nikon, you can scan to Raw depending upon ... This is a strong function of resolution. ...
    (rec.photo.digital)
  • Re: 11x14, no way??
    ... > you use a 4000 ppi scanner to sample an image, ... > blades of grass in the foreground that are quite sharp and well-defined ... resolution scan to capture detail for a good 13 x 19 print. ...
    (rec.photo.digital)
  • Re: filmscanner vs hi-res flatbed
    ... This is just a measure of how much contrast the scanner can reproduce at different resolutions. ... Assessing scanner performance requires consideration of resolution and MTF together, as well as other parameters such as density and dynamic ranges. ... In a dedicated desktop film scanner the emphasis in the design is to get the maximum MTF right up to the limit of resolution even if some significant MTF is present beyond that limit. ...
    (comp.periphs.scanners)
  • Re: The 2000 ppi test
    ... > make that look sharp then the soft look to the film is not the printer ... while the other used a 400 ppi file at the final print size. ... They can use the extra resolution; the main issue is extra resolution causes higher ... Then your scanner is the limitation. ...
    (rec.photo.equipment.35mm)
  • Re: Sprintscan 35+, 10 bits vs 8 bits
    ... most scanning programs preview at what they consider "enough" resolution. ... You're still stuck in the scanner program with inadequate and limited set of editing tools. ... In this case, you're obviously right (though, you know, people make compromises for speed, storage space and all, and I don't think mine is so terrible a compromise if done carefully). ...
    (comp.periphs.scanners)