Ok, that is a little clearer. However, to be picky the resizing of the 4000
dpi image did not technically resample the image in accordance with what you
claimed but it did change the effective resolution. In this case, in
contrast to my assumption, the resizing was upward rather than downward so
the effective resolution was reduced as you say. Since we had been talking
about 4x5 originals initially and later medium format was brought into the
discussion, I must have gotten confused and blinded to the fact that the
original could have been a scan from a 35mm. I also did not anticipate from
your comments that you took a snippet that the scanned image had been
resized prior so as to produce an effective 400 dpi prior to snipping the
section.
I apologize for my confusion.
filmscanners_owner@halftone.co.uk <> wrote:
> Laurie,
>
> The images were resized first. The 4000 dpi 35mm scan, at about
> 1.3x0.8 inches, was resized by reducing resolution to 400 without
> resampling, yielding obviously a 13 x 8 in image. After saving, I
> then took that image and resampled it to 360 dpi without changing
> dimensions.
>
> Finally, I just cut out a small section of each image for printing
> purposes but took care not to resample. Before printing, I confirmed
> that PS7 showed the 400dpi and the 360dpi values were retained.
>
> I believe the results are reliable.
>
> Stan
>
> -----Original Message-----
> From: filmscanners_owner@halftone.co.uk
> [mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Laurie Solomon
> Sent: Monday, October 28, 2002 11:59 AM
> To: snsok@cox.net
> Subject: [filmscanners] RE: Suggestions for scanning 4x5
> transparencies
>
>
>> The "400" was not resampled from the original 4000 dpi. This is a
>> snippet. The "360" was bicubic resampled in PS7 before going to the
>> printer.
>
> Like Paul, I would not have expected you to find any difference in
> detail or patterns in this case unless you scanned an already
> halftoned image. Such differences really have to be exaggerated to
> be readily noticed even under a loupe.
>
> However, having said that, I will note that by merely snipping as you
> put it from the original 4000 dpi image without resampling, you do
> not have a 400 dpi image but a 4000 dpi section of an image; and if
> you merely resized the image without carrying out any resampling by
> changing the dimensions, then you have also effectively changed the
> effective resolution from 4000 dpi to something greater if you made
> the image smaller. Thus, we really have no knowledge of the dpi of
> the so-called 400 dpi image that you sent to the printer to be able
> to do an accurrate comparision to begin with for putrposes of this
> discussion.
>
> filmscanners_owner@halftone.co.uk <> wrote:
>> I printed a small area from the same digital image at 360 and at 400
>> dpi.
>>
>>
>>
>> The "400" was not resampled from the original 4000 dpi. This is a
>> snippet. The "360" was bicubic resampled in PS7 before going to the
>> printer. The difference in size is just a slight error in snipping.
>>
>> Under the loupe, I can't see any difference in detail or in the
>> patterns within the azalea petals.
>>
>> Stan
>>
>> -----Original Message-----
>> From: filmscanners_owner@halftone.co.uk
>> [mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Laurie Solomon
>> Sent: Sunday, October 27, 2002 6:40 PM
>> To: snsok@cox.net
>> Subject: [filmscanners] RE: Suggestions for scanning 4x5
>> transparencies
>>
>>
>>> No, it's been proven by people on one of the Epson lists (perhaps it
>>> was the old Leben list) that the driver resamples to exactly 720ppi.
>>
>> I belong to both those lists (or I did belong to the Leben list until
>> it went defunct) but I do not remember seeing any such proof. I do
>> remember some discussion about this on both lists and that is were I
>> got my information from. Some one may have said what you claim and I
>> will take your word on that; but that some one proved it may be
>> overstating things a little and certainly with respect to at what
>> stage in the printing process this driver resampling takes place. If
>> I remember correctly, the discussion was somewhat vague and ambiguous
>> as to when the resampling took place in the process and if all
>> resampling had to go through the 720 dpi conversion first before
>> being resampled to 1440 or 2880 dpi or if it was a direct input
>> resolution to the end resample resolution if that end resolution was
>> to be 1440 dpi or 2880 dpi.
>>
>>> For instance, if you create an image with alternating one-pixel
>>> black and white lines, and then set the resolution to 700ppi
>>> (pixels per inch), you've created an image whose spatial frequency
>>> is 350lpi (lines per inch).
>>
>> While I will make no claims to completely comprehending the technical
>> arguments and specifics of the engineering nor do I wish to argue
>> those things, I do think that your example is a bad one in that it is
>> an example of exactly the oppositie of what I said. I said that the
>> multiples of 720 had to be even multiples which would be along the
>> lines of the following
>>
>
90,120,150,180,210,240,270,300,330,360,390,420,450,480,510,540,570,600,630,6
>> 60,690....750,780,810,...,1440,..., and 2880 - not uneven or odd
>> multiples which 700 dpi would be. I would even go as far as to
>> suggest that the reason that Epson talks of those resolutions like
>> 720, 1440, 2880, and 5760 un terms of dpi rather than ppi may be
>> precisely because it is in printing terms which does account for
>> dithering and stands as such as being equivalent in that regard to
>> halftones whose resolutions take into account the line screen
>> multiple of the halftone dots in stating halftone resolutions. At any
>> rate, it is because you have selected an uneven multiple of the 720
>> figure that you wound up with the extra line of black and an extra
>> line of white (or double width line on one of the lines of each). In
>> that regard, I believe you example illustrates the reasoning behind
>> my statement and supports my contention that it is more frequently
>> than not factors such as imputing an uneven multiple of the 720 dpi
>> figure that produces the aliasing and artifacts more than the
>> closeness of the match between the two numbers.
>>
>> Like you, I find that most of this sort of discussion seems to be
>> academic in the case of my experiences since I find that I have
>> experienced and seen few defects like aliasing and artifacts as long
>> as the file I input into the Epson printer has a resolution between
>> 200 and 360 ppi/dpi resolution. When I experience morie patterns it
>> is usually due to the fact that I scanned a previously halftoned
>> image.
>>
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