Resolution of a Photocopier
Mark Franzels
I compared a scanned copy of a 300 dpi document
printed on an inkjet printer versus that taken by a photocopier. The
photocopier seems to have better quality. What is the equivalent
resolution of a
photocopier. Is it laser copy? I'm asking this because I wonder
whether to just photocopy a
b/w photo or scan/print it for id purposes.
Also what newsgroup especially deal with scanners
and photo editing. I presume this rec.photo.digital
is about digital photography and not exactly
about photo editing. Thanks.
Mark
Ofnuts
> Hi,
>
> I compared a scanned copy of a 300 dpi document
> printed on an inkjet printer versus that taken by a photocopier. The
> photocopier seems to have better quality. What is the equivalent
> resolution of a
> photocopier. Is it laser copy? I'm asking this because I wonder
> whether to just photocopy a
> b/w photo or scan/print it for id purposes.
How old was the copier? Recent copiers seem to be always a
scanner/printer combo under the hood.
--
Bertrand
Bob Larter
> Hi,
>
> I compared a scanned copy of a 300 dpi document
> printed on an inkjet printer versus that taken by a photocopier. The
> photocopier seems to have better quality. What is the equivalent
> resolution of a
> photocopier.
Unless it's a digital copier, it doesn't have an equivalent resolution,
because the scan is optical, all the way to the drum.
> Is it laser copy? I'm asking this because I wonder
> whether to just photocopy a
> b/w photo or scan/print it for id purposes.
>
> Also what newsgroup especially deal with scanners
> and photo editing. I presume this rec.photo.digital
> is about digital photography and not exactly
> about photo editing. Thanks.
No, it's fine to discuss photo editing here.
--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------
J. Clarke
An original Xerox had no digital elements at all--it scanned a white light
across the page and the image was focussed on the drum. Resolution was
limited by the optics and the toner grain size. On the other hand, while it
did OK on half tones, it was horrible on large black areas and really bad
for gray scale.
Don Stauffer
> Mark Franzels wrote:
>> Hi,
>>
>> I compared a scanned copy of a 300 dpi document
>> printed on an inkjet printer versus that taken by a photocopier. The
>> photocopier seems to have better quality. What is the equivalent
>> resolution of a
>> photocopier.
>
> Unless it's a digital copier, it doesn't have an equivalent resolution,
> because the scan is optical, all the way to the drum.
>
measuring image resolution, for a century or more before the digital
imaging technology arrived.
For instance, most professional films gave resolution measurement
results in their data sheets. Lenses were measured by several types of
resolution tests, the best eventually were MTF methods, but bar charts
and knife edge scans were common.
Pat
I think my copier scans at 2400 dpi. There is no difference between
scanning, storing and printing or just copying (which is scanning and
printing).
The major difference between a copier and a ink-jet is that a copier
(at least mine) is CMYB and a ink-jet is RBY.
J�rgen Exner
>Bob Larter wrote:
>> Mark Franzels wrote:
>>> I compared a scanned copy of a 300 dpi document
>>> printed on an inkjet printer versus that taken by a photocopier. The
>>> photocopier seems to have better quality. What is the equivalent
>>> resolution of a
>>> photocopier.
>>
>> Unless it's a digital copier, it doesn't have an equivalent resolution,
>> because the scan is optical, all the way to the drum.
>>
>Analog systems DO have a resolution. Folks were working with, and
>measuring image resolution, for a century or more before the digital
>imaging technology arrived.
True. But those resolutions were measured in microns, not in DPI or SPI
or PPI and they cannot easily be compared to each other.
jue
Mark Franzels
So the average non digital photocopier machine is only good for black
and
white and not grayscale? But comparing it to a scanner and printer set
at black and white (not grayscale), the photocopier seems to produce
better resolution and definition. Also since a laser print uses a
drum,
so a photocopier printing has same nature as the laser print except
the latter is digital?
Mark
Bob Larter
Yeah, okay, you're technically correct, but it's not a "resolution" that
relates to 300DPI, which is what the OP was wanting to know. I seriously
doubt that trying to figure out the MTF of the optics of a non-digital
photocopier would have been at all helpful to the OP. ;^)
Mark Franzels
I know what MTF means or Modular Transfer Function from my
experiences with microscopes and studying their optics once.
I just want it explain why a photocopier machine seems to have
better black and white scanning ability than a 300 dpi scanner...
it seems that in black and white (not grayscale), the photocopier
is more superior? How and why?
Mark
>
> - Show quoted text -
Bob Larter
> On Apr 9, 9:57 pm, "J. Clarke" <jclarke.use...@cox.net> wrote:
>> Ofnuts wrote:
>>> Mark Franzels wrote:
>>>> Hi,
>>>> I compared a scanned copy of a 300 dpi document
>>>> printed on an inkjet printer versus that taken by a photocopier. The
>>>> photocopier seems to have better quality. What is the equivalent
>>>> resolution of a
>>>> photocopier. Is it laser copy? I'm asking this because I wonder
>>>> whether to just photocopy a
>>>> b/w photo or scan/print it for id purposes.
>>> How old was the copier? Recent copiers seem to be always a
>>> scanner/printer combo under the hood.
>> An original Xerox had no digital elements at all--it scanned a white light
>> across the page and the image was focussed on the drum. Resolution was
>> limited by the optics and the toner grain size. On the other hand, while it
>> did OK on half tones, it was horrible on large black areas and really bad
>> for gray scale.
>
> So the average non digital photocopier machine is only good for black
> and
> white and not grayscale?
Correct. (Although you can use a halftone sheet to copy greyscale images.)
> But comparing it to a scanner and printer set
> at black and white (not grayscale), the photocopier seems to produce
> better resolution and definition. Also since a laser print uses a
> drum,
> so a photocopier printing has same nature as the laser print except
> the latter is digital?
Correct. In fact, the very first laser printers were actually modified
photocopiers.
Bob Larter
> On Apr 10, 2:18 pm, Bob Larter <bobbylar...@gmail.com> wrote:
>> Don Stauffer wrote:
>>> Bob Larter wrote:
>>>> Mark Franzels wrote:
>>>>> Hi,
>>>>> I compared a scanned copy of a 300 dpi document
>>>>> printed on an inkjet printer versus that taken by a photocopier. The
>>>>> photocopier seems to have better quality. What is the equivalent
>>>>> resolution of a
>>>>> photocopier.
>>>> Unless it's a digital copier, it doesn't have an equivalent
>>>> resolution, because the scan is optical, all the way to the drum.
>>> Analog systems DO have a resolution. Folks were working with, and
>>> measuring image resolution, for a century or more before the digital
>>> imaging technology arrived.
>>> For instance, most professional films gave resolution measurement
>>> results in their data sheets. Lenses were measured by several types of
>>> resolution tests, the best eventually were MTF methods, but bar charts
>>> and knife edge scans were common.
>> Yeah, okay, you're technically correct, but it's not a "resolution" that
>> relates to 300DPI, which is what the OP was wanting to know. I seriously
>> doubt that trying to figure out the MTF of the optics of a non-digital
>> photocopier would have been at all helpful to the OP. ;^)
>
> experiences with microscopes and studying their optics once.
> I just want it explain why a photocopier machine seems to have
> better black and white scanning ability than a 300 dpi scanner...
> it seems that in black and white (not grayscale), the photocopier
> is more superior? How and why?
In an analog copier, the ultimate resolution is a function of the
quality of the optics, & of the toner particle size, rather than the
size of a CCD pixel. This is typically somewhat finer than a 300DPI
array - ie smaller than 1/300th of an inch. Photocopiers are also very
high contrast, which increases the apparent sharpness of the final print.
In practice, if you want to scan black & white pages with the apparent
sharpness of a photocopier, scanning at 600DPI & then increasing the
contrast setting very high (say to 3/4s) should do the job.
Mark Franzels
>
I see. With the 600 dpi scanner with high contrast setting. What
must be the printer output, laser or inkjet so that the quality
would match a photocopier? I think inkjet printers can smudge
the image a bit or no difference to a laser? Also what about
color photocopier? They still use drum and optics only?
Mark
Bob Larter
> must be the printer output, laser or inkjet so that the quality
> would match a photocopier?
Leaving it at the defaults should work okay. Otherwise, set it similarly
to the above.
> I think inkjet printers can smudge
> the image a bit
Yes. They'll dither the image.
> or no difference to a laser? Also what about
> color photocopier? They still use drum and optics only?
No. Colour copiers are nearly all digital. You can probably safely
assume that they're 600 DPI.
Mark Franzels
But laser also dither. Maybe inkjet can smudge more
simply due to the fact that liquid diffuses at the surface of
the paper while toner powder simply fuses to the paper
dried up. (?)
Mark
>
> > or no difference to a laser? Also what about
> > color photocopier? They still use drum and optics only?
>
> No. Colour copiers are nearly all digital. You can probably safely
> assume that they're 600 DPI.
>
> --
> W
> . | ,. w , "Some people are alive only because
> \|/ \|/ it is illegal to kill them." Perna condita delenda est
Don Stauffer
>
> Yeah, okay, you're technically correct, but it's not a "resolution" that
> relates to 300DPI, which is what the OP was wanting to know. I seriously
> doubt that trying to figure out the MTF of the optics of a non-digital
> photocopier would have been at all helpful to the OP. ;^)
>
>
The reason I brought it up was the fact that I used to work with digital
types who believed, that since they weren't sampled data systems, analog
systems had INFINITE resolution. It was only the sampling process that
creates resolution problems.
Of course, as I tried to explain, film IS a sampled system, but the
sampling points (film grains) are just not on a strictly periodic array.
Also, that low pass filtering is essentially, from an information theory
standpoint, a sampling process.
Anyway, you would be surprised how widespread the feeling is that analog
systems are inherently infinite resolution.
Pat
A photocopier is a scanner and printer -- they are no longer analog.
They are strictly digital. I don't know about anyone else's, but mine
does a pretty decent job on photos. In fact it has a photo mode.
Mark Franzels
> Mark Franzels wrote:
> > On Apr 9, 9:57 pm, "J. Clarke" <jclarke.use...@cox.net> wrote:
> >> Ofnuts wrote:
> >>> Mark Franzels wrote:
> >>>> Hi,
> >>>> I compared a scanned copy of a 300 dpi document
> >>>> printed on an inkjet printer versus that taken by a photocopier. The
> >>>> photocopier seems to have better quality. What is the equivalent
> >>>> resolution of a
> >>>> photocopier. Is it laser copy? I'm asking this because I wonder
> >>>> whether to just photocopy a
> >>>> b/w photo or scan/print it for id purposes.
> >>> How old was the copier? Recent copiers seem to be always a
> >>> scanner/printer combo under the hood.
> >> An original Xerox had no digital elements at all--it scanned a white light
> >> across the page and the image was focussed on the drum. Resolution was
> >> limited by the optics and the toner grain size. On the other hand, while it
> >> did OK on half tones, it was horrible on large black areas and really bad
> >> for gray scale.
>
> > So the average non digital photocopier machine is only good for black
> > and
> > white and not grayscale?
>
> Correct. (Although you can use a halftone sheet to copy greyscale images.)
Let me clarify. When you said that "while it did
OK on half tones, it was horrible on large black
areas and really bad for gray scale", do you
mean the material to be photocopied or the
paper that is printed?? Earlier today I went to
a photocopier shop and got my colored company ID
photocopied. Then I tried to scan it at home and set
it to BW (not Grayscale). Nothing can be made
out of the ID since the picture is blotted with
just black and white. So the photocopier used
grayscale to print the paper and not BW. When
you said grayscale is bad for photocopier. Do
you mean the source or the printed output???
Mark
>
> > But comparing it to a scanner and printer set
> > at black and white (not grayscale), the photocopier seems to produce
> > better resolution and definition. Also since a laser print uses a
> > drum,
> > so a photocopier printing has same nature as the laser print except
> > the latter is digital?
>
> Correct. In fact, the very first laser printers were actually modified
> photocopiers.
>
> --
> W
> . | ,. w , "Some people are alive only because
> \|/ \|/ it is illegal to kill them." Perna condita delenda est
Bob Larter
> A photocopier is a scanner and printer -- they are no longer analog.
> They are strictly digital.
Not so. Large analog copiers are still very common. Where they are
getting rare is in the smaller, desktop machines.
Bob Larter
That depends on your printer driver. For example; PostScript laser
printers will usually halftone greys, rather than dithering them.
> Maybe inkjet can smudge more
> simply due to the fact that liquid diffuses at the surface of
> the paper while toner powder simply fuses to the paper
> dried up. (?)
Good quality inkjet paper doesn't do that. Take a look at such a
printout some time, under high magnification. You can clearly see the
individual ink dots.
Pat
I don't know what kind of copier Bob Larter is using, but on mine; if
you photocopy something -- almost anything -- it's hard to tell the
copy from the original. For documents including certificates,
diplomas, etc. it is nearly impossible to tell. The copier copies the
image, paper color, everything. Photos are pretty darned good, esp.
if you use photo-quality paper. The surface finish isn't the same, so
you can tell the copied photo from the original. It's a huge step
above my all-in-one or my scanner. Plus it's lightening fast.
The biggest difference is the cost. My copier originally cost about
3X the cost of all of my other office equipment COMBINED. You get
better results when you have better equipment.
The reason they put better anti-counterfeiting stuff on money, now, is
because copiers are so good. They will copy everything except the
watermark and security strip and micro-printing. So a photo is a
piece of cake for them.
Bob Larter
> Bob Larter wrote:
>
>> Yeah, okay, you're technically correct, but it's not a "resolution"
>> that relates to 300DPI, which is what the OP was wanting to know. I
>> seriously doubt that trying to figure out the MTF of the optics of a
>> non-digital photocopier would have been at all helpful to the OP. ;^)
>
> The reason I brought it up was the fact that I used to work with digital
> types who believed, that since they weren't sampled data systems, analog
> systems had INFINITE resolution. It was only the sampling process that
> creates resolution problems.
No, of course not.
> Of course, as I tried to explain, film IS a sampled system, but the
> sampling points (film grains) are just not on a strictly periodic array.
>
> Also, that low pass filtering is essentially, from an information theory
> standpoint, a sampling process.
>
> Anyway, you would be surprised how widespread the feeling is that analog
> systems are inherently infinite resolution.
Indeed. I've seen a few film-photographers imply that in this very
newsgroup. ;^)
Bob Larter
> I don't know what kind of copier Bob Larter is using,
I was talking about your ordinary, monochrome, analog office copier.
I've already said that my comments don't apply to modern digital
copiers, or to colour copiers.
> but on mine; if
> you photocopy something -- almost anything -- it's hard to tell the
> copy from the original. For documents including certificates,
> diplomas, etc. it is nearly impossible to tell. The copier copies the
> image, paper color, everything. Photos are pretty darned good, esp.
> if you use photo-quality paper. The surface finish isn't the same, so
> you can tell the copied photo from the original. It's a huge step
> above my all-in-one or my scanner. Plus it's lightening fast.
>
> The biggest difference is the cost. My copier originally cost about
> 3X the cost of all of my other office equipment COMBINED. You get
> better results when you have better equipment.
Well yes, obviously.
Pat
> Pat wrote:
> > I don't know what kind of copier Bob Larter is using,
>
> I was talking about your ordinary, monochrome, analog office copier.
> I've already said that my comments don't apply to modern digital
> copiers, or to colour copiers.
They aren't "ordinary" anymore. I haven't seen one of those in years
and don't know where I would find one. I don't think they even make
them any more. I'm already on my 2nd digital one and I'm not
particularly up-to-date.
Now I'm wondering if they still make ditto machines (mimeographs).
Ah, that smell of ammonia ....