a high res question

[JodiFrye]

ok, I am not used to the higher resolution of my new camera. With my other Kodak point and shoot it gave me 300 res for a 4 X 6 picture which seemed great for printing my multiple image album pages . With the new camera for an approx 4 X 6 it gives me 470 resolution. I'm almost scared to send it to the printer. It would be letter size paper with multiple 4 X 6 pics at 470 res. My printer is the Epson 785 epx which prints with res up to 2880 X 720. Am I being ridiculous to worry about this or should i resample ? Help

[Chuck Snyder]

Jodi, no harm likely done printing at 470, although if you downsample to 360
ppi, you get an even multiple of your printer's native resolution of 720
dpi. Some sources I've read indicate that it's good to have that even
multiple, but.... Anything 300 or more will give you a fine print, I'm
quite confident!

Chuck

[JodiFrye]

Thank you very much Chuck. I just don't know enough about this stuff. That's why I come here...I knew you'd answer ;) I'm not complaining about the high res 8 X 10's I get though ....yay ! I'll go ahead and lower it to 360 and see what i get. So, generally, resampling this way isn't such a bad thing ? I never thought I'd have to consider taking pixels away for printing !

[Ray]

Jodi,

My camera makes picture of 3072 x 2048. So, at 6 x 4, it makes 512 pixels per inch. I've never had
to resample or downsize the number of pixels to get them to print. I have an HP 940Cvr and it
discards the extra information is doesn't need. It may takes a few extra seconds to send the
information to the printer, this I can't really tell. It doesn't take more ink because its ink
consumption has been consistent since I got it, and at that time, I had a 2.2 Mp camera (compared to
a 6Mp now).

Ray

[Chuck Snyder]

Ray, like you, I'm becoming a believer in the view that printers don't
'waste ink' when you send them more pixels than they need. However, I'm
trying to dredge up a reference that I read once which indicated that excess
image resolution could actually cause a degradation in the printed image.
That may have been more myth than fact, but I'm still going to look for it
just to satisfy my curiosity.

Chuck

[Peter Duniho]

"JodiFrye" <lwsfrye@mybizz.net> wrote in message
news:2ccd80ee.-1@webx.la2eafNXanI...

> ok, I am not used to the higher resolution of my new camera. With
> my other Kodak point and shoot it gave me 300 res for a 4 X 6
> picture which seemed great for printing my multiple image album
> pages . With the new camera for an approx 4 X 6 it gives me 470
> resolution. I'm almost scared to send it to the printer.

I'm not sure what you're asking. 4x6 should print as 4x6 (assuming no
changes to the print settings), no matter what the image resolution is given
as. The only difference is how much detail there is, and whether the
printer is capable of showing all of that detail at that size.

Don't be scared to send it to the printer. Embrace all those extra
pixels...they are good for you. :)

Pete

[Peter Duniho]

"Chuck Snyder" <csnyder@houston.rr.com> wrote in message
news:6332FB78BDC6EE6BC5CB756208E4372A@in.webx.la2e afNXanI...

> Ray, like you, I'm becoming a believer in the view that printers don't
> 'waste ink' when you send them more pixels than they need. However, I'm
> trying to dredge up a reference that I read once which indicated that

excess

> image resolution could actually cause a degradation in the printed image.
> That may have been more myth than fact, but I'm still going to look for it
> just to satisfy my curiosity.

It just depends. It may have even been a rampant problem in the early days
of color printers (though there was no such problem with my ImageWriter II).
But I believe that these days, the printer driver has been designed
carefully to take the best advantage of the printer hardware, a luxury that
Adobe doesn't have (since they have to work on all hardware).

To print an image created with a different resolution than being used to
print it, *some* component somewhere will have to resample the image. IMHO,
it is much better to let the printer driver do the resampling, than to do it
in advance with a piece of software that doesn't know the fine details of
the printer's performance characteristics.

Same thing with respect to adjusting the image resolution to be an even
fraction of the printer's resolution. At the point that the image is
captured, if you have the option of doing this, that's a good idea. But
once you have the digital image in the computer, you should let the printer
driver do as much of the resampling as possible, even if that means feeding
it an image with a resolution that's not an even fraction of the printer's
resolution.

Finally, as far as the "extra ink" thing goes, I still have no idea where
that came from, and I can say with great confidence that the printer will
use the same amount of ink regardless of the resolution of the original
image. The *print* resolution may well affect ink consumption (just feel
how much "wetter" a piece of paper feels after being printed at 2880 dpi vs
720 dpi, for example), but the original data being sent to the printer will
not affect ink consumption in any way.

Pete

[JodiFrye]

Pete, I was more concerned with the printer than anything else. I was afraid to throw too much at it considering it had never printed above 300 res since i bought it ( I never gave it more than that ) and I get awesome prints out of it. I don't want to mess up my relationship with it...I guess I'm a freak about my equipment. Chuck, I'll be waiting to see what info you come up with...if it tosses out what it doesn't need then fine, I have nothing to be concerned about.

[Chuck Snyder]

Pete, one thing still has me baffled on image resolution vs. printer
resolution: the difference between a pixel and a printer 'dot'. Image
resolution is easy - it's the number of pixels per inch, with each pixel
being a square consisting one of 16.7 million colors. On the other hand, a
printer has to use multiple 'dots' of cyan, magenta, yellow, and black ink
to form its equivalent of a pixel - some references say as many as 50 dots
in a matrix to comprise a pixel. My understanding is that the dots are put
in close proximity to each other so that the eye sees them as a single
color - but they're still discrete dots. The $64 question is: is the dpi
of a printer counting the individual dots of color in an inch of print, or
is it somehow a 'pixel equivalent' number where the actual number of dots
per inch is much larger? If it's the former, the relationship between image
ppi and printer dpi isn't one-to-one; if it's the latter, then a 1:1
correspondence is possible. It would be great if it was a pixel equivalent:
then one could 'tune' the images in Elements to feed the printer its desired
resolution. I'm sure the better printers have good interpolation
algorithms; not so sure about the ones that come free with a computer....
:-)

Chuck

[Peter Duniho]

"Chuck Snyder" <csnyder@houston.rr.com> wrote in message
news:93209C738567B32F80389E5C78245B8E@in.webx.la2e afNXanI...

> [...] The $64 question is: is the dpi
> of a printer counting the individual dots of color in an inch of print, or
> is it somehow a 'pixel equivalent' number where the actual number of dots
> per inch is much larger?

Printer resolution is reported in the maximum number of dots printable, and
does not take into account the dithering required to print 24-bit color on
what is effectively a 4- to 8-bit device (depending on how many colors of
ink the printer uses).

*However*, just because you lose effective resolution due to the dithering
(just as you would when using a halftone screen in a conventional printing
process), that doesn't mean that providing the printer with as high a
resolution image as possible isn't useful. There are actually a variety of
dithering techniques in use (one common one being "error diffusion"), but
all of them can benefit from additional image data.

The reason comes down again to the question of where the resampling is done.
The printer driver, being intimately familiar with the hardware, can do THE
most effective job of resampling in order to produce an image that most
closely matches the original digital data. It knows the exact shades of
each of the inks being used, and it knows how it to blend those shades just
so to match the original image. It can also adjust the dithering so as to
preserve apparent lines in the image, helping to reduce the appearance of
aliasing in the printed image.

Let's take an extreme example and look at it. Consider a 300 dpi B&W laser
printer using half-toning (which is essentially just another kind of
dithering). Let's say you choose a half-tone screen that drops the
effective resolution down to about 50 dpi (I guess we want a lot of
gray-scale resolution :) ). Now, print an image that has a single diagonal
line on it, first at 300 dpi, and then at 50 dpi.

You *will* be able to see a noticeable difference between the two printouts.
While the effective resolution for both is still just 50 dpi, you will find
that the image printed at 300 dpi still has less "jaggies" than the one
printed at 50 dpi. Yes, the "grain" of the half-tone screen will make the
edge of the line a little fuzzier, but you'll get more of an anti-aliased
effect rather than a hard edge at the edge of the line.

Another way to think about it is to realize that there's "real" resolution
and "effective" resolution. "Real" resolution is how many dots that can be
reproduced, and "effective" is how much detail can actually be reproduced.
What "effective" is describing is, what is the smallest "feature" that you
would be able to resolve at that resolution? Sort of like the resolution of
spy satellites, when they say they can resolve down to 10 meters or 1 meter
or whatever. But with a spy satellite, just because you can only resolve
down to 10 meters, that doesn't mean that a car only 5 meters long won't
show up. It just means that you won't be able to tell exactly that it's a
car.

Same thing with printed output. At the "effective" resolution, you'll find
the limits of being able to identify a feature in the image clearly. But
that doesn't mean that there won't be any additional detail smaller than
that. It just means it will be harder to tell what that additional detail
is.

Finally, as far as "the ones that come free with a computer", I think you'll
find that, other than the maximum resolution the printer is capable of (the
"free" ones are usually down in the 720dpi range, while the expensive ones
are up in the 2880dpi range), they are using substantially the same software
to run the printer, and thus would take the same advantage in the dithering
algorithms that the more expensive printers do.

In fact, the drivers that came with my Epson 2200 appear to be used for all
(or almost all) of the current Epson line, and likewise the HP drivers I
downloaded a few weeks ago just to play with also appear to cover an entire
HP product line (their "photo" printers).

So I would still send as high a resolution image as possible to the less
expensive printers. Obviously you'll reach a point of diminishing returns.
The driver can only do so much, and can't create resolution in the printer
where none exists. I doubt sending a 2880 dpi image to a 720 dpi printer is
going to be much better than sending a 720 or 1440 dpi image, if at all.
But up to and including the actual resolution of the printer, more dots are
better.

If all one is trying to do is print a picture at a particular size on the
printer, I do not think it is EVER useful to resample the picture in
Elements or a similar editing program. All such programs allow you to
specify the final printed size without changing the underlying pixel data,
and that's the right way to print a specific size.

All IMHO, of course.

Pete

[Peter Duniho]

"JodiFrye" <lwsfrye@mybizz.net> wrote in message
news:2ccd80ee.6@webx.la2eafNXanI...

> Pete, I was more concerned with the printer than anything else.
> [...] I don't want to mess up my relationship with it

Um...so this is more about your interpersonal relationship between you and
your printer than a technical issue.

Okay, that sounds reasonable to me. I don't kick my PC when it misbehaves,
and I think everyone ought to be on good speaking terms with their computer
peripherals. :)

Pete

[Chuck Snyder]

Pete, you gave us a lot to think about - thanks.

I do want to pursue your very last point - about not ever resampling for
printing in Elements. I think that may be true above a certain image
resolution; however, for lower resolution - like 72 ppi - my printer will
faithfully reproduce the very noticeable pixellation of the image - as it
should. (There have actually been a couple instances where I wanted to print
something that showed individual pixels for demo purposes) If, on the other
hand, I sequentially resample the image until the resolution is, say 180
ppi, the resultant picture - while definitely 'softer' - will not display
any significant pixellation at the same print size as the previous case.
I'll take 'soft' rather than 'pixellated' in most cases. Resampling within
Elements has its place.

Chuck

[Beth Haney]

I have a headache. :)

[Grant Dixon]

Beth

I think Leen Koper has given you the best advice. I agree that the best way
would be to copy the pictures photographically (digital or film). A two
light set up metering of a grey card is standard and can be found in most
books that cover copy photography. Once set up you can do lots of images in
a short time.

Grant

[Peter Duniho]

"Chuck Snyder" <csnyder@houston.rr.com> wrote in message
news:0F1BC022EB3FF5DA8EA9FE69990B9F52@in.webx.la2e afNXanI...

> [...] I think that may be true above a certain image
> resolution; however, for lower resolution - like 72 ppi - my printer will
> faithfully reproduce the very noticeable pixellation of the image - as it
> should.

Sorry, yes, that's true. I should have qualified my statement to
circumstances where one is resampling *down*, throwing away data. Adding
data is trickier, and the results are not really dependent on the printer
hardware.

With a few notable exceptions, a printer driver generally will not upsample
with any sort of sophistication, if at all. The Epson driver is one
exception and I'm sure there are others -- it has an "Edge Smoothing" option
that enables anti-aliasing, and it works quite well as long as there's not
too huge a difference between the original resolution and the upsampled
print resolution.

An image editing program like Elements would probably do a better job
(though, I'd use the printer driver setting if available, and compare the
two methods) especially when the resolution difference is large, and you
also get more control that way (since you can do it in multiple passes),
which is not important when downsampling.

Basically, I'm mainly just arguing against the practice of downsampling an
image to 300 or 360 dpi (for example) when the original has a higher
resolution. Pretty much any ink jet printer can take advantage of the
additional resolution if you have it.

Pete

[Chuck Snyder]

Pete, thanks - makes a lot of sense.

One other problem with resolution that has occurred with some inkjets,
although I haven't heard any chatter about it lately: if the resolution
after playing with image size, cropping, etc. comes out to a number with a
decimal value, some printers can't seem to handle that number and experience
printing errors such as parallel lines. I've not experienced that with my
HP, but it's been advised to resample ever so slightly to get rid of that
decimal. Any thoughts?

Chuck

[Peter Duniho]

"Chuck Snyder" <csnyder@houston.rr.com> wrote in message
news:7F7B95823B7F53A5B009B7E33BDF7F0B@in.webx.la2e afNXanI...

> [...] if the resolution [...] comes out to a number with a
> decimal value, some printers can't seem to handle that number and

experience

> printing errors such as parallel lines. I've not experienced that with my
> HP, but it's been advised to resample ever so slightly to get rid of that
> decimal. Any thoughts?

I've never seen that either, but I'd never say it could never happen. I
would hope any name-brand printer, even those made ten or fifteen years ago,
shouldn't exhibit a problem like that, but I guess you never know. It would
be a software issue though, so a new printer driver would fix the problem
(which means it's possible people have seen it during a brief window of time
when a buggy printer driver was provided).

I will point out that without extra work on the user's part (adjusting the
print size by changing the image resolution with or without resampling), one
is almost *always* dealing with a fractional resolution somewhere in the
loop. So if this were an issue worth worrying about, I'd think it'd show up
a lot more often. Most people do not ever touch the image's resolution
setting.

So, I'd say that for sure one should not waste any time worrying about
fractional resolution, if that's otherwise consistent with their goals, but
that if they DO see weird printing anomalies, it might be worth ensure the
image has an integer resolution, just in case that's what's going on.

Pete

[Barbara Brundage]

Okay, on the subject of resolution, here's one that's making my head ache. I've been fooling around with my new canon s400, which would be an amazing camera in the hands of someone qualified to use it (not me, yet) and I saved part of an image as a jpeg using save for web.

Fine. But I noticed when I looked at the resulting jpg in mac os x preview, the detail wasn't as impressive as it looked in Elements. Well, I was fooling around looking in the preview prefs to change another setting and I saw that "ignore dpi" is on by default. So I turned it off (i.e. told the computer, yes, consider dpi now), expecting maybe to see the image shrink down to approximately print size as a result. Instead it got bigger.

Can anyone explain that? It seems a direct contradiction of everything that's ever been said about absolute resolution for onscreen display.

[Bert Bigelow]

As I recall from many readings, the problem (printer vs. image resolution) is this: Chuck, you said most of this. The printer uses multiple dots of ink to create a pixel. If the resolution is too high...i.e., pixels are too small...then the printer cannot cram enough ink dots into the pixel area to accurately reproduce the color specified by the C, M, Y and K values. Therefore, resolutions higher than 300 dpi can actually DEGRADE the print quality.

[Peter Duniho]

"Barbara Brundage" <member@adobeforums.com> wrote in message
news:2ccd80ee.16@webx.la2eafNXanI...

> [...] I was fooling around looking in the preview prefs to
> change another setting and I saw that "ignore dpi" is on
> by default. So I turned it off (i.e. told the computer, yes,
> consider dpi now), expecting maybe to see the image
> shrink down to approximately print size as a result.
> Instead it got bigger.

Well, it all depends on the resolution that is stored with the image AND on
what exactly the preview program does when it is supposedly "ignoring" the
resolution of the image.

Is "Ignore DPI" the exact wording of the checkbox? I did a search of
Apple's Mac OS X support database and didn't see anything relevant.

That said, I think what you saw makes sense. I'm guessing (without having
actually used that feature) that "save for web" sets the resolution to 72
dpi. The Mac display is probably 96 dpi. When the preview application is
ignoring the DPI in the image, you get a one-for-one pixel mapping. But
when you turn that off, it has to stretch the image to get it to come out
the "same size" on the monitor.

Depending on what the actual numbers are, the amount it gets bigger would
vary. But showing a 72 dpi image on a 96 dpi display would be a 33%
increase in size.

Pete