Do anyone know if I use Nikon CP 950 to make a photo for printout of 4" x 6", which resolution should be chosen to have the finest quality? Is it the case I choose 1600x1200 will be same as 1024x768?

-- Chris (chrisho88@yahoo.com), June 21, 1999

Answers

To achieve the best results, go with 1600x1200. This will give you an on-paper resolution of 300dpi. (Pretty much the standard for photo- quality output) Using 1024x768 will only give you a printed resolution of 192dpi...Still OK, but you are spreading only 66% of the information into the same physical area. As a rule, the higher resolution you start with, the better "on-paper" results you will achieve. As an owner of an Epson 1200, I am wishing that my camera could output 3200x2400 images! :)

-- andy (andycure@hotmail.com), June 21, 1999.

While I'd normally side with Andy, I'd have to say more isn't always better. Having enough resolution is the key, too much just makes for trouble with the printer being able to get enough printer dots on the page to dither in the color value for each pixel and still leave enough white space to reflect some light from the page. I know that sounds odd, but here's the reasoning:

Each printed pixel must be composed of a matrix of printer(ink) dots in order to represent the tonal range necessary to depict a photo. Why does it take more than one dot to represent a pixel? Because each dot is usually only one of 6 primary(magenta, cyan, yellow) or near primary colors(secondary shades of magenta, cyan and yellow), black or white in even the best of consumer printers(from all current chatter, Andy's Epson 1200 is probably the new King Of The Hill.) So in essence, while it's great to have a higher DPI printer, DPI is not PPI. For most standard printers I'll bet you can figure between 1/6th and 1/4 the PPI of the DPI numbers they use and get a good idea of how large or small a decent print you can get out of them for a given resolution image. I was very surprised to learn that my Epson did a better job of printing a 1024x1280 image at 8x10" than it did at 4x5". I would guess the 4x5" image suffered from tonal compression because there weren't enough printer dots to represent the range of tones in the pixels of the image, so I got a dark, murky, print. Possibly all that ink being crammed into a smaller dark area didn't help either. With too much ink it's very hard to get a very bright image(not enough white reflective area left on the page with the older 4 color inkjets.)

128 PPI with a 720 DPI printer yields a matrix of almost 32 dots for each pixel. Half that if it's a 720x360 dpi printer. With 5 possible colors per dot (magenta,yellow,cyan,white,black) that leaves 5 to the 32nd color possibilities per pixel(actually quite a bit less as I suspect the printer uses the periphery of each "block" of dots to blend with the periphery of the surrounding "blocks.") Which probably makes for a much smoother transition between pixels. I'm sure there's a middle ground which looks acceptably smooth and still has sharp edges, I just can't always seem to find it. :-)

256 PPI with a 720 DPI printer yields a matrix of almost 8 whole dots for each pixel! Big Whoop-didi-do![yeah, I actually say it -so I'm a nerd at heart, so what?] With 5 possibles per dot, that yields at best 390,625 possible colors for a pixel with no peripheral blending. YEEEEEEUCK! You're back to just a bit better than an older 256K color laptop's display without a contrast or a brightness control. P-U! [a rose by any other stench... :-)]

Think carefully about this one folks. Those 1440 DPI printers are great, but they're actually only 1440x720 DPI printers. But still a major step up when you consider the 3 extra inks and other improvements that must have been made over the years. I know I'm shopping for a 750 or 1200 in the months to come. I'd like the 1200, but the price is tougher to justify unless you really need the larger format capabilities.

On my (now outdated) Epson Stylus Color (I know it's old, but where were all you Johnny-Come-Lately 1200 owners when I bought mine back in Jan. of 1995? :-)) I manage to get decent 8x10"'s from a 1024x1280 image when printing at 720 DPI, which averages out to just about 128 PPI. It may be a tribute to the Epson printer driver's interpolation ability, but it does look pretty good. Behind a piece of glass at 18"-24" you'd probably have a tough time swearing it wasn't a standard enlargement.

My take on it is this: More resolution is always better in case you run into an output device or a medium that can handle it. But if you do some test shots of various typical scenes at different resolutions and print them out you can certainly see for yourself and develop your own rule of thumb. I'll bet that a 1024x768 printed as a 6x4" or so print would look pretty decent at 720 DPI. Perhaps as a 4x3" or so print on a 1440 DPI machine. Maybe a bit larger.

How about some hard data from some of you 1440 DPI printer owners? How about printing a few images at 128PPI and a few more at 256PPI and writing in to give us the "hard proven skinny"?

-- Gerald M. Payne (gmp@francorp.francomm.com), June 21, 1999.

Gerald:

I don't agree with you entirely, at least not for the newer Epson printers. I used to resample all of my images to 300 or 360 ppi in Photoshop, based on the assumption that too much information would reduce print quality. With the Epson 1200 in 1440x720 mode on Photo paper, I cannot see any difference in prints made from typical 360 ppi or excessively detailed 1024 ppi images. The printer driver does an excellent job of downsampling the image to a reasonable resolution before printing. The only difference is that larger images (say 50 MB) take a little longer to spool.

I haven't done enough testing to see if a 360 ppi image prints better than 300 on the Epson 1200, but I suspect that the difference is negligible. I can see a slight difference between 270 and 300 ppi at very close distances. However 270 ppi is fine for prints that aren't viewed at point blank range. I would still use 300 ppi for small prints (e.g. 4x6), which are usually viewed up close. However, I don't mean to say that an image printed at 180 dpi viewed at 2 feet wouldn't be a little better than one printed at 360 ppi and viewed at 1 foot.

I tried to print a few 11x16s on the 1200 using output from the LS-2000. The resulting resolution of ~230 ppi just doesn't quite cut it for my purposes. However, the scanner limits the quality beyond just the resolution. Eric

-- Eric B. (ericblair@earthlink.net), June 22, 1999.

Eric, if you'll re-read my comments I prefaced/or included in them that I was referring primarily to my experiences with the 720 DPI original Epson Stylus Color printer. It may just be that one of the advances I attributed to the newer models is greatly improved internal down sampling ability. I'm all for it! Also we were discussing digicam sized images, not 50MB scanned files. Personally, if the software downsampled results and the machine downsampled results are the same I'd prefer to downsample once and not have to wait for it everytime I spooled one out to print. zzzzzzzzzzz... ;-)

I think that you're also being a bit heavy handed expecting 360 PPI from a printer only capable of 1440 DPI in the horizontal plane and limited to half that vertically. That only gives you a matrix of just 8 single colored dots to represent the tonal value of each pixel. That's a pretty limited dynamic range for each pixel isn't it? But these are just opinions, and as such, worth very little except to those who possess them. I wonder just how much info the down-sampling in the print driver is throwing away?

Tell you what though: I'd give a few bucks to know just what actual PPI the printer driver and firmware are aiming for in downsampling our images to print them. It certainly seems that tailoring our files to that size would eliminate any thrashing about in the software algorithms that try to convert them into patterns of single color dots. :-)

I still think it's wasteful and largely useless to store images larger than is needed for a particular output medium that you are satisfied with. It is also a limiting factor on how many images you can cram onto a card before you have to put the #@$%! camera down and miss that one you'd die for. I'd like to get my hot little hands on a newer printer(think Epson 1200 or 750) in the next few months, so perhaps I'll be pleasantly surprised. I wasn't knocking the newer, higher resolution units, I was just pointing out that the ASSUMPTION that you need 360 or 300 PPI output is unfounded and totally dependant on the DPI resolution of the output device and media you're actually using and the tonal range demands of the subject being depicted. If you'll read the original question, you'll note there was no mention of which printer would be used for the task in question and I thought that assuming it would be a unit capable of 1440 DPI/360 PPI or 300 PPI was a great leap of faith. Most people aren't on the cutting edge of any technology, certainly not printers. :-)

Since you have a 1200, how about giving us your take on the largest and smallest size you could expect to print a 1600x1200 or 1024x768 image captured by a digital camera and still get an "acceptable" or preferred result. I repeat, the image must be captured by a digicam, as it seems to me that scanned images play differently sometimes. I'm not sure whether it's in-camera sharpening algorithms or the color sampling from the CCD's or what, but they do seem to behave differently to some degree. I really prefer to leave my PDR-M1 set to soft and do my own sharpening in processing.

Would you try it for us and post some results for interested parties? If so, you have my thanks, and that of others I'm sure.

-- Gerald M. Payne (gmp@francorp.francomm.com), June 23, 1999.

Eric,

I just did the math (should have done it before I opened my big, er, keyboard...) and it does seem that an 8 dot matrix would represent a pretty decent color range when you're dealing with a machine capable of presenting 8 different colors at each dot position.

ie; 8x8x8x8x8x8x8x8 = 16.78 million tones per pixel

maybe a tad less, if you steal a few tonal values to blend in with the surrounding pixels, but much better than the 360K values you get with a 5 color ink printer (CMYK and white). Heck, it may not even be necessary to blend values from pixel to pixel with such small dots.

I totally overlooked that the newer models have more ink possibilities and therefore can support higher PPI's per DPI rating than their 5 color ancestors.

A point for you guys arguing that 360 DPI is possible with the newer models! Consider me a convert. Somebody, pass the holy ink... :-)

Now what I want to know is how far can those interpolation routines in the Epson drivers stretch the print before it gets too grainy? What's the MINIMUM file size in pixels(1024x1280?) from which you can still get a decent 8x10"? 180PPI? Or will it go lower with the finer dots and increased tonal range per pixel?

I haven't been this interested in a printer, since I first saw the motorcycle AD for the original Epson Color Stylus in the fall of 1994. :-) Does anyone know if the 750 is comparable to the 1200 in terms of printed resolution? I know they are both touted to be 1440x720 DPI units, but do they perform similarly?

-- Gerald M. Payne (gmp@francorp.francomm.com), June 23, 1999.

From what I can tell from the Epson web site (http://www.epson.com/printer), the 750 and 1200 seem to be the same printhead-wise (6-color, 6-picoliter drop, 48 nozzles per color, print speed, even the noise level and operating environment specs). The main differences are the carriage width, the print languages, the 750 has a 256K buffer vs. the 1200's 128K, and the 1200's color cartridge seems to have a greater capacity than the 750's.

Personally, I don't perceive a need for the wide carriage, so I think I'm going to be placing an order for the 750 soon.

Hope this helps!

-- Andrew Y. Wang (wangay1@texaco.com), June 25, 1999.