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Old Feb 22, 2004, 3:53 PM   #11
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I also agree with slipe. I once sent a 60,000x40,000 pixel image to Wal*Mart to print at 4x6" as a test. Came out just fine. You can upsize one of your images and send it to the printer to test.

Do some experiments. Don't take anyone's word for it when it is really easy to find out for yourself. There is the possibility that the resampling algorithm your printer driver uses is bad enough that it will produce bad results if fed to much information. Unlikely, but possible.
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Old Feb 22, 2004, 7:09 PM   #12
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Slipe, first let me say that I enjoy reading your posts and find them very useful.

I may have oversimplified my point by saying that image degradation is likely if too much information is presented. I was originally thinking in terms of scanning and applied that process to photo sizes.

We agree that the image has to be resampled at some point in the process either by the printer or the software and yes the printer is the last piece of hardware and will dictate (under normal conditions unless it is forced/tricked or what have you) the required dpi required from the software. It is the print drivers (basically little instruction or resource manuals) not the print spooler that dictates how data is printed. The spooler is more like a memory buffer that keeps print jobs in order.

By relying on the print driverís sampling algorithm instead of the photo editors sampling algorithm you are at the mercy of the printer. Depending on the quality of the software and the operator this may be a good thing. I must however believe that the sampling algorithm in, PS, PS Elements and other photo specific software is more sophisticated than the average printer (which tries to blend graphics, text, resolution, speed, ect all into one package to satisfy everyone). After all if all software and hardware worked perfectly together we wouldnít have incompatible driver errors.

Now I am sure that you can argue if you adjust the size of the document in your photo editor and then send it to a printer the image will be resampled twice and it is better to limit your resamples. To tell you the truth I havenít given it that much thought because I too generally send my full size document directly to the printer.

Since we do not know any more about nirvanajackís equipment and we all have different software/hardware packages and post production capabilities the only way to really solve the original question posed is to take the same picture at both resolutions, print them out using whatever technique he uses and compare the two. It sounds like Bill did a similar experiment with Wal*Mart to compare his finished product.

This is already turning out to be a long post on my part so I will offer this link which touches on the idea about too much information I was trying to relay: http://www.scantips.com/basics03.html

However a much better and more useful link with a great chart about resolution and print sizes on page 4 of 7 is:
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Old Feb 22, 2004, 8:50 PM   #13
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If you could find a way to send the printer the exact resolution it will use in pixels to print a photo at a given setting you might possibly do a little better with a sophisticated resample routing. But I know of no way to do that. Iíve looked in vain for the past year for a white paper from one on the printer manufacturers to give me a clue.

Back when 8 picolitres was a super tiny dot I read that some printers were using as many as 24 dots to represent a pixel. Now that those dots are down to 2 picolitres I wouldnít want to guess what the dot to pixel ratio is. At one time Epson was recommending at least 240 PPI for best quality photos. I donít think that has increased and might have even possibly decreased as printer resolution has increased due to the smaller dots. I canít see any improvement over 180 PPI with my 4 picolitre photo inkjet and Iíve looked closely.

My guess is that the number is probably something like exactly 187.372 or 236.877 PPI to not get a resample in the printer driver. Miss that by even a tiny fraction and the printer driver is going to have to resample the entire thing. You might as well give it all of the pixels you have and make that the only resample unless you are better than I at figuring out exactly how many pixels your printer can use at given settings.

You are correct that it is the driver and not the spooler that resamples. The process is complex, which is why it takes even a fast processor a while to spool a photo quality print job. Even with 6 colors and a lot of dots it canít get a particular pixel perfect. So it adjust the adjacent pixels to give the overall impression of the right color. Of course the pixels adjacent to those need adjusting to compensate for those adjustments and so on. 4 color printers do a lot more of that. The end result is highly dependent on how well the driver does all of that and Iím sure Canon, Epson and HP spend a lot of development work on those drivers. Iím not totally convinced they are not sophisticated enough to not make better use of the pixels than a simple resample filter. That is just a wild guess and moot anyway as I have no real way to check or do anything other than send all my pixels to the printer.

Photoshop through at least version 5 sent the image to the printer at 300PPI regardless of how much you fed it. I think they got so many support calls about Photoshop cheating their 2400 DPI printer of pixels that they just dumped the message that it was sending the image to the printer at 300PPI. They sent the image at 300PPI because there was no printer that could use any more than that and there was no sense sending the extra pixels. I suspect they are still sending it to the printer at 300PPI and just not displaying the message anymore. So you are probably getting a resample if you send to the printer at higher than that anyway. I would suspect other programs do the same even though they donít display the message. I also suspect the Fuji Frontier at Wal-Mart does the same thing. My guess is that with Photoshop at least it does no good to upsample to more than 300PPI for printing. Iím sure that is the case with earlier versions. But if the image ends up over 300PPI without resample you might just as well send that to the printer.

There are some things in the peimag article I didnít agree with but it is very good. The only thing I saw about degrading quality with too many pixels was the comment of too much detail showing facial hair etc. I think we are talking here about getting the best detail. I wasnít terribly impressed with the guy whose 20 X 24 print from 6Mp approached medium format film.

I really like Wayne Fultonís site. I corresponded with him a few times a few years back when it wasnít so big time. I wouldnít clutter his in-box now. It was a real revelation to me and improved my scans immeasurably.
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Old Feb 23, 2004, 9:17 PM   #14
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Default Choose the higher resolution

The higher resolution will give more info to the printer and should print a more detailed shot. Modern printers account for the different resolution by downsampling the image and do a good job of it. You won't loose any quality through printing the higher resolution shots.
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