Jaggies in small prints

I was doing some small prints (5.5x3.5 inch postcard size) using Lightroom yesterday. I noticed that some 15deg off horizontal white lines on a blue background had very obvious jaggies. I then exported the same photos as TIF and imported the TIF into QImage Pro and printed them again same size - perfect no sign of jaggies. What is going wrong in Lightroom? I was definitely not printing with the draft mode printing button selected. I can only assume that the re-scaling algorithm Lightroom uses for down-sizing is less than optimum. Has anyone else experienced this and is there a way to cure the problem in Lightroom?
Jaggies in small prints
What are the images starting as. Raw? something else?



Don



Don Ricklin, MacBook 1.83Ghz Duo 2 Core running 10.4.9 %26amp; Win XP, Pentax *ist D

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Jaggies in small prints
They are Nikon D1H RAW files. Lightroom does a nice job of printing them at 8x5.5 inches but intoduces jaggies when printed postcard size.

I correct what I just said - the jaggies are just noticable on A5 size prints.

What output resolution were you setting in Lightroom? For small print, either 360ppi or 480ppi is suggested.

Jeff,

Is this documented anywhere? I haven't seen anything in the user guide that a larger ppi (adobe says dpi) should be used for smaller prints. Only that 240 is generally acceptable for many print jobs. I've been using 300 ppi for my HP DJ 90 printer (because it's native resolution is 600) and the smaller prints (5x7) have been noticeably poorer than QImage.

Well, human vision what it is, smaller prints need more ppi than large prints due to the fact you'll hold them closer (since viewing distance is about 2x the diagonal).



So, for small prints, use a high ppi and for larger prints use a lower ppi.



Depending on the options in QImage, it'll rerez (or uprez) to 600ppi but I thing that's overkill. Try 480ppi for small 5x7 prints.

And, the fact it's called dpi in LR 1.0 is a mistake-that will be corrected...



:~)

Ah, thank you, thank you for the confo that that'll be corrected! If you'd like me to lecture the person who used that instead of ppi, give me a shout!



:)

Thanks Jeff!

Regards,

Kevin

Its my understanding that each printer has a native resolution. And if images are sent to the printer in anything other that that resolution, then the printer driver will initiate resampling to get to the native resolution. Be it up or down.



There are two downsides to this. First a better job of resampling can be done outside of the printer driver. And second, if you allow the printer to resample, then it is doing so over what you have done as your final print sharpening - which now isnt quite so final.



This is one of the benefits of a program like Qimage it resamples to native resolution and THEN does the final print sharpening. I believe that LR also resamples first and then print sharpens (if requested). But LR doesnt force the resampling to the printers native resolution (as Qimage does); it resamples in accordance with the dpi (ie ppi) we have specified in the Print Module.



So when printing from LR, I think it makes sense to specify ppi in accordance with the printers native res. And this is how I print from LR. At least I do so when using my Epson 3800 with its 360 ppi native res. For my Epson 1290, with its 720 ppi native res, unless updated versions of LR allow me to set the higher ppi, I may stick with Qimage.

Just a small suggestion david that you may wish to use 300 ppi for the printing from LR as it is a direct multiple of your 600ppi printer and requires therefore simpler calculation.

Well, no...the old ''send it a number divisible by the printer resolution'' is an old wives tale...sound good and makes sense until you examine the way inkjet printers form dots.



I know for a ''fact'' that Epson doesn't do ANY resampling...their method of forming dots (variable size) is via an elaborate error diffusion method. It's much more like a sieve where the print driver allows some data to form dots while the excess (if any) is merely dropped off. The Epson driver (and I suspect the HP/Canon bubble-jet tech) really doesn't have a ''real'' native resolution...only an ''effective resolution''.



You would be far better off simply resizing without resampling to get your image size to be what you want-and let the ppi fall where they may. Even if it's an odd intermediate size.



It's the resampling to a specific ppi ratio that is wasteful and ineffective. Yes, you can upsample...but it will only do you any good if you also run additional sharpening or pixel manipulation because the resampling actually introduces softness.



The advantage-particularly in a Lightroom type environment-is that for small print you need more ppi and for large you need less. So, ideally LR should just allow you to send real and unsampled resolution to your printer. Currently it doesn't....and I think that will change.

Thanks for all the comments and replies. I will try some experiments such as setting the print resolution in the Prin Job panel such that the file I send it requires no re-sizing at all to print at the size I require. I will reportr back if this makes a difference.



Dave

I've just done some experiments printing small prints around 5.5x3.5 on my Canon ip8500 printer

Print sent at 300dpi - obvious jaggies

Print sent at 480 dpi better but not nearly as good as QImage (which uses 600dpi)

2000x1273 pixle image sent to printer 400dpi 5'' wide so no rescaling require better but again not nearly as good as QImage



Dave

I've tried similar tests using LR 200ppi 3.5x5 prints, 480ppi (a little better) and Qimage 600ppi. Qimage is definitely better (noticible) for smaller prints. I've printed 8x10s in LR and haven't noticed a large difference when using 300ppi as opposed to Qimage's 600.

Does anyone know if there will still be a 480 limitation in LR for ppi? I think the beta was not restricted to this.

Kevin

re: Qimage, Kevin and David: Is it not possible that the ''better'' pix printed via Q is a result of sharpening? - Maybe even a tiny increase in saturation?
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I don't think it is - I really didn't see much difference at larger sizes, just 5x7 and smaller. In QImage, I have sharpening set to lower than its default setting. In LR I was using medium. I thought both Qimage and LR sharpened after re-sizing/.rezing? Not sure about LR. Also, I don't think QImage should be altering the colors/saturation at print time. I've only tested on my main printer HP DJ90.