What ppi resolution to send to the printer

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I posted this on another forum (not as nice as Da Cafe though ) after the subject of print ppi mentioned with at least one person thinking that only 100 ppi needed for a good print! This may or may not be the case depending on original image quality and content and a myriad of other things but goes against current thinking including my own.

So I thought that it may be of interest here perhaps more to those that are new to printing and getting conflicting opinions. Of course it may even raise more questions than it answers and YMMV

One of the subjects was related to how many ppi needed for a good print resolving the maximum information contained in the capture data. While there is a lot more to making a good print the ability to resolve the finest detail contained within your captured data must surely rank quite highly?

So in this case we are talking about what PPI the printer needs to make the most of our image data.

I believe that in the case of Epson the driver reports to the OS that it expects image input of either 360 or 720 ppi, Canon would expect 300 or 600 ppi. For output to the print paper then the DPI (droplets per inch) will be controlled by the driver based on paper type and quality selected and is likely to be several times that of the image ppi.

Anyway the discussion did get me thinking and wondering how good my cheapo Canon MP495 everyday inkjet would cope. This printer must be among the cheapest you can buy at £45 ($58). It uses two cartridges, one black and one containing CYM, the cost of the two at retail prices nearly equal to the cost of the printer!

The result for such a cheap printer took me by surprise.

There are many test that you could undertake for assessing print quality, I decided to limit this to two one being a resolution test based on fine lines (from Mike Chaney Qimage ) and sending the printer data at 600 ppi and 150 ppi and a composite of sections of a real raw image from a Pentax K1 from DPR at 600 and 100 ppi.

Both files had enough pixels at native resolution to print images @ 600 ppi that fitted well within A4 paper borders. It should be noted that with larger image requirements you will run out of pixels from the native file resolution and of course you will have to upscale via your editing app PS or LR or allow the print driver to do this. The general consensus is that you should let Adobe handle it as the processing algorithms should do a better job than leaving it to the printer driver.

Not having any best quality A4 paper these were printed on Canon Satin a semi gloss paper at best quality setting. To show the actual print I needed to scan the images and used my Epson V500 @ 600 SPI. To enable the differences to be viewed clearly on the web I cropped and zoomed the images.

You will just have to trust me when I tell you that the differences you see correspond to what I saw and describe on the A4 prints or of course even better grab some images yourself and print
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.

This is a section of an image when printed is sized at 6.7" x 4.4 (marked the print with 2" line to give idea of the zoom). As can be seen the left side of the image is from a print @ 150 ppi and the right hand side printed at 600 ppi. I do not have 20/20 vision and need to wear reading glasses but what I can tell you is viewing the print at 10-12" reveals the detail improvement you see here pretty precisely.
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This is the DPR composite from the K1, just using the 100ppi and 600 ppi versions. For this I just made a screen grab of both images within PS. Once again the gain in IQ seen on the right is what I see on the printed version viewing at the same distance as the first image. The print area in this case 7.5" x 4.5"
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The surprise for me is that the little cheapo printer really handled these images very nicely indeed at least IMHO.
 

Growltiger

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So it is well worth printing at the highest resolution the printer can handle. I'm not sure why anyone would not do that.

The biggest limitation of your cheap printer is probably colour rendition rather than resolution. I have two Canon printers and they both have 8 inks rather than 4. Every time I turn one on it grinds away drinking the valuable ink. But at least they never clog.
 
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So it is well worth printing at the highest resolution the printer can handle. I'm not sure why anyone would not do that.
Well it could be the easiest route to make sure you do not leave IQ on the table. Normally you would uprez to 300 ppi with Canon if the file native resolution fell below 300 ppi. If above 300 ppi you would uprez to 600 ppi. It is generally not a good idea to downrez i.e. if native ppi came in at 450 ppi go up to 600 rather than down to 300.

But if you start with a less than optimal image or the image content does not contain fine detail then there is likely to be very little to gain by upping the ppi to printer best res.
It should also be mentioned that the data should be treated appropriately for the medium and the ppi figures e.g. at 300 ppi you would apply lower radius for output sharpening than you would for 600 ppi

The biggest limitation of your cheap printer is probably colour rendition rather than resolution. I have two Canon printers and they both have 8 inks rather than 4. Every time I turn one on it grinds away drinking the valuable ink. But at least they never clog.
I agree but have to say it is capable of producing pleasing colour renditions at 6x4", at least as good as the output from the high street labs, but as you observe loves to drink ink
 
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Just wanted to finish this with a couple of examples one containing reasonable data the other with not the best data to show the effects.

The poorer example first shot with a 1.9 MP point and shoot camera, no manual override of exposure or focus and JPEG only. This would print from original full size image 5"x4" @ 300 ppi

The full image with red rectangle showing the crop for printing.
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Cropped area compared at 96ppi and 300 ppi image enlarged due to scan
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On the actual prints there is very little to choose between either 300 ppi, marginally more detail in the boats name, the ladders and Yamaha engine but nothing to write home about.

So really garbage in garbage out regardless of ppi - maybe the image could have been massaged a little in post but I doubt a noticeable improvement to be had due to data limitations.

The next image from a 36 MP capture which would print @ 24"x16" @ 300 ppi from the native file.

This showing the image extents and the crop area used
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The cropped scanned area from two prints one at 100 ppi and one at 300 ppi. It should be very obvious which is which.
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The details that are improved e.g. the overall sharpness of the brickwork, the bridge cables and the telephone wires above the cables (missing completely from the 100 ppi image) give the printed image more of a three dimensional feel.

Viewing and comparing the images from a 'correct distance' of approx 43" there appears to be very little difference, other than perhaps better feeling of depth on the 300 ppi print. But moving closer reveals the improved details.

For me at least the answer is very clear. If you are not worried about leaving image quality behind on the table then just print without worrying about ppi settings. But if you are concerned about presenting the best image you can then treat your data with care and respect.
 
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Lightroom 5.7 using Print module with standard sharpening applied to both images.

Don't forget that these are from scanned prints @ 600 ppi then combined in PS and output again Save for Web. So image quality will suffer but the point is that the differential is being shown and these represent what I see when viewing prints side by side

There is a difference in WB between full and cropped
 
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No the native image data would print 24x16 @ 300 ppi so it was output at that and also output sending only 100 ppi for the same image size. The 600 mentioned was from the scan and should have been labelled SPI to differentiate - that is why it is important IMHO to correctly differentiate DPI, PPI, SPI and LPI - clearly I failed :oops:

LR uses the printer page settings to limit the print size in this case to A4 so the original image needed to be cropped to make sure that it could fit within this size.
 
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SPI = Samples per Inch. A better description, technically more accurate than PPI which is OK to use and much better than DPI. Unfortunately even the scanner manufacturers tend to quote DPI, although they can be excused as it should be very obvious that it refers to sampling rate per inch with their machine

LPI = Lines per Inch. Usually for offset printing e.g newsprint 85 lpi, standard sheet feed offset 150 lpi. If you are supplying a photo for offset printing the standard image resolution is 266-300 ppi at 100% image size, for printing at 133-150 lpi, giving a 2:1 ratio. Fine art printing will require higher lpi and consequently higher ppi.

While I know that some dismiss this as pedantic nonsense and just settle on the catch all dpi, it can soon become confusing in conversation about printing when someone quotes dpi when they really mean ppi and commercially it could lead to a very costly mistake in both time and money
 
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If I remember correctly, with regards to dpi on inkjet printers, not all dots are equal. Some vendors but not all are able to print multi-colours (multi layers) onto a single dot while other can only print the CMYK and rely on promixity of primary colours (juxtaposition) to fool the eye instead of superposition. In addition some are pigmented some not.
 

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