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Qimage Print Quality Challenge

Testing your printer's resolution

When set to its highest interpolation setting (Max), Qimage sends data to the print driver at the resolution requested by the driver which is almost always either 600 PPI (Canon, HP and a few other printers) or 720 PPI (Epson printers). Before reading our quality challenge in the next section, you may want to test your printer if you need to be convinced that an inkjet printer can resolve detail beyond 200-300 PPI. Since the printer tests outlined in this section are performed by sending prints already prepared at the resolution of your print driver, this is not a test where we are comparing Qimage to other software. We are simply sending a test image to the printer to determine the level of detail that can be resolved by your printer, paper, and ink. If you think or have heard from others that interpolating to 600 or 720 PPI is overkill, run the tests here first and judge for yourself, otherwise you can jump straight to the quality challenge.

There has been a lot of talk lately on the web questioning the rationale for sending more than about 240 - 300 PPI to a printer. Some argue that sending more than about 240 PPI does not improve prints and also question whether the unaided eye can see more than 240 PPI even if it improves printed results. Others cite studies based on human visual acuity and try to equate results of tests related to the human eye directly to print DPI, often ignoring issues such as Nyquist frequency, aliasing, and other important aspects that affect print quality and resolution. Many of the "studies" that come to such conclusions are based on poorly chosen mathematically derived test charts or photos that don't contain enough detail or original data to properly test printer resolution limits. It's difficult to test printer resolution when, for example, you print a 10x8 print from a 6 MP camera where you only have about 300 PPI of data to start with since interpolating to 600 or 720 PPI will result in only subtle differences when compared to simply printing the original 240-300 PPI image. Print a 4x6 or even a 5x7 where you are starting with more than 300 PPI of detail in the original image, and differences in print quality go from subtle to obvious. As cameras break the 8 MP barrier and beyond, the size at which detail above 240-300 PPI can be realized and easily detected in print will increase, allowing detail far beyond 300 PPI to be resolved even at 8x10 and larger print sizes.

There are many variables that affect print resolution and your ability to "see" the differences between prints sent to your printer at various resolutions. To make sure you get the most from your printer, take our simple resolution test. The test involves nothing more than downloading a test image, loading it into a photo editor or printing application, and printing that image with no changes, resizing, or sharpening. If you want to see what your printer can deliver in order to make the decision for yourself whether printing at the highest possible resolution is really worth it, just take a few minutes to print and review the following test. The ZIP files below contain the test image to print and instructions for printing. Be sure to download the test image that is designed for your printer:

Download test image & instructions for Epson printers (456 KB)

Download test image & instructions for Canon/HP printers (456 KB)

Note:

Epson test image will work for any printer running at 720 PPI native driver resolution
Canon test image will work for any printer running at 600 PPI native driver resolution

Your test results:

Use the results of your test to determine where to set the interpolation "level" in Qimage under "Prints", "Print Interpolation". Qimage's "Max" interpolation level corresponds to the highest resolution in the test, followed by "High" for the second highest resolution, "Med" for the third highest, and "Low" for the lowest resolution listed in the test. If you can see the difference in any of the columns (A,B,C,D) between the highest resolution in the test and the second highest resolution for example, select "Max" interpolation level in Qimage so that Qimage will send all data at the highest possible resolution. If you see no difference between the highest and second highest resolutions but going to the third highest does make a difference, select "High" interpolation level in Qimage, etc.

Note that it is a good idea to use your best quality glossy paper and the highest possible quality settings in the print driver when you print your test to be sure you account for the best possible resolution that your printer can deliver. Paper makes a big difference. Some (even excellent quality) glossy papers may not be well suited for your printer and may return "grainy" results. In addition, matte papers, swellable polymer papers, and other papers that "soak up" some of the ink rather than allowing it to sit on the surface of the paper can resolve far less resolution than other papers. For this reason, you may not need to run *all* of your papers at max resolution. When in doubt, use the above test to determine the "resolution potential" of all of your papers... or if just want to be sure you are getting the best possible prints every time, just set Qimage's interpolation to "Max" and never worry about it again.

Photographic example:

Now that you've tested the upper limits of your printer using a test chart, you may be wondering how noticeable the effects are on a real photograph. Can you see the same differences in detail between resolutions on a photograph? The differences can often be more subtle than a geometric test chart, but similar observations can be made. Just download and print the test photo below using the same methods used above for the test chart.

Download test photo & instructions for Epson printers (1.8 MB)

Download test photo & instructions for Canon/HP printers (1.8 MB)

The Qimage Print Quality Challenge

Overview:

If you are interested in getting the best photographic prints possible from your printer, take a moment to read the information on this page. It will point out some key concepts in printing and should lead the way to an understanding of what it takes to produce a true professional quality print from a digital image.

The Three Pillars of Printing

There are three major factors that contribute to being able to create optimal quality prints with maximum detail while guaranteeing near perfect color accuracy. Note that depending on the original images being printed, the actual printer model, print driver settings, and other parameters, the influence of each of the following factors may vary from one setup to the next.

1. Proper setup: The first pillar of obtaining quality prints is the proper setup of software options and print driver parameters. It is essential that the software you are using to print photos be set up to produce maximum quality prints (since one or more draft modes may be available). In addition, it is important to ensure that the print driver be set up properly under "File", "Printer Setup" to ensure the proper paper type, resolution, color options, etc. are selected to produce the highest quality prints.

2. Interpolation: The second pillar is interpolation. Most people do not realize that interpolation (resampling) of the original image is almost always needed! The only exception is when printing an original image at the one print size that just happens to match the resolution (PPI) of your print driver. All printers have a "native" resolution. This is the resolution that they report to Windows (and to software programs) and is the PPI that is used by the print driver. As an example, all Epson photo printers have a native resolution of 720 PPI even though some of the printers are capable of 1440 DPI, 2880 DPI, etc. This simply means that the driver operates at 720 PPI but the ink droplets themselves are placed on the page at 1440 DPI, 2880 DPI, etc. In this example, a typical 3 megapixel image at 2048 x 1536 resolution can only be printed at one size without additional interpolation on a 720 PPI print driver: 2.84 inches x 2.13 inches. If any size other than a 2.84 x 2.13 inch print is produced, the data must be interpolated (stretched or shrunk) to achieve the result. As you can see, a 2048 x 1536 image can only occupy a 2.84 x 2.13 inch rectangle on a 720 PPI print driver. The methods used by software to stretch the data to occupy more/less pixels on the printer can have a large affect on print quality.

3. Color management (optional*): The third pillar is managing color in your prints. While this pillar is considered optional because it is possible to achieve acceptable color accuracy without color management, proper color management is really the only way to guarantee a high level of color accuracy across a broad spectrum of color in prints. For a digital image to be rendered with accurate color ensuring that all subtle shades of color are accurately represented in print, ICC profiles should be used to define exactly how the original image is encoded and how the printer responds to color. Given a profile that describes color in the original image and a profile that describes color for the printer, the software can ensure that all printed colors are represented properly and accurately. Again, utilizing this third pillar can advance color accuracy from an "acceptable" level to an "extremely high" level of accuracy. The difference in using versus not using color management on any particular system will vary greatly with printer model, print driver settings, image produced by the camera/scanner capturing the original image, and a host of other factors. Since some of these factors are nearly impossible to evaluate objectively, it is often necessary to compare prints produced with/without color management before it can become obvious what you were "missing" without color management.

* Calibration of equipment and creation of custom ICC profiles is beyond the scope of printing applications. While both Qimage and some high end photo editors offer the ability to utilize ICC profiles for color management, additional software is required to create these profiles. Note that color must be managed from start to finish so it is just as important to have an accurate ICC profile for your camera or scanner as it is your monitor and printer. Some relatively inexpensive tools are available that allow creation of ICC profiles for monitors, cameras, scanners, and printers such as our own Profile Prism or other products like Monaco EZ Color or WiziWYG.

Printing Photos (Methods)

• Photo editors: Photo editors offer some functionality that is essential in the creative aspect of digital imaging such as cloning out and removal of unwanted objects in photos, insertion of objects or subjects that were not really in the original, adding or changing lighting effects, etc. While many photo editors offer sophisticated image editing capabilities, not even the highest quality, most expensive editors offer more than a "crude" printing algorithm that simply dumps an image to your printer's print driver. Photo editors leave the burden of manually sizing, figuring out the appropriate PPI to use for your printer, and other tasks up to the user or (worse) the print driver itself. As you will see in the next section, a raw pixel dump of data is certainly not the best printing method when quality is of paramount importance.

• Photo printing software: There are many software programs available, some that come packaged with printers, that are designed to handle printing multiple images, a job that is traditionally difficult using a single image oriented photo editor. Although these photo printing packages generally eliminate most of the burden associated with printing multiple images at different sizes and manually resizing images, most are still designed to simply dump the raw data to a specified size, letting the print driver do the work of "stretching" the image to the appropriate size. Further, almost all dedicated photo printing applications do not allow you to manage color in your images using ICC profiles, an important part of obtaining quality prints that is left almost exclusively to the top end (read expensive) photo editors.

• Qimage: Qimage offers the highest possible print quality by addressing the three pillars of printing in an optimal fashion:

  1. Proper Setup: Nearly all photo editors and photo printing software do not store printer settings, forcing the user to rehash all driver setup operations every time the software is used. This normally forces the user to repeat the same selection for paper size, paper type, resolution, color options, etc. The need to reset these values every time you print is a recipe for human error and missed settings. Qimage remembers all printer settings so that they only have to be set once. In addition, if you choose to use ICC profiles to manage color in your prints, Qimage Pro will even keep track of the ICC profile used with each printer (if you have more than one) and will offer to restore the settings used with that particular profile.

  2. Interpolation: As outlined above, interpolation is almost always required in creating digital prints. Most photo printing software and photo editors simply hand the raw image data to your printer's driver and assume that the driver knows how to deal with the data. As you can see from the examples below, interpolation is a job best left to high quality printing software. A typical example of printing from a photo editor is a case where a photographer starts by opening a 3 megapixel image. The photo editor informs us that this image (at 300 PPI which is generally accepted as photo quality) is only "good" for a size of 6.83 inches x 5.12 inches. Seeing this, we use the photo editor's bicubic spline resample routine to resample this image from 2048 x 1536 up to 3000 x 2250 because we know that we want a 10 inch wide print. Now we have a resampled (interpolated) image that is 3000 x 2250 at 300 PPI and we are ready to print. When we print that image at 10 x 7.5 inches on our printer though, the print driver is running at 720 PPI and spraying its final dot pattern at 1440 DPI, 2880 DPI, etc.. We have just handed the print driver 300 PPI data when it needs 720 PPI to work with. This forces the print driver to resample (interpolate) the image a second time to achieve the proper size on a 720 PPI print driver. Why is this a bad idea? Because with each resampling, the image is degraded to some degree, losing possibly vital details. In addition, print drivers vary in quality and accuracy of interpolation, so you don't want to leave this important step up to a print driver that may use a low quality resampling routine. Finally, most photo editors only offer bicubic spline resampling. Qimage uses a higher quality Lanczos interpolation method that is more accurate and sharper than the spline interpolation used in most photo editors. To even approach the quality of Qimage prints, you would have to use your photo editor to resample all the way up to your printer driver's PPI each time you print, and you may still not be able to achieve quite the same quality due to the higher quality interpolation and other printing innovations used in Qimage. Furthermore, to resample all your images to 720 PPI (for example) prior to printing them means that you have to manually resample the image every time you want to print at a different size because the amount of resampling needed for different size prints will vary! Qimage handles all these tasks automatically while providing the most common correction tools as well, such as a crop tool, red eye and blemish correction, noise filters, etc. With Qimage, you will never have to worry about resampling or interpolating images again and will never have to deal with PPI or DPI calculations. Qimage performs one high quality Lanczos resample at print time, eliminating extra work on you and your print driver, and ensuring the highest possible print quality. Working with your original images without ever having to worry about PPI, DPI or resaving the image at different resolutions may take some getting used to but we're sure you'll find more productive things to do with the time you save while getting higher quality results as well.

  3. Color Management: Software that makes utilizing color management through ICC profiles easy and effective is very hard to find, especially at the price point of Qimage. Qimage offers a true color management workflow that ensures that you can manage color properly provided you have accurate ICC profiles for your images and monitor/printer. Note that these profiles must be obtained or created separately (creation of custom ICC profiles is covered in our Color Management Section and is not a function of Qimage).

• Why doesn't all printing software print like Qimage?: The simple answer is; it's not easy. There are some Windows limitations that make it difficult to pass large amounts of data to print drivers. Due to these limitations, the data has to be managed properly and not just dumped to the printer with one command. Qimage can easily print a 13 x 19 photo, resampling the data to 600 PPI, 720 PPI or whatever your print driver requires. A 13 x 19 print at 720 PPI, however, requires that Windows and the print driver be capable of handling the 384 megabytes of data being passed from Qimage to the print driver without crashing Windows and without filling the spool drive. Since reliable code to do this can get a bit complex, it is easier for most software to just hand over that original 3 megapixel image to the print driver and say, "Here, you deal with getting it to cover a 13 x 19 page". While that is certainly easier to code and will run faster, it will never ensure that you get optimal print quality, or even consistent quality.

The Print Quality Challenge

We present you with some examples of the professional quality level that can be achieved in prints from Qimage, but don't take our word for it. Take the Qimage print quality challenge and see for yourself. Just download the demo and follow example 1 in the help under "Learn by Example" to ensure that Qimage is set for its highest quality output. Then print the same image from both Qimage and whatever you are currently using to print photos. Then examine your prints closely and see what you've been missing! Note that although Qimage will always achieve optimum quality output, the difference between prints produced from Qimage versus other software varies with image resolution, print size, how effective the print driver's interpolation methods are, etc. The key here is to realize that Qimage offers the highest possible print quality and is consistent at producing that quality level across printers, drivers, operating systems, paper, etc. The examples below are intended to show the consistency and high quality of Qimage prints from one end of the spectrum to the other.

Test 1: Enlargement of Low Resolution Images
on an Epson Photo 1270 Printer

The original image (43x43 grayscale image)
The image below shows a 200% zoom of the original image

Purpose:

• The purpose of test 1 is to compare print quality of enlargements from low resolution images by: (1) simply printing the original image at the desired size and (2) manually resampling in PhotoShop to obtain the same level of interpolation that is used by Qimage automatically.

Notes:

• The 43x43 original image above was printed at a size of 1.33 x 1.33 inches. At this size, the original image only contains about 32 PPI of information, so printing this image at 360 PPI represents about an 11x "expansion" or "zoom". A large expansion was chosen to better highlight the differences between print algorithms.

• Printer, paper, ink, and print driver settings were identical in both programs: 360 PPI print on plain paper with Epson 1270, no color management.

• Results were scanned with the same scanner and same scanner settings: 300 PPI scan

Example 1: "Straight" Printing

• Prior to printing, both Qimage and PhotoShop were set up for their highest quality printing options. In Qimage, this amounts to clicking "Prints", "Print Interpolation" and setting the interpolation level (on the left side) to "Max". In PhotoShop, click "File", "Print" and set "Print Quality" to "High".

Qimage 4.12, printing steps: Enter "1.33" in both size boxes and click "OK" Double click on image to add to queue Click the "Print" speed button on top row of icons Click "OK" on the print dialog to print one copy	PhotoShop 6.0.1, printing steps: Click "File", "Open" and open the image Click "File", "Print Options" Enter "1.33" in "Height" and click "OK" Click "File", "Print" Click "OK" on the print dialog to print one copy
Notes: This is a case of extreme upsampling where a high level of interpolation is needed. Due to the advanced interpolation used by Qimage, the result is smooth and sharp.	Notes: In cases of extreme upsampling where an original is being printed at very large sizes, pixelization can ruin the image, obscuring the overall intent of the photo.
Overall observation: When using low resolution images or printing at very large sizes where data must be "stretched" extensively, the benefits of Qimage's interpolation are obvious and make a huge difference in print quality. While this example is an extreme case, it can be relevant when printing images from digital cameras for large posters or billboards.

Example 2: Resample in PhotoShop Prior to Printing

• Prior to printing, both Qimage and PhotoShop were set up for their highest quality printing options. In Qimage, this amounts to clicking "Prints", "Print Interpolation" and setting the interpolation level (on the left side) to "Max". In PhotoShop, click "File", "Print" and set "Print Quality" to "High".

Qimage 4.12, printing steps: Enter "1.33" in both size boxes and click "OK" Double click on image to add to queue Click the "Print" speed button on top row of icons Click "OK" on the print dialog to print one copy	PhotoShop 6.0.1, printing steps: Click "File", "Open" and open the image Click "Image", "Mode", "RGB Color" Click "Image", "Image Size" Enter "360" in "Resolution" and "1.33" in "Height" Check "Resample" and "Bicubic", then click "OK" Click "File", "Print" Click "OK" on the print dialog to print one copy
Notes: Since Qimage's interpolation is automatic, there is no change from the result in example 1 above.	Notes: After taking the time to manually resample the image to the same PPI that is used by Qimage Pro, the result is better, but PhotoShop's bicubic interpolation is no match for Qimage's more advanced Lanczos interpolation.
Overall observation: PhotoShop provides a method for manually resampling images prior to printing. Resampling the image results in a major improvement in print quality when stretching images to very large print sizes, but PhotoShop's bicubic interpolation does not do as good a job as Qimage's more advanced Lanczos interpolation. In addition, Qimage Pro maximizes print quality for images with any resolution printed at any print size automatically. If resampling in PhotoShop, a different, manual resampling must be performed each time the user wishes to create a different print size.

Test 2: Printing an Image that is Already 300 PPI
on an Epson Photo 1270 Printer

The original image (crop of a D1 original photo)
The image below shows a 200% zoom of the original image

Purpose:

• The purpose of test 2 is to compare print quality when the original is already a high resolution 300 PPI (photo quality) image by: (1) simply printing the original image and (2) manually resampling in PhotoShop to obtain the same level of interpolation that is used by Qimage automatically (the printer's base PPI).

Notes:

• The 2000 x 1312 D1 image (in Adobe color space) was printed at a size of 6.67 x 4.37 inches (300 PPI).

• Printer, paper, ink, and print driver settings were identical in both programs: 1440 DPI print on Matte Heavyweight paper with Epson 1270, custom ICC profile used.

• Results were scanned with the same scanner and same scanner settings: 600 PPI scan

• The above area was cropped from the prints.

Example 1: "Straight" Printing

• Prior to printing, both Qimage and PhotoShop were set up for their highest quality printing options. In Qimage, this amounts to clicking "Prints", "Print Interpolation" and setting the interpolation level (on the left side) to "Max". In PhotoShop, click "File", "Print" and set "Print Quality" to "High".

Qimage 4.12, printing steps: Enter "6.67" x "4.37" in sizes and click "OK" Double click on image to add to queue Click the "Print" speed button Click "OK" on the print dialog to print one copy	PhotoShop 6.0.1, printing steps: Click "File", "Open" and open the image Click "File", "Print Options" Enter "4.37" in "Height" and click "OK" Click "File", "Print" Click "OK" on the print dialog to print one copy
Notes: Qimage automatically renders the image with maximum detail: smooth and sharp edges with good separation between small details.	Notes: Notice the reduced level of detail when printing images with no manual resampling in PhotoShop. Edges are not well defined and look jagged in many areas.
Overall observation: Even when we start with an image that already has photo quality resolution (300 PPI), simply handing the image to the print driver (as PhotoShop does) results in a print with jagged edges and loss of overall detail. The simple fact that Qimage Pro used its high quality Lanczos interpolation and didn't leave that step to the print driver, produces a smoother, sharper print, with better definition of small details.

Example 2: Resample in PhotoShop to 720 PPI (the printer's base PPI)

• Prior to printing, both Qimage and PhotoShop were set up for their highest quality printing options. In Qimage, this amounts to clicking "Prints", "Print Interpolation" and setting the interpolation level (on the left side) to "Max". In PhotoShop, click "File", "Print" and set "Print Quality" to "High".

Qimage 4.12, printing steps: Enter "6.67" x "4.37" in sizes and click "OK" Double click on image to add to queue Click the "Print" speed button Click "OK" on the print dialog to print one copy	PhotoShop 6.0.1, printing steps: Click "File", "Open" and open the image Click "Image", "Image Size" Enter "720" in "Resolution" Check "Resample" and "Bicubic", then "OK" Click "File", "Print" Click "OK" on the print dialog to print one copy
Notes: Since Qimage's interpolation is automatic, there is no change from the result in example 1 above	Notes: After taking the time to manually resample the image to the same PPI that is used by Qimage, the result is better. The print is now much smoother, but is not as sharp (edges are not well defined) and some of the smaller letters appear smeared together.
Overall observation: PhotoShop provides a method for manually resampling images prior to printing. Resampling the image results in a slight improvement in print quality in this case, where we start with a high resolution original and print at a relatively small size. PhotoShop's bicubic interpolation, however, does not do as good a job as Qimage's more advanced Lanczos interpolation. In addition, Qimage Pro maximizes print quality for images with any resolution printed at any print size automatically. If resampling in PhotoShop, a different, manual resampling must be performed each time the user wishes to create a different print size.

Test 3: Printing Very High Resolution Images at Average Print Sizes
on a Canon S900 Printer

The original image (Fuji S2 original photo)
The image below shows a downsampled version of the image printed

Purpose:

• The purpose of test 3 is to compare print quality when very high resolution original images are printed at average print sizes. In this test, we start with a 4256 x 2848 Fuji S2 original and print the image at a height of 5 inches, resulting in a 7.47 x 5 inch print. Since we start with a 12 MP image, the original image contains 570 PPI when printed at 7.47 x 5 inches. How important will Qimage's advanced Lanczos printing be in this case, where we start with an image that has more than enough resolution for true photo quality at the given print size?

Notes:

• The 4256 x 2848 S2 image (in sRGB color space) was printed at a size of 7.47 x 5 inches.

• Printer, paper, ink, and print driver settings were identical in both programs: highest photo quality print on Canon Photo Paper Pro with Canon S900, custom ICC profile used.

• Results were scanned with the same scanner and same scanner settings: 600 PPI scan

• Prior to printing, both Qimage and PhotoShop were set up for their highest quality printing options. In Qimage, this amounts to clicking "Prints", "Print Interpolation" and setting the interpolation level (on the left side) to "Max". In PhotoShop, click "File", "Print" and set "Print Quality" to "High".

Overall Conclusion:

The tests and examples presented here involve no "trickery" and are not just marketing hype. We invite you to take any image that contains fine detail at any resolution and print it to any size you like and compare the results between Qimage and any other software capable of printing images. If you examine the prints closely, we believe you will be able to see similar results to those outlined on this page. All of the differences noted in all of the above tests are normally visible with the unaided eye for an observer with 20/20 near vision by simply looking closely at the print. Since evaluating overall print quality in these tests requires examining small, highly detailed areas of images, the difference in print quality between Qimage and other software will depend somewhat on the content of the images themselves. If you start with an image that appears soft or doesn't contain many sharp edges for example, the difference between a Qimage print and a print from some other software may be less noticeable.

Most people who print images are concerned with getting the highest quality print with the least amount of manipulation. With Qimage, you can be assured that all of your prints are of optimal quality, regardless of the resolution of the image you started with or the final print size chosen. Qimage is able to achieve this level of print quality regardless of the printer brand/model used. This is important because print drivers vary greatly in their ability to stretch or shrink images. Some do an acceptable job, while others do a notably poor job with the task of final interpolation. Since Qimage always performs interpolation on its own, the print driver interpolation variable is removed from the printing equation, ensuring that optimal quality is achieved regardless of your choice of printer.

Acknowledgements:

Qimage Pro is copyright Digital Domain Inc.

PhotoShop is copyright Adobe Systems Inc.