Resizing photographs can be a tricky business.
The key is to re-size without *interpolating the digital file to a new, “bigger-better” size. When you interpolate upward by adding digital data to a photograph, the quality of your photographs start to degrade.
*”In computer graphics, image scaling is the process of resizing a digital image. Scaling is a non-trivial process that involves a trade-off between efficiency, smoothness and sharpness. As the size of an image is increased, so the pixels which comprise the image become increasingly visible, making the image appear “soft”. Conversely, reducing an image will tend to enhance its smoothness and apparent sharpness.” [Source: http://en.wikipedia.org/wiki/Image_scaling ]
“So how can you re-size a photo and still keep the quality the same?”
Perhaps a better question is: “If I need to make a print of my original TIFF file, and the print has to be ‘huge’, what can I do to increase the size of the photograph, while keeping the quality of the printed photograph at very respectable Pixels Per Inch (Resolution)?”
OK, now that a more definite question has been artificially raised, I’ll tell you what my Professional Printer has advised me on more than one occasion; and after working with this Printer for some time, I can tell you that what she has advised is very good advice, and it works.
With my own eyes (yes, but of course), I’ve seen the difference in the printout from digital files I gave her from jpegs, compared to much better quality digital files in the tiff format.
Large printouts from tiffs are superior! (IMHO). TIFF is a ‘lossless’ file format: “Unlike standard JPEG, TIFF files using lossless compression (or no compression at all) can be edited and re-saved without suffering a compression loss. Other TIFF file options include multiple layers or pages.” [Source: http://en.wikipedia.org/wiki/Tagged_Image_File_Format]
The File from the Camera:
The files from my camera come out as JPEG files at 180ppi.
After uploading the JPEG files to my computer, before editing anything, I save them as TIFF files (NO compression). I prefer using XnView ( http://xnview.com/ ) to make this file format change to my photo files – right from the beginning.
I’ll use ‘resizing/resampling‘ to mean increasing or decreasing the print or dimension size of an image file. ‘Editing‘ would mean adding special effects, cleaning up dust, etc., from an image.
- THE POINT IS: Save your Original JPEG files to TIFF BEFORE ‘Editing’ or ‘Resizing’ an image.
After saving the original JPEG files, which are 3 or 4MB in size, the same TIFF files automatically become 20 or 21MB in size (this is what I get with my camera & files – you will likely get something different).
The key is NOT to edit your digital files in the JPEG format. From what I understand, each time you edit from a JPEG file, and then save it, the quality gradually decreases as well. Maybe the degrading of the file is minute, but when making a print from these ‘overly edited and saved JPEG image files, defects may start to become noticeable.
The Digital File & the PPI Standard:
The next thing to keep in mind is that the PPI (Pixels Per Inch) Standard of your files should not dip below 150 as you adjust for your print output size.
According to my Printer, the quality of the printed photo starts looking ‘pixely‘ if the PPI drops below 150. The printout will also show pixels/jaggies if the image is interpolated to ridiculous proportions (to what degree of up-sampling an image becomes ‘ridiculous’, that is a judgment call – you may have a differing opinion).
- You see, the method explained here is NOT about adding pixels to increase image size: We are simply decreasing the PPI, while keeping the image size (XnView’s “Screen Size”) at 100%. This in turn, increases the length and width of the photograph dimensions. When you decrease, and reach that 150PPI Standard, that is the LARGEST Print Size, in my opinion, that will look fantastic (in most cases). Any lower PPI, and you risk image quality. But then again, everyone will have different expectations, right!
“PPI can also describe the resolution in pixels, of an image to be printed within a specified space. For instance, a 100×100-pixel image that is printed in a 1-inch square could be said to have 100 pixels per inch, regardless of the printer’s DPI capability. Used in this way, the measurement is only meaningful when printing an image.” [Source: http://en.wikipedia.org/wiki/Pixels_per_inch]
You may often hear that a digital file MUST be 300PPI for a “good” printout. Well, I’ll be the last person in the world to say “I know” it all. However, from my own experience and seeing my images printed using an EPSON Stylus Pro 9600, on Textured Fine Art Paper, at 1440 dpi (dots per inch), with a resolution of 150ppi, from a TIFF file, and as big as 46-inches in the longest print dimension – well, this printing combination makes for one very fine high-quality and detailed printout. Other printers, dpi and paper may cause other results, of course!
How to save as TIFF & Increase Print Dimensions Using XnView:
1) Upload images to your computer.
2) Start XnView.
3) Locate the JPEG image file you want to work with and double click on it.
4) Go to FILE, SAVE AS. Select TIFF Revision 6.
5) Click on the OPTIONS button. See the image below for my settings:
6) Click on OK, and then SAVE.
7) Now, you have your TIFF File. You should see that the file extension of the image is now, .tif.
Eight – 8) At this point, you can work with and edit the image, and in this case, we want to increase the size of the image dimension to get a bigger printout, but keep the resolution at the ‘acceptable’ 150ppi. Let’s just assume that the original image file was 300ppi, and then go from there.
9) Click on IMAGE and then RE-SIZE (or use SHIFT S hotkey) – see image below.
9) The Units (resolution) is 300, Print Out size would be 7.68 x 10.24 inches (roughly less than A4 Sized), and the W & H are at 100% (Screen Size). Make sure the Keep Ratio square is checked, and I usually use the Hanning Resample Method. Lanczos is also very good.
10) At this point, you want to change the settings to get the largest print size you can get, while keeping the Units at 150 (minimum) and the W & H staying at 100% in the “Screen Size” section. (see the image below).
11) Look at the screen shot above: You see what has happened? When you decrease the Units to 150, the W & H changes to 50% in “Screen Size”. At this point you need to change the W & H to 100 (see the image below)
12) Once you have changed the Screen Size W & H to 100%, the W & H of the Print Size increases to 15.36 x 20.48 inches. At these settings, you can still create a very good print, at a larger dimension size, and without image quality compromise.
13) Let’s say now that you want to use this same digital file to create a 72-inch printout on the longest side, and you are curious about what the Units would be at that size, as well as, keeping the Screen Size at roughly 100% (see the images below). But first, let’s back up the truck and try something ridiculous…
Enter 72-inches in the Height box (Print Size Section). This increases the Screen Size (interpolated %/resampling %) to 352%. Your Units (Resolution) have stayed the same, at 150PPI, but other things have changed.
If you hit the OK button using these settings, you will end up with an interpolated digital file that is HUGE, and has a whole bunch of artificially added pixels just to accommodate the pushed/enlarged image size! (the new file data is in the strip below)
The new file size is 250.98MB!!! And the new file dimensions (Print Size) are 8,110 x 10,813 pixels!!! Outrageous! Did I mention that this file is HUGE!
Now, look at a section of this image at 100%.
Sure, it’s big, but the image is soft, is not very clear, and has “jaggies”. It would have been much worse if increased from the JPEG original.
Now, have a look a 100% section of the 20MB TIFF file that has NOT been interpolated. Remember, the PPI was just adjusted from 300 to 150ppi. This image is very clean because it has NOT be interpolated in any way.
Of course, you can’t print this one out at 72-inches, but who cares! It will look great at 20.48 inches.
If you try printing the other one, the huge interpolated one, you will more than likely see quite a quality decrease when printed at a large size, AND MAYBE, it won’t look as good at 20.48-inches because the pixels were screwed around with.
And yet, someone may still say: “You can make a 20.48 inch photograph from the 8,110 x 10,813 pixel file!”
“Ah, yeah, that’s interesting!” However, why waste 250MB of hard drive space to make a printout, for which you can make the same sized printout (of better quality because it has NOT been tampered with/interpolated/resampled), from a 20MB TIFF file? And, isn’t 526PPI a little overkill? (see the number details in the image above)
14) JUST FOR KICKS! What if you want to see what the Units will be while keeping the Screen Size at roughly 100% (101% in this case) and making a print at 72-inches? The screen shot above shows what settings you would end up working with to make a 72-inch print. The resolution (Units) of the image is reduced to 43ppi: The resolution falls way below the 150PPI Standard for which we’ve been using as our minimum. In other words, at 43PPI the printout could end up being horrible!
- DON’T TAKE MY WORD FOR IT. Try it yourself, take the image file to your printer, have them blow up, and printout a small section of the photograph with settings at 72-inches (longest side), and set the “Units” smaller than 150PPI. If it meets your requirements, then by all means, make the print. If not, however, then try making a smaller print by reducing the “Print Size.”
In my humble opinion, there are limits to the size of a good printout, and it depends on working with a very good TIFF file, setting a minimum PPI ‘Standard’ (minimum at 150PPI), and NOT interpolating/resampling the file – if possible.
This is where the bigger sized Mega Pixels Cameras come in handy – you get bigger sized originals to work with.