PNG vs TIFF graphic in comic book style

When you begin to scan your photo collection of paper prints, slides, and negatives, one of the biggest questions you’re going to have to answer for yourself is which file format will you want to save all of your scanned photos with.

For those interested in saving the highest quality images, two of the most popular formats that often stand out are the PNG and the TIFF. But, which one would be best for archiving scanned photographs?

The decision-making process starts out seeming a bit tricky because not only do both the PNG and TIFF produce high-quality images, save with transparencies, and save with 16-bits per channel, but they also both maintain their original image quality even if they have been edited and re-saved over and over.

But, the choice start getting a little clearer once we compare the characteristics that actual separate the two.

PNG

Portable Network Graphic   ●  Pronounced PEE-en-JEE  ●  Extension: .png

  • Created in 1996 by the PNG working group to be an improved replacement for the GIF file
  • The format was designed for transferring images on the Internet
  • Reduced file sizes without any loss of image quality (using lossless compression)
  • Can only hold full-color non-palette-based RGB or RGBA (with alpha channel)
  • “Web-friendly” support for display on the internet by web browsers
  • Limited (not standardized) support for storing metadata with XMP (when supported by the application)

TIFF

Tagged Image File Format  ●  Pronounced TIF like “Tiffany”  ●  Extension: .tif or .tiff

  • Created in 1986 by the Aldus Corporation (later acquired by Adobe Systems in 1994) for use in desktop publishing
  • The format was designed as an attempt to get desktop scanner vendors to agree on a common scanned image file format across multiple computer platforms
  • Files are usually stored uncompressed, but the option to reduce the file size is also available (using lossless compression [ZIP or LZW] and sometimes even lossy compression when supported by the application)
  • Can store “layers” within (useful in high-end editing applications like Adobe Photoshop)
  • Can hold all color, color depths and color groups (e.g. RGB as well as CMYK, LAB, etc.)
  • Full built-in support for storing standardized EXIF and IPTC metadata fields inside the file (e.g. “date taken” and “captions”)
  • Can store multiple images, such as the pages of a scanned or faxed document (similar to a PDF file)

Make Sure the PNG or TIFF Is Even the Right Choice For You

I think it's important to bring up how critical it is to know whether the PNG or the TIFF is even the right choice for you. You may have been led to believe these were your two best options, and this is why you arrived at this post.

Even though these are two of the most popular file formats for images in general, it doesn't necessarily mean either one of these will be the best for your own photo scanning needs that also matches your level of goals for your photo collections.

Choosing the right file format to archive your scanned items is kind of like picking a tool for each situation in a household project. Sometimes what you are working on requires a flat head screwdriver. Other times you need a Phillips head screwdriver. Yet other times, many are surprised what they really need is a nail and hammer instead.

Each item in your list to be scanned might need a different file type to be used — documents, film, and prints, etc., “One size” likely won't “fit all” here.

Below is a special video that's a section taken from one of my lessons called “Digital Masters and File Types” in my video training course on scanning and organizing photos. Until now you needed to be a Member, but for a limited time, I'm also making this portion available for you to watch too.

Think of this as a Mini-Lesson on learning the best file types for scanning your photo collections!

The Main Reasons I Still Don't Recommend the PNG File Format Over the TIFF for Archiving Your Scanned Photo Collections

I think the PNG file format is fantastic and really has many benefits. In fact, I use it all the time on this website for certain images where I know they will produce a more detailed image than a JPEG would and with a smaller file size.

It's not that the PNG can't or should never be used with your scanning project, it's just that there are other formats more suited for the purpose of archiving scanned photos.

If you're looking for a bit more information, let me pick 4 of my favorite points and go into some additional detail.

1

There Are Formats Designed For Scanning

The TIFF file format was created in the mid-1980's for use in desktop publishing and was then designed to become the go-to standard format for saving scanned photographs and has been for over 3 decades.

And the PNG file literally tells us in its name that it wasn't designed for such a purpose. PNG is short for Portable Network Graphic — key word there is “portable.” And this makes sense because files meant to be transferred around the internet do need to be as portable as possible — especially on devices like smartphones and tablets trying to access cellular networks in areas with poor service.

But, when I think about saving and archiving my scanned photograph collection, portability isn't something I'm concerned with at all. Archiving isn't about movement. Frankly, it's the opposite. I'm thinking about “longevity”, “compatibility” and “no compromises.”

If the TIFF file is the standard for scanned photos, for me, there would have to be a hugely compelling reason to choose another format; especially when most of us are only storing away a single master image for every single photograph from our original (analog) paper print, slide, and negative collection.

Whichever file format you choose to archive your scanned items in needs to give you confidence that they will be your one-and-only authoritative version of the (analog) originals you scanned them from.

2

Lack of Scanner Software Support

Even though there are a lot of file formats and often variations of each of them to choose from, when you're actually in your scanning software ready to save a photograph you just scanned, you will quickly find out that even the most popular scanning software only gives you a small handful of options to choose from — and the PNG format likely isn't one of them.

If the PNG format was really a strong contender for saving scanned items with, isn't it strange — strike that, incredibly strange — that after all of these years it still has not been added to the list of file type options to choose from in major scanning software?

It's not an option to choose from. It's not there.

Wouldn't scanner manufacturers and scanning software developers want you to easily have access to saving in this format it was meant to be used for saving scanned items?

File format options in the popular scanning application “Epson Scan” that comes free with all Epson branded flatbed scanners (v. 3.9.4 – “Professional” mode)

So, this means if your goal is to archive your scanned images in the PNG format while scanning with software that can't natively save in the PNG format, you're going to have to go through an additional step later to convert the file format from one to the other.

First, you will save your scanned images in an alternate file format that is available as an option in your scanning software, and then next you will “batch” re-save each one of them using the PNG format using another application that can handle this conversion process.

If you're good with computers and comfortable working in your computer's file system, this procedure likely won't give you pause. But, if you are a beginner or just not at all confident with your file system, this conversion process could be overwhelming for you and therefore likely a step you typically would choose to avoid at the risk of doing it wrong.

File format options in the popular and stand-along scanning software VueScan Pro (v. 9.6.47- “Professional” mode)

Something important to keep in mind when doing the conversion is you will want to make sure to first save your scans from your scanning software in a lossless format (and not a lossy one like the JPEG format). This way you aren't losing any image detail before re-saving it in your other application in the lossless PNG format (in an attempt to preserve what has already been lost). And most often, unless you are using a high-end scanning application that gives you a RAW file option, the only lossless format to choose from in most scanning software is the TIFF.

3

Non-Standardized Metadata Implementation

What's really neat about working with your scanned photo collection is the ability to tell stories with all of these old photos. And the best way to do this is to add important descriptive information that is stored inside of each that can be accessed by someone using an application that has the ability to read and display this information.

This added information is referred to as “metadata” and a few popular examples would be the “shoot date” of when the photo was actually taken, a “caption” of description of what we're seeing in the photograph, the name of the person who took the photo, and the location of where the photo was taken.

How Photo Metadata Works

The best method of doing this has been using an application that will allow you to click in these metadata fields and manually add or change this descriptive information. For many years now, this data is has been stored inside the file using one of two standardized sets of “metadata” fields named EXIF and IPTC (With RAW file formats, the metadata is sometimes stored in sidecar files).

In the simplest of explanations, the EXIF (Exchangeable Image File Format) holds camera information such as the model of the camera, the date the photo was taken, what type of lens was used, was the flash attachment used, etc. And the IPTC (International Press Telecommunications Council) holds information that helps to inform what's in the photograph, who took the picture, and who is now the caretaker for it.

Even though most other file formats adopted this standardized way of writing metadata into the EXIF and IPTC tagsets, the PNG format has never been built or even updated to correctly take advantage of these pre-established standards. Stated very well by the PNG's Wikipedia page:

The PNG specification does not include a standard for embedding EXIF image data from sources such as digital cameras. Instead, PNG has various dedicated ancillary chunks for storing the metadata that other file formats (such as JPEG) would typically store in EXIF format.

PNG's Current Metadata Support

At the time I published the original version of this article you are reading, I don't believe there was any support for the popular metadata fields with the PNG file. This was the biggest reason I included the word “hurt” in the title of this article — because withholding the ability to safely add descriptive metadata to a scanned photo would definitely be detrimental to your photo collections.

However, through the years since, there has been an increasing amount of “limited” support. And I say limited because it's currently hard for me to quantify for sure how much backing there really is industry-wide (with all the photo software out there) with the PNG's non-standardized metadata implementation.

It's my understanding that instead of writing metadata in the standardized methods inside your files in the way other file formats all follow, when your metadata is written to a PNG file, it's saved in these unique “ancillary” chunks within the file.

An analogy for this might be instead of leaving your car registration and owners manual in the glove box like everyone else, you decide instead to hide it in the trunk under the spare tire. They're there, and technically accessible, but who would even know to look there?

Now, also to my understanding, when you load a PNG file, it's up to the application then to find and then decipher what this “ancillary” chunk of information is and then decide what to do with it. Which means, some applications will support reading and writing known metadata information to PNG files, and some won't.

In the worst case, if you load a bunch of your precious metadata-rich PNG photos in an application that doesn't handle this non-standardized metadata properly, and it not only doesn't read it, but it inadvertently strips them all out or corrupts them. Apparently, unlike the other chunk type called “critical”, data written in “ancillary” chunks are supposed to be safely ignored if the application isn't familiar with how to interpret it. However, it's up to the application's developer to follow and honor this protocol.

So, this is just all to say, be very careful when working with new and unfamiliar applications and workflows if you're saving metadata in your PNG files. I would hate for you to lose all of that information you've painstakingly added.

Adobe XMP Implementation

Adobe is working hard to support their Extensible Metadata Platform (XMP) which is a file labeling technology that lets you embed metadata into files. Applications that support XMP, can also apparently make it possible to exchange metadata from files with metadata in the standardized EXIF and IPTC tagsets.

What this means is if you stick with applications written by Adobe (Adobe Bridge, Adobe Lightroom Classic, etc.), you will likely find a reliable workflow when working with PNG metadata. Also, you will likely find success with other photo applications who are actively trying to be as useful as possible to their customers by also adopting XMP or even any other metadata implementations that have become popular.

If you're moving forward with saving your scanned photos in the PNG format, and you wish to utilize the EXIF and IPTC metadata entry fields found in the best (non-destructive) photo managers, just take this as a stern warning that PNG's are breaking new ground here.

Experiment with your workflows to make sure your metadata is being carried over from one step to the next before moving on. And be sure to have backups of your entire collection just in case something ever goes wrong.

4

Unexpected File Size Savings

For someone who's seriously considering saving their scanned photos in the PNG format, the main reason they are choosing to deviate from the standardized TIFF format is likely because they've read or heard from someone how much smaller PNG file sizes are in comparison — and therefore will take up much less space on their storage drive.

It is true, the PNG file format can be used to produce really small-sized images when it's used with the right type of image. But, most people will be surprised to discover that when you're saving scanned family photographs, the amount of file storage savings you will gain isn't nearly as much as you might expect.

The “JPEG Comparison”

Most of us are so used to viewing and sending lots of high-quality photographs (images) over the internet that we have probably lost the perspective of what has been given up in order to make this happen so easily.

Likely, what most of us are sharing are small (low resolution) and highly-compressed (file size reduced) images that are saved in a ubiquitous file format called the JPEG (sometimes written as JPG).

It's a miraculous format because the images can appear to the human eye as having quite a lot of detail and yet the file sizes can be tremendously small, making them transfer from one device to another over the internet with ease.

I explained how JPEG's compression is different and the drawbacks you need to be aware of in the video above. So, you're now mostly up to speed with how it works.

Now, take this photograph from my family photo collection as an example. I have it saved and archived as an uncompressed TIFF file and it takes up an unapologetic 25.5 megabytes (MB's) of space on my storage drive.

If I convert this file to the highly-compressed and portable JPEG format, even with the compression setting set to a modest 80% quality (out of 100%), check out how small the file size was able to be reduced down to:

ImageTIFFJPGStorage Savings
25.5 MB885 KB (.885 MB)96.53 %
File Settings/TypeUncompressedLossy Compression – 80% Quality

This photograph was shrunk down to less than 1 megabyte (MB) of file storage space — 96.5% smaller! — yet still maintains a high-enough level of image quality that it's suitable to be passed around via email or social networks and be enjoyed.

The big compromise with JPEG images is that in order for the file sizes to be so incredibly small and therefore “portable,” they have to go through a process called “lossy compression” that uses irreversible “inexact approximations and partial data discarding to represent the content.” However, if done with the appropriate settings, like in the example above, the quality of the image will still be acceptable for the purpose it was created for.

How PNG File Size “Compression” Works

The PNG format is different from the JPEG format in that it attempts to replicate the original exactly. It instead uses “lossless compression” which means your images will be saved without having any of the data (details) of your photo “tossed out.” So, you won't lose any image quality and your images will take up less space on your hard drive than if they were saved with an uncompressed format (like the “uncompressed” version of the TIFF file).

But, it is this lack of image detail loss that keeps the PNG format from producing file sizes as small as the JPEG format can achieve from highly detailed and low-contrast scanned photographs.

As an experiment for this article, I scanned two additional paper prints, each slightly different in dimension and colors. In my scanning software, I also saved them as uncompressed TIFF files. Then I loaded all three of them up in the latest version of Adobe Lightroom Classic and created a second version of each by converting them to the PNG format (with settings maintaining all of the color and bit depth as possible from the TIFF).

Now, take a look at this chart I created that will give you an idea of the file storage space savings of each of the photographs when compared to the “highly-compressed” JPEG version we just talked about.

ImageTIFFPNGStorage Savings
34.3 MB28.1 MB18.08 %
33.2 MB26.8 MB19.28 %
24.5 MB20.8 MB15.10 %
File Settings/TypeUncompressedLossless Compression

You'll quickly notice that unlike the JPEG version that was able to be compressed over 96%, the average PNG compression (storage savings) I was able to achieve was about 17.5% — an average of the three. And specifically, the same image I used in the JPEG example had a compression savings of only 15.10%.

Now, 17.5% certainly isn't a tiny number and shouldn't be discarded as insignificant. But, when we go back to our goal for our archived master images to be the authoritative version of the (analog) originals you scanned them from, is 17.5% really enough storage savings to deviate from the using the go-to standardized file format for saving and archiving scanned photographs?

To me, it's not enough to make it worth it. Especially when considering most of us will be saving our massive scanned photo collections on an external storage drive dedicated to just this one project. And you can get a storage drive with more space than you will ever need for the average photo collection — with even a lot of space left over — for between $50 and $70. A negligible price to archive your irreplaceable one-of-a-kind memories.

TIFF with Lossless Compression Alternative

An alternative option for those wishing to take advantage of the feature-rich TIFF format, but still reap the modest file size reduction found in the PNG, is to save your scanned photos using a variation of the TIFF format that utilizes the same type of “lossless compression.”

To add to this experiment, I saved all of the same scanned images we discussed above in the TIFF format using ZIP lossless compression, and look how the results turned out when compared to the file sizes of the PNG.

They are nearly identical.

ImageTIFF (Original)PNGTIFF
34.3 MB28.1 MB28.3 MB
33.2 MB26.8 MB27.1 MB
24.5 MB20.8 MB20.7 MB
File Settings/TypeUncompressedLossless CompressionUsing ZIP Lossless Compression

I want to thank Peter Fuller all the way over there in beautiful Wellington, New Zealand for providing me with this question. A very interesting one indeed.

And if you have a question of your own you would like me to cover in an article like this one, ask away using my contact form.

Cheers!

From your site and the other information I've found on the net, I think we should scan our photo collections in TIFF, at 600 dpi, using your naming convention/workflow. You don't cover TIFF versus other formats in your articles, but I see you are using that format and there seems to be general acceptance that it is the best format for archiving.

What do you think of the PNG format?

Peter Fuller
Wellington, New Zealand

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