“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? “
Wellington, New Zealand
Peter, that is a great question. And you're right, up until now I have not covered what I feel is the best file format(s) to save scanned photos with. But, as you astutely noticed, I did sort of allude to my personal choice in a couple of my posts. Especially in some of my images I used in my 3-part “naming convention” series you brought up called What Everyone Ought to Know When Naming Your Scanned Photos.
I think your question actually deserves a slightly more complex answer than I could normally get away with. Had you simply asked, “Which do you prefer for scanning photos, the TIFF or PNG format?”, I would feel comfortable quickly answering you that in my humble opinion, the TIFF format is by far more superior for the purpose of scanning photos. But, since you brought up your interest in “archiving” your photographs, I want to make sure I elaborate a bit more to explain why our personal goals of scanning need to be considered when making the final decision which file format to save our master image files.
PNG vs. TIFF Files – So Which IS Better?
PNG files (Portable Network Graphic) were invented to replace the GIF format (Graphics Interchange Format) that was quite popular at the time for images on the internet. They really weren't intended to be used for professional-quality photos. Currently on the internet, you will primarily see JPEG and PNG files followed by the lingering GIFS.
PNG files:
- can only be saved compressed (“lossless” – reduces file size)
- can hold an alpha channel
I use PNG files here on the SYEL website a good portion of the time because they have small files sizes and I love being able to use the alpha channel. This is a fancy way of describing a “compositing” process where the image can have a transparent background so you can lay it on top of another image and use it as the first image's background. It's very cool! And in case you're wondering, no, JPEG files don't do alpha channels.
TIFF files (Tagged Image File Format) on the other hand:
- can be opened with almost every image program (it's an extremely common format)
- can be saved compressed or uncompressed
- can store “layers” within (great for use with Adobe's high-end Photoshop for example)
- can hold all color, color depths and color groups (like RGB and CMYK)
- can save 16-bits per channel scans (your 48-bit scanner setting)
- can store IPTC metadata (captions etc.)
In my opinion, one of the biggest reasons not to use the PNG format for photo scanning – and more importantly archiving photos – is because it's a form of compression. It's a form of compression called “lossless,” which as you might already know, means that your photo will be saved without having any of the data (details) of your photo “tossed out.” However, the image is still undergoing a very complex process using a mathematical algorithm to compress the file so that it will take up less space on your hard drive.
So let me explain why this should be important to you.
Do You Have Basic or Advanced Goals?
To keep it simple, if you are about to scan your entire photo collection, you are probably going to fall into one of the following two categories. First, you might be the type of person that just wants to get a good-looking scan of all of your photographs as quickly and easily as possible. If you feel this might describe your needs, I like to say that you are someone with basic goals.
Now don't take that the wrong way. I don't mean to say basic in a negative way. The fact that you are even wanting to scan your photos already says a lot about how much you care about your collection.
When Peter brought up archiving, to me it implies he's stepping into the shoes of someone in the second category. Someone with advanced goals is a person I feel is invested from the very beginning to make the decisions that will insure everything they do throughout the workflow of scanning, correcting and managing their photos, will preserve every last bit of image quality (detail) they reasonably can. Those with advanced goals also are willing to sacrifice more of their time and possibly money – which in many cases is not that much more – for the ability to create and store these higher quality images.
Let me quickly add, having advanced goals is by no means exclusive to those seeking the level of perfection a lifelong professional in the graphic arts field would produce. You don't need to be an expert to have advanced goals. We all have our own personal limitations and expectations for our collection.
Settings panel when saving a TIFF file in Photoshop CS5. (Mac) Notice there are three compression options or none
What I Really Think of Compression
I believe in my heart, that if you are going to really go at archiving your entire photo collection – I mean really give it your all – you should scan them with adequately high DPI settings, save them “raw” without lots of filters and computations altering the outcome of the master image during the scan, and save and archive them uncompressed. I know this might be asking a lot of you, but the sacrifice has its rewards.
If you are considering compressing your images, to save hard drive space or ease the processing load on your current computer, just know you are taking steps toward the side of people with more basic goals. I just want to make sure you understand this.
Many may disagree with me, but I consider compression, even the lossless kind, to be an act of compromise to the overall integrity of your collection.
The hugely popular JPEG file format (Joint Photographic Experts Group) also uses compression. And it's even more severe because it's a form of lossy compression. Lossy means your file size will typically be even smaller than that of lossless, but at the cost of reduced image quality. And once the detail is gone – it's gone. If you're lucky, your eye won't be able to see what's now missing.
Even worse, every time you re-save a JPEG as a JPEG, you are “tossing out” even more information in addition to the information you got rid of before. It's compounding detail loss!
Non-destructive image managers will however automatically protect you from this additional image loss when you make edits to your photos inside. This is why I highly recommend everyone start using one. (Check out Use 1 of These 4 Photo Managers If You Care About Your Photo Collection)
Additionally, and I know this is really more theoretical, the second you bring to the table the option of compressing your masters, you introduce a greater possibility for file corruption. You're putting more trust in that mathematical formula to “destruct” your photo now and “reconstruct” it later than you may want to give it. Some formats have so many variant types of compression, who is to say that “shareware” graphics program you found one day off the internet to compress your images will be around 20 years from now? What if their proprietary scheme doesn't open correctly in the version of Photoshop you buy in the future? Then what are you going to do?
The Best Format to Save Your Scanned Photos
You are the safest saving your master images in the most common, nonproprietary format that you possible can. And if you are swinging towards the advanced side of goals for your collection, you want to save your files uncompressed. Yes, uncompressed files are huge, but so are the capacities of average priced hard drives on store shelves today.
The two most common formats that I feel safe recommending to you are JPEG (high-quality setting) for those with basic goals and TIFF (uncompressed) for those with advanced goals. It's also the two formats all of the major scanning services feel safe saving your precious memories in as well.
Wow! And I bet Peter thought this would be a simple answer to a simple question! Leave it to me – just get me all wound up and it all comes out!
I hope that all made sense. If I left out anything you are wondering about, just ask me in the comments below. I will be glad to answer them for you!
Thanks for that question Peter from over there in beautiful Wellington, New Zealand! 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!
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I have to disagree with you, and agree with the other commenters that that lossless compression is OK – not some ‘shareware’ algorithm and is, at this point, a de-facto standard. You say that you think about compression as destructing your photo and trusting the computer to be able to reconstruct it – what about the hard drive that saves your photo? Isn’t that going through a process that you have to trust to be able to read it again?
If you are dealing with – or the intended output is with – 8 or 16-bit RGB files, PNG is a perfectly good – superior, I would say – format to save in.
Otherwise, thank you for the information.
Curtis, you seem to be a bit misinformed regarding the inner workings of compression.
It’s good you pointed out the difference between lossy and lossless compression. These are absolutely factors that one should consider when deciding what format to save a file in. However, you then state that “compression, even the lossless kind, to be an act of compromise to the overall integrity of your collection.” In actuality, this is simply not true.
Lossless compression will not compromise any of the integrity. It’s just a mathematical algorithm for maximizing how the data is stored on the drive, taking advantage of patterns and minimizing redundancy. When you open a PNG file in an editor or viewer, it removes the compression, and you have access to the image in its full original quality.
Please do not be misguided regarding lossless compression. If you’re worried about integrity, this is not an issue at all. The place where lossless compression DOES matter is speed. If you’re scanning and manipulating a large volume of images, PNG may be slower overall. However, PNG is so widely supported and the algorithm has had decades to be fully adopted and adapted to, so this isn’t too much of an issue.
Good article otherwise!
Excellent article. Only thing I’d add is to be conscious that Windows file names are limited to 255 characters when you include directories and subdirectories as part of the full name or file designation.
What does the author mean when he says “every time you save a jpeg, you lose some quality.” When would we re-save them?
Since JPG (JPEG) is a lossy format, every time such a file is saved, it loses some data and quality to keep a small file size. Quality loss from repeated saves will often be most noticeable in large areas of relatively uniform color, such as a clear blue sky. Instead of having a relatively uniform blue, the sky will show distinct bands of slightly different values of blue where some of the color data has been discarded. The same applies to the entire image, but is most visible in areas of uniform color such as the sky.
Any time you make a change (edit), such as adjusting the brightness, contrast, color balance, cropping, etc. and save your change, you’re re-saving your file. Since it’s usually recommended to save each change before making another edit, just in case your computer crashes or some other problem occurs, if you decide to make multiple edits to a single image, you could easily re-save that image 4 or more times. Since a JPG loses some data and quality each time it gets saved, if you’re making extensive edits to one, you can easily end up destroying its quality beyond any hope of recovery. If you have only a JPG file to work with, open it in your editing program, SAVE AS a TIF or PNG, before making any edits. Saving in either of those formats won’t recover any data lost when the file was originally saved as a JPG, but it will prevent further data loss with repeated saves. When you’ve finished editing, you can save a copy of your edited file as a JPG if you really want that format.
Its not quite as bleak as you claim, as technically whilever that JPEG is open in your editor then all edits are being done on the uncompressed copy in RAM. No matter how many times you save it, you are only performing one re-compression from that copy in RAM.
It only becomes problematic if you are using batch scripted command-line application to make the edits as those DON’T keep it in RAM between actions, but then the simple answer to that is to make a copy of the original as PNG and do all work on that, only saving to JPEG once finished.
The same applies to an editor, any work-in-progress save should be made as a PNG or other lossless format, only convert to JPEG once you are finished. Or even better, keep it as a PNG so no further quality is lost.
“Its not quite as bleak as you claim, as technically whilever that JPEG is open in your editor then all edits are being done on the uncompressed copy in RAM. No matter how many times you save it, you are only performing one re-compression from that copy in RAM.”
Technically spoken thats nonsense.
Without any knowledge which editor is used there is no possibility to predict if the behavior you assume is a matter of fact. There are in fact applications which will work with the newly saved data after saving the image.
With one of these your quality will subsequently get worse and worse with every saving.
Also there is no “uncompressed copy” in RAM after loading a jpeg.
The damage which was done while saving, cannot be undone while loading from such a file.
Thats the LOSS in lossy compression algorithms.
You will have an uncompressed copy of all the remaining information in RAM and if you save this again after loading from such a file, there will be further loss of information.
:/ nah.. Too much text…
Still would use JPG!
This is one of the most informative articles and blogs I have ever read on this subject. I was pretty well convinced that I will use Tiff as my output but there are a couple of you who suggested that if I have VueScan Pro, I should use dng + jpeg. No one really commented further about that so I am a bit confused. I do have that program and I use Lightroom. I have all my Nikon digital pictures in Lightroom as NEF (Nikon raw)files. LR does allow you to import your files as dng but I did not do that. My intention is to import all of my scanned files into Lightroom as Tiff’s since I have not yet used the dng capability but the contributors to this blog aroused my curiosity. Can anyone comment further, either positively or negatively, regarding the dng + jpeg method?
Hi,Great Article. Thank you so much for sharing!
Cheers!
My choice for archival would be PNG because the format is widely supported and decompression is fast. For work in progress I would use either TIFF or BMP without compression, or PSD.
One reason why PNG is not a good choice for direct output from scanning software is that compression to this format is rather slow. This becomes significant when working with large files. So it makes no sense to spend time compressing a scan that still needs editing (inluding simple edits such as cropping or rotation), especially if compression only reduces the size to around 50% of the original. If the scanner does encoding on the fly without a temporary uncompressed file, and the CPU can’t keep up, then the scanning head would be requird to stop, and possibly create a tear in the image.
If you expect data coruption, then an uncompressed format has an advantage. As long as the file size doesn’t change and unreadable sectors are replaced with other data instead of omitted, then corruption will only affect the pixels that could not be read. A compressed file will be corrupted by a 1 byte error until the end. Recovery might be possible for some formats, but it is not trivial.
JPEG-LS is an interesting format with faster compression and better ratio than PNG, comparable decompression speed, but unfortunately it doesn’t support metadata.
Interesting article. Thank you for publishing it. I am confused, however, about the compression vs. non-compression issue. To get right to it, I’m not sure why using compression makes a person a basic need person, or why that’s relevant.
From my perspective, using more disk space than one needs to doesn’t make sense. If you can store the exact same file for less, than it makes sense to do so, regardless of whether you’re a basic person, advanced person, or an upside-down pineapple cake. Just using more space because you have “advanced” needs, without a benefit for that increased space usage, all to retain a mental image of oneself as an advanced user, doesn’t make sense. This is like saying “basic people pay $1.99 for a taco, but advanced people should pay $3.99 for the exact same taco”.
Well, why?
I guess I’m just not getting it.
Interesting article, though.
Hi Rex,
I believe why Curtis refers to some people as ‘basic needs’ people is that they need only to have an acceptable quality of digital image. They’re generally not concerned about preserving the maximum possible file data and quality that other people, who may want to do so in case they want to edit their images for particular needs in the future. So far as compression goes, if it’s LOSSLESS compression, then no data or quality is lost to the compression operation. On the other hand, LOSSY compression does discard some data and quality. The greater the amount of compression, the greater the loss of data and quality. While the TIF/TIFF format is generally LOSSLESS, it can be set to use JPG/JPEG LOSSY compression, at least in some programs. If the same image is scanned as a TIF, then again as a JPG, the two files will NOT be identical since the JPG format always applies at least some compression. Thus, you don’t have the “exact same file for less” with the JPG instead of the TIF version. For people who just want a digital copy of an original photo, particularly if all they want to do with the digital image is email it or post it on a blog or web site, the JPG version, which will be smaller than the TIF version, will most likely meet their needs, regardless of the amount of compression applied. Becaused the JPG format is LOSSY, each time a JPG file is opened, edited in any way, then re-saved, it is compressed again so repeated saves continue to reduce the amount of data in the file and the file’s quality. TIF and PNG formats, both using LOSSLESS compression, if any, normally give larger file sizes but don’t lose any image quality. For those who want to retain the maximum possible quality and/or do extensive editing, possibly intending to eventually print their images, TIF and PNG are better formats to use. Such files can always be converted to JPG after editing and, if necessary, resizing, for use in email or posting online. Hopefully this will clarify things for you.
Ah, okay, so he’s talking about lossy compression then? He doesn’t have an objection to flipping on LZW or ZIP compression when saving the TIFF?
If so, that makes complete sense.
For some reason, I thought he was saying “Don’t use LZW or ZIP compression on TIFF files if you’re an advanced user”, and that’s what I didn’t understand. I thought there was some philosophical objection to any compression for “advanced” users.
It sounds like my interpretation was incorrect.
Thanks for the help!