Why is 31 characters the max for file names?

[Rick Lightbody]

I'm new to digital photography (though not to photography) and want to get started on the right foot, so I've been reading the DAM Book, etc.  I very much appreciate how  carefully Peter builds his "argument" and lays out his strategies.  But he does not seem to explain (at least up until chapter 4, which is how far I've gotten!) exactly what the 31-character file name limit is based on.  And I've not found such an explanation anywhere in this forum.  And yet I *have* found evidence that lots of photographers have been concerned (and even agonized) over how to make sure their own customized naming scheme will comply with this limit.

Although I'm not Mac-savvy, I did some research and found that the old Mac HFS file system was limited to 31 bytes or characters (see: http://en.wikipedia.org/wiki/Comparison_of_file_systems ) .  But that file system was superseded in 1998 by HFS+, which--like Windows NTFS and most other modern file systems--allows for 255 character file names.  Now I don't think anyone would benefit from or be tempted to have, say, 100-character long files names.  But 40 or 45-character names--yes, I think in some cases they would definitely permit greater flexibility (and readability) and would drastically reduce the amount of time people spend fretting about how to stay within the limits.

So my question here is:  In what systems or scenarios (of relevance in 2007) do file names with, say, 32 to 64 characters become a problem, and how important is that likely to be?  Thanks in advance to Peter or whoever else can answer this for me.

- Rick

[peterkrogh]

Rick,
You're right that many people would probably not hit a problem with longer filenames, at least on the OS level.  Probably the most likely snag would be associated with web applications.  Some of them have old chunks of code in there that throw up on long filenames. (I can't remember exactly, but I recently ran across a place where some old code - in iView, I think - made it choke on filenames longer than 8 characters.)

My reasons for advocating that standard is twofold:

1. I will always try to only recommend the most universal, compatible solution available.
2. I think people are better off not putting too much emphasis on entering content in filenames

Eventually this won't be a problem.  The problem is that if there is an issue, it can be a real pain to work around.

Peter

[andris]

FYI - Recently got bit by a long filename issue in Photoshop surprisingly.  We send images to a print house to produce large batch contact sheets.  Not sure what version of photoshop they're using, but it truncates long filenames and inserts four digits of its own hex garbage at the end of the filename when batch processing. I'm not sure whether they were using automate -> Contact sheet or their own actions.

I've also had issues with clients using out of date hardware/software with long filename issues.

Short filenames definitely avoid headaches in the long run.

Andris

[danaltick]

Here's the name of one of my files that I burned to a CD last weekend and took up to Costco to have printed altick_071118_0603_CCLus_12x16.jpg.  I used Costco's Lustre profile to softproof the image and sized it for a 12x16 vertical at 300dpi.  Because I commonly use 300dpi I don't include that in the name.  As you can see, I'm pushing the 31 character limit here, but still keeping it below.  Because I do spend a little time sharpening these after resizing, I go ahead and catalog them in case I might want to make more prints down the road.  I do the softproofing to the master file as separate layers in a group.  Peter talks about how to handle the derivative files later in the book.

Dan