Metadata?

[Compass Call]

Can anybody please explain to me what 'METADATA' is?

I was cropping a JPEG image sent to me by a mate and I got a warning that it contained 'METADATA' and that this would be lost if I continued the cropping. I have cancelled the job until I know what it is. :confused:

CC

[25F]

Additional data that isn't part of the "thing" itself. Keep a copy of the original and crop away to your heart's content.

The metadata might be (for example) a description of a photo, or the date it was taken, etc.

[Bodie]

Consider Metadata as 'Data About Data'. There’s nothing hard about this one.

The simplest example I can give is of a Database. Lets say we have a "Job" table containing 4 fields -> Job ID, Job Run Time, Job Customer Process, Job Completion Date.

Each field is responsible for holding data. However, the reason for holding the data (or even what the data is for) may not be so obvious to a future user, especially in the above (contrived) example. To solve this problem, we could make notes to explain what each field "is" and "does". Example:

"Job Comletion Date refers to the REQUIRED date a job should be completed, not the ACTUAL date" and so on...

This is metadata - 'Data about Data'.

Hope this helps

Bodie

[fobotcso]

Interesting question with two good answers that have informed me.

So, when I get a JPEG image from a Mac, it comes with a big file with the image and a little file that I cannot read on a PC. That'll be the "meta" file then? What am I losing?

[25F]

The little file that you can't open is probably the resource fork of a Mac file. I could be wrong. (Macs store files in two parts - data and resource forks).

The metadata you're losing is probably metadata embedded within the JPEG data, i.e. within the data fork. The format is fairly open-ended so it's hard to say what you're losing - particularly not knowing where the image came from. However I do know that some cameras will store the date along with the picture.

[fobotcso]

Ta! I'm talking about simple picture files from scanning or a digicam.

I can see the image files without difficulty.

[BOAC]

This is FASCINATING. I am a total newcomer to digicams and have just got and played with a Nikon COOLPIX. In W98 and Nikkon 'View 5' (the bundled viewer) all the photo data appears with the piccy, but the ONLY file I have is a single JPG per shot, and I can edit/crop etc with Paintshop to my heart's content without any warnings, but when I view the result post-fiddle in the NIKKON prog., the data has gone. WHERE is it stored?

[Agent86]

BOAC,

Not sure about the Nikon software but the Canon software stores the info about each image in it's own database. This is what it stores:

File Name
Camera Model Name
Shooting Date/Time
Shooting Mode
Tv( Shutter Speed )
Av( Aperture Value )
Metering Mode
Exposure Compensation
Digital Zoom
Image Size
Image Quality
Flash
White Balance
Active AF Points
Parameters
Contrast Normal
Sharpness Normal
Color saturation Normal
File Size
Serial Number
Drive Mode
Owner's Name.

Sadly this all disappears if you lose the database and is not linked if you save the image as another file post-fiddle.

I am assuming (dangerous, I know) that the Nikon system uses a similar system. Check your help file. With a little name swapping you may be able to link the data to a modified file.

MAx

[fobotcso]

BOAC, sounds good to me up to the point where you try to view the result in the Nikon viewer. It is not unusual for JPG formats to differ (as mentioned above in my case of the Mac version being different from the PC format.) I suspect that the compression algorithm of the Nikon is special to hardware.

When you save your result after the PaintShop fiddle, try playing with the saving options.

Can the Nikon viewer accept any other formats such as "tif" or "gif" or "pcx" etc? And can you see other "jpg" pictures from other sources (such as the Web) in the Nikon viewer?

[edditted for crap speling]

[DistantRumble]

All picture formats to a lesser or greater extent have descriptive information in the header (eg size, resolution, and so forth)