digital 'negative'?

[itf]

I know very little about digital and the various file types, but I'm very curious to know if there is any way of tracking changes made to a digital image file? Is there a file type that an adjusted image cannot be saved as? Providing, in effect, a digital negative. Is that what RAW is?

I'm curious because I wonder what might happen somewhere down the track; someone is trying to put together a series of photographs showing a particular time and place, but can't figure out if that was an actual scene or someone's fantasy.

Of course, a file type that won't save changes doesn't ensure that the knowledge that that is an unedited file type lives on. So it would possibly make no difference to the future person anyway; the digi-neg file might not be recognised as such. Further, are people going to go to great lengths to keep that unedited file when they have the edited masterpiece of the same photo?

I've elaborated a bit on my original question; is there a digital negative? Thoughts on the rest?

rich

 

[payasam]

Some people save their raw files to CD or DVD. Most reliable back-up.

 

[drewbarb]

Just about everything about digital is a negative, IMO. 😀

Seriously though, sitemistic is right- there is no file format that can't be changed. The best thing to do is just to save your RAW files or TIFFs or whatever your earliest file is to an external drive and/or disc. Keep you original files untouched, and be sure to click "Save As" after you make changes to create a new file.

 

[ChrisN]

You can achieve what you have described (a digital negative, and a track of changes made) by adopting a particular workflow (a set of standard practices) that is designed to achieve this.

Start with a digital file, either from the camera (preferably in RAW format - has more/better information than JPG) or as a hi-resolution scan from the negative scanner saved as a TIFF file (again, TIFF is better than JPG).

These "original" high-quality image files can be regarded as an orignal digital negative, to be set as "read-only" and copied to safe storage (two copies, stored separately on CD, DVD or off-line hard disks). When you want to work on the image, you make a working copy to manipulate in Photoshop or similar program.

There are now some image editing programs that track "non-destructive" changes - that is they don't write the changes to the image file, they just keep a record of the sequence of changes, so you can apply the same changes repeatably to the copy of the original file.

Be aware that there is an image standard format being promoted by Adobe as a "digital negative" - the DNG file (with .dng file extension). Adobe offer programs to convert your RAW files or TIFF files to DNG format. Some digital camera makers have adopted this and you can configure the camera to write the files in JPG, RAW or DNG format. There are many pros and cons here - it is something you need to research for yourself and consider factors related to image size and compatibility, and your confidence in the standard surviving.

 

[delft]

Hi Itf,

The Canon dslr's have an option to add some 'validation' info into the raw files, which can be used to show that these raw files ar unaltered, i.e. as shot in-camera. You have to pay big bucks for the validation software to read this data, though.

greetings,

Dirk