Digital image corruption

[Glaucoides]

Thanks, everyone, for your replies to my question about urine on SD cards causing image corruption!

Is it easy to tell if digital images are corrupted? Do corrupted images always show obvious signs of corruption, such as missing parts of the image? Or could corruption be more subtle, perhaps just causing slight color changes?

In other words, if an image doesn't look obviously corrupted, can I assume that it is not corrupted and that the colors in the image are accurate?

Thanks!

 

[snowbear]

Anytime I've gotten corrupted image files, I usually can't open them.

 

[The_Traveler]

You have misconception about digital files. They are long strings of 1; and 0's and, except when their position in relation to certain significant points is known, they have no meaning until 'read.'
Water or salt deposition might cause areas to be unreadable or have significant defect but it would be an amazing stroke if the color was just off a little bit.

 

[Overread]

As Traveller says digital data is just a string of binary numbers (0 and 1). As a result corruption will generally mean any attempt to read that date will fail; either the software won't be able to open the file; or it might do so but errors will be very apparent because the arrangement of the code will have gaps and be broken.

Colour is thus vastly more likely to be accurate, however that depends on how accurately you set the white balance for the shot (or how accurately the camera set it). As photography is dominantly an artistic pursuit most people are not after perfect colour reproduction and instead go for a pleasing result; so generally the cameras white balance is good enough; or the auto setting in photoshop for setting white balance on a RAW Shot is good enough. Some might use the eye-dropper tool to get it a little more accurate; but in the end the only way is to set custom white balance in the light for the shot - its not as commonly done, but if you want faithful colour capture its the only proper way.

 

[dennybeall]

Like any digital file a digital picture file has a leading segment that tells the computer information about the file. Corruption of a file most likely effects this information part of the file and that's when you can't open the file.
When bits other than that area are lost or changed it only effects that tiny little spot so is most likely not noticeable.

 

[greybeard]

A digital picture file isn't like a analog negative, it is a digital description of an image. The computer sees this string of (1's and 0's) as a recipe for making a picture and reconstructs the image according to the information in the file. If any part of the file becomes corrupt the computer usually just rejects it and sends the user a file read error. If it reads then it is probably good. If you are worried about the integrity of your card, just copy it onto another card and you should be good to go.