.jpeg compression: Maybe a stupid question and I think that I know the answer, but I'm going to ask it here for clarification anyway. We all know that the .jpeg format compresses the...

Bison Bud

Maybe a stupid question and I think that I know the answer, but I'm going to ask it here for clarification anyway. We all know that the .jpeg format compresses the picture data and that the data deleted is gone forever unless otherwise backed up with another type file that doesn't use compression. This can be a good thing or a bad thing depending on how you look at it. Anyway, this compression obviously takes place when the original edited RAW file is converted to .jpeg, but does this also happen every time I make a copy of the .jpeg file? If I do a simple file copy to move a .jpeg file from one location to another, do I get the complete original .jpeg data or is it compressed again even if the picture is unedited?

rjaywallace Loc: Wisconsin

I would expect to experience no compression on subsequent JPEG copies. Other more expert minds may differ. /Ralph

whitewolfowner

Bison Bud wrote:

Maybe a stupid question and I think that I know th... (show quote)

For starters, how can throwing away data on a digital photograph be a good thing? Why spend all the money on a good camera and then destroy what it can produce?

rmalarz Loc: Tempe, Arizona

The compression process occurs during the save. Simply copying or moving a jpg from one location to another does not involve compression.

Opening a jpg, looking at it (as in no modifications), and saving it again will lose data. Open, look, and close will not alter the file.
--Bob

Bison Bud wrote:

Maybe a stupid question and I think that I know th... (show quote)

dsmeltz Loc: Philadelphia

My understanding is that if you make a copy it retains the data in the original file. That is you go to the file folder, click on the file click, on copy and then paste it somewhere. If you open the file in a program and then save it to a new name, that is a whole different thing. Then you may have loss.

rmalarz Loc: Tempe, Arizona

Open and save will lose data, renaming has nothing to do with it, the save does.
--Bob

dsmeltz wrote:

My understanding is that if you make a copy it retains the data in the original file. That is you go to the file folder, click on the file click, on copy and then paste it somewhere. If you open the file in a program and then save it to a new name, that is a whole different thing. Then you may have loss.

CatMarley Loc: North Carolina

Bison Bud wrote:

Maybe a stupid question and I think that I know th... (show quote)

Only if you edit it, not if you just copy.

CatMarley Loc: North Carolina

whitewolfowner wrote:

For starters, how can throwing away data on a digital photograph be a good thing? Why spend all the money on a good camera and then destroy what it can produce?

Depends on why you took the photo. I often take a photo to prove a point, or to send to a workman regarding some job around the house, or to show my daughter a new critter or birds nest. Jpegs take little space. A good thing! Besides, the Fuji jpegs are really so good, I rarely have to do anything to them other than crop out some odds and ends to improve the composition.

Bison Bud

Thanks, I now know that compression only occurs with a save or change in the file, which is what I thought, but was not sure. This is good news as I have been archiving my edited photos in the .jpeg format and .tiff files take up a lot of room. Thanks for the prompt and informative responses!

whitewolfowner

CatMarley wrote:

Depends on why you took the photo. I often take a photo to prove a point, or to send to a workman regarding some job around the house, or to show my daughter a new critter or birds nest. Jpegs take little space. A good thing! Besides, the Fuji jpegs are really so good, I rarely have to do anything to them other than crop out some odds and ends to improve the composition.

You are trying to compare apples to apples, not apples to oranges. Saying you have to do little to nothing to a jpeg is not fixing a RAW file.

dsmeltz Loc: Philadelphia

whitewolfowner wrote:

You are trying to compare apples to apples, not apples to oranges. Saying you have to do little to nothing to a jpeg is not fixing a RAW file.

"saying you have to do little to nothing to a jpeg"!! Actually what they should say is "you CAN DO LITTLE that is useful to a jpeg", which is why you shoot RAW.

rmalarz Loc: Tempe, Arizona

First off, Cat's statement is quite accurate and complete. It has nothing to do with RAW, and neither does this thread.
--Bob

whitewolfowner wrote:

You are trying to compare apples to apples, not apples to oranges. Saying you have to do little to nothing to a jpeg is not fixing a RAW file.

CatMarley Loc: North Carolina

whitewolfowner wrote:

You are trying to compare apples to apples, not apples to oranges. Saying you have to do little to nothing to a jpeg is not fixing a RAW file.

I am not comparing them at all! I am answering someone who said about jpegs: "For starters, how can throwing away data on a digital photograph be a good thing?" And having jpegs of stunning quality to which nothing needs to, or should be, done is one such answer to processing raw files!

CatMarley Loc: North Carolina

dsmeltz wrote:

"saying you have to do little to nothing to a jpeg"!! Actually what they should say is "you CAN DO LITTLE that is useful to a jpeg", which is why you shoot RAW.

Nonsense! You must not have worked much with jpeg files. Contrast, color values, detail editing, and many other useful improvements can be done with jpegs. But the Fuji jpegs are usually so well done in camera, that I wouldn't change a thing!

BebuLamar

When software compress an image to JPEG it throws away things that we don't really see so the quality doesn't suffer much. When we edit the JPEG we may try to make things invisible visible but those are lost in the compression.