Question about jpeg to tiff conversion: So, a question for you computer/tech savvy people. I use Picasa3 which has a function for converting jpegs to tiffs. 4,5,6 meg jpegs are...

Retired CPO Loc: Travel full time in an RV

So, a question for you computer/tech savvy people. I use Picasa3 which has a function for converting jpegs to tiffs. 4,5,6 meg jpegs are converted into @ 20 meg tiffs. Where does all the extra info come from?

GoofyNewfie Loc: Kansas City

Read about compression here:
https://www.cambridgeincolour.com/tutorials/imagetypes.htm

Retired CPO Loc: Travel full time in an RV

GoofyNewfie wrote:

Read about compression here:
https://www.cambridgeincolour.com/tutorials/imagetypes.htm

Thank you. I think I already knew the basics. What I'm asking is, how does @8 meg of information turn into @20 meg of information? Where does that extra 16 meg of information come from? I have always thought that a 8 meg photo has 8 meg of information and a 20 meg photo of the same subject has an extra 16 meg of information consisting of fine detail that the 8 meg photo lacks. Am I totally out in left field? Is the jpeg conversion to a tiff a genuine tiff or is Picasa selling a pig in a poke?

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Retired CPO wrote:

Thank you. I think I already knew the basics. What I'm asking is, how does @8 meg of information turn into @20 meg of information? Where does that extra 16 meg of information come from? I have always thought that a 8 meg photo has 8 meg of information and a 20 meg photo of the same subject has an extra 16 meg of information consisting of fine detail that the 8 meg photo lacks. Am I totally out in left field? Is the jpeg conversion to a tiff a genuine tiff or is Picasa selling a pig in a poke?

You are coming at this from the wrong point of view. The question is how does 20 gb of information turn into 8 gb. The answer is compression. The Tiff file is not compressed, but the jpeg produced by your camera is compressed, in this case by a factor of 2.5X

In order to view that file in Picasa or any other software, their is a decompression algorithm - a CODEC (COmpression DECompression) - that reconstructs the image to its full resolution. When you save that file it will become compressed again if you save it as a jpeg.

This is the somewhat technical explanation https://en.wikipedia.org/wiki/JPEG

And this is a layman's explanation -

srt101fan

Retired CPO wrote:

So, a question for you computer/tech savvy people. I use Picasa3 which has a function for converting jpegs to tiffs. 4,5,6 meg jpegs are converted into @ 20 meg tiffs. Where does all the extra info come from?

Good question, Chief; I also don't understand why a JPEG to TIFF conversion results in a larger file.

Gene's answer partially got me there but I 'm still not sure why the converted JPEG file should be larger.

Are there 2 JPEG files involved in this process? The JPEG you start with, and a decompressed, larger JPEG generated when you open the original? And is the TIFF based on the decompressed JPEG?

Confused and curious.....

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

srt101fan wrote:

Good question, Chief; I also don't understand why a JPEG to TIFF conversion results in a larger file.

Gene's answer partially got me there but I 'm still not sure why the converted JPEG file should be larger.

Are there 2 JPEG files involved in this process? The JPEG you start with, and a decompressed, larger JPEG generated when you open the original? And is the TIFF based on the decompressed JPEG?

Confused and curious.....

Compression is always present in jpeg. The quality setting will determine how small the file size is. If you check the number of pixels in an 8 mb compressed jpeg and compare it to the 20 mb uncompressed tiif, they will be exactly the same. The tiff version is the actual size, the jpeg is the compressed version. The file doesn't get bigger when you go to uncompressed tiff, it gets smaller when you go from tiff (the actual, uncompressed size) to jpeg - which can be compressed 50% for high quality, and up to 90% for low quality.

Your camera does start off with a jpeg file. It converts the raw data captured by the camera to a compressed format.

srt101fan

Gene51 wrote:

Compression is always present in jpeg. The quality... (show quote)

Thanks Gene!

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

srt101fan wrote:

Good question, Chief; I also don't understand why a JPEG to TIFF conversion results in a larger file.

Gene's answer partially got me there but I 'm still not sure why the converted JPEG file should be larger.

Are there 2 JPEG files involved in this process? The JPEG you start with, and a decompressed, larger JPEG generated when you open the original? And is the TIFF based on the decompressed JPEG?

Confused and curious.....

Don't know if this analogy helps, but if you think about a sleeping bag or a down comforter, they usually arrive in a 'stuff bag' or in some kind of compressed state - like a JPEG. When you take them out of the packaging they fluff up, get a lot bigger which provides the insulation / warmth that you desire. When you want to store them you put them back in the 'stuff bag' / packaging. They take up much less space since the air has been squeezed out, and how much you compress them is up to you. However, the number of times you uncompress and recompress the sleeping bag or comforter will eventually break down the fabric so its thermal qualities can deteriorate.

With TIFF it's more like keeping things at their normal 'fluffed up' state all the time.

Keep warm and cosy!

selmslie Loc: Fernandina Beach, FL, USA

Retired CPO wrote:

So, a question for you computer/tech savvy people. I use Picasa3 which has a function for converting jpegs to tiffs. 4,5,6 meg jpegs are converted into @ 20 meg tiffs. Where does all the extra info come from?

As Gene51 points out, you need to look at it from the other side.

With an uncompressed TIFF, you are probably looking at a 16-bit file (48-bits or 6 bytes per pixel for all three colors). A 20 mb TIFF is actually quite small, less than 3.5 MP.

At 48-bits (6 bytes) per pixel, 3.5 MP needs 3.5x6=21 meg. But an 8-bit TIFF (3 bytes per pixel) is only half that, 3.5x3=10.5 meg.

So the going from 10.5 meg to 6 meg is not really that much compression and you probably don't lose much information that anyone can see.

The real problem is that, every time you load, edit and re-save a JPEG, more information is lost and eventually the image is degraded. But degradation (banding) can also happen to an 8-bit TIFF despite the lossless compression.

So it's good practice to convert to 16-bit TIFF before editing an image. You can repeatedly edit and save with out the degradation that comes with compression.

Better yet, do all of your editing during the raw conversion and save only once.

srt101fan

Peterff wrote:

Don't know if this analogy helps, but if you think... (show quote)

Thanks Peter; interesting analogy...

No problem keeping warm - it's gonna get hot around here this weekend!

TonyBot

Peterff wrote:

Don't know if this analogy helps, but if you think... (show quote)

It is a good analogy, Peter. How about this one:

Jpeg - you've got 15 one-gallon jugs in a row, but only three have water in them. Jpeg *ignores* the empty ones (inserts a "skip" order) and automatically "skips" until it finds another jug thats got water in it that it *will* pick up. Jpeg says why waste storage space when there is nothing there?
Tiff - same 15 jugs with only three with water in them. Tiff picks up every one of them - no "skip" orders - *every single one* of them suckers gets attended to.

That is also why it is better to edit in Tiff or another non-compressed format - where the areas where Jpeg has "skipped", there is NOTHING there, and you cannot do anything to nothing. With Tiff, there is not *nothing* there - and while "zero" seems like it is "nothing", it is a real value and can be edited.

Maybe my "skip" and "nothing" terms are not exactly correct, it is how I remember them.
Hope I haven't confused you too much.

bpulv Loc: Buena Park, CA

Retired CPO wrote:

So, a question for you computer/tech savvy people. I use Picasa3 which has a function for converting jpegs to tiffs. 4,5,6 meg jpegs are converted into @ 20 meg tiffs. Where does all the extra info come from?

It doesn't! You can't get something for nothing. I don't see any point in converting jpg to tiff.

artBob Loc: Near Chicago

bpulv wrote:

It doesn't! You can't get something for nothing. I don't see any point in converting jpg to tiff.

If you are going to edit and then save as a jpeg, the reason to go to tiff is to keep all the info. Every time you edit and save a jpeg, you lose more data. Save as tiff (or photoshop) edit, and then save the edit as a jpeg, keeping the original tiff.

selmslie Loc: Fernandina Beach, FL, USA

bpulv wrote:

It doesn't! You can't get something for nothing. I don't see any point in converting jpg to tiff.

The point is to avoid banding when you adjust colors or contrasts in smooth toned aread.

jeep_daddy Loc: Prescott AZ

Retired CPO wrote:

Thank you. I think I already knew the basics. What I'm asking is, how does @8 meg of information turn into @20 meg of information? Where does that extra 16 meg of information come from? I have always thought that a 8 meg photo has 8 meg of information and a 20 meg photo of the same subject has an extra 16 meg of information consisting of fine detail that the 8 meg photo lacks. Am I totally out in left field? Is the jpeg conversion to a tiff a genuine tiff or is Picasa selling a pig in a poke?

Interpolation my friend. This is where an algorithm takes place in the application that guesses that next to one color should be a color that is of a similar shade and intensity. It's guessing and filling in space.