Converting a JPG to a TIFF

[Leximou]

I work with seniors that are learning computer in a one-on-one atmosphere. One of my students stumped me and in searching the web, I find no answers so I am turning to this group to possibly help.

Her camera takes *.jpg (default) digital images at 2592 X 1944 (2231kb). Now, if that file is converted to a *.tif the resultant size is still 2592 X 1944 but the file size is now 8034kb.

Where does all the extra information come from? Why is the file now so much larger? Does the compressed info get released from the file header?

I continue to learn from these senior students every day, but this question is valid and I can find no answer.

[Mr. Pickles]

When you open the JPG, it uncompresses itself so to speak. In other words, a TIF is always huge when compared to a JPG.

[dougsmit]

Whenever we are working with a image, each component of the image is represented by a numerical value separately from all the others. When we save the file, Tiff saves each of these values separately. JPG, however, applies a formula that allows it to toss out part of the information to make the file smaller while doing as little damage to it as possible. We specify the amount of this 'compression' by setting the level in Adobe products between 1 and 12 (some other programs use different scales). Every time we save a JPG, the formula is applied anew so we might be losing a different part of the information from that lost the last time so it is advised that we avoid opening and saving JPG's repeatedly keeping our losses to a minimum. Tiffs have no such loss. Whichever format we had to begin with, it is converted to a fully detailed image when we open the file but JPG will have to guess what some of the details are since it threw the real values out. Opening a JPG and resaving it as a TIFF will make the file as large as an image that has always been TIFF but the quality is still diminished by the previous save as a JPG (you can not recover what has been lost). Still, it is OK to do this since you will not be compounding the loss by a second JPG save so some people convert their out-of-camera JPG's to TIFF's so they can keep as much as possible intact.

As an exercise, students should save an image at the lowest quality JPG (Adobe level 1) and then reopen it to see what happened to the image. The same thing happens when we save at Level 12 or any other value but it is just not as severe.

Have the students noticed that some JPG's are larger files than others? This is because images with a lot of fine detail have trouble finding information to toss out compared to images with large expanses of blue sky, white snow or black shadows. Even grain/noise makes a difference. If you are shooting ISO 100 on a CF card that predicts there are 100 shots left and change the ISO to 1600 the camera will revise that prediction and show a lower number remaining. This just allows for the fact that grainy/noisy images have more fine detail in that noise and the JPG compression routine will not be able to cut away as efficiently at any given level.

I apologize for the length of this reply and hope I have not misstated too much in the effort to make it clear. The routine that allows JPG's to compress images and maintain a reasonable amount of quality amazes me. For students, the best thing to do to learn is to try out various levels and resave with minor changes a dozen times. Compare what happens to the last save of a level 12 to the last save of a level 1 and to the original image (obviously, I hope, using a different file name so you do not overwrite the original!!!).

[dsp]

The short answer is that the tiff doesn't have "extra" information, the jpg is missing some. Tiffs are not compressed jpegs are, as stated above by Doug.

[Mr. Pickles]

TIFF's can be compressed (usually not, but there are TIFF options in a SaveAs in PS), but not to the extent of a JPG.

[Rense]

A little more on this subject:

saving an image as a jpg performs a compression where you loose information.
saving as a tiff can compress, but you never loose information.

See more at this link

[Celluloid]

Hello everyone, this is my first post. Leximou,I will try to answer this question.

Reference: A 2592x1944 image is 5 megapixels and 2231kb is 2.23 megabytes. This about the file size one would expect for a 5mp camera.

There are 2 types of compression used in making data fit into a smaller size file. Lossy and lossless. As you might expect, lossy compression means some data is lost and lossless means all the data can be recovered.

JPEG (or JPG, .jpg), as commonly used for digital imaging, always uses lossy compression. This lossy compression is adjustable. In Photoshop JPEG quality is on a sliding scale from 0-12, and in Canon cameras the choices are normal and fine.

TIFF (*.tif) has many variations, but commonly it is either uncompressed or losslessly compressed. So, tif files are almost always significantly larger than even the highest quality JPEGs.

So now the question becomes why use TIFF at all? Well, each time a JPEG image is changed and saved, the lossy compression is reapplied and there is a cumulative degradation of the image. You may not notice this loss if you only save one or two additional times, but it is definitely there.

JPEG is really best suited as a delivery format. Saving as JPEG should be the final step before uploading to the web or printing. TIFF and other lossless formats are intermediate or working formats, best suited for image editing. A typical workflow might be. Camera Raw->TIFF->JPEG-> Upload to Internet or print. Other lossless image editing formats are Photoshop (.psd), JPEG2000 (.jp2, or .jpf), and HD Photo (.wdp).

[W.Smith]

You can, however, compress TIFFs by zipping them. Saving a loooot of space, but no image quality loss.

[Celluloid]

Wow, I feel like an idiot for posting an answer to a question that had already been answered about 7 times. The assbackwards newest first format had me confused because I have Never seen that on a forum before.

Anyway to add something useful, TIFF apparently has 100's of format variations, but commonly it can be uncompressed, lossless LZW compressed and lossless ZIP compressed. There is even a JPEG compressed TIFF format! How's that for confusing. In addition, the Canon *.cr2, Nikon *.nef, and Adobe *.dng RAW formats are all based on TIFF.

[dsp]

Originally Posted by Celluloid

Wow, I feel like an idiot for posting an answer to a question that had already been answered about 7 times. The assbackwards newest first format had me confused because I have Never seen that on a forum before.

Anyway to add something useful, TIFF apparently has 100's of format variations, but commonly it can be uncompressed, lossless LZW compressed and lossless ZIP compressed. There is even a JPEG compressed TIFF format! How's that for confusing. In addition, the Canon *.cr2, Nikon *.nef, and Adobe *.dng RAW formats are all based on TIFF.

Trying to help is never a bad thing...
You can go to your control panel, then to "Edit Options" and then about half way down is "Thread Display Options", you can set thread display mode to Linear - Oldest First and you should be good to go....