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View Full Version : Thought I understood Jpeg and Tiff but. . .



Samegapiz
06-26-2005, 12:51 PM
Why when you save a Jpeg does the file size get much much larger?
I thought when the camera took a picture in jpeg, it would compress it losing bits of information for ever. So surely a Tiff, applying it's compression (lossless) only has 2.8mb to work with it's saving size will be about 2.7mb not 14mb.

Does that mean taking a picture in Jpeg and saving it in Tiff, is the same as saving it in Tiff.

So how does a Tiff make files bigger, does it get back the information?

Rhys
06-26-2005, 01:30 PM
Why when you save a Jpeg does the file size get much much larger?
I thought when the camera took a picture in jpeg, it would compress it losing bits of information for ever. So surely a Tiff, applying it's compression (lossless) only has 2.8mb to work with it's saving size will be about 2.7mb not 14mb.

Does that mean taking a picture in Jpeg and saving it in Tiff, is the same as saving it in Tiff.

So how does a Tiff make files bigger, does it get back the information?

Nope. You can't recover lost image data. You can, however, save a horribly heavily compressed file to a larger size which is utterly pointless.

D Thompson
06-26-2005, 02:13 PM
Does that mean taking a picture in Jpeg and saving it in Tiff, is the same as saving it in Tiff.

So how does a Tiff make files bigger, does it get back the information?
No, it is not the same, nor does it get back the info. I am assuming you are using jpeg in camera and then saving as tiff in PS or similiar program. Saving as a tiff before any post processing the jpeg will help you from any more loss, but the file is already compressed and info lost. The file is bigger because of the way the info is stored. Shoot in the best quality you can. I now only shoot in the RAW format, but I used to use the large fine jpeg on my 20D. The first thing I would do to the jpeg once I got it out of camera was to save as a tiff.

Dennis

Samegapiz
06-26-2005, 02:39 PM
ok thanks guys for the info,
my camera only captures in jpegs, but I always keep it at the lowest compession rate, and then save as a tiff for important photos, or a high quality jpeg for most pictures. And being an amateur, I don't think i'll notice or worry to much about the difference . .

thanks again for helping me to understand

fotobydave
06-26-2005, 04:30 PM
if you read a jpg file into a reader but do not change it, there is no reason to save it as a tiff file. Only if you make changes to it would there be any reason to save it. High quality jpg files will loose very little if any quality.

John_Reed
06-26-2005, 05:06 PM
Why when you save a Jpeg does the file size get much much larger?
I thought when the camera took a picture in jpeg, it would compress it losing bits of information for ever. So surely a Tiff, applying it's compression (lossless) only has 2.8mb to work with it's saving size will be about 2.7mb not 14mb.

Does that mean taking a picture in Jpeg and saving it in Tiff, is the same as saving it in Tiff.

So how does a Tiff make files bigger, does it get back the information?...when you download it into your computer in the small JPG image format, it stays compressed until you open it. When you do open it, your photo editing program un-compresses the JPG file to re-create the original pixels from which it came in your camera. So the size of that un-compressed file is naturally larger than the compressed JPG file, and in fact, should be identical in size to a TIFF file made from the same original pixels. Now, how closely it matches the original pixels depends on how much JPG compression was used to perform the original compression. For example, if you chose FINE JPG instead of NORMAL JPG (don't know how your camera names these options), the resulting JPG file would be larger for FINE than it would for NORMAL, and the "pixel match" would be better.

In any case, you are best advised, if you're saving that first JPG file you downloaded from the camera, to save it someplace and KEEP it as your "golden original," and ONLY edit copies of that file. You won't gain any more detail from that original by converting it to TIFF, what's there is there.