JPEG Files: Keeping Originals

[molucca]

I have been saving to high quality JPEG, too. Then cropping and resaving. The JPEG from the camera is the sensor data with post processing. RAW is sensor data. I would expect the camera is using compression to reduce the file size, and introduces some loss. Saving the file again with compression would most likely introduce some degregration. This is a question I still have.

I can save the opened file without compression (lossles). The camera must be about 6:1. What happens if I save to the same compression?

No idea what happens when PSP saves to its format.

Rich

[soenda]

I have been saving to high quality JPEG, too. Then cropping and resaving. The JPEG from the camera is the sensor data with post processing. RAW is sensor data. I would expect the camera is using compression to reduce the file size, and introduces some loss. Saving the file again with compression would most likely introduce some degregration. This is a question I still have.

I can save the opened file without compression (lossles). The camera must be about 6:1. What happens if I save to the same compression?

No idea what happens when PSP saves to its format.

Rich

One of the messages in the Wiki article seems to be that cropping a jpeg, except under certain specific conditions or while using special applications, can introduce loss. It seems counterintuitive, but I think it's one of the mistakes I had been making after processing photos as psp files and converting them back to jpegs. If I understand correctly, unless you have an application specifically for loss-lessly cropping jpegs, you should go back to the editing format---psp, tif, or whatever, to do further adjustments like cropping.

But I'm easily confused, and I could be wrong.

As for the whole compression issue---I'm still working on trying to figure that one out.

[Trev]

One of the messages in the Wiki article seems to be that cropping a jpeg, except under certain specific conditions or while using special applications, can introduce loss. It seems counterintuitive, but I think it's one of the mistakes I had been making after processing photos as psp files and converting them back to jpegs. If I understand correctly, unless you have an application specifically for loss-lessly cropping jpegs, you should go back to the editing format---psp, tif, or whatever, to do further adjustments like cropping.

But I'm easily confused, and I could be wrong.

As for the whole compression issue---I'm still working on trying to figure that one out.

Well you can not crop losslessly as cropping cuts of some of the image, but if you save as jpeg then depending on how much compression is used then some pixels are noted as to there position and colour the discarded. Hence the lose. When the image is opened those pixels are painted in but are not the original. doing this over and over will gradually produce rubbish. So save your originals in a save place and even mark as read only if you want the only work on a copy after all your enhassment you could save it in lossless format PSP, PSD, Tiff or png Ect. and then do a resize if need be and save as .jpeg for the web. And incidentally rotating a jpeg by increments of 90 degrees is lossless as no pixels are changed only resorted.

[soenda]

Well you can not crop losslessly as cropping cuts of some of the image, but if you save as jpeg then depending on how much compression is used then some pixels are noted as to there position and colour the discarded. Hence the lose. When the image is opened those pixels are painted in but are not the original. doing this over and over will gradually produce rubbish. So save your originals in a save place and even mark as read only if you want the only work on a copy after all your enhassment you could save it in lossless format PSP, PSD, Tiff or png Ect. and then do a resize if need be and save as .jpeg for the web. And incidentally rotating a jpeg by increments of 90 degrees is lossless as no pixels are changed only resorted.

So you really can rotate the jpegs 90 degrees without loss? Cool! I saw this as I was researching the whole lossy jpeg issue before I posted my original question. But I put it in the "too good to be true" category.

It would save a lot of time if I could batch rotate all my portrait format shots on my first pass of the jpeg files. I generally look for duds before doing the conversion to psp files, but sometimes without rotating the file I can't tell the keepers from the tossers. If there's no loss from 90 degree rotation, then I won't waste time converting duds I could eliminate as jpegs.

Thanks very much, Trev.

[remi]

It would save a lot of time if I could batch rotate all my portrait format shots on my first pass of the jpeg files.

The free image viewer IrfanView is able to rotate your JPEG files losless:

1. Start IrfanViews thumbnail viewer
2. Select all the files you want to rotate
3. Press "Shift+J" and select the option "Auto-Rotation (by EXIF information)" and IrfanView interpretes the rotation information, saved by your digital camera within the JPEG file and rotates all your images into the right angle (horizontal to vertical or vertical to horizontal) - losless.

Regards,
Remi

[Crypto]

personally, I would save in a format such as TIFF. This is an uncompressed format and it's format can be used on any PC/MAC. By saving proprietary formats such as PSP, you limit its use to PC's that have the software installed, unless converted to a more common format. Also, what if you change software down the road?

I would only save in this proprietary format if I have done a lot of post processing or have created several layers and may return to it often to keep making changes or even undo changes.

On the JPEG loss issue, You have to save the same JPEG many many times to see real degredation in image quality. However, it does depend on how much postprocessing that was done and the quality of the original image.

Those that have the option to shoot in the RAW (albeit, proprietary as well) format, In my opinion, this is the best Archival solution. Convert to JPEG's when you want to use them. Most RAW processing software never alters the original RAW file. They are much smaller than TIFF's or proprietary files (PSP) and you're guaranteed the highest quality image your camera can produce.

[soenda]

personally, I would save in a format such as TIFF. This is an uncompressed format and it's format can be used on any PC/MAC. By saving proprietary formats such as PSP, you limit its use to PC's that have the software installed, unless converted to a more common format. Also, what if you change software down the road?

I would only save in this proprietary format if I have done a lot of post processing or have created several layers and may return to it often to keep making changes or even undo changes.

On the JPEG loss issue, You have to save the same JPEG many many times to see real degredation in image quality. However, it does depend on how much postprocessing that was done and the quality of the original image.

Those that have the option to shoot in the RAW (albeit, proprietary as well) format, In my opinion, this is the best Archival solution. Convert to JPEG's when you want to use them. Most RAW processing software never alters the original RAW file. They are much smaller than TIFF's or proprietary files (PSP) and you're guaranteed the highest quality image your camera can produce.

You make an extremely good point about the long term bet I'm making by saving psp files as archives. I'm old enough to remember Betamax video and even 8-track tape. Ouch. This I gotta think about.

I was surprised to see you say that RAW files are much smaller than TIFFs or psp files. I was under the impression that they were very much larger. In fact, that understanding had been part of my reluctance to bite the bullet and move up to a fancier camera. I do all my editing on a five-year-old laptop, and I thought it would choke on RAW files. This certainly encourages me to find out more about it. I understand that RAW files offer infinitely more opportunity to correct for things like white balance, which would be very nice indeed.

Thank you once again, Crypto. I should be anteing up tuition credit fees for the education I'm getting. (Please don't hold me to it, though. I'll be your first student AND your first drop out.)