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Old Oct 17, 2002, 3:16 AM   #1
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Default Confused on .JPG file size when doing "save as"

I use MGI Photo Suite II or sometimes MGI Photo Suite 4 to view and adjust my photos.
My question is when I get the photos from my camera, I do a save-as at 95% on the JPG format, I have also done a save-as at 25% and when I view the two photos on my computer, I see NO differance in the photos, they both look just as good.
What I do notice is of course that the file size is much smaller at 25% than at 95%, which I understand.
If they both look good, can I just save all my JPG's at lets say 25%? :?:
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Old Oct 17, 2002, 4:16 AM   #2
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When you say 'They both look as good' - you must be careful. JPEG IS NOT LOSSLESS distortions concatenate!.

The JPEG compression amount, crudely shown as % for smaller file sizes, will eventually become overloaded and fail when there is significant detail in the original picture. Softening of edge detail may also become apparent. 100% usually means it's close to the original (uncompressed) file size. BUT it's too late to think it is, because it probably came off the card as a .JPG, already compressed in the cam

Your cam will have already compressed the original scene. When you open the file to edit the pic, information (detail) is already starting to be lost. Each time you save as a JPEG, more information is being lost - but you should look at the detail at say 300X zoom, and plain areas for 'blocking artefacts'. Subsequent compressions in the pc, may not follow the same compression algorithm (decisions) as the original software in the cam.

Each time you open your small file, highly compressed pics and re-save after changes, the pic quality will degrade further (Try it several times!)

I use lossless editing for simple crops and resizing. When I do edit, I keep the original cam file un-edited, and try to edit a copy in 1 or 2 JPEG saves. If I'm working on an image over several sessions, I leave it as a (large) bitmap file then compress once when finished.

I don't know what others do, but if a cam pic on flash card is about 1Mb, I select the % compression after final editing to produce about a 1.5Mb file (i.e less compression than cam on original pic). Hard disc/CD storage is still cheap at this file size!

To be on the safe side, always keep the original pic file. Shoot some high random detailed scenes (lots of grass/trees etc). Decide what level is OK for you, at the output image size you need. Clearly a large print would need more pixels and less compression than say a thumbnail for a pc monitor. Hope this helps.
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Old Oct 17, 2002, 7:15 AM   #3
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Default Save original, 100% for printing, 50-80% for display

Good question!

If you ever plan to print anything larger than a 4x6 from your image, then save it at 100%. Each time you edit and re-save the file, you lose a little with JPEG, even at 100%. SO... if you want the highest quality print, use what came out of the camera. If editing is required, always save it at 100%.

On the other hand, if you just want it for screen display or for web posting, save it at 50 - 80% quality. Experiment with the quality and filesize of a few, and see what you like. Personally, I feel most people won't notice the difference in a JPEG compressed to 50% quality vs. one at 100%. There's a good reason to compress pics posted on the web, because they will have smaller filesize, and the page will load more quickly.

The bottom line? It's a personal choice, but like voxmagna cautioned you, save your original, or at the very least save a copy at 100% quality, so you can always preserve the best quality available if you need it.
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Old Oct 17, 2002, 7:59 AM   #4
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A thought occurs to me, that if you had unlimited storage/CD's etc, You would open the original (compressed) cam .JPG once, save it as a lossless bit map, TIFF etc (100% .JPG is probably near transparent), edit the bitmap and save as an archive copy. Then carry out one JPEG compression to suit webpage, email, or print when you need it.

The only prob. I would have is 3Mpix= 18Mb per image - that's a lot of storage. Now wouldn't it be nice, if photo-editors could output a script file containing all the picture edits (It's actually there already in the undo list!) - which could be re-run with the original image file.
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Old Oct 17, 2002, 9:57 AM   #5
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Even though voxmagna (and others) have already said it, it cannot be overemphasized, Save a copy of your image exactly as it came from the camera with no editing, renaming, rotating, or any other change whatsoever!! Those are your digital negatives, don't mess with them.

Take a look at the images you have saved at 25% and 95% JPEG compression in more detail. In particular, overlay them and use difference as the blending method.

Another way to look at the differences is to look at a shot with solid color to a contrasting edge, e.g., overcast sky against a roof line. Use your photo editor's magic wand tool with a zero (or very small) range to select the sky in both images (25% & 95% saves). You will see that different areas are being selected.

Or do the comparison with an image you create with only two colors. When you look in detail at the boundry, you should see more "smearing" in the 25% compression image.
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Old Oct 17, 2002, 10:39 AM   #6
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Thanks guys! I learned a lot, I will burn a CD of the origionals off the camera of the inportant shots.
The only problem is the camera gives the shot a number and I hope that will not be a problem when I clean off the card to put more photos on it.
I have a Sanyo that used SM cards and I will be getting a Nikon coolpix 2500 which uses CF cards, I hope when I clean off those cards, that the earlyer photo numbers that the camera gives them will not cause me a problem, if the numbers are the same like for instance 0001 was picture #1 in the camera than when the card is filled I erase the card to stert over and I get another 0001 number for photo #1 and that second 0001 number is not going to be able to get placed on the CD, without getting a notice about "everwrite file yes or no?".
So if that is the case, I WILL have to rename the picture.
It is hard to explain, I hope you can tell what I am trying to explain.
Whew!...I am long winded!
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Old Oct 17, 2002, 11:04 AM   #7
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Yep, there are threads going on here right this moment about this. Some cams actually keep incrementing up. But mine, and it seems others, will put 00001 on any blank card. Wich is why you must copy to pc and rename - being the only operation, before putting on your shades and reading that post from BillDrew.

I'm differing slightly because I've found renaming, assuming you follow the rules and checks before deleting, consistently safe. However, I never want 2 or more files anywhere that have the same name (00001 etc), and I do accept that to run a show later from the cam to TV, copies of the original cam files might need to be renamed back to 00001 etc. Note 'original copy'. Some cams won't replay files whose size has been changed after edit & save!

Write a volume name on each card (with pen & pc). You could have 2 or 3 0001's! Your cam software might offer a batch/unique filename facility. HOUSEKEEPING is VERY IMPORTANT.

This is what I do: Copy cam files to a directory you might call 'Photosraw' Rename them in a batch utility to eg hols.0001 etc. keep new filenames simple and limit to the same or fewer characters than the cam puts on. Create sub-directories as 'themes' if you like and move renamed files to them. COPY the files you need to edit or finally store to CD to a new directory. Work on the copies. Make a CD from the copy directory to take to Wal-Mart. When you get the CD back, delete the edited copies from the HD if you want.

I run CD backup software so I know my 'photosraw' and copies get on CD weekly. But also, I wait until there's 640MB worth of files in 'Photosraw' then burn a CD 'disc at once' and delete from HD to create space. Avoid burning CDpacket mode - it's dead flaky.

NB VERY IMPORTANT before deleting any files from flash or hard drive, make sure the backup file copies and any CD backups can be read!!!
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Old Oct 17, 2002, 12:42 PM   #8
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Default Easy Housekeeping

When using an HP Photosmart to download flash cards (also microdrives) or using a MindStor, theses devices automatically created a new folder with the date & time as the folder name. This make managing theses files incredibly easy.

Usually reformating the whole card in the camera is the fastest way to go. It sure beats deleting individual pictures, and let the camera re-start from afresh! My camera remember the frame #, but if a new date&timed folder is created each time, it's hard to overwrite the same frame!
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Old Oct 17, 2002, 1:05 PM   #9
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Renaming is *very* likely to be a safe change, esp if it is done via your OS. If you are dragging the image into some kind of program, then saving it with a different name, you might be making changes. The really safe way is not to change anything.

One way to avoid having to rename your originals is to put them in separate directories. If you name the directories with the date the pictures were taken, that will also help locate them later. If you have several sets taken on the same day, just add a suffix to the date, e.g.,
2002_10_17a
2002_10_17b

Once you have the original saved (and verified), make whatever changes you want. You don't have to worry since you can always go back to the originals if needed.

I also suggest keeping a "shooter's diary" - just a simple ASCII file saying what shots were taken that day. Something like, "Oct 17, 2002 - Cousin Wilma's wedding" will make finding your pictures easier. Put a copy of that on your CD as well so you have an index of all the shots to date on every CD.
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Old Oct 17, 2002, 3:36 PM   #10
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OK with the dated directory naming. But same file names from cam across several directories? When a hard disc crashes and files need recovery, the name always sticks with the disc clusters containing the file, and to be safe usually 8 characters 'cos most recovery progs work from basic DOS. I'm afraid the directory paths are often lost! If you've backed up on CD you should be OK.

ACDsee is a viewer which creates the description link for you and puts any text below the thumbnail, - or the file description view when you have so many pics the thumbnails are slow to open. I think it also tracks the description to the file when you move a file to a different directory. If you're worried the viewer might fall over, your text is in a file with a simple structure you can still read. Try It!

Latest version 5 is Exif friendly. This is one of the best tools I've used. Font color's not working tonite - sorry the post look's a bit boring.

http://www.acdsystems.com/English/Pr...DSee/index.htm
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