When JPEGs are edited & saved in Picture Manager is this lossless

M

Mark Fletcher

Microsoft's Picture Manager contains various edit options. If I am working
with JPEG format photos and use these options and resave (possibly several
times) is the resaving process lossy or lossless? I would like to be sure
that I don't loose further information each time I save them.
 
B

Bob Buckland ?:-\)

Hi Mark,

The basic JPEG choice is a lossy format. In some apps, such as http://www.irfanview.com you can choose the quality vs size setting
to 100% to minimize the effects. You don't always lose anything noticeable in the graphics, but it depends on what you're editing
and changing.

========
Microsoft's Picture Manager contains various edit options. If I am working
with JPEG format photos and use these options and resave (possibly several
times) is the resaving process lossy or lossless? I would like to be sure
that I don't loose further information each time I save them. >>
--
Let us know if this helped you,

Bob Buckland ?:)
MS Office System Products MVP

Pricing and Packages for '2007 Microsoft Office System'
http://microsoft.com/office/preview
 
M

Mark Fletcher

This does not really answer my question. I know that JPEG is a lossy format
and that I can compress (say) a TIFF file by resaving it as a JPEG and that
information is lost in the process. But my question was about resaving
something which is already a JPEG file. When I resave, do I loose further
information? In Picture Manager there is no choice as to the level of
compression when resaving an existing JPEG and a simple Save As command
results in an identical file size so I assume that there is no further
compression but I would like confirmation that that is the case particularly
where I have carried out editing e.g. cropping or rotating the file.
 
B

Bob Buckland ?:-\)

Hi Mark,

As I mentioned, you may lose data, but depending on the settings in the app you use for saving to a JPEG file for the 'quality'
level of a JPEG the loss may or may not be visibly noticable.

Try a couple of representative sample graphic copies to see if the result you get is suitable for your needs. MS Office Picture
Manager is a 'light duty' only app for picture editing and generally does lose some data, just as making a 'xerox' copy of a copy of
a copy will.

The other app I mentioned is 'donation ware' and does give you the flexibility to change the settings.

==========
This does not really answer my question. I know that JPEG is a lossy format
and that I can compress (say) a TIFF file by resaving it as a JPEG and that
information is lost in the process. But my question was about resaving
something which is already a JPEG file. When I resave, do I loose further
information? In Picture Manager there is no choice as to the level of
compression when resaving an existing JPEG and a simple Save As command
results in an identical file size so I assume that there is no further
compression but I would like confirmation that that is the case particularly
where I have carried out editing e.g. cropping or rotating the file. >>
--
Let us know if this helped you,

Bob Buckland ?:)
MS Office System Products MVP

Pricing and Packages for '2007 Microsoft Office System'
http://microsoft.com/office/preview
 
M

Mark Fletcher

Thanks very much for this further response which pretty much answers my
question. I will take a look at infanview. I like the simplicity of Picture
Manager and I am not obsessive about invisible loss of info. In fact I am
compressing 60meg TIFF files (scanned photo slides) into 3meg JPEGs and can't
really tell any difference between the TIFFs and the JPEGs except at huge
magnifications and then only just. But I didn't want to degrade the image
further. I keep reading that you should use TIFFs for archiving but the
file size is so massive that I can't see the point unless there is likely to
be visible loss of quality when doing further editing. I will experiment.

Thanks

Mark
 
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