From: Mayayana <mayayana@invalid.nospam>
Subject: Re: A lightroom question
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From: "Mayayana" <mayayana@invalid.nospam>
Subject: Re: A lightroom question
Date: Sun, 29 Oct 2017 20:30:11 -0400
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"Savageduck" <savageduck1@{REMOVESPAM}> wrote

| The original JPEG has lost all it is ever going to lose, there is no 
| save" in LR.

  You take a picture as JPG. That's loss #1.
You then edit it, say 5 times. Each time it's
saved in LR and there's no loss to the original.
That's good. LR is saving the bitmap image
along with a history of changes you've made.
Each time you work on it, you're really working
on the bitmap and LR is saving that, along with
the edit history data. What's different
is that LR is hiding that complication and you
don't need to keep track of various saved files.
LR is doing that for you. But once you decide
to export it as an edited image in JPG that's
loss #2. You can't edit the image and then save
a new image as JPG without a second loss. You
can do 5 lossless edits inside LR, but the final
save will be lossy.

  I don't mean to complicate things. It's just
that most people are not familiar with the differences
in file formats, so I think it's worth reiterating
that JPG is lossy. Otherwise it's very easy to drop
out data unnecessarily. The LR feature is nice, but
it's still a process that drops out data twice if you
edit the photo.

  So you take a JPG, put it into LR, edit as you
like, and eventually save a version as JPG. I take
a photo as JPG, save my first edit as BMP or TIF,
then save all other versions the same way. I end
up with a folder containing numerous versions of
the photo. You end up with a history in LR. If I
edit it 5 times and maybe save 5 versions there's
no loss. If necessary I might eventually convert
one of those to JPG to send to someone.

  We both then end up with 2 lossy steps: The original
JPG photo and the final JPG save of an edited image.
The only difference is that LR is managing the file
storage for you so you don't need to save TIFs or
maintain systematic file storage.

| > That's basically what LR is doing -- saving some kind of backup bitmap 
| Nope, an XMP sidecar file is not some kind of backup bitmap image. It is a
| set of instructions detailing the edits and adjustments.
| <>
| <>

   We discussed this once before. It's all bitmaps.
Any raster image is essentially a bitmap. A JPG
is a compressed bitmap with some data dropped
out. A TIF is usually just a compressed bitmap.
A GIF is a bitmap. A PNG is a bitmap. Those are
all just different ways to store the image data.
Proprietary formats, like Paint Shop Pro's PSP
or the PS PSD, store the image plus editing
history, unmerged layers, etc. But the image is
still going to be a bitmap -- a grid of pixel color
values. That's what goes to the printer or the
computer screen. That's what you're applying filters,
sharpening, etc to. Those are all just mathematical
formulae applied to bitmaps. Increase the pixel
values and you've lightened. Increase the difference
between contiguous pixels and you've sharpened.
Of course it gets very sophisticated when it can do
things like remove a chain link fence from the image,
but it's still essentially the same thing.