Leo, I thought I understood your explanation regarding pixels and
resolutions, etc. I was wrong. Perhaps you can help me unscramble the omelet
(sorry about the metaphor) concerning different formats. I just bought a camera
that allows me to take photographs in JPG or JPG plus RAW or just RAW!
If I take a picture in RAW, the resulting picture is about 24 MB. Then if I
put it through the supplied software (Silkypix), I can then save it as a JPG,
which becomes an 8 MB; or as TIF, which becomes about 45 MB. I asked myself
what’s the point in having a picture containing 24 MB of data if I can’t use
it? I can view the RAW picture using FastStone and even save it as a PNG
format. I’m thinking here of preserving as much data as possible. Should I just
use the JPG format initially and then, if need be, manipulate various aspects
with programs such as FastStone or Photoshop? I can very quickly fill my hard
drive with just a few different formats which all look (to the amateur) much of
a ‘muchness.’ Please help! Preferably with less words than War and Peace.
In this excerpt from
Answercast #69, I look at various file formats for images, how they compare,
and how they are used.
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Well, hopefully, this will be less than War and Peace!
First of all, the article that you are referencing on
pixels and resolution is actually independent of file formats.
Pixels, resolution, height by width, color depth; that actually applies to
pretty much all of the pictures. What we need to talk about here are some of
the many differences in file formats.
RAW image file format
Let’s start with RAW because I think a lot of people don’t really understand
what RAW is.
As its name implies, it’s a “raw” format and that is going to be specific to
the camera that you’re using. In other words, the RAW format output (by say a
Nikon camera) is going to be dramatically different inside than the
RAW format output by say a Canon camera. It’s “raw” because it’s actually
storing information that is optimized for and specific to that particular
camera: that particular camera’s hardware, that particular’s camera’s light
sensors, the actual photo cells that they use to grab the picture.
That is probably the most accurate representation of the picture before any
manipulation is done on it. In fact, in my case, it’s what I save.
Now, as you point out, a RAW file is actually fairly useless for sharing.
You can’t post a RAW picture up on the web; you can’t post a RAW picture in a
photo-sharing site because it implies that everybody who would be able to view
that picture would have a RAW decoder for every possible camera’s RAW
format. And of course, they don’t.
So, then, we start looking at other formats.
Before I leave to other formats, the one thing I’ll point out then with
RAW is that the size of the file (in your case, say 24 MB) may or may not
relate to the size of the image, the number of pixels in the image. The problem
here is that RAW formats contain a lot of information (as I said) that is
specific to the camera.
So, the file size is kind of interesting.
It’s true that the RAW file format is typically larger than the file formats
you’ll eventually use. We’ll talk about exactly why that is in a moment. So,
let’s move on to some of those other file formats.
JPEG image file format
The most common file format that you’ll find on the internet for photographs
is JPEG (or JPG). JPEG is a standard; it’s supported by almost every image
display program, every web browser, every everything… almost.
Now, the interesting thing about JPEG is that it is by definition a “lossy”
file format. So what that means is that when you convert your original image
(the .raw format) into a JPEG, some information will be lost.
This is why I actually save all of my pictures as RAW so that I have
everything possible, should I then want to go in and manipulate the image some
more. JPEG loses something.
As you point out, you may not notice. You may not notice that, gosh, the
colors are ever so slightly different or the pixels are every so slightly
miniscule-ly less sharp than they would have been had it been in the RAW
format. That’s kind of the point of JPEG. It actually takes advantage of human
eyesight and things we do and don’t see in order to compress the image, to
make it smaller, to actually use less data to render out an image that is of
acceptable quality… and even there, the acceptable quality can be
RAW format contains every bit of information about every pixel. JPEG? You
can adjust it. When you save a file as .jpeg in an image manipulation program,
usually you can adjust the quality of the image.
You can say, “Use lots of data to save this image because I want it to be as
sharp and as appropriate as possible.” Or, you can go to the other extreme and
the picture will be very unrecognizable because everything interesting has been
So, in my case, like I said, I save as RAW. What that implies is: in order
for me to do anything with a picture that I want to then use somewhere
else – I must first edit it.
I happen to do it in Photoshop. I edit my images. I crop them. I adjust
colors. I do various things to them and then the result of that work I save in
JPEG format – usually at a fairly high quality level – because at that point,
the size of the image isn’t going to be as big. Because, usually I end up
So, that’s one approach.
What format to save?
Now, many cameras (mine included) have the option of saving one, the other,
or both: JPEG, RAW or both.
My… I guess you would say “recommendation” would be that if you are (I
don’t know…) an advanced amateur or a pro, I’d be tempted to save in RAW
format – knowing that in order to do anything to any picture, you’re going to
then have to manipulate it: to save it in JPEG to do whatever.
If on the other hand, all you’re really interested in doing is having some
snapshots that you can deal with quickly and easily and upload to the web, it
may not be important. That level of detail may not be important to you. In
which case, having your camera save JPEG is more than sufficient.
Would you ever save both? You know, I did for a while but there just wasn’t
a point. I keep all my originals in RAW format. As long as you keep all of your
originals (all of your unmodified originals) in whatever format they come out
of the camera, then you know that you can always go back to those to make
changes, to crop new versions, to do whatever it is you want.
TIF & PNG file formats
You mentioned a TIF file format.
TIF, in particular, tends to be a bad file format for photo sharing: mostly
because it either isn’t compressed or isn’t compressed well. That’s why you
see that your TIF file ended up becoming actually bigger than the original –
because it had to normalize.
It’s a standard format; most programs certainly understand it – but it had
to normalize all of this information that was unique to your camera in the RAW
file format into a format that then has the information in a very generic and
as it turns out, uncompressed format.
PNG is, I suppose, a bit of a trade-off in that it is a “lossless” format.
The conversion from RAW to anything, from RAW to PNG will still involve just a
little of bit of loss; but the compression algorithm in PNG is a lossless one,
which means you get what you put in.
Choosing a format
So, it is a complicated topic, like I said. That’s why, for the most part,
if what you’re mostly interested in is simply doing snapshots and easy-to-share, easy-to-send pictures, JPEG’s plenty. JPEG’s fine. You’ll never, ever
notice the difference.
On other hand, if you start getting a little bit more serious, if you want
to start playing with things like colors and contrast and light balance and a
whole bunch of random things that programs like Photoshop make accessible to
you, then my recommendation (or at least my experience) is that saving in RAW
format is usually the way to go.
Then, producing JPEGs, the way you want the JPEGs to look, is the second
step that’s required for every picture you want to share with