I just spent all night finding out how to work with RAW images in
Photoshop as I had heard that the RAW images retain more
information than the JPEG's and, therefore, more can be done with
them.
However, I found that all the tools for using RAW images convert to
JPEG first anyways! I could understand TIFF, but going to JPEG
seems to defeat the purpose of shooting them in RAW.
Others have already posted a variety of responses, so I'll inject
only my two cents. The main advantage to RAW may not always be
apparent when looking at a well-exposed, properly balanced photo.
Many people will say they've shot in RAW and compared against JPEG
with no visible difference. I don't doubt that this is sometimes
true. The main advantage to RAW is the flexibility it gives you to
tweak less-than-perfect shots. Such shots may be near-perfect and
just requiring that something extra to make them great, or you may
be trying to salvage a poor shot and make it viewable.
These are what I feel to be the key places where you'll notice the
difference:
1. Exposure Adjustment and Post Processing
If you convert from RAW to 16-bit TIFF, you'll have 10 bits per
pixel per color instead of 8. You won't necessarily notice the
difference on a well-exposed shot straight from the camera.
However, what if your shot is underexposed or features too little
contrast and you need to reset the white and black points to expand
the histogram? With 8-bits, you'll open up holes: certain shades
will simply be missing from your final results. Go too far and
you'll notice this visibly as "posterization."
Also, the 10-bit advantage extends beyond this. Any time you
process an image,you get round-off mathematical error in the final
result. These errors accumulate as you continue to apply post
processing. 10-bit data can express a value with 4x greater
precision, and so accumulates visible errors much more slowly.
Finally, and going back to exposure adjustment, try to save a very
underexposed shot without RAW. If you just adjust levels, you may
be able to bring some detail out of the darkness. However, colors
will be desaturated. This is part of Canon's noise reduction.
Desaturating colors at low-levels also reduces shadow noise. Good
for noise, bad for saving an underexposed shot. For this, you can
convert from RAW to 16-bit linear TIFF and avoid this desaturation.
2. Dynamic Range
Often, a shot will feature highlights that are just blown out to
white due to the wide dynamic range of the shot or to overexposure.
Often, the RAW data file will actually preserve detail in these
highlights. I'm not sure why this detail is lost during conversion
to JPEG or regular TIFF, but the detail can be retrieved using
linear conversion. I posted an example of this in the forum, but
I'll post the links again here.
First shot: RAW-to-TIFF (using low contrast, to try to preserve as
much dynamic range as possible)
http://www.pbase.com/image/3295638
Second shot: RAW-to-TIFF combined with RAW-to-linear-TIFF (using
Breezebrowswer, which merges the two together to preserve highlight
detail)
http://www.pbase.com/image/3295639
Notice the third house from the left - the white one. In the first
shot, the house is blown out. You can't make out the horizontal
lines of the house's siding. No amount of adjustment will bring
back the detail. Note that this was already converted with contrast
set to low, so one can't retort that low contrast setting would
have prevented this.
The second shot reveals this detail, making the house look more
natural and less of a solid white square. The sky is also less
washed out.
Hope this help whet your appetite for using RAW.
David
Matt
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