U of S | Mailing List Archive | alt-photo-process-l | Re: "Raw" for dummies ?

Re: "Raw" for dummies ?



Judy wrote:

> Could someone do a very brief "raw for dummies" -- once over lightly, why
> I should use it, why it's better than just ad hoc touch-up/ adjustments in
> Photoshop (and sometimes not even that)? How much do folks really use it,
> or is it mostly just nice to know it's there ?

To add a few points to what Don wrote:

The responses of the photosensor in a digital camera do not constitute a
color image as they leave the sensor.  They must be interpreted by software
and converted to a usable image format.  Some image processing (sharpening,
contrast changes, color saturation, white balance, etc.) may also be done
during the conversion.  When you set your G5 for JPEG, this conversion is
done in the camera and the original sensor data is erased once the JPEG has
been generated.  If you shoot RAW, you will do the conversion with your
computer after downloading the RAW files from the camera.

RAW gives several advantages: (1) it captures all of the sensor data and
allows various conversions to be done without destroying the original
sensor data -- all in-camera conversions lose some of the original sensor
data; (2) it allows the conversion to be done by a more powerful processor
-- the one in your PC -- operating at relative leisure, rather than the
less powerful one in the camera that has to do the conversion quickly to be
ready for another exposure; at least theoretically, this means that more
computationally-intensive algorithms can be used on RAW images;  (3) it
allows you to save the image in better-quality formats, such as 16-bit
TIFF, rather than JPEG (some cameras will save in TIFF format, generally
instead of RAW; many will do only RAW or JPEG, sometimes both RAW and
JPEG); (4) it allows your digital images to be improved in the future --
when more advanced conversion algorithms become available, you can
re-convert the RAW files; and (5) it allows you to change your mind about
your pre-set in-camera processing choices (white balance, contrast,
sharpening, color saturation, etc.).  Those choices are incorporated into
the in-camera converted image, but are stored merely as instructions for
the conversion software in the case of a RAW image.  You can let the
conversion software use the stored choices by default, or you can change
the settings at the time of conversion.  And because you still have the
original RAW file, you can try as many choices as you like.

All that said, if you like the results you are getting now, you may not
notice any obvious benefit to shooting RAW.  However, if you are getting
blown-out highlights with JPEGs, you may find it helpful to lower the
contrast in RAW conversions.  (You can also do this with your JPEGs by
setting the camera's contrast lower.  You may also -- or alternatively --
want to set the camera to routinely underexpose by 1/2 or 2/3 stop, or
perhaps even a bit more, until your images look the way you want them.)

Best regards,

etienne