Curious RAW quirk?

Hi all!

I took in-house photos at a party, setting the WB to flash and using an
external Canon flash on my Eos 5D MarkII.
What puzzles me is when I work on the Raw photo in Photoshop CS3 and the
white balance shows as "as shot", if I change it to "Flash" (which was the
WB setting on my camera) , I get a cooler temp. Why please this difference?

Thanks,

Marcel

celcius wrote:
Hi all!

I took in-house photos at a party, setting the WB to flash and using an
external Canon flash on my Eos 5D MarkII.
What puzzles me is when I work on the Raw photo in Photoshop CS3 and
the white balance shows as "as shot", if I change it to "Flash" (which
was the WB setting on my camera) , I get a cooler temp. Why please this
difference?

The RAW processor has a different idea of what "Flash" means than does
the camera!
How much a difference?
I generally find that if I leave the WB on auto, it does a superb job on
85% of my shots. The "auto" function in the processor, though, sometimes
comes up better than the camera's; sometimes not as good.

--
john mcwilliams

celcius wrote:
Hi all!

I took in-house photos at a party, setting the WB to flash and using an
external Canon flash on my Eos 5D MarkII.
What puzzles me is when I work on the Raw photo in Photoshop CS3 and
the white balance shows as "as shot", if I change it to "Flash" (which
was the WB setting on my camera) , I get a cooler temp. Why please this
difference?

A quick look at the EXIF for my camera (Sony a900)for flash shots hasa
bizarre light source temperature (below). Additionally, there is a
"Light Source" value set to "Daylight" (if in that mode) or "Unknown" if
I set the light source temperature directly (say to 5500K).

Then the "White Balance" field is set to "Color Temperature/Color Filter".

And bizzarely, the "Color Temperature" field is set to 21400 (!) with no
"K" unit noted.

(DL exiftool to really delve into what is delivered from the camera).

In the end, I believe ACR analyzes the image to come up with a
temperature (assuming I suppose that it's on average mid-grey) for the
"As shot" value.

A bit mysterious, overall.

On Mon, 12 Oct 2009 11:22:29 -0400, "celcius" wrote:
: Hi all!
:
: I took in-house photos at a party, setting the WB to flash and using an
: external Canon flash on my Eos 5D MarkII.
: What puzzles me is when I work on the Raw photo in Photoshop CS3 and the
: white balance shows as "as shot", if I change it to "Flash" (which was the
: WB setting on my camera), I get a cooler temp. Why please this difference?

Don't take this as gospel, but I believe it's the case that setting the WB has
no effect on an EOS Canon in RAW mode. No WB correction is applied; it's left
entirely up to the post-porcessor. What Photoshop is showing you as "as shot"
(Canon's own software calls it "shot settings") is merely the camera's
recommendation of what WB to use in post-processing. It may or may not be what
you set it to be on the camera.

JPEG is a different matter. If you tell the camera to use a specific WB
correction, that's what the camera uses in its conversion of the image to
JPEG.

BTW, my impression is that Canon sets the "flash" WB assuming that the flash
output is colder than even its own flashguns produce in practical use. So if
you bounce the light off of anything but a pure white reflector, the "flash"
WB will produce a result that is too red.

Bob

"Robert Coe" wrote in message
news
On Mon, 12 Oct 2009 11:22:29 -0400, "celcius"
wrote:


Don't take this as gospel, but I believe it's the case that setting the WB
has
no effect on an EOS Canon in RAW mode. No WB correction is applied; it's
left
entirely up to the post-porcessor. What Photoshop is showing you as "as
shot"
(Canon's own software calls it "shot settings") is merely the camera's
recommendation of what WB to use in post-processing. It may or may not be
what
you set it to be on the camera.

JPEG is a different matter. If you tell the camera to use a specific WB
correction, that's what the camera uses in its conversion of the image to
JPEG.

Both of the above are correct. Good response.

"Robert Coe" wrote in message
news
On Mon, 12 Oct 2009 11:22:29 -0400, "celcius"
wrote:
: Hi all!
:
: I took in-house photos at a party, setting the WB to flash and using an
: external Canon flash on my Eos 5D MarkII.
: What puzzles me is when I work on the Raw photo in Photoshop CS3 and
the
: white balance shows as "as shot", if I change it to "Flash" (which was
the
: WB setting on my camera), I get a cooler temp. Why please this
difference?

Don't take this as gospel, but I believe it's the case that setting the WB
has
no effect on an EOS Canon in RAW mode. No WB correction is applied; it's
left
entirely up to the post-porcessor. What Photoshop is showing you as "as
shot"
(Canon's own software calls it "shot settings") is merely the camera's
recommendation of what WB to use in post-processing. It may or may not be
what
you set it to be on the camera.

JPEG is a different matter. If you tell the camera to use a specific WB
correction, that's what the camera uses in its conversion of the image to
JPEG.

BTW, my impression is that Canon sets the "flash" WB assuming that the
flash
output is colder than even its own flashguns produce in practical use. So
if
you bounce the light off of anything but a pure white reflector, the
"flash"
WB will produce a result that is too red.

Bob

Hi Bob!
I think you've got a point in saying that setting the WB on the camera has
very little incidence in Raw mode. John says that leaving it on "auto" is
fine.
I thought, reading the posts here in the past, that it was always better to
set the proper WB even when shooting in Raw mode. Now, I'm back to square 1
;-)
Mind you, the beauty here is the fact that being in Raw, everything.. or
almost is possible.
Marcel

"celcius" wrote:
I think you've got a point in saying that setting the WB on the camera has
very little incidence in Raw mode. John says that leaving it on "auto" is
fine.

WB has no effect on the camera raw data. It is a
correction applied only when that data is converted to a
JPEG. The camera always generates a JPEG for viewing,
which is also used to generate an histogram. But if you
don't "shoot JPEG", it is not saved as a file.

I thought, reading the posts here in the past, that it was always better to
set the proper WB even when shooting in Raw mode. Now, I'm back to square 1
;-)

Setting WB depends on what you want. It can be, for
example, set to provide no correction in order to get an
accurate histogram. It can be set to "auto", just to
provide Exif data for what the camera calculates as the
correct adjustment. It can be set manually to whatever
you think is "correct" to perhaps get more a more
accurate looking preview image.

All of those are reasonable settings, and none of them
provide exactly the same results.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

On Mon, 12 Oct 2009 14:56:34 -0800, (Floyd L.
Davidson) wrote:

"celcius" wrote:
I think you've got a point in saying that setting the WB on the camera has
very little incidence in Raw mode. John says that leaving it on "auto" is
fine.

WB has no effect on the camera raw data. It is a
correction applied only when that data is converted to a
JPEG. The camera always generates a JPEG for viewing,
which is also used to generate an histogram. But if you
don't "shoot JPEG", it is not saved as a file.

To be precise a copy of the JPEG used for in camera review and the
histogram(s) is saved within the RAW file it self.

me wrote:
On Mon, 12 Oct 2009 14:56:34 -0800, (Floyd L.
Davidson) wrote:

"celcius" wrote:
I think you've got a point in saying that setting the WB on the camera has
very little incidence in Raw mode. John says that leaving it on "auto" is
fine.

WB has no effect on the camera raw data. It is a
correction applied only when that data is converted to a
JPEG. The camera always generates a JPEG for viewing,
which is also used to generate an histogram. But if you
don't "shoot JPEG", it is not saved as a file.

To be precise a copy of the JPEG used for in camera
review and the histogram(s) is saved within the RAW
file it self.

But it is *not* saved as a JPEG file, it has to be
extracted.

Just how precise that is also depends on the camera.
For example, with a Nikon camera it is the same image
data but an extracted file differs significantly. The
distinction might not be significant, but the embedded
image does not contain the Exif data (the extraction
process may add some from the NEF file though), and that
includes lacking the 160x120 embedded thumbnail in the
camera generated JPEG file.

One odd result of the above is that if the thumbnail is
extracted from the NEF file, written to a JPEG file
and then put on a CF card, the camera will not be able
to display it from that file. It can display either the
NEF or the camera generated JPEG file though.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

"celcius" wrote in message
...
Hi all!

I took in-house photos at a party, setting the WB to flash and using an
external Canon flash on my Eos 5D MarkII.
What puzzles me is when I work on the Raw photo in Photoshop CS3 and the
white balance shows as "as shot", if I change it to "Flash" (which was the
WB setting on my camera) , I get a cooler temp. Why please this
difference?

Thanks,

Marcel


Thank you all!
Since I shoot exclusively in Raw, I've learned something very useful today.
I used to shoot only in JEPG, but this group and others have convinced me to
use Raw. This has served me well since I was able to save photos that might
have been completely wasted otherwise. I find Raw especially useful when I
shoot with flash and it seems the risk of getting a so so photo is greater.
Cheers,
Marcel