ISO and actual sensitivity in DSLR's (D70, *istD, 20D, S3...)

writes:

The output of a raw converter is far from an identity function, and far
from a linear transformation, even with all the tweakable parameters set
to their defaults. The exception: Canon's raw converter when the
special 16-bit linear output mode is selected.

I think that even that is not the RAW data, scaled. The blackpoint is
already subtracted, and color-balancing is applied, IIRC.

Probably. But in that case, data values in the 16-bit data *are*
linearly proportional to scene light intensity, something not true when
any sort of gamma encoding has been done. It's not raw A/D output, but
it's close to raw light measurmements with an unknown scale factor.

Dave

In message ,
(Dave Martindale) wrote:

Alan Browne writes:

The exception: Canon's raw converter when the
special 16-bit linear output mode is selected.

I don't suppose that's available for free AND reads the Maxxum 7D?
g

I think it's freely downloadable, but only works on Canon raw images.

But you might look into dcraw, a free/open source raw converter.

The Astrophoto program IRIS loads many RAW files and shows them in all
their RAWness (uncolor-balanced and un-blackpointed), first with a
greyscale, and then with each of the three color planes separated and
interpolated to the full MP count, with a menu option. In IRIS, you
always set visual whitepoint and blackpoint yourself.
--


John P Sheehy

In message ,
Alan Browne wrote:

wrote:

is no one "unchanged" RAW conversion. It is always interpretation.

I know what result I got under controlled lighting, aperture and ISO
setting. It is too close to the C d'I result to ignore. Their result
traces back to the CIPA standard. So, either a coincidence or a
confirmed result. Please feel free to do the same.

No one is denying that most cameras and converters have a somewhat
standardized output level for RAW conversion. The question is the
relevance to the camera, especially to the RAW shooter, to whom the
camera's "ISO" and mid-grey-point are just an arbitrary frame of
reference.
--


John P Sheehy

Dave Martindale wrote:

Alan Browne writes:


The exception: Canon's raw converter when the
special 16-bit linear output mode is selected.


I don't suppose that's available for free AND reads the Maxxum 7D?
g


I think it's freely downloadable, but only works on Canon raw images.

was a joke, Dave


But you might look into dcraw, a free/open source raw converter.

I will.

--
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-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.

wrote:

In message ,
Alan Browne wrote:


wrote:


is no one "unchanged" RAW conversion. It is always interpretation.


I know what result I got under controlled lighting, aperture and ISO
setting. It is too close to the C d'I result to ignore. Their result
traces back to the CIPA standard. So, either a coincidence or a
confirmed result. Please feel free to do the same.


No one is denying that most cameras and converters have a somewhat
standardized output level for RAW conversion. The question is the
relevance to the camera, especially to the RAW shooter, to whom the
camera's "ISO" and mid-grey-point are just an arbitrary frame of
reference.

I don't believe the grey point is so arbitrary when all conditions are
controlled, but as I said, please try your own test as I described it.

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.

Dave Martindale wrote:

Alan Browne writes:


The exception: Canon's raw converter when the
special 16-bit linear output mode is selected.


I don't suppose that's available for free AND reads the Maxxum 7D?
g


I think it's freely downloadable, but only works on Canon raw images.

But you might look into dcraw, a free/open source raw converter.

Aw crap. CMD line. Is there a GUI for this thing?

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.

wrote in :

If only the histograms were more accurate; even if you are shooting
jpegs, they can easily miss clipping in the red and especially the blue
channels. On most cameras that have RAW, they only show you the JPEG
luminance histogram.

That sux - of course. The RAW contains much more.


/Roland

Alan Browne wrote in news:d2ee12$28j$3
@inews.gazeta.pl:

Aw crap. CMD line. Is there a GUI for this thing?

Remember - google is your friend.

Googling for dcraw gui gives:

http://ptj.rozeta.com.pl/Soft/RawPhoto
http://www.aim-dtp.net/aim/digicam/dcraw/index.htm
http://ufraw.sourceforge.net/



/Roland

Roland Karlsson wrote:

Alan Browne wrote in news:d2ee12$28j$3
@inews.gazeta.pl:


Aw crap. CMD line. Is there a GUI for this thing?


Remember - google is your friend.

Googling for dcraw gui gives:

http://ptj.rozeta.com.pl/Soft/RawPhoto
http://www.aim-dtp.net/aim/digicam/dcraw/index.htm
http://ufraw.sourceforge.net/

Why, thank you, Rolland.

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.