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custom white balance/exposure questions ?

 
 
picture taker
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      07-10-2006
gary, thanks for the reply,
ill have to experment,
thank you

Gary Eickmeier wrote:
>
> Not sure how to set WB with flash using Expodisc. Maybe just put the
> disc on, flash an exposure with a typical subject distance, and use
> that. Would be best if you could have a mostly white area to do it with,
> but experiment.
>


 
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Gary Eickmeier
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      07-11-2006


picture taker wrote:
> gary, thanks for the reply,
> ill have to experment,
> thank you
>
> Gary Eickmeier wrote:
>
>>Not sure how to set WB with flash using Expodisc. Maybe just put the
>>disc on, flash an exposure with a typical subject distance, and use
>>that. Would be best if you could have a mostly white area to do it with,
>>but experiment.


I think the book said something about shooting into a mirror, but that
would only give you the WB for the flash, not the total lighting
situation. My Oly E20 can do WB with flash by aiming at a white surface.
Only difference would be put the disc on the lens first.

Gary Eickmeier
 
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ronviers@gmail.com
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      07-11-2006
If you are shooting raw and do a custom wb then your histogram will be
more accurate because the colors will line up on top of each other and
be less likely to clip. If you camera does not have a three channel
histogram it will show no clipping until you get a chance to look at it
in post.


picture taker wrote:
> hi,
> i understand exposure shutter speed,f-stop ,iso etc , shoot with a
> canon 20d ,capture raw files all the time, convert with cs2 and adjust
> the wb if i feel it needs it .
> i have never fully understood whte balance / custom white balance etc
>
> when people refer to a custom white balance are they trying to make
> everything equal ,meaning the reference of 18% that is often mentioned
> about custom white balance ?.
>
> say there is a shinny red dress or a white one for that matter and
> they look a lot brighter than the other colors, by doing the custom
> white balance does the camera then read the dresses as the same and
> won't blow out the details ? .
>
> what is the difference between using a reference card ( gray card ,
> expo disc etc ) to set the custom white balance but ive also heard it
> referd to as usnig it to set the exposure not the white balance ?
>
> say you are in a gymnasium shooting basketball with an expodisc for you
> to use as reference on the end of the lens pointed at the lights to set
> your custom wb in camera and you crank up the iso does it matter if you
> set the custom wb at a differnt iso than what you will be shooting ?.
> same situation in the same gym ,now your shooting with a flash
> should you just leave the custom set or reshoot the custom wb with the
> expodisc attached while using the flash ?.
>
> thank you


 
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picture taker
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Posts: n/a
 
      07-11-2006
ron, thanks for the reply,
im using a canon 20d
does it make a difference if you have the image size set to raw & jpeg
while dong a custom white balance , or better to put on joeg then
change your image quality to raw and jpeg ?
im thinking not but figured i would ask .

thank you

http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:
> If you are shooting raw and do a custom wb then your histogram will be
> more accurate because the colors will line up on top of each other and
> be less likely to clip. If you camera does not have a three channel
> histogram it will show no clipping until you get a chance to look at it
> in post.
>
>
> picture taker wrote:
> > hi,
> > i understand exposure shutter speed,f-stop ,iso etc , shoot with a
> > canon 20d ,capture raw files all the time, convert with cs2 and adjust
> > the wb if i feel it needs it .
> > i have never fully understood whte balance / custom white balance etc
> >
> > when people refer to a custom white balance are they trying to make
> > everything equal ,meaning the reference of 18% that is often mentioned
> > about custom white balance ?.
> >
> > say there is a shinny red dress or a white one for that matter and
> > they look a lot brighter than the other colors, by doing the custom
> > white balance does the camera then read the dresses as the same and
> > won't blow out the details ? .
> >
> > what is the difference between using a reference card ( gray card ,
> > expo disc etc ) to set the custom white balance but ive also heard it
> > referd to as usnig it to set the exposure not the white balance ?
> >
> > say you are in a gymnasium shooting basketball with an expodisc for you
> > to use as reference on the end of the lens pointed at the lights to set
> > your custom wb in camera and you crank up the iso does it matter if you
> > set the custom wb at a differnt iso than what you will be shooting ?.
> > same situation in the same gym ,now your shooting with a flash
> > should you just leave the custom set or reshoot the custom wb with the
> > expodisc attached while using the flash ?.
> >
> > thank you


 
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Matt Ion
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      07-11-2006
picture taker wrote:
> matt, thank you for the reply,
> ill be looking at the lights in the supermarket next time im there lol
> , makes alot of sense




> so you don't think it really matters if shooting raw to do a custom WB
> or not if shooting raw ?


Like I said, it WILL embed the WB information in the file, so the RAW
conversion software knows where to start and make life a bit easier, and
if you've set a custom WB, it will avoid needing to guess at it later...
but no, it's not necessary.

Note that most cameras do have the option to embed a JPG in the RAW file
as well, and many viewers will just pull up that JPG for a quick view;
also, some cameras (Canons at least) store a separate .THM "thumbnail"
file, which is also a small JPG... the WB setting WILL affect the look
of these files. If you're processing the RAW, it won't matter, but the
thumbnails and/or quick views may look "off".

> the hardest challenge for me is to be able to capture a black tux and
> white gown with out blowing the highlights or underexposing the black.
> thanks.


I know what you mean - we have a "tuxedo" cat (all black and white) and
taking a good picture of her is a PITA. Having the extra dynamic range
of RAW can certainly be helpful.
 
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ronviers@gmail.com
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Posts: n/a
 
      07-11-2006
hmm, good question. I do not know. I have not tried shooting jpg's of
any kind. My guess is that a jpg for purposes of wbing would be the
equivalent to a raw for the same purpose. The question is more than
academic from the standpoint that a photographer could pre-shoot the
custom wb images for wedding, for example, then quickly set them as
needed. Having the wb images as small files would save a lot of
memory. Conceivably you could get an entire wedding on a single 4GB
card. Hopefully one of the smart photographers will chime in here with
an answer.

Good luck,
Ron

picture taker wrote:
> ron, thanks for the reply,
> im using a canon 20d
> does it make a difference if you have the image size set to raw & jpeg
> while dong a custom white balance , or better to put on joeg then
> change your image quality to raw and jpeg ?
> im thinking not but figured i would ask .
>
> thank you
>
> (E-Mail Removed) wrote:
> > If you are shooting raw and do a custom wb then your histogram will be
> > more accurate because the colors will line up on top of each other and
> > be less likely to clip. If you camera does not have a three channel
> > histogram it will show no clipping until you get a chance to look at it
> > in post.
> >
> >
> > picture taker wrote:
> > > hi,
> > > i understand exposure shutter speed,f-stop ,iso etc , shoot with a
> > > canon 20d ,capture raw files all the time, convert with cs2 and adjust
> > > the wb if i feel it needs it .
> > > i have never fully understood whte balance / custom white balance etc
> > >
> > > when people refer to a custom white balance are they trying to make
> > > everything equal ,meaning the reference of 18% that is often mentioned
> > > about custom white balance ?.
> > >
> > > say there is a shinny red dress or a white one for that matter and
> > > they look a lot brighter than the other colors, by doing the custom
> > > white balance does the camera then read the dresses as the same and
> > > won't blow out the details ? .
> > >
> > > what is the difference between using a reference card ( gray card ,
> > > expo disc etc ) to set the custom white balance but ive also heard it
> > > referd to as usnig it to set the exposure not the white balance ?
> > >
> > > say you are in a gymnasium shooting basketball with an expodisc for you
> > > to use as reference on the end of the lens pointed at the lights to set
> > > your custom wb in camera and you crank up the iso does it matter if you
> > > set the custom wb at a differnt iso than what you will be shooting ?.
> > > same situation in the same gym ,now your shooting with a flash
> > > should you just leave the custom set or reshoot the custom wb with the
> > > expodisc attached while using the flash ?.
> > >
> > > thank you


 
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Ben Brugman
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Posts: n/a
 
      07-12-2006

<(E-Mail Removed)> schreef in bericht
news:(E-Mail Removed) ups.com...
> If you are shooting raw and do a custom wb then your histogram will be
> more accurate because the colors will line up on top of each other and
> be less likely to clip. If you camera does not have a three channel
> histogram it will show no clipping until you get a chance to look at it
> in post.
>

White balancing is done after the raw is made. So it does not
influence the Raw's histogram.

Your suggestion would only have an advantage if the colors
in the picture would line up. For most pictures this is not
the case. For pictures where clipping occurs in one channel
it is most often because that color is more dominant.

ben


 
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ronviers@gmail.com
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Posts: n/a
 
      07-12-2006
Hi Ben,
Are you sure? It seems to me that I have far less single channel
clipping when I do a custom wb. I would not have mentioned it if I had
not done testing. I am convinced I get a more accurate histogram on my
Canon 300d if I do a custom wb.

Thanks,
Ron


Ben Brugman wrote:
> <(E-Mail Removed)> schreef in bericht
> news:(E-Mail Removed) ups.com...
> > If you are shooting raw and do a custom wb then your histogram will be
> > more accurate because the colors will line up on top of each other and
> > be less likely to clip. If you camera does not have a three channel
> > histogram it will show no clipping until you get a chance to look at it
> > in post.
> >

> White balancing is done after the raw is made. So it does not
> influence the Raw's histogram.
>
> Your suggestion would only have an advantage if the colors
> in the picture would line up. For most pictures this is not
> the case. For pictures where clipping occurs in one channel
> it is most often because that color is more dominant.
>
> ben


 
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Ben Brugman
Guest
Posts: n/a
 
      07-12-2006

<(E-Mail Removed)> schreef in bericht
news:(E-Mail Removed) ups.com...
> Hi Ben,
> Are you sure? It seems to me that I have far less single channel
> clipping when I do a custom wb. I would not have mentioned it if I had
> not done testing. I am convinced I get a more accurate histogram on my
> Canon 300d if I do a custom wb.


I do not know for the 300d, but from what you write I suspect that
the histogram is derived from an internal or external jpeg.

After digitization of the data from the sensor the data is only
compressed (lossless or losy) and some header information
is added. The individual values of the subpixels are not altered.


Other not likely scenario's.
On your Canon 300d some processing is done on the RAW file
influenced by the WB settings.
The white balance setting influences the Exposure.
The white balance setting influences the DA convertor.

(All three seem extremely unlikely to me, but I do not have a
300d and have not tested the 300d).

ben


>
> Thanks,
> Ron
>
>
> Ben Brugman wrote:
>> <(E-Mail Removed)> schreef in bericht
>> news:(E-Mail Removed) ups.com...
>> > If you are shooting raw and do a custom wb then your histogram will be
>> > more accurate because the colors will line up on top of each other and
>> > be less likely to clip. If you camera does not have a three channel
>> > histogram it will show no clipping until you get a chance to look at it
>> > in post.
>> >

>> White balancing is done after the raw is made. So it does not
>> influence the Raw's histogram.
>>
>> Your suggestion would only have an advantage if the colors
>> in the picture would line up. For most pictures this is not
>> the case. For pictures where clipping occurs in one channel
>> it is most often because that color is more dominant.
>>
>> ben

>



 
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ronviers@gmail.com
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Posts: n/a
 
      07-12-2006
Thank you for not dismissing my opinion out of hand. Recently I
photographed a bright orange flower on a high key background using
tungsten halogen. The first three exposures I adjusted only the
aperture (because this was a very deep flower). Then I realized I had
forgot to do a custom wb. So I did the custom wb then re-shot with the
same settings. In each case i kept the information about a third stop
from the right side of the histogram. After examining each image in
post I had dramatic clipping on one channel all three precustom wb and
no clipping after custom wb. Admittedly this was a test with a
dominant color but I have had similar results with a turtle in tall
grass and other subjects. Does this seem like a valid test? My guess
is that the custom wb only has an influence on the way the histogram is
displayed but your scenarios are definite possibilities. I would like
to know what is going on.

Thanks for the reply,
Ron


Ben Brugman wrote:
> <(E-Mail Removed)> schreef in bericht
> news:(E-Mail Removed) ups.com...
> > Hi Ben,
> > Are you sure? It seems to me that I have far less single channel
> > clipping when I do a custom wb. I would not have mentioned it if I had
> > not done testing. I am convinced I get a more accurate histogram on my
> > Canon 300d if I do a custom wb.

>
> I do not know for the 300d, but from what you write I suspect that
> the histogram is derived from an internal or external jpeg.
>
> After digitization of the data from the sensor the data is only
> compressed (lossless or losy) and some header information
> is added. The individual values of the subpixels are not altered.
>
>
> Other not likely scenario's.
> On your Canon 300d some processing is done on the RAW file
> influenced by the WB settings.
> The white balance setting influences the Exposure.
> The white balance setting influences the DA convertor.
>
> (All three seem extremely unlikely to me, but I do not have a
> 300d and have not tested the 300d).
>
> ben
>
>
> >
> > Thanks,
> > Ron
> >
> >
> > Ben Brugman wrote:
> >> <(E-Mail Removed)> schreef in bericht
> >> news:(E-Mail Removed) ups.com...
> >> > If you are shooting raw and do a custom wb then your histogram will be
> >> > more accurate because the colors will line up on top of each other and
> >> > be less likely to clip. If you camera does not have a three channel
> >> > histogram it will show no clipping until you get a chance to look at it
> >> > in post.
> >> >
> >> White balancing is done after the raw is made. So it does not
> >> influence the Raw's histogram.
> >>
> >> Your suggestion would only have an advantage if the colors
> >> in the picture would line up. For most pictures this is not
> >> the case. For pictures where clipping occurs in one channel
> >> it is most often because that color is more dominant.
> >>
> >> ben

> >


 
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