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how to questions: pre-exposure and #25 red filter

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Anonymous
April 20, 2005 1:04:31 AM

Archived from groups: rec.photo.digital (More info?)

first question: #25 red filter
When I take B&W film photos with the red filter I get a wonderfully dark sky
with very contrasty clouds...

Is there a way to simulate this effect while using the red filter on a
digital camera? Should I set the white balance with the filter screwed on?

second question: pre-exposure
I just read about the use of pre-exposure to bring up the shaddows with
little effect on highlights. (exposing film to 18% gray card at zone II
before exposing the image)

How can I simulate this with digital? Presumably there would be a correct
way to layer 2 images of different exposures?

Thx! :) 

--
Mark Lauter

Photos, Ideas & Opinions
http://www.marklauter.com
Anonymous
April 20, 2005 1:04:32 AM

Archived from groups: rec.photo.digital (More info?)

I seem to recall a good tutorial on this at luminous-landscape.com..?
Anonymous
April 20, 2005 1:04:32 AM

Archived from groups: rec.photo.digital (More info?)

By the way, maybe I misunderstood your initial question, but you *are*
aware of RGB separation (and the use of the channel mixer in photoshop
if you have it), to get equivalent, if not better, filter effects?

And here's the l-l link:

http://www.luminous-landscape.com/tutorials/blended_exp...
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Anonymous
April 20, 2005 3:59:00 AM

Archived from groups: rec.photo.digital (More info?)

Mark Lauter wrote:
> first question: #25 red filter
> When I take B&W film photos with the red filter I get a wonderfully
> dark sky with very contrasty clouds...
>
> Is there a way to simulate this effect while using the red filter on a
> digital camera? Should I set the white balance with the filter
> screwed on?

You don't need the filter at all, although in some cameras you could use
it. I suggest you leave the camera set to color (or RAW) and then use
software after the exposure to to turn it into a gray scale image and you
can play with the settings before turning it into or as you do so to get the
same effect as using a red filter. You can even make it stronger or weaker
at will.

>
> second question: pre-exposure
> I just read about the use of pre-exposure to bring up the shaddows
> with little effect on highlights. (exposing film to 18% gray card at
> zone II before exposing the image)
>
> How can I simulate this with digital? Presumably there would be a
> correct way to layer 2 images of different exposures?

That again would generally be done in post exposure processing.

>
> Thx! :) 

--
Joseph Meehan

Dia's Muire duit
Anonymous
April 20, 2005 4:24:41 AM

Archived from groups: rec.photo.digital (More info?)

"Mark Lauter" <available_upon_request@just_ask_in_a_post.com> writes:

> first question: #25 red filter
> When I take B&W film photos with the red filter I get a wonderfully dark sky
> with very contrasty clouds...
>
> Is there a way to simulate this effect while using the red filter on a
> digital camera? Should I set the white balance with the filter screwed on?

If you're actually using a red filter on the camera, you aren't
*simulating* the effect!

It should work to set the camera in B&W mode and put the red filter
on. But play around the first time and keep an eye on your histogram
-- because with a #25 you're gonna get pretty much all your light in
the red channel, with pretty much zip in the blue and green channels,
which may cause confusion to some of the automation. Make sure the
automation isn't ruining it for you before you shoot a lot of
important stuff!

Because the #25 filter is so drastic, though, you're probably better
off *not* using the filter, and simply extracting the red channel in
Photoshop later.

As with nearly anything in photoshop, there are a myriad ways of doing
it. One of them is to actually extract the red channel. Another,
perhaps easier (and workable for *other* filter effects as well) is to
use the channel mixer tool with "monochrome" checked, and select 100%
red channel, 0% blue 0% green. Still a third way in new enough
versions is to use the "photo filters" adjustment and tell it to apply
a #25.

(Snipping your other question since I don't have a clearcut answer I
can explain clearly; sorry!)
--
David Dyer-Bennet, <mailto:D d-b@dd-b.net>, <http://www.dd-b.net/dd-b/&gt;
RKBA: <http://noguns-nomoney.com/&gt; <http://www.dd-b.net/carry/&gt;
Pics: <http://dd-b.lighthunters.net/&gt; <http://www.dd-b.net/dd-b/SnapshotAlbum/&gt;
Dragaera/Steven Brust: <http://dragaera.info/&gt;
Anonymous
April 20, 2005 4:34:01 AM

Archived from groups: rec.photo.digital (More info?)

> > How can I simulate this with digital? Presumably there would be a
> > correct way to layer 2 images of different exposures?
>
> That again would generally be done in post exposure processing.

I've been shooting digital for 3 years - this isn't a noob question. Of
course it would be done post exposure processing - how?

--
Mark Lauter

Photos, Ideas & Opinions
http://www.marklauter.com
Anonymous
April 20, 2005 6:32:10 AM

Archived from groups: rec.photo.digital (More info?)

"Mark Lauter" <available_upon_request@just_ask_in_a_post.com> wrote in message news:<Zrh9e.9092$5f.898@tornado.tampabay.rr.com>...
> > > How can I simulate this with digital? Presumably there would be a
> > > correct way to layer 2 images of different exposures?
> >
> > That again would generally be done in post exposure processing.
>
> I've been shooting digital for 3 years - this isn't a noob question. Of
> course it would be done post exposure processing - how?

Various colour filters (red, yellow, blue) could be simulated by
splitting the image into R, G and B channels.

Red would be by boosting the red channel (or darkening the G and B
channels).
Yellow would be by boosting both the green and blue channel (or
darkening the R channel).
Blue would be by boosting the blue channel (or by darkening the R and
G channels)

Then recombine the channels and then desaturate the image.

I have done this in Corel PhotoPaint (version 8) and should be similar
on the other software packages.
Anonymous
April 20, 2005 4:52:17 PM

Archived from groups: rec.photo.digital (More info?)

Mark Lauter wrote:
>>> How can I simulate this with digital? Presumably there would be a
>>> correct way to layer 2 images of different exposures?
>>
>> That again would generally be done in post exposure processing.
>
> I've been shooting digital for 3 years - this isn't a noob question.
> Of course it would be done post exposure processing - how?

That "how" depends on the software you are using. I might add that it
may also be done at the time of exposure not just post-processing, but I
would generally suggest post-processing.

The fun of it is not just duplicating a red filter, but finding out all
the different ways you can play with it and fine tune it to your desire.
Start by checking out what options your software has to adjust each color
band. subtracting blue or adding red and play with the secondary colors as
well or in combination. You get a lot of control there that would have been
almost impossible in silver based photography.

--
Joseph Meehan

Dia's Muire duit
Anonymous
April 20, 2005 6:17:13 PM

Archived from groups: rec.photo.digital (More info?)

In message <8Xg9e.7265$0d6.5955@tornado.ohiordc.rr.com>,
"Joseph Meehan" <sligojoe_Spamno@hotmail.com> wrote:

> You don't need the filter at all, although in some cameras you could use
>it. I suggest you leave the camera set to color (or RAW) and then use
>software after the exposure to to turn it into a gray scale image and you
>can play with the settings before turning it into or as you do so to get the
>same effect as using a red filter. You can even make it stronger or weaker
>at will.

Not exactly; the deep red filter, even if you only use the red channel
in your output, will change the response curve within the width of the
red channel.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
April 20, 2005 10:09:14 PM

Archived from groups: rec.photo.digital (More info?)

<chrlz@go.com> wrote in message

> By the way, maybe I misunderstood your initial question, but you *are*
> aware of RGB separation (and the use of the channel mixer in photoshop
> if you have it), to get equivalent, if not better, filter effects?

Yes and no. Aware of it, familiar with its use, not sure how to use it
appropriately or creatively.

> And here's the l-l link:
>
> http://www.luminous-landscape.com/tutorials/blended_exp...

Thanks! :) 

--
Mark Lauter

Photos, Ideas & Opinions
http://www.marklauter.com
Anonymous
April 20, 2005 10:09:15 PM

Archived from groups: rec.photo.digital (More info?)

> Then recombine the channels and then desaturate the image.
>
> I have done this in Corel PhotoPaint (version 8) and should be similar
> on the other software packages.

I also have photopaint 8 - how do you recombine the channels?

--
Mark Lauter

Photos, Ideas & Opinions
http://www.marklauter.com
Anonymous
April 20, 2005 10:12:03 PM

Archived from groups: rec.photo.digital (More info?)

> That "how" depends on the software you are using. I might add that
it
> may also be done at the time of exposure not just post-processing, but I
> would generally suggest post-processing.

Photoshop. As for post processing - you can't add information to the image
that isn't there to begin with so I'd assume some work at shutter time would
be appropriate. I'm trying to relate the film process (which makes perfect
sense to me) to the digital process.

--
Mark Lauter

Photos, Ideas & Opinions
http://www.marklauter.com
Anonymous
April 20, 2005 10:12:46 PM

Archived from groups: rec.photo.digital (More info?)

> > You don't need the filter at all, although in some cameras you could
use
> >it. I suggest you leave the camera set to color (or RAW) and then use
> >software after the exposure to to turn it into a gray scale image and you
> >can play with the settings before turning it into or as you do so to get
the
> >same effect as using a red filter. You can even make it stronger or
weaker
> >at will.

> Not exactly; the deep red filter, even if you only use the red channel
> in your output, will change the response curve within the width of the
> red channel.

that's what I thought.

--
Mark Lauter

Photos, Ideas & Opinions
http://www.marklauter.com
Anonymous
April 20, 2005 10:19:27 PM

Archived from groups: rec.photo.digital (More info?)

> > When I take B&W film photos with the red filter I get a wonderfully dark
sky
> > with very contrasty clouds...
> >
> > Is there a way to simulate this effect while using the red filter on a
> > digital camera? Should I set the white balance with the filter screwed
on?
>
> If you're actually using a red filter on the camera, you aren't
> *simulating* the effect!

I mean simulating the dark sky - as in what is the best way to convert these
images to B&W?

> It should work to set the camera in B&W mode and put the red filter
> on.

This cam doesn't have B&W mode. The one I have that does have B&W mode is
really only a direct conversion to grayscale, so there's not much use for
it.

> But play around the first time and keep an eye on your histogram
> -- because with a #25 you're gonna get pretty much all your light in
> the red channel, with pretty much zip in the blue and green channels,
> which may cause confusion to some of the automation. Make sure the
> automation isn't ruining it for you before you shoot a lot of
> important stuff!

It's mostly something my girlfriend is hacking around with, but it gave me
some ideas.. FWIW, I never shoot anything important. The only thing lost
is time and
what better way to lose time than shooting the camera :) 

> (Snipping your other question since I don't have a clearcut answer I
> can explain clearly; sorry!)

np :) 

--
Mark Lauter

Photos, Ideas & Opinions
http://www.marklauter.com
Anonymous
April 20, 2005 10:19:28 PM

Archived from groups: rec.photo.digital (More info?)

Mark Lauter <available_upon_request@just_ask_in_a_post.com> wrote:

[..]
> > It should work to set the camera in B&W mode and put the red filter on.
>
> This cam doesn't have B&W mode. The one I have that does have B&W mode is
> really only a direct conversion to grayscale, so there's not much use for
> it.

That's what black and white *is.* :-)

Put the red filter on, and you'll get the filtered light, mapped to
grayscale.
Anonymous
April 20, 2005 11:42:25 PM

Archived from groups: rec.photo.digital (More info?)

Mark Lauter wrote:
>> That "how" depends on the software you are using. I might add
>> that it may also be done at the time of exposure not just
>> post-processing, but I would generally suggest post-processing.
>
> Photoshop. As for post processing - you can't add information to the
> image that isn't there to begin with so I'd assume some work at
> shutter time would be appropriate. I'm trying to relate the film
> process (which makes perfect sense to me) to the digital process.

You are not "adding" anything when you use a filter. The idea of a
filter is it removes stuff. In this case the digital camera captures enough
information that is is possible to remove that same stuff (light colors
other than red) in post process. You can play with it by removing only
green, or other colors as well and you can change the amounts of each color
you remove. You can even change the cutoff curves.


--
Joseph Meehan

Dia's Muire duit
April 20, 2005 11:42:26 PM

Archived from groups: rec.photo.digital (More info?)

Joseph Meehan wrote:

> Mark Lauter wrote:
>
>>> That "how" depends on the software you are using. I might add
>>>that it may also be done at the time of exposure not just
>>>post-processing, but I would generally suggest post-processing.
>>
>>Photoshop. As for post processing - you can't add information to the
>>image that isn't there to begin with so I'd assume some work at
>>shutter time would be appropriate. I'm trying to relate the film
>>process (which makes perfect sense to me) to the digital process.
>
>
> You are not "adding" anything when you use a filter. The idea of a
> filter is it removes stuff. In this case the digital camera captures enough
> information that is is possible to remove that same stuff (light colors
> other than red) in post process. You can play with it by removing only
> green, or other colors as well and you can change the amounts of each color
> you remove. You can even change the cutoff curves.


Theoretically you could get some benefit from using a colored filter on
digital if it blocks out the blue & green allowing a deeper exposure of
the reds without blowing out the greens & blues. Then you'd still have
blues & greens to add to the mix & brighter reds rather than pulling the
reds out of the shadows. But generally speaking it's more flexible to
just do it in post processing.

People get into really complicated techniques for processing color into
B&W, you can find lots of opinions and complicated techniques. Probably
the simplest in photoshop is add an adjustment layer to desaturate and
below that an adjustment later for color balance or levels/curves and
adjust individual color channels.

The quickest way to preview is without adjustment layers, go to the
channels tab below layers and click the individual color channels to
make them the only one displaying. This is a quick way to see which
channel highlights which aspect of the exposure.
Anonymous
April 21, 2005 4:06:19 AM

Archived from groups: rec.photo.digital (More info?)

> >> That "how" depends on the software you are using. I might add
> >> that it may also be done at the time of exposure not just
> >> post-processing, but I would generally suggest post-processing.
> >
> > Photoshop. As for post processing - you can't add information to the
> > image that isn't there to begin with so I'd assume some work at
> > shutter time would be appropriate. I'm trying to relate the film
> > process (which makes perfect sense to me) to the digital process.
>
> You are not "adding" anything when you use a filter. The idea of a
> filter is it removes stuff. In this case the digital camera captures
enough
> information that is is possible to remove that same stuff (light colors
> other than red) in post process. You can play with it by removing only
> green, or other colors as well and you can change the amounts of each
color
> you remove. You can even change the cutoff curves.

We're talking about different topics - in this case I was talking about the
pre-exposure technique used with film to bring up the shaddows, not filters.

--
Mark Lauter

Photos, Ideas & Opinions
http://www.marklauter.com
Anonymous
April 21, 2005 4:12:54 AM

Archived from groups: rec.photo.digital (More info?)

"Paul Mitchum" <usenet@mile23.c0m> wrote

> > > It should work to set the camera in B&W mode and put the red filter
on.
> >
> > This cam doesn't have B&W mode. The one I have that does have B&W mode
is
> > really only a direct conversion to grayscale, so there's not much use
for
> > it.
>
> That's what black and white *is.* :-)

No, it's *not*. B&W film doesn't offer identical response to each color,
grayscale conversion does. That's why simple grayscale conversions aren't
used for color to B&W conversion.

> Put the red filter on, and you'll get the filtered light, mapped to
> grayscale.

FWIW, I gave it a try. It does increase contrast slightly, but doesn't give
the same response as I get with film. Doesn't matter since the camera with
B&W mode doesn't have a place to screw on a filter. :) 

--
Mark Lauter

Photos, Ideas & Opinions
http://www.marklauter.com
Anonymous
April 21, 2005 7:41:24 AM

Archived from groups: rec.photo.digital (More info?)

Mark Lauter wrote:
>>>> That "how" depends on the software you are using. I might add
>>>> that it may also be done at the time of exposure not just
>>>> post-processing, but I would generally suggest post-processing.
>>>
>>> Photoshop. As for post processing - you can't add information to
>>> the image that isn't there to begin with so I'd assume some work at
>>> shutter time would be appropriate. I'm trying to relate the film
>>> process (which makes perfect sense to me) to the digital process.
>>
>> You are not "adding" anything when you use a filter. The idea
>> of a filter is it removes stuff. In this case the digital camera
>> captures enough information that is is possible to remove that same
>> stuff (light colors other than red) in post process. You can play
>> with it by removing only green, or other colors as well and you can
>> change the amounts of each color you remove. You can even change
>> the cutoff curves.
>
> We're talking about different topics - in this case I was talking
> about the pre-exposure technique used with film to bring up the
> shaddows, not filters.

OK I see your point, but then I would suggest adjusting your exposure
based on shadow not highlight then using post processing for any change
based on color you might like similar to using a colored filter. While it
will not do exactly what you wanted to do, I believe you will find it will
work very well, maybe better, depending you your final goal. I would also
suggest shooting in RAW in this case.

--
Joseph Meehan

Dia's Muire duit
Anonymous
April 21, 2005 4:27:15 PM

Archived from groups: rec.photo.digital (More info?)

> OK I see your point, but then I would suggest adjusting your exposure
> based on shadow not highlight then using post processing for any change
> based on color you might like similar to using a colored filter. While it
> will not do exactly what you wanted to do, I believe you will find it will
> work very well, maybe better, depending you your final goal. I would also
> suggest shooting in RAW in this case.

In that case I will need to hurry up and buy a RAW capable camera <g>

The problem with metering for the shaddows in a very contrasty situation is
the highlights get blown, the opposite problem for metering for the
highlights. If I meter for both, take 2 photos then I wonder how to merge
them. I've experimented, but figure I might have missed the "best" way.

--
Mark Lauter

Photos, Ideas & Opinions
http://www.marklauter.com
April 21, 2005 4:27:16 PM

Archived from groups: rec.photo.digital (More info?)

Mark Lauter wrote:
>
> In that case I will need to hurry up and buy a RAW capable camera <g>
>
> The problem with metering for the shaddows in a very contrasty situation is
> the highlights get blown, the opposite problem for metering for the
> highlights. If I meter for both, take 2 photos then I wonder how to merge
> them. I've experimented, but figure I might have missed the "best" way.


In PS I usually use a very large soft edged eraser (on a mask if it's
complicated) or draw a selection and feather the edge if it's a really
complicated edge. Usually a broad brush one-stroke type of approach is
effective and fast.
Anonymous
April 21, 2005 5:43:36 PM

Archived from groups: rec.photo.digital (More info?)

Mark Lauter wrote:
>> OK I see your point, but then I would suggest adjusting your
>> exposure based on shadow not highlight then using post processing
>> for any change based on color you might like similar to using a
>> colored filter. While it will not do exactly what you wanted to do,
>> I believe you will find it will work very well, maybe better,
>> depending you your final goal. I would also suggest shooting in RAW
>> in this case.
>
> In that case I will need to hurry up and buy a RAW capable camera <g>
>
> The problem with metering for the shaddows in a very contrasty
> situation is the highlights get blown, the opposite problem for
> metering for the highlights. If I meter for both, take 2 photos then
> I wonder how to merge them. I've experimented, but figure I might
> have missed the "best" way.

Raw may help, as might filtering the original exposure, but if you are
going to filter the original exposure I would suggest locking the white
balance and shooting color and then post processing.

--
Joseph Meehan

Dia's Muire duit
!