Replicating "multiple exposures" in photoshop

I own a Canon 300D, which will not allow me to take multiple exposures,
and a Canon T2 which does do multiples. I do digital as well as
regular film work. I find the digital camera helps me with my film
shots by giving me some insight into how certain experimental shots
will turn out. I avoid having to waste film, paper, and chemicals by
"previewing" my shots digitally.

Anyway, I am experimenting with multiple exposures and I'd like to be
able to do my initial experimentation with my digital camera and then
convert the results over to film for my final shots. What I would like
to know is how I can take 2 seperate images and in photoshop convert
them to a single image that will represent approx. what I would get by
taking the the shots on my film camera. I'm thinking that putting both
image as a layer and then setting one layer to "lighten" or "screen"
may do the trick, but I'm not sure of the blending modes that would be
correct for me to convert f-stops.

Example of what I am thinking:

image A taken digitally at f8/250
image B taken digitally at f11/125

to see what this image would approximate taken with film (multiple
exposure)
photoshop:
I have 3 layers
--black base layer
--image A (Burn 50%)
--image B (Burn 50%)

This would give me a rough idea of the image I would get on film if I
exposed A at f8/125 and B at f11/60 (half the time each of the
originals). I'm not sure if I need to use burn, lighten or screen or
something else. or if this way of calculating would even be correct.
Can any photoshop guru's out there help me on this?

wrote in news:1101072967.509810.310530
@z14g2000cwz.googlegroups.com:

...

You can use Normal blending.

You shall not compensate. You take each photo as
it is a single photo, then you just blend. No need
for exposing half the time.


/Roland

wrote in news:1101072967.509810.310530
@z14g2000cwz.googlegroups.com:

...

You can use Normal blending.

You shall not compensate. You take each photo as
it is a single photo, then you just blend. No need
for exposing half the time.


/Roland

When I take the shot on my film camera, they will be half exposure
each. Otherwise the photo will come out over-exposed. (remember I'm
doing multiple exposures) - Unless I compensate on the original shots.
But for the example assume I take the 2 individual photo's at 100%
correct exposures.

I'm not sure normal blending will work as I've done a few tests already
and the image comes out quite a bit flatter than the film shot. I want
to replicate (in photoshop) the light reacting to the film in my
camera, not just have the image look good on screen - as my final shot
will be done completely with film.

When I take the shot on my film camera, they will be half exposure
each. Otherwise the photo will come out over-exposed. (remember I'm
doing multiple exposures) - Unless I compensate on the original shots.
But for the example assume I take the 2 individual photo's at 100%
correct exposures.

I'm not sure normal blending will work as I've done a few tests already
and the image comes out quite a bit flatter than the film shot. I want
to replicate (in photoshop) the light reacting to the film in my
camera, not just have the image look good on screen - as my final shot
will be done completely with film.

wrote in news:1101074094.107493.139820
@f14g2000cwb.googlegroups.com:

When I take the shot on my film camera, they will be half exposure
each. Otherwise the photo will come out over-exposed. (remember I'm
doing multiple exposures) - Unless I compensate on the original shots.
But for the example assume I take the 2 individual photo's at 100%
correct exposures.

Yepp - that is correct.

I'm not sure normal blending will work as I've done a few tests already
and the image comes out quite a bit flatter than the film shot. I want
to replicate (in photoshop) the light reacting to the film in my
camera, not just have the image look good on screen - as my final shot
will be done completely with film.

Double exposures do generally decrease the contrast.

The Normal blending will take (A+B)/2. If A=B, then you
will get the result A and you will have the same image.
No change of contrast - just as exposing more does not
change the contrast.

But if A!=B, then the images will act as preexposure
for each other. One example is if image A goes from
exposure 0.1 to exposure 0.9 and image B is a constant
0.5, then the result will go from 0.3 to 0.7, decreasing
the contrast from 0.8 to 0.4. This is an extreme example.
But real blended images will do the same - maybe less
extreme.


/Roland

wrote in news:1101074094.107493.139820
@f14g2000cwb.googlegroups.com:

When I take the shot on my film camera, they will be half exposure
each. Otherwise the photo will come out over-exposed. (remember I'm
doing multiple exposures) - Unless I compensate on the original shots.
But for the example assume I take the 2 individual photo's at 100%
correct exposures.

Yepp - that is correct.

I'm not sure normal blending will work as I've done a few tests already
and the image comes out quite a bit flatter than the film shot. I want
to replicate (in photoshop) the light reacting to the film in my
camera, not just have the image look good on screen - as my final shot
will be done completely with film.

Double exposures do generally decrease the contrast.

The Normal blending will take (A+B)/2. If A=B, then you
will get the result A and you will have the same image.
No change of contrast - just as exposing more does not
change the contrast.

But if A!=B, then the images will act as preexposure
for each other. One example is if image A goes from
exposure 0.1 to exposure 0.9 and image B is a constant
0.5, then the result will go from 0.3 to 0.7, decreasing
the contrast from 0.8 to 0.4. This is an extreme example.
But real blended images will do the same - maybe less
extreme.


/Roland

wrote:
When I take the shot on my film camera, they will be half exposure
each. Otherwise the photo will come out over-exposed. (remember I'm
doing multiple exposures) - Unless I compensate on the original shots.
But for the example assume I take the 2 individual photo's at 100%
correct exposures.

I'm not sure normal blending will work as I've done a few tests already
and the image comes out quite a bit flatter than the film shot. I want
to replicate (in photoshop) the light reacting to the film in my
camera, not just have the image look good on screen - as my final shot
will be done completely with film.


Yes, 'Normal' blend mode is the normally correct one. Don't forget to
change the opacity or you won't be able to see anything behind that
layer. Of course, changing the opacity in Photoshop is the digital
equivilant of the exposure compensation in film double exposure. It's
just easier and more flexible digitally.

Clyde

wrote:
When I take the shot on my film camera, they will be half exposure
each. Otherwise the photo will come out over-exposed. (remember I'm
doing multiple exposures) - Unless I compensate on the original shots.
But for the example assume I take the 2 individual photo's at 100%
correct exposures.

I'm not sure normal blending will work as I've done a few tests already
and the image comes out quite a bit flatter than the film shot. I want
to replicate (in photoshop) the light reacting to the film in my
camera, not just have the image look good on screen - as my final shot
will be done completely with film.


Yes, 'Normal' blend mode is the normally correct one. Don't forget to
change the opacity or you won't be able to see anything behind that
layer. Of course, changing the opacity in Photoshop is the digital
equivilant of the exposure compensation in film double exposure. It's
just easier and more flexible digitally.

Clyde

Ah, I see. ok, but what about layering order though? I'm noticing
when I have one layer over the other both blended 50%/50%, the top
layer is dominant - this is why I was thinking lighten instead of
normal... as the effects seem to be the same regardless of layer
order... I'm not sure yet about the way lighten blends color though.