Adobe Photoshop Training with Dan Margulis

Hello all,

I'm wanting to take my digital camera techniques (Sigma SD-9 w/ Foveon chip) to the next level and was curious about the techniques for mixing/blending/whatever two different exposures. I know all about taking an exposure for the highlights and a second one for the shadows but I'm unclear on the technique for using (I assume) channel mixer for combining the two to get an "extended" dynamic range.

Thanks,

Terry

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Terry

Here is a tutorial which addresses this issue

www.creativepro.com/story/feature/19197.html

Regards

Raymond

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Terry,

Also check recent posts about layer "blending options". It's a good way to use 2 exposures.

Lee

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First, I don't think there are that many cases where one needs to go to the trouble of taking two exposures unless you're trying to make some sort of artistic effect, as where the foreground object doesn't move but the background does. In that case the double exposure can do things that Photoshop can't. But most of the time if you're just trying for more highlight and shadow detail this can be gotten out of a single exposure with the right technique.

The Shadow/Highlight command of Photoshop CS has a lot of utility in opening shadow detail because it has a quasi-sharpening function in addition to stretching the range of the shadow. If you want more control, or Photoshop CS isn't available, the following double-exposure trick will work, and will also work most of the time if you only have a single exposure.

1. Start with one image good for the highlights and another good for the shadows. Obviously, they must be the same size and register with each other exactly.

2. With both images open and the good hilite picture active, Image: Calculations>Source 1=Good Hilites: Gray ;Source 2=Good Shadows: Gray; Mode=Soft LIght, Destination=Selection.

3. Select: Invert Selection

4. Layer: Duplicate Layer

5: Image: Apply Image, Source=Good Shadows, Mode=Normal

You now have unified the two images roughly as desired, with the good shadow picture dominant in the dark half and the good highlight dominant in the white half. If you like it as is, you're done. If not, activate Blending Options in the Layers palette. Move the bottom right slider over to the left to disallow the blend in the highlights, which wasn't going to be happening anyway because the highlights were masked out when step 5 happened.

Then, split the lower right slider with the option key+click, move the left half of it to the left until the blend is more to your liking. If necessary, cut the opacity of the top layer when done.

If you don't have a second image with better shadows, but are trying to make better shadows on your own, the same technique will work. The only change would be:

5. Image: Apply Image, Source=Same Image, Mode= Screen.

Dan Margulis

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I think there may be two different situations being referred to by the same "name" here.

When this was first discussed, the technique was mentioned as a way to effectively extend the dynamic range of a D-SLR by taking multiple images at different exposures and then compositing them. When that is done, it is the "mid-tones" of both images that are desirable, but of course the mid-tones of one will be the brighter areas of the scene and the mid-tones of the other will be the darker areas of the scene.

Personally the only time I wind up doing this is landscapes where it is otherwise impossible to bring a shot within the dynamic range of the camera. At Arches National Park, for example, there are certain rocks that are lit beautifully while others are in shadow, and combining images can help create a single image showing detail in both the lit and shadowed rocks.

Not sure if this is on-topic or not, since it relates to both capturing & processing of images, but in any case I wanted to make sure there was some clarity on the idea.--David

--David Cardinal

Pro Shooters LLC

http://www.proshooters.com

http://www.nikondigital.org

There are two sets of sliders on the bottom and a slider which controls overall opacity above. Can you clarify a bit more?

Secondly, I shot an assignment last night which fell into this niche category. I was assigned to photograph lighting fixtures, which which translucent but with a pattern that was etched in the exterior housing that needed to be visible. The client was the light manufacturer. The job needed to show how the light was used in a hallway, which was not large enough to place fill lights on one side. The difference between keeping detail in the lights and the overall lighting of the hallway was more than 9 f-stopswell beyond digital and film's ability to retain detail in deep shadows (dark woods doors) and the lights themselves. We had no place to place lighting, which would have boosted the shadows to the point where I could have recorded the highlights as well in the lights. Normally, the lights are not critical, but they were the star in this shoot. We didn't have much choice but to shoot two exposures, one for the lights and one for the room. What I planned on doing was dropping one shot over the other in layers in PS, then fooling with the opacity until I got what I liked. I tried what Dan suggested above (great to get help in your mailbox when you most need and least expect it!) but adding a feathering on the selection so the light doesn't fall off as fast. I still think I'm do for some layer masking for some detail work, but if anyone else wants to throw proven suggestions my way, I'd very very grateful.

Happy New Year, to one and all. Given the international nature of this list, I suppose some of us are closer to the New Tear than others

-- Mike DeSantis, DeSantis Photography

www.desantisphotography.com

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Mike DeSantis writes,

I was referring to the bottom right slider, that is, under Blend If Gray, Underlying layer. This is an powerful and complex function, particularly if you know your channel structure, but the method I was recommending is simple.

You start with a layer on the bottom that's good for the highlight. On top you have a blended layer that tries to incorporate a better shadow but has more or less the same highlight information as the bottom layer. Chances are, this has made a big improvement but not enough. Most likely the image was lightened too much in the midtone.

The blending sliders by default let Photoshop layering take its normal course. That is, we see the top layer and not the bottom layer. The bottom slider says to use the top layer for any value on the bottom layer between pure white and pure black, i.e. always. If you start to horse around with it, you'll see a combination of layers.

If you move the bottom right slider very slightly to the left, this excludes areas that are quite light in the bottom layer. In those areas, the bottom layer will show through. In this particular case, you shouldn't see any difference at all because the top and bottom layers are nearly identical in their lightest ranges.

If you continue to move the slider to the left, you will suddenly see parts of the top layer disappear and be replaced by the bottom layer. It's still a single image, of course, but now there is a disagreeable hard break where it merges the top layer into the bottom.

To correct this, hold down the Option key and click on the slider. This will split it in half and you can move the halves independently. If you now move the left half of the slider further to the left, the hard break will disappear and no feathering will be needed. However, once you get the hang of it, you'll want to reposition both the left and right halves of the slider to get exactly the effect you want.

The rule is: lightness is to the right. Any part of the picture where the bottom layer is lighter than the right half of the lower right slider, you're going to see the bottom layer and not the top. Any part where it's darker than the left half of the same slider, you're going to see the top layer exclusively. And for any part where the bottom layer is darker than the right half but lighter than the left half, then Photoshop makes a smooth merge between the two layers.

Happy New Year to the entire group.

Dan Margulis

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Date: Wed, 31 Dec 2003 22:29:04 -0500

From: "Michael Demyan"

Subject: RE: Mixing/blending shadow and highlight exposures

Most digital SLR's take photos in the "RAW" mode which allow a minimum of 4 stops exposure adjustment to the RAW file.

Taking one photo at 1/3 to 1/2 stop under blowing out the highlights will provide all you need. You can then extract as many TIFF images from this one shot as you like varying the exposure on each shot and Pin Register one over another using layer masks or any other method of blending that suits the purpose and image.

I use the RAW image whenever I am presented with a tricky lighting situation since each extraction is from the same base file (negative). No need to deal with changes in position and lighting.

My Word!

Michael C. Demyan

Fine Photography & Digital Graphic Design

www.mikedemyan.com

www.pbase.com/mdemyan