Exposure and Focus Layering

This question pertains to nature photography technique and the use

of Adobe Photoshop. I have heard about, but not yet tried using two

separate frames to help improve (or even out) foreground and

background exposure for landscape photography and combining them in

Photoshop. This understandably would be a good alternative to using

Split ND filters.

My question is has anyone tried separate frames while focusing at

different portions of the scene to increase depth of field by

combining everything in Photoshop? I have done a multiple exposure

picture focusing first on the background and than on the foreground.

This did not have the desired affect even though it was interesting.

Has anyone tried this technique on different exposures (frames)

separating both foreground and background meter settings and focusing

to optimize even exposure and increase depth of field? This of

course combined in Adobe Photoshop via layers, etc. Would I get the

same zoom effect even on separate frames?

The technique I've read about is to keep the focus point the same and then

shoot at different combinations of f-stop & shutter speed and to build up the

apparent depth of fiel that way.<P>In other words if your metered exposure is

f/16 @ 1/30th, then shoot at different combinations of f-stop and shutter speed

that add up to this illumination level

Yes, it's possible and have been done. I've seen discussion of this technique and images generated by it somewhere on the web. Sorry, don't remember where.

This is most commonly used in macro photography where DoF problems are especially bothersome.

The way it works is as follows. You make several exposures of the same subject varying nothing but focus. Each image becomes a layer in Photoshop. Next you divide the image in horizontal strips (as many as you have layers) and apply gradient masks to each layer in such a way that the closest-focused image/layer is the bottommost strip and the fartherest-focused image/layer is the topmost strip. The hard part about it is the correct positioning and boundary blurring of layer masks.

The images I've seen look quite nice and used many image/layers -- around eight, I think.

I have tried this in some landscape situations where I wanted to have sharp focus on a foreground element, such as a clump of wildflowers, while also maintaining focus on a background feature, such as a hill. Obviously, success requires that the different frames be identical in exposure and position, changing only the focus.

I found that simply changing the point of focus from close to far results in a slight displacement of the apparent position of near objects on the film plane (i.e., near by objects do not register in exactly the same positions in frames taken with different points of focus). This makes it difficult to blend layers. One solution suggested by an earlier poster would be to use many exposures (layers) so that the displacement was minimal from frame to frame. That strikes me as fairly laborious. I have, however, had good results using just two exposures in cases where the middle ground allows easy blending of images in Photoshop. An example of this would be photographing from a high point (above a river valley or canyon) with a foreground plant in focus in the first frame--the second frame would focus on the opposite side of the valley or canyon. If the middle ground is occupied by shadowed area in the valley or canyon without important photographic detail, then it is much easier to blend the two layers in Photoshop.

With 35mm and most MF cameras, and some LF cameras, changing the focus requires you to move the lens toward or away from the film while the film remains fixed. This causes the scene to change slightly at different focus positions because the lens is seeing it from a different vantage point.<P>

A camera that allows you to focus by moving the film while keeping the lens fixed, such as a monorail large format camera, will work best for this technique, as the subsequent images will maintain the same relationship between all the parts of the scene. They can then be layered and the desired parts of each image selected.

"A camera that allows you to focus by moving the film while keeping the lens fixed, such as a monorail large format camera, will work best for this technique, as the subsequent images will maintain the same relationship between all the parts of the scene. They can then be layered and the desired parts of each image selected."

Alan -

No, it won't. The sizes will be changed, although to a slightly lesser degree...

You either need extremely careful zooming, or resizing in Photoshop.

"No, it won't. The sizes will be changed, although to a slightly lesser degree..."<P>

I reckon that's true, but keeping the lens fixed (relative to the subject) and refocusing by moving the film plane should still offer the best means of getting a series of images that can be layered. Of course, if you're using a view camera, you'd probably just use tilts to get everything in focus in just one image...

Tilts help sometimes, but not always. Also you need lenses with excess coverage, which means more expensive. And heavier, which doesn't help either. Stopping down to f/64 or so is usually better!

LF user