HDR question

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wildtracks

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Martin Prothero
Edit My Images
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Coming from manual cameras (35mm and 5"x4") and shooting slide film, I am delighted to learn about HDR.

I'm in the process of soaking up as much info as I can about it and I have a specific question I am hoping someone can answer for me.

When you create 3 or more images ready to use for the HDR 'composition', does the final programme use just the exposure info or is is literally overlaying the individual images?

If it is the latter, does that mean that you can focus on foreground for one shot, mid for another and infintiy another and combine into a killer DOF image. Or does it not work that way? Has anyone experimented with this?

Obviously you can't refocus if you are creating the files from one raw image.

But the refocus idea would mean fantastic DOF at faster speeds or using a reasonable large aperture in lower light conditions.

Am I barking up the wrong tree here?:thinking:
 
Would be brilliant if it worked.variable DOF.

The HDR procedure overlays several images in layers to produces a 32 bit layer image. ( well that's the way Photoshop does it). You can then adjust the HDR images characteristic to produce the desired result.
It wouldn't produce the result you are trying to obtain. All you'd end up with is an unsharp image, as the unsharp parts would be overlayed on sharp ones.And I'm not sure if Photoshop would HDR images with the same exposure range. I've never tried it.

You could produce the result you are trying to archive, by taking you images, removing, the unsharp portions and then merging the sharp ones. depending on the subject this can be either relatively easy ( depending on your retouching skills) or a real pain if there is a lot of detail involved

The classic use of this technique is a wonderful landscape with a couple really close to the camera.
The normal DOF would not have encompassed both subjects. The 2 are shot separately , then combined. Done properly it's sometimes difficult to "see the join". Special attention has to be paid to lighting and the relative perspective and positioning of the two shots to ensure it looks genuine.
 
Chappers - Thanks for that...
I see more clearly now. If I had 3 images and one is in focus, the other two would still be out of focus. I just wasn't thinking it through.

What I was hoping for was 3 images, each with a different exposure (as in HDR technique) but each with a different point of focus, making a wonderfully deep DOF.

Nice place my imagination...:cuckoo:
 
Who knows what you want may be in the next version of Photoshop.
 
wildtracks said:
Chappers - Thanks for that...
I see more clearly now. If I had 3 images and one is in focus, the other two would still be out of focus. I just wasn't thinking it through.

What I was hoping for was 3 images, each with a different exposure (as in HDR technique) but each with a different point of focus, making a wonderfully deep DOF.

Nice place my imagination...:cuckoo:
Click to expand...

No you're not going mad, it's quite an established method and its generic term is Focus Stacking it's used a lot in Macro photography. There are several commercial software applications that can do this.

Just Google 'focus stacking' and the world's your oyster.
 
What happens when you ask CS2 to HDR three images where each image is well exposed and focussed for just one part of the image? Might you get an 'ethereal' look like I spotted elsewhere on this forum the other day, that you can get by Multiply blending a layer with the image with another layer with a 30-pixel Gaussian blur of the image?
 
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