Digital Scheimpflug ?Please help on how to accomplish this.

Hi everyone, in a recent post by Tony Kuyper, he mentioned "digital Scheimpflug" to get sharp focus from near to far.
If I am right, that means at least two exposures, with different focus - one near, one far, and then merging the sharpest parts of the two images.
I haven't made it to the merging part yet.
Just recently I shot a few photo's with that technique but while reviewing the images on my LCD, I already noticed that the two frames are not identical due to the different focus - the framing changes slightly but too much in order to align both files, (I guess). I wonder if that has to be taken into account while merging, or if I did something wrong while shooting the two frames. Was the focus difference too far (just 2 -3 feet and then infinity)?
Any help, links, tutorials...? Tony would you help me here...?
Thanks everyone!

Were you using an internal focus lens?

Basil

Dietrich,
I haven't seen Tony's post, but I have experimented with this technique quite a bit and have had some success, but I have found that the best way to focus stack is to use software designed for it. The following link makes reference to several packages I have tried.
http://en.wikipedia.org/wiki/Focus_stacking
CombineZM is free, but has a steep learning curve. It works quite well though and is very powerful for free software. Helicon Focus works well, is very powerful, and is easier to use, but is expensive. I own Photo Acute Studio and just recently they added focus stacking ability. It's features for focus stacking are not as comprehensive as the other two packages I mentioned, but it seems to work. I need to test more.
As you've discovered, when you change the focus, the focal length of your lenses changes, even if minutely, and this makes blending images challenging to say the least. You would actually need to resize all images to make things line up. I found I wasn't patient enough for this, and that's what drove me to search out some software. All the packages I mentioned do the resizing automatically. This technique of focus stacking is quite popular in scientific circles for photo microscopy. I'd post some images, but I am migrating my hard drives right now, but I will try to do so later. Good luck with this. If you find any new info, please post.
Paul

As Paul mentioned, Helicon Focus software is a package that does correct the change in scale and perspective that occurs. I thought I'd add that they have a free download you can try before buying and nice photo examples on their web site, www.heliconsoft.com.

There were beautiful posters of mineral specimens made using focus stacking at a Gem & Mineral Show I went to earlier this year and I'm looking forward to playing with this technique myself, perhaps during the holiday break!

Cindy

Thanks for your answers!
Good to know that what I experienced (different framing) has to be considered and corrected.
Thanks for the hints on the software and the resources. I haven't looked at them yet, but I sure will (I just came home from and had couple of beers... )
Basil, puh you are asking me questions, but I think it is not internal focus. My lens is the
Canon EF 24-105mm IS, USM.

The simplest way is to buy the TS-E's from Canon. No software needed!

I couldn't figure out whether your lens is IF or not - Canon Switzerland doesn't list the specs in much detail (Nikon guy here). In any case, IF lenses shorten their focal length as you focus closer, which could of course cause the problems you were experiencing. Hope you get it sorted...

Basil

Hi Basil, thanks for doing research on my lens - i have'nt investigated this myself yet. I think I will try one of the software-packages.

Check out the Helicon software Dietrich. I downloaded a 30 day free trial and it works just like they advertise. I shot a series of three exposures with different focus points and the program put the three images together perfectly, made a beautiful 12 x 18 print, sharp from front to back.