Photoshop technique: incremental transform

[Paul Schilliger]

My problem is this: I have taken a large group of people in a very small place. I had no possibility to use a normal lens and as a result of using a slight wide -angle, the faces and bodies of people become increasingly wide towards the side s. Now, I have two alternatives: delivering the picture as it is and being curse d by the ladies who are not advantaged, or retouching the shots digitally. But I do not know of a technique that allows incremental resizing and would correct t he effect without having the people at the center being transformed in two dimen tional things. Is there a possibility to work this in Photoshop? This would be n ice as well to correct other wide-angle shots that show too much stretching.

[Richard M. Coda]

You might be able to copy a selection to a new layer, adjust that, and then merge it back together... it's worth a try. Or you could just tell them that "that's the extra 10 pounds that the camera adds. <grin>".

[Bruce Wehman]

There might be a plug-in that will do this very thing, however, the best way I have come up with is to drag a selection between heads and right out to the border, including the top and bottom borders as well. Feather it a little and use the distort function to drag the side border in toward the center of the image. You will have to do it for each side and more for the people on the edge, since they are distorted more. You can't do it too much or else it will look funny, but it does a passable job.

[Struan Gray]

One way to do this is to transform the perspective from the wide-angle rectilinear view of the short lens to a cylindrical view, as if the shot had been taken with a rotating panoramic camera. Helmut Dersch's free Panorama Tools program will do this, and his website has an article showing the visual effect - look under "About wide angle perspective".

The main site is here, but is temporarily closed:

http://www.fh-furtwangen.de/~dersch/

Fortunately, there are at least two mirrors:

http://www.all-in-one.ee/~dersch/

http://home.no.net/dmaurer/%7Edersch/Index.htm

Finally, you can do this in Photoshop if you create a distortion map for the distort filter using gradient fills or an external numerical program, but it's a royal pain to get right.

[Michael Chmilar]

If you have access to a 3D package, you could do this:

Create a sphere. Stick your image onto the sphere as a texture map (like a sticking a label onto a ball). Create an orthographic camera looking at the texture map. Render it.

Or, you could do it for real: print out your photo; paste it to a large ball; rephotograph it. :-)

This texture mapping process is really just distorting the image, and then resampling it. You don't really need full 3D capability to do it, you just need to compute the distortion function, based on a sphere. It should be possible to write a photoshop filter that can do this in the 2D domain. It would be a very handy filter to have.

[Jonathan Brewer]

Try making selections around the areas that have distortion. Just leave the parts that are alright alone. Use transform-the skew tool to adjust that part of the image. You can work this little by little with the skew tool. Click on and adjust the top, bottom, and sides, leaving the center the least affected. If you don't like the results, just click on revert, and start over.

Using the skew tool will leave a gap between the selections you've adjusted and the rest of the original image which you'll have to deal with and replace, but it is the simplest fix.

[Paul Schilliger]

Thanks for the tips! Lot of things and techniques to investigate... I have used the sides selections transforms as before and it was good enough, as all faces were in the center line of the im age. But if the corners were important, there are some tips here I should try. However, it would be nice havi ng a photoshop filter to do that job in a smooth progressive manner. It would be useful to be able to transform a very wide streched 6x12 into a nice balanced 6x9 image.

[Kevan O'Meara]

It's a bit late, but "photo window" does distortion maps, allowing you to stretch, align, and otherwise manipulate your image in a variety of geometric ways. Useful for removing lens distortion, perspective distortion, aligning two images. You can download a free trial version or buy it for around $50.

[Paul Schilliger]

Thanks Kevan. This maybe a product that I was suggested before, the difference i s that it is not incremental, meaning image in the center is compressed too. Where does one get hold of the tr ial version?

[Massimo Squillace]

Paul,

The product Kevan mentions is probably "Picture Window 3.1".

It is priced $49.95 for the standard version, but you will want the "Pro" version at $89.95 since the features you need are there (and a lot more).

The trial version (a time-limited "Pro" edition) can be downloaded from www.dl-c.com .

This software package was written by a photographer which also happens to be the programmer who created the first version of Lotus 1-2-3, and I think it deserves wider recognition than what it already enjoys.

Hope this helps.

PS: Congratulations for you Web site. I especially like the natural quality of the greens in your beautiful shots.

[Paul Schilliger]

Thanks Massimo. I just checked the website, it is new to me. The software is unf ortunately not Mac supported yet. Thanks for your comment!

Paul