Re: Digital camera again...

thanks Peter for the information... and very clearly put -- tho not
simple.

Judy

On Wed, 4 Aug 2004, Peter Marshall wrote:

> Judy,
>
> Most of the zoom lenses on cheaper digital cameras have considerable
> barrel or pincushion distortion, and PTLens can correct this. It is
> obviously more noticeable on subjects with straight lines, such as
> architecture, but other things do look different after processing. Of
> course the distorted version may look better.
>
> Working close-up may produce different values of barrel or pincushion
> distortion, and if it was important to get things correct you would
> probably want to shoot a suitable test target with plenty of straight
> lines at the same distance (and to cover the range of focal lengths you
> use - the program extrapolates for focal length values between those you
> calibrate.)
>
> Panorama Tools (PT) is a set of routines first written quite a while back
> for correcting images, and its main use is in correcting the various parts
> of a multi-image panorama so they will fit together. You can also convert
> from one perspective to another - so I can take images shot in cylindrical
> perspective on a swing lens camera and convert to rectilinear should I
> wish. It is a powerful set of tools for manipulating images, but the
> interface only speaks maths. So a number of people have written Windows
> and Mac programs that provide a nice, easy to use front end for it. Some
> are reasonably priced, and certainly for Windows there are also good free
> versions, such as Hugin (which I wrote about on About Photography last
> year.)
>
> PTLens is one such, simplifying things even more by concentrating on just
> one aspect of the many things PT can do. As you can see from the web site
> it is really very simple in use.
>
> The situation got muddier a few years back when a large corporation was
> granted a US Patent on things that apparently included much prior work, by
> Dersch and I understand others, and tried to block the distribution of PT.
> However the software has remained available although they forced Dersch to
> remove it from his own site at least for a while. I've not kept up with
> the state of play on this. It happened with the Ambrotype too.
>
> Most of my information comes not from magazines, but from lists like this
> one, and various web sites dealing with photography. I often come across
> things I've forgotten on my own pages!
>
> Regards
>
> Peter Marshall
> Photography Guide at About http://photography.about.com/
> email: photography.guide@about.com
> _________________________________________________________________
> London's Industrial Heritage: http://petermarshallphotos.co.uk/
> The Buildings of London etc: http://londonphotographs.co.uk/
> My London Diary http://mylondondiary.co.uk/
> and elsewhere......
>
>> Peter, you say
>>
>>> PTLens does make a fairly dramatic difference on images from my Canon
>>> Digital Ixus. I use it as a plugin on PS7. It has a number of
>>> correction
>>> factors for different focal lengths and uses the appropriate one based
>>
>> Could you please give an idea of the kind of correction you would use
>> if for? I think of my problem as being unusual because of the nature of
>> the project and the close quarters... But it's not?
>>
>> Also, what is the "Panorama Tools" you mention in your last
>> sentence... Is that the "P" in PTL? Or?
>>
>>
>> meanwhile, thanks very much for the info...It's all something I've
>> never heard of and need to study. (I guess you have to read computer
>> magazines?)
>>
>>
>> Judy
>>
>> On Tue, 3 Aug 2004, Peter Marshall wrote:
>>> I've not used Debarrelizer, but you can also do this using the PTLens
>>> plugin, which is basically a free front end for this aspect of
>>> Panorama
>>> Tools (also free.)
>>> http://epaperpress.com/ptlens/
>>>
>>> Unfortunately PTLens is Windows only, but there is a similar program,
>>> LensFix, for Mac, but this isn't free, and I think Debarrelizer is
>>> cheaper.
>>> http://www.kekus.com/plugin/index.html
>>>
>>> You can use PTLens to correct distortion on any lens, and you can
>>> either
>>> create your own correction factors for new lenses or send some test
>>> images
>>> to the author who will do it for free to add to those he already
>>> distributes. I wrote about it in a feature a few weeks ago, the
>>> relevant
>>> page is:
>>>
>>> http://photography.about.com/od/digitalcameras/a/a062504_5.htm
>>>
>>> and on the previous page I also tell you how you can spend a few
>>> hundred
>>> dollars on stuff that does much the same thing but only for specific
>>> cameras and lenses.
>>>
>>> PTLens does make a fairly dramatic difference on images from my Canon
>>> Digital Ixus. I use it as a plugin on PS7. It has a number of
>>> correction
>>> factors for different focal lengths and uses the appropriate one
>>> based on
>>> the EXIF data.
>>>
>>> Panorama Tools is really an amazing piece of software by Professor
>>> Helmut
>>> Dersch, freely available but giving better results than some very
>>> expensive solutions.
>>>
>>>
>>>
>>> Peter Marshall
>>> Photography Guide at About http://photography.about.com/
>>> email: photography.guide@about.com
>>> _________________________________________________________________
>>> London's Industrial Heritage: http://petermarshallphotos.co.uk/
>>> The Buildings of London etc: http://londonphotographs.co.uk/
>>> My London Diary http://mylondondiary.co.uk/
>>> and elsewhere......
>>>
>>
>>
>
Received on Thu Aug 5 20:18:30 2004