[SEL] A Welding Question - Apprentices

[Elden DuRand]

Joe:

I don't have a problem with field of focus with a film camera, providing there's enough light to be able to stop the lens down and get a good exposure.  With a digital camera (a cheap one like I have) there is no iris so the f-stop cannot be set.  

What I refer to as distortion is the geometrical distortion.  In other words, if you were to take a photo of a curved data plate, one that's bent around a cylinder, for instance, it would appear to be taller in the center than on the ends because the plate is closer at the center than at the ends.

I was wondering if there is software that will correct for that distortion.

Take care - Elden  

> -----Original Message-----
> From: sel-bounces at lists.stationary-engine.com
> [mailto:sel-bounces at lists.stationary-engine.com]On
>  Behalf Of
> JR504 at aol.com
> Sent: Sunday, August 19, 2007 05:34 PM
> To: sel at lists.stationary-engine.com
> Subject: Re: [SEL] A Welding Question - Apprentices
> 
> 
>  
> In a message dated 8/19/2007 5:05:05 P.M. Eastern 
> Daylight Time,  
> edurand at mchsi.com writes:
> 
> Question:  Does your software have the ability to 
> remove the  distortion 
> caused when photographing a curved plate?  I know 
> this  distortion can be 
> diminished by using a long lens and backing off 
> but the  distortion will only be 
> lessened.
> 
> Take care - Elden  
> 
> 
> 
> Hi Elden,
> On my 35mm Camera when I need extended depth of 
> field focus I used a  smaller 
> aperture, because if you lengthen the time the 
> film is exposed it gives  you 
> greater focal length.  And even though I'm sure 
> you've tried it, try to  find 
> the center of your focus range and then snap the 
> picture.  
> What I mean is:
> Focus on the closest part of the image, then move 
> to the furthest part of  
> the image, then split the difference to take the 
> picture.  If your exposure  
> time is long enough it will look better on the 
> film than through the lens.
> I can't say if the same thing holds true for 
> digital cameras.
> Hope that helps.
> Joe Rappa
> Mexico, NY