Perspective Correction or Distortion

Monday, January 16, 2012

Perspective Correction or Distortion

     Perspective correction or distortion is 1 useful feature in most editing software programs. Perspective is simply how repeating items in a photo get smaller and smaller as they get farther away from the camera. An example is of train tracks that seem to get so small at about a mile, that they almost seem to disappear, hence the term "vanishing point". The term perspective correction allows for a lens to reduce this distortion. The longer the focal length, the farther the camera has to be to the onjects. So on a tabletop, for example, all items on a tabletop will be "relatively equidistant" to the camera with a long lens. Whereas, with a short focal length lens, the closest item might be as close as an inch, whereas the farthest item might be 2 feet away.

     Not everyone has several lenses, so they might have a zoom that can create the same effect of distortion or distortion correction.However, in Photoshop and other softwares you can exaggerate the distortion or correct the distortion when the lens is not enough. So let's look at both the correction and the distortion.

 Here's a trio of Manoil toys that I have listed this week on E-Bay

Step 1:  Select All

After "Select All" ,you get the white and black lines around the photo

Step 2: 

Edit>>Transform>>Perspective

When you apply Edit>>Transform>>Perspective,

You will get small little squares at the 4 corners of the photo.

When You move the mouse to any  of these squares,

 and press down and pull the cursor (the small arrow),

the distortion or correction will occur.

Step 3:

Deselect the image (see below)

The 4 smaller squares in the 4corners vanish.

Step 3

Step 4: Fill in the empty areas because of the new distortion.

tHere's another image of the same Manoil  convertible that I sold last year.

Because it was a single image, I purposely distorted the perspective in order to make the image more interesting.

However, let's say I was shooting this for the Manoil company or even photographing a "rear car" suck as a Buick for GM, they would insist that there be no distortion.

A handy feature of Photoshop, and perhaps other software programs is the "grid".

The "grid" is simply a repeating pattern of squares that go over the image.

The grid allows you to compare different parts of an image to see if there is distortion.

In the above example, the grid is too large.

This is how you show the grid.

Of course, when you are finished, you simply do the same command and it disappears.

Here is how you adjust the grid size.

The grid that I currently have is too big for a small image.

It's good for a large image.

A grid every 1 inch is "OK".

A subdivision is simply have many grid lines that you have between 2 main grid lines

Here's another choice.

This is the best choice for this particular image.

tHere's the  grid every .5 inches with 4 subdivisions.

tI used the same series of cammands from the 3 items above for the single car.

Select All>>Edit>>Transform>>Perspective

I widened the back of the car. I could have did the opposite to the front of the car,

 that is, to narrow the front.

The top photo is the original image, 

while the bottom is the corrected perspective image.

Notice the wider back of the car in the bottom image.

Thanks for dropping by to visit,

and Have a good morning, good afternoon, or good evening, 

wherever you may be.