Pro Photo
Perspective and Crop
Perspective and Crop of a 3D world with a 2D photograph sometimes requires photo manipulation.
Imaging a 3D World
By Tim Maxwell
Imaging a 3D world with a photograph sometimes requires some slight photo manipulation. Often times, adjusting a photo is very basic, such as straightening the image with the horizon or cropping the image to bring more emphasis to the subject. Other times it can be slightly more difficult, such as fixing the perspective of a photograph.
For crop and straightening, those are things I automatically check and correct on each image I take, except when it is desirable to leave as is.
Perspective Correction
For perspective correction, these types of corrections generally come into play with buildings or images where there are defined lines. I’ve always thought it interesting how perspective in a 3D world, viewed with our eyes, can be so much different than what we see in a photograph.
If one were to look at a perfectly rectangular 20-story building from 300 feet away, straight on, our brain will interpret the building as perfectly rectangular. And while the building is perfectly rectangular, our eyes do not see it as such. If you follow the lines up from the left and right sides of the building, one will see they are not straight. The left side is angled slightly in and the right side is angled slightly in. If one were to draw an imaginary line up from the left and the right, eventually the left and the right lines would converge (in photography, these are called converging lines). Our brain, knowing we live in a three-dimensional world, adjusts for what our eyes actually see, and interprets the building as being rectangular.
Unfortunately (or fortunately depending on your perspective), in photography, the camera captures the converging lines perfectly. When photographing, for example, a cityscape, or a building/room from a side angle, the image can look off. This is where perspective correction comes in.
Here are some before and after images.
Example 1
The image below is an untouched photo I took of the Assembly Room from Independence Hall in Philadelphia. This image has a few things that need adjustment.
1. It needs to be cropped as there is an arm of person in the far left-middle. Besides the arm, it may be advantageous to center the image a little better.
2. The image was taken from an angle. If you look at the back wall and follow some lines up, they lean toward the right. I will want to correct that.
3. The image also needs color and light corrections.
The adjusted image is the result after fixing the issues. The crop is nice, the lines on the back wall are straight, and it has good color & light.
Image that needs to be adjusted:
Adjusted Image:
Example 2
This is an image from Lake Carolyn in Irving Texas. The building is about a 20-story building. The image was taken at an angle from the building, so it appears to be leaning to the right. This image needs to be cropped as well as needing the perspective corrected. Add light adjustments / color grading and you have a fine image in the end.
Image that needs to be adjusted:
Adjusted Image:
Example 3
We’re back at Independence Hall in Philadelphia, but outside in the courtyard. This image was taken close to the building, looking up. It was a handheld shot, so not only is the perspective off, but it is not straight.
This will need a crop, straightening, as well as a perspective fix. The problem here is the image was taken so close, fixing the perspective will not make it look 100% right, but I think it did come out well in this case.
In the final image I also adjusted the light & color and decided to remove the tree since it was distracting from the subject (it didn’t add any value to the composition).
Image that needs to be adjusted:
Adjusted Image:
