Using Perspective Crop Tool for re-angling shots

You might sometimes want to take a photo from an angle that is not easily feasible so you compromise and take it from another angle. A common scenario is trying to take a picture of a painting dead on only to realize later you were pretty far off so you want to adjust the photo. In my case I wanted to take the photo facing straight into a construction building window opening but I could not get close enough.

My motivation was to estimate how thick the floor cement between each floors were when all I really knew was the height of the window opening. (note since it’s all relative and a matter of proportions we don’t really need to re-angle the photo to approximate this as we could measure this proportion directly from angled photo. However for demonstrations purposes we will do it anyways).

Steps

Step 1. Select Perspective Crop Tool

Open your image in Photoshop then left click and hold on the crop tool from the toolbox and select “Perspective Crop” from the drop-down.

Step 2. Select edge points

Once the perspective crop tool is activated

1. Click on each corner to re-angle your image.
2. Press the enter key to finish.

Left Image: While using Perspective Crop Tool. Right Image: After pressing enter.

Step 3. Measure the height of the window opening

1. Select the Marquee tool (I prefer to use the Marquee Tool rather than the Ruler tool to make measurements). To activate it you can press m or click the icon in the toolbox.

2. Measure window opening by left clicking and dragging from one edge to the other. We get a measurement of roughly 119px.

3. Measure the cement slab by repeating the same process (to deselect region from step 2. you can press CTRL+D). We get a measurement of roughly 13px.

Step 4. Calculate with proportions

We know for a fact that the window hole opening is 9 foot 11 inches that’s a total of 119 inches.

We now have a simple ratio where 119 inches is equivalent to 119 pixels (WOAW this is a complete coincidence, whatever number you get just follow the procedure). We now want to find out what 13 px is equivalent to in inches.

119 pixels / 119 inches = 13 pixels / x inches

(119 inches * 13 pixels) / (119 pixels * x inches)

x inches = 13 pixels

x = 13 inches or 1 foot 1 inch

Conclusion

The closest distance and closest angle you can get to the actual desired shot the more accurate you will get with this approach but this gives you a quick an dirty way to make such approximations.