Guessing Furniture Dimensions from a Photo
Is there a way to estimate the sizes of objects in a photo? April 20, 2011
Question
Is there a way I can get the dimensions of an object in a photo? A potential client gave me a photo of a table she wanted built. It's a dining table, so I can safely assume it's about 30 high. How can I get the other dimensions?
Forum Responses
(Furniture Making Forum)
From contributor D:
You can pretty accurately derive everything from the known dimension by the following cross multiplication formula: Say the height of the table in the photo is 4 inches. Since you know the actual height of the table to be 30 inches, then the scale of the photo is 4 inches = 30 inches, so your equation for everything else is 4/30 = x/y, with x representing the dimension in the photo, y representing the actual dimension. To get the length, measure the length in the photo, say 6 inches, plug that into x. That makes the equation 4/30 = 6/y. If you multiply 6 x 30 (=180) and divide by 4, you get y (45). So, the length would be 45 inches. Just do that for all the dimensions, and you'll be pretty accurate.
From contributor V:
Contributor D is correct in his methods. I'll add that this is most effective at vertical dimensioning when the photo is taken straight on to the table height, as in his example. Odd angles make for very tricky computation/guesswork. Dimensions in perspective can be calculated, I'm told, but the math is well beyond my ability. Wide angle lenses can really complicate things.
If you get a few good dimensions, then it is fairly easy to extrapolate from there. When you draw the project, just keep a discerning eye in place so it comes together nicely.
From contributor W:
Also keep in mind that once you have calculated dimensions, compare them with ergonomic standards. Then ask the customer where they will be using the table and the number of people they want to have sitting for a meal. Most of the time when someone has asked me to make something from a photograph, it is the style they want, but to fit their purpose.
There is a Krenov story about a lady who wanted one of his wall hung cabinets. He asked and went to see where it was to be used. He then made her a table. She was happy.
From contributor G:
More as an amusing side note that an answer to your table problem... The rule of thumb for scaling things from pictures or paintings with a human face square on (and the item in about the same plane as the face) is to allow 63mm between pupil centers.
From contributor L:
Since you know the table is 30" or so, you can take an architect's scale and find the scale that matches up. Draw lines out from the photo at change points and use your scale to estimate. This should put you in the ballpark.
From contributor A:
It would be nice if you could scan it then use a modeling program to give you all the dimensions.
From contributor N:
SketchUp allows you to import photos and make drawings from them.
From contributor Q:
I would just call the client and ask what the desired dimensions are.
From contributor U:
It sort of depends on what you mean by "object." If the object is part of a flat image - say, a table in a photo - then the measure tool is the way to go. With some additional work, you could make a selection of the object, then check the info panel for the selection dimensions. Same goes if the object is the lone contents of a layer. Load the layer as a selection and check the info panel.
