Replies

1. 
   Alan | Apr 18, 2002 05:54am | #1

   Terry,

   VERY difficult.  If the piece is photographed straight on, that is at a right angle to the point of view it might be possible.  The picture would also have to contain an object of known size right next to the parts you want to measure.  If such an object is there, then measure it, and then some simple algebra will give you the measurements of the piece.  For example, if there is a yard stick on the floor right next to the bed (it must also be at a right angle to the point of view) and it measures an inch in the photo, then you know that the scale--in that part of the photo--is 1"=3'.

   N.B., if, for example, the yardstick is next to the footboard, and the point of view is looking at the footboard with the headboard in the distance, the scale will not work for the headboard.  As you know, objects appear smaller as they recede in space.  The only way you could measure the headboard would be if the headboard has an element the same size as the footboard.  For example, if the footboard is 6' wide (2" on your ruler) and the headboard measures 1 1/2", then for the headboard the scale would be 1 1/2"=3'.

   If, however, the bed is photographed at an angle, it would be impossible to get anything approaching accurate measurements.  Again, because objects appear smaller as they get farther away, the closer object would appear larger than a farther object--even if they are exactly the same size.  Another aberration is that parallel lines seem to converge as they recede in space; so the board at the far corner of the footboard, for example, would measure narrower than it would at the near corner.  So if the photograph shows the bed at an angle no scale correct for the side near the footboard would be accurate for the side nearer the headboard.  All these aberrations vary with the angle of view, the length of the lens used, and the distance from the camera to the object.  Again, all this assumes there is an object of a known size next to the part you wish to measure.

   You could get close if you know the size of the bed.  You would proceed the same way.  E.g.  if you know it's a king-size bed (which if I remember correctly are 6'x7') you could use those measurements to determine your scale.  But all the same problems of perspective would assail your efforts.

   In short (hmmmm...) it might be possible to get an approximation, but you could not get anything like an exact measurement.  It would be most unlikely that you could size the width of the stock, for instance, or really get any "measurement" you could trust.

   My advice would be to use the photograph as a source of inspiration rather than a plan.  Sit down with your drafting board and draw a bed with the proportions you think look good, using the photographed bed to help you give it the style you want.

   Awfully long and not very helpful, wasn't it?  Sorry, but I'm one of those who gets paid to talk for a living.

   Alan

1. 
   Danford_C_ | Apr 18, 2002 07:00am | #2

   Awfully long and not very helpful, wasn't it?  Sorry, but I'm one of those who gets paid to talk for a living.

   So, are we to assume you are in politics? :-)

   Dano"Form and Function are One" - Frank L. Wright

2. 
   roninfante | Apr 18, 2002 01:11pm | #3

   Greene's book, "American Furniture of the 18th Century" (I hope that's the right title) has a helpful discussion of this topic.

3. 
   ETG | Apr 18, 2002 02:45pm | #4

   Terry:

   I've used photographs a number of times to "scale" a drawing for a piece of furniture.  It not as complicated as some have indicated.  As pointed out, you do need to keep in mind that angle shots can distort the actual size.  What you have to keep in mind is the piece of furniture itself - if it's a dining table then surely it's not going to be 18 inches tall or 48 inches tall.   Use common sense and it will work.

   Take the dining table as an example - they are usually around 30 inches high - measure the actual height of the table in the photograph and then get a scaling ratio - say the table measures 1 inch high in the photo.  Then you have a 1 to 30 ratio for all the measurements (assuming you pick 30 inches high as your "standard" for table height).

   Remember this process is still an approximation - it can be reasonably accurate but does not meet the requirements for exact replication of a piece.  That still requires physically measuring the item.

   Try it - it can be fun - Good Luck!

4. 
   blutt | Apr 18, 2002 04:18pm | #5

   The book that RONINFANTE mentioned "American Furniture of the 18th Century" has the most indepth explanation of the process I have read.  There are a few sections specifically on different types of perspective drawing and using photos to determine dimensions.  If you are interested in trying this, get ready to draft, the cost of the book would be worth every penny.  In addition it is a fantastic reference for understanding the development of historic styles, methods of work and construction tequniques.  I highly recommend this book.  I am a firm believer that our understanding the past expands the potential for the future.

5. 
   theRev | Apr 18, 2002 04:22pm | #6

   Terry,

   I would suggest a book on drawing, especially one on perspective drawing. There are techniques on perspective drawing which let you apply a scale to the different axes of the rendered drawing. If you couldn't do that, why wwould one use it? Granted, a photo will have a more ambiguous angle than a specifically rendered perspective drawing, but the concept of proportion/scale is the same. One axis is a base scale, and the other axes (not evil ones, as Bush might suggest) are proportioned as to the rate they receed back into the zero point in the horizon. I can't explain it well, and if I take up too much bandwidth in my reply, Dano might get upset <g> (just kidding, Dano). Go to the library or hit the web, once you see it, you'll understand how the scaling works and you can apply it to photos.

   Just hit the web and found this. Take some time and go thru this and I think you'll find out the technique you need.

   http://www.stpauls.nsw.edu.au/~IndArts/mppone.html

   Scott

   
   

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   Edited 4/18/2002 9:37:00 AM ET by the rev

1. 
   quatersawn | Apr 18, 2002 09:30pm | #7

   It's really not all that hard, although the variables discussed will prevent exact measurment in most cases. I try to find a piece of wood in the photo or something I can reasonably assume is a certain thicknes or length. I.E. the table top is 1" thick, then I apply that to the other dimensions and do some sanity checks along the way. I did that with a photo of an adirondack chair a few years ago. I figured the slats to be 2" wide, and just began scaling it from that known constant, or a least assumed constant. Worked out great. Good luck.

1. 
   TerryH13 | Apr 19, 2002 01:44am | #8

   Thanks to all. Your answers are basically what I thought they would be and are of great help. I did have some assumtions when I asked the question but you know what assume can get you.

   Again thanks to all.

   Terry