How to define a real world scale to object within a photo using Designer

[KRoberts]

I'm needing to assign dimensions to an object in a photo that is being used as a template within Designer.
My question is how to assign a known measurement to an object within the photo? I'd seen it done on a youtube video but I can't find the video and have forgotten the steps on how to do this.
In the photo I know that each chisel is 9" long and X" wide, I want to assign that measurement to each of them so that I can trace them in their actual size and then make a pattern for cutting their outlines on a CNC machine.

Thanks

[R C-R]

Keep in mind that the length & width of the objects in the photo will not be exactly the same as their real world versions because the camera will not be perfectly perpendicular to any of them. (Think about how the photo would look as the camera's position was moved around & tilted to keep all of them in the frame.)

[Old Bruce]

3 minutes ago, R C-R said:

Keep in mind that the length & width of the objects in the photo will not be exactly the same as their real world versions because the camera will not be perfectly perpendicular to any of them. (Think about how the photo would look as the camera's position was moved around & tilted to keep all of them in the frame.)

Actually the best way to do this sort of photography is to use a longer than normal lens and be back a good deal. Then you have to deal with the problem of the plane of the subjects having to be parallel to the sensor/film plane of the camera. Lots of physical work.

[R C-R]

4 minutes ago, Old Bruce said:

Actually the best way to do this sort of photography is to use a longer than normal lens and be back a good deal. Then you have to deal with the problem of the plane of the subjects having to be parallel to the sensor/film plane of the camera. Lots of physical work.

True, but even with a long lens & careful camera positioning to make the plane of the object & of the photo the same, there still will be a small error you can't totally eliminate.

[Ron P.]

Don't really need a long lens. Good quality Macro lenses work great for this too, Wide-angle and ultra-wide do not. Too much lens distortion to add to the sensor and plane deviations.

I agree with Old Bruce, a lot of physical work if you're going to be accurate.

[Old Bruce]

5 hours ago, Ron P. said:

Good quality Macro lenses work great for this too.

My Good quality Macro is actually a (short) telephoto design. I like to keep a bit of distance from what I am photographing.

[Alfred]

39 minutes ago, Old Bruce said:

My Good quality Macro is actually a (short) telephoto design. I like to keep a bit of distance from what I am photographing.

My favourite lens on my old 35mm film camera was a 28mm-70mm zoom. It allowed me to fill the frame with a person’s head without standing uncomfortably close to the subject, and I could also get good macro shots of plants and suchlike.

[Ron P.]

2 hours ago, Old Bruce said:

My Good quality Macro is actually a (short) telephoto design. I like to keep a bit of distance from what I am photographing.

I had a 100 f/2.8 Macro that I loved. I also used a 70-200mm, and a 150-600mm for macro type photos. I was amazed the first time shooting some flowers at 600mm.

 

[R C-R]

8 hours ago, Ron P. said:

Don't really need a long lens. Good quality Macro lenses work great for this too...

For either type there is still the problem of getting the camera perfectly perpendicular to the object & the distortion of the length & width of the object due to parallax errors. If the object is flat enough, it would be better to use a flatbed scanner to get a more accurate representation of the objects actual dimensions.