measurments from photograph to c a d

[whensparksfly]

Can measurements be taken of a photograph directly to a c a d program

 

[Screwdriver]

There is a feature in Sketchup which allows you to match a photo by building a 3d model around a picture or a series of pictures.

Before you get too excited, it might be Sketchup Pro which isn't free...

S.

 

[whensparksfly]

How good is sketch up would mind paying for a good one

 

[Wendelspanswick]

In AutoCAD you can import a photo as one of the layers, scale it till you are happy and then dimension it. I haven't tried the same with Draftsight* but I imagine that you can do the same as Draftsight is a clone of AutoCAD.

*There is a free version of Draftsight:
http://www.3ds.com/products-services/draftsight-cad-software/free-download/

 

[Screwdriver]

Sketchup is free (and totally awesome!). Sketchup Pro is expensive, several hundred quid. I seem to have accidentally ended up with the pro version somehow...

Here's what I use it for mostly:

I built the shed using sketchup (I'm not a builder) now I use it to organise it.

S.

 

[eSCHEn]

Technically yes you can using the methods above.

You must remember that unless your camera allows you to take orthographically projected photos (it won't) then the resulting pictures will be skewed by perspective.

 

[Kayos]

Technically yes you can using the methods above.

You must remember that unless your camera allows you to take orthographically projected photos (it won't) then the resulting pictures will be skewed by perspective.

I have one that does
It also has a distance scale in the focus screen and can imprint a grid on the negative, however I do admit I have a camera problem

 

[Screwdriver]

Technically yes you can using the methods above.

You must remember that unless your camera allows you to take orthographically projected photos (it won't) then the resulting pictures will be skewed by perspective.

In Sketchup the program calculates dimensions and perspective on the fly based on a set of reference points you input. So you can take a picture of a box (or a house) and it will correctly scale taking perspective and field of view into account.

https://help.sketchup.com/en/article/3000115

It is a bit fiddly mind. On the plus side, it also applies the best image set (if you use more than one photo) to apply the photograph as a texture to the model.

There was also a program called Canoma that did a similar thing.

 

[eSCHEn]

I have one that does
It also has a distance scale in the focus screen and can imprint a grid on the negative, however I do admit I have a camera problem

I knew one of you camera types would have one lol

It wasn't "can't" more that it's specialized and if you're asking then very good chance you don't have.

Saw a program which used a 100+ meg sensor with Ortho lens. They could directly trace skyscrapers in their entirety from a single photo. Amazing.

In Sketchup the program calculates dimensions and perspective on the fly based on a set of reference points you input. So you can take a picture of a box (or a house) and it will correctly scale taking perspective and field of view into account.

https://help.sketchup.com/en/article/3000115

It is a bit fiddly mind. On the plus side, it also applies the best image set (if you use more than one photo) to apply the photograph as a texture to the model.

There was also a program called Canoma that did a similar thing.

Cool, didn't know you can unproject in sketchup. Is it accurate?

 

[Kayos]

I also use ortho film for experimental shots, the camera came in a job lot of stuff, however it takes 620 film and respooling is a faff, hence experimenting with the 120 ortho film I thought would fit........

 

[eSCHEn]

So (and sorry to OP for digressing here) does your camera need special film as well as the lens to do Ortho?

Must say I come from a digital aspect here, mainly 3D computer graphics.

 

[Kayos]

To get the full orthographic effect you use orthographic film, which is very slow, usually 25 ish and has reduced red sensitivity so it can be developed under a dim red light "by eye" rather than to a time

It's also high contrast so lines are clearly defined, if used as a portrait film then lips appear dark red, some very famous b&w shots are ortho

 

[Screwdriver]

Cool, didn't know you can unproject in sketchup. Is it accurate?

It will be as accurate as you can set your reference points. The bonus is, you can incorporate a number of different photographic angles in the same model. I assume any errors would then average themselves out.

 

[Kayos]

Back to the OP
I use chessboard targets to make lens correction profiles, the software does the maths but they are defined size and if you know the distance could be used for accuracy?

Or I may be talking rubbish

 

[Sarto]

In Draftsight is very possible to scale and trace photographs (even with Gimp you can).

If you take the photo, try to keep the camera square and centered to the target (less distortion in the center of the lenses).
While in the process, insert a rule or a chessboard of known dimensions, at the same height of your target.
Keep a uniform lighting and avoid heavy shadows, if possible.

If in doubt, look at the way people in CSI take the photos!

Hope this help.