image size and measuring distance

[sylviawild]

Hello! Im no expert when it comes to using autoCAD and I may seem like an obvious solution, but im having trouble when it comes to attaching an image to autoCAD. I set the scale to 1:1 but when it comes to measuring distance it changes depending on if the exact same image attached is bigger or smaller. I used this program a few months back and it was working fine and I havent done anything different, but something changed and I dont know what it is. For example i link an image and the distance is 0,19 mm and i attach the exact same image but a little bigger and the distance changes to 312 mm (example of how different the measurments are) when it was working for me just fine before. I hope somebody knows why this is happening to me. Thank you in advance!

[chriscowgill7373]

do you have any screenshots of what you are seeing?  Typicaly images dont have any scale set to them, you can guess and get it close.   A little bigger is a relative term.  What scale does it say in the properties palette for the two images?  What are the dimensions showing in the properties palette?

[sylviawild]

Sorry, it´s a little hard for me to explain. Im still pretty new to autoCAD so i dont really know most of the functions and I´m using it to measure X- Rays. I set the scale to 1:1 but depending on how big or small i make the image (linked the screenshot of what i mean when i say making the image bigger or smaller) it gives me a different distance and i dont know how to make it always the same size since i have to measure over 30 x rays and for it to be to scale and give me an accurate distance. It may have an easy solution but i really have no clue how to fix this. I´ve been trying for a really long time now. 

[RSomppi · Accepted solution]

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@sylviawild wrote:

I set the scale to 1:1 but depending on how big or small i make the image (linked the screenshot of what i mean when i say making the image bigger or smaller) it gives me a different distance and i dont know how to make it always the same size since i have to measure over 30 x rays and for it to be to scale and give me an accurate distance. It may have an easy solution but i really have no clue how to fix this. I´ve been trying for a really long time now. 

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Your explanation is a bit vague but if I'm understanding correctly, your making a mistake by "sizing" your image differently. You should be very deliberate when doing that. Find a known dimension and use the scale command and the reference option to make the size of your image 1:1 with your measurements. Then all measurement should be accurate.

[sylviawild]

yes, i took an x ray of a coin and measured it in person and then measured it on autoCAD and it came out exactly the same regardless of the size of the image, but at some point that changed. Now i just dont know how to make the images attached the same size so that the scale is 1:1, because even thought i make the scale 1:1 the measurments change drastically depending on the size of the image. I get what you are trying to tell me, but i just dont know how to do that and I´ve tried looking online and asking people that know how to use autoCAD but nobody knew how to help me.

[RSomppi]

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@sylviawild wrote:

I´ve tried looking online and asking people that know how to use autoCAD but nobody knew how to help me.

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Because they can't see your screen and your description is inaccurate.

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@sylviawild wrote:

measured it in person and then measured it on autoCAD and it came out exactly the same regardless of the size of the image, but at some point that changed. Now i just dont know how to make the images attached the same size so that the scale is 1:1, because even thought i make the scale 1:1 the measurments change drastically depending on the size of the image.

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It's getting clearer. Screen shots or a screencast, and sharing your file would be helpful since your words aren't getting us anywhere.

[pendean]

@sylviawild Pictures are not scaled: depending on your zoom level in he DWG file, your pasted image can come in at just about any scale possible out there. You appear to see this often, but assume somehow there is an alternate reality 😉

>>>.... Im still pretty new to autoCAD ...<<<
I think you are assuming too much from no-scale pictures in a 30-year old CAD program not designed to be a picture scaler/editor, at least not without this add-on https://www.autodesk.com/products/autocad/included-toolsets/autocad-raster-design

HTH

[Pointdump · Accepted solution]

Hi Sylvia,
Welcome to the Autodesk Forums.
That's a tough question! All I can think of is to measure some known part of the photo in AutoCAD and scale accordingly.
Dave

[fatal.error · Accepted solution]

As everybody states, the only way to accurate scale an image is by adding a real scale object on it. 

Assuming the light gray disc as a 20mm coin, you can scale the image with the following directions:

Draw a red line along the x-ray coin.

Then draw a true 20mm yellow line.

Type ALIGN ("alinear" for spanish version), select the image and press Enter.

Specify first point source (click on the red 1).

Specify first destination point (click on the yellow 3).

Specify second point source (click on the red 2).

Specify second destination point (click on the yellow 4).

When prompting for a third point source, press Enter.

Press Yes to scale the objects based on alignment points.

[arshadmirza786]

Alternate command is "Scale with Reference" 

[sylviawild]

Thank you so much everybody! I know I did a really crappy job at explaining myself, but despite that you guys were very helpful! 

[tnpgeeks]

Can anyone here measure a fish in a picture for me? paid work