Easy way to acheive a 1:1 ratio for a picture of an object in photoshop?

[Cast]

I have a question regarding sizing...

A 1:1 ratio can be obtained when using a scanner.

Is there an easy way to acheive a 1:1 ratio for a picture of an object in photoshop? Without having to put something in the image (coin, ruler etc) and having to perfectly align the camera and plane. Just curious becuase even using a coin or other reference then centerering, aligning the ground plane etc, it always turns up a little off, no matter what.

 

[puraidodes]

If I understand you correctly are you asking if there is a way when we take a photo of an object it must remain the same physical size in the photo too?

If so, I don't think it is possible unless you have a pretty sophisticated measuring device or any camera app(like AR ruler app) that can measure and take photos at the same time...
The camera is always away from the object which would make the perspective distance reduce the actual size of the object on camera.

Placing a small object like a coin to get the proportion right is the easiest way.

Or if you know the measured size then after taking a high res photo-> just use the perspective crop tool -> straighten/flatten it -> create a new document with the actual size at 300 Res -> place the straightened/flattened photo into the document- > print it out at the actual size(if that is what you are looking for)!

 

[thebestcpu]

Hi @Cast
I like @puraidodes ideas and here are some more thoughts.

You don't give a lot of details about the types of images you are taking. In general, it would be very difficult under all circumstances to tell the exact size of an object without a reference.,

However, If you are taking pictures with a tripod or copy stand here is one option to consider.

- Set up the camera on tripod/copy stand with the zoom/focus all set to go
- Place a Quilters grid or vinyl grid on the flat surface you are going to place the image
- Take a picture
- remove the grid and take a picture with the product
- You can overlay the product image with the grid image in photoshop (with e.g. darken blend mode) and have a scale show up right over/under the product itself)

Since the product and the grid are taken with the camera parameters fixed, you can make an easy measurement and then scale you image to print at the exact size.

Here are a couple links to examples of grids (I have used similar ones with my copy stand work)

https://www.amazon.com/gp/product/B004BQXG3M/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&th=1

https://www.amazon.com/gp/product/B0033P9BNG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

If this direction is of interest and you have more questions just ask.
John Wheeler

 

[Cast]

Thank you for the helpful replies. It is highly appriciated.