I'm photographing objects with a scale/ruler (5cm or 30cm) beside them. I'm printing them on a 300dpi printer. How do I tell photoshop to size them as per the scale in the photo . i.e. highlight the 5cm scale and get P/shop to adjust my image so that the 5cm scale will actually be 5cm on my 300dpi print.
If your ruler is horizontal or vertical then just set up guides against Photoshop's ruler and transform > scale the picture of the ruler in the image to match the guides. Before setting up rulers make sure you have your document set up to 300 ppi
Thanks for that. Mostly they are vertical or horizontal but I get third party images sometimes and they can be any old way up. I'll work with your idea thanks.
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You'll have to do some math, there is no automatic way for Photoshop to recognize or adjust your print based on a scale in the image.
Thanks for the reply Kevin. There's so much scaling\sizing stuff that Pshop does that it seems like it should do this but I can't seem to find an obvious route. I've seen third party software for forensics (footprints and fingerprints) where you just click on both ends of the scale and enter the actual measurements into a dialogue box. You save the image at 300dpi or whatever dpi your printer is and your print is "actual" size. Obviously I'm not giving that company enough credit....
The Print PPI would need to vary. It depends on Camera sensor resolution, the lens Focal length, the distance the ruler is from the camera and the ruler would need to be on a plane parallel to the camera sensor plane. You would not be print with a 300ppi resolution. You do not want to interpolate your image that just lowers the image quality. You would use the ruler tool to measure ruler in the image and adjust the Print PPI Image size un-check resample keep adjusting the print ppi till the rules tool measure the ruler 1:1
JJ, thanks for that. Looks a lot more complicated than I hoped. I'll try what you suggest.