Resize photo for printing

[kenskopp]

Hello Community,

I am a model train enthusiast and have used Photoshop Elements 11 to make photo backdrops for my train layout. So far I have done scenery photos and had enlargements made at COSTCO to mount on my walls. I now have to take photos I took of the backs of building in a small town and get them the right size to match the model buildings I have purchased. I am working in HO scale which is 1/87 scale. I have taken the photos with a NIKON 3100DSLR. Up to this point I have printed a couple photos on 8 x 10 on plain paper. They are still a little bit bigger than I would like. I am not sure how to resize them so that when I print 8 x 10 the cars in the photo are the same size as my HO scale (1/87) cars. Any suggestions on how to do this? Thank you, Ken Skopp

[Steve Grisetti]

I suppose you could try measuring the buildings in Photoshop Elements to ensure that they're the size you want. The easiest way to measure objects in Photoshop is to open the Info palette (under the Window menu) and then drag the Marquee Selection tool over the objects you want to measure.

[Bob]

It gets a little tricky when you try to print such that an object in the photo matches a particular scale. Here's one way to do it.

First, we need to know how are the printed car should be. Assuming a typical passenger car is about 4.5 feet high, 1/87 of that comes out pretty close to 5/8 inch. You would normally print between 200 and 300 pixels per inch. If you use 300, that comes out to about 188 pixels high (= 5/8 * 300).

Now we need to know how big the car is in the photo. Open the photo in Photoshop Elements using Expert Mode. Open the Image Size dialog (ctrl+alt+i) and uncheck the box labeled "Resample Image". Set the Resolution value to 300 to match what we used to calculate the print height and click OK. Now turn on the Rulers if they are not showing already (ctrl+r). Right click on either ruler and select "pixels". You can now measure the height of the car in the image. You can use the method Steve mentioned, or you can click on the top ruler and drag down a guide -- you need two, one at the top of the car and one at the ground. You can zoom in and read the pixel values on the ruler on the left. The difference between the two is the height in pixels. If you wish, you can click on the square where the two rulers meet in the upper left corner and drag into the image -- a cross will appear where the origin of the scale will be set, move it to align in height with one of the guides. You can then read the height directly without having to subtract one value from the other.

Once you know the height in pixels of the car in the photo, compare it to the value we calculated for the print (188). If the height in the photo is greater you will need to scale down the photo. If smaller, you need to scale up. Divide the pixel size in the print by the pixel size in the photo. That will give you the scaling factor. Open the Image Size dialog again. This time, check the box labeled "Resample Image". Make sure "constrain proportions" is checked also. At the top of the dialog box, there will be a section called "Pixel Dimensions". Make sure the units are "Pixels". Take the value for the height and multiply it by the scaling factor you just calculated. Round to the nearest pixel and type that into the height field replacing the previous value and click ok.

Your photo should be scaled properly now. But, you need to ensure that when you print, it won't be scaled again by the print routine. To do that, use the crop tool and crop it to 8 x 10. Photoshop will display the pixel dimensions as you adjust the crop handles, I'm not sure if Elements does that also. You want to crop it so that it is exactly 2400 pixels by 3000 pixels. Make sure you didn't change the resolution. Print this to 8 x 10 inches and the car should be 5/8" high.

If you save the resized photo, don't overwrite the original. It's best to work with a copy.

[kenskopp]

Thank you Bob for the information. I will give it a try and let you know when I have it figured out.

Ken Skopp