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I have been looking at photos of rock walls, brick walls etc to print to use on my layout. When I have printed them (1:87 print size) it prints out at 1:87 of the size of the picture, which does make sense. Is there a method to use to have the picture print at 1:87 HO Scale?
How do you guys do this and, if I can get it to work, what type of paper do you use for printing ?
How do I do it? A lot of experimenting. If your photo program has a display ruler and grid option its helpful. Just adjust the image to the finished size you want and then print with the 'no resize' option. When I get it right I usually print on card stock. Printing on packing labels works for stick on details and road markings. That's how I did the grates and lines on my fire station floor.
Your printer is probably printing at about 300 pixels per inch, but your monitor is only displaying at about 80 pixels per inch. So if you have an image that is 1000 pixels wide, it will appear on your monitor about 12.5 inches wide (1000/80), but when you print it out it will appear 3.3 inches wide (1000/300) on paper.
When sizing an image, figure out how wide you want it and multiply that by your printer's resolution to get the number of pixels you need. If the wall of your building is 8 inches wide in HO scale, make the image 2400 pixels wide, assuming you're printing at 300 dpi.
Here's a site that prints out brick sheets in various scales. It's in PDF format so you shouldn't have to worry about sizing things properly. http://paperbrick.co.uk/
If you can find an object in the picture with a known size then you can use it to scale the picture.
For example: Doors are often 36 inches wide. If it prints at a scale 18 inches wide then double your print size. (Yes, I took the easy one.)
You will probably have to do some experimenting. Remember that it doesn't have to be exact. It only has to look OK to you. If anyone approaches your model with a scale rule then you should immediately chase them away.
Steve has the right idea about scaling. If you know the DPI of your printer, you can pretty easily calculate how large an image should be in order to print at a specific size. To get the item properly sized for HO, you need only identify something in the image of a known size, then you can determine how large (in pixels) to make the full image.
To add to what Gary said about the grid, in HO scale a scale foot is 3.5mm. You can set the grid size to 3.5mm and then each grid line will be one scale foot apart.
Here's what it looks like in Inkscape...
Go to File: Document Properties and select the Grid tab. Click the New button to open a new grid. Set the Grid Units to millimeters. Set the X and Y spacing to 3.5.
Then size your image appropriately. If you're modeling a brick wall 23 feet long, then scale your image to be 23 grid units wide.
One thing to keep in mind is that if you have to enlarge the image to get it to the right size, the image quality will probably suffer. You want to work with large, hi-res images that need to be downsized to the right size.
