No brain rescaling

[Darwin]

I've noticed recurring questions regarding how to figure out the math when changing the scale of a model. Here is a nearly brainless method for doing scale conversions, assuming that the starting point is a hardcopy and scanning is required. First step....when setting up the scanner, make the scanning resolution (pixels per inch or pixels per cm, whichever measurement system you are comfortable with) the same as the scale of the hardcopy model. For exampe, if the original scale is 1:200, set the scanning resolution to 200 dpi. Scan the images. Once you have the scans done, use your favorite image manipulation software to make printable pages. When you create your new pages, set the image resolution to equal the desired final scale. For example, if the desired scale is 1:400, set the new page resolution to 400. Downsizing is easy...when the new page is created, just paste the scanned page into the new page. If enlarging, you will have to cut the individual parts from the scanned image and paste them into the new pages.....and, for large parts, you may have to "cut" them into sections in order to get them to fit onto the new pages. Once you have a set of new images, print and start murdering paper. This technique works best with ship models, where the scale is usually in three digits. For airplanes and vehicles, where the normal scale is in two digits, set the scanner/new image resolutions to 10 times the scale (for example, if the scale is 1:33, set the correspoinding image resolution to 330 dpi). If this results in too high a resolution for your computer or printer to handle, multiply by 5 instead of 10.

[jmueller]

Please, don't do it. To get all the details in an accuarate way, you need to scan (at least) 300 dpi, especially when upscaling. For downscaling you might get away with it.
Do the scanning higher or equal to 300 dpi (I do 600 dpi) and do some thinking. All image manipulation softwares can do scaling by percentage and the math is really not that difficult.

Greeings
Jan

[Darwin]

I'm not going to let such a negative reaction go unanswered. First, if you would think about what I've actually said in this tip before reacting, you would realize that in almost all cases in which an enlargement is desired, the scanning resolution will be at least 300 dpi. For ships, in just about all instances where enlargement is wanted, the scale of the hardcopy is going to be 1:300 or smaller....giving you at least the minimum 300 dpi Jan recommends. For aircraft/armor, in the vast majority of cases that enlargement is desired, the scale will be 1:48 or smaller. Follow my recommendation for two-digit scales and multiply by 10, the minimum scanner setting will be 480 dpi...well within Jan's recommended minimum. For reducing model size, Jan admits the initial resolution is not so critical. For the vast majority of modellers, a 150 or 200 dpi scan gives them as much detail as they desire. Basic truth...the level of detail of a typical Fiddlers Green or Maly Modelarz model will make the majority of paper modellers happy as a pig in slop. If you are in the elitest minority that insists on a level of detail that brings out the cigarette butts in the scuppers, this tip is definitely not for you, nor are you the intended audience for the tip, since you probably are savvy enough to work the math in your head. One sad truth I've learned in my lifetime is that there are some individuals who cannot sum two three digit numbers and get the same answer twice in a row even using a hand calculator. I encounter them almost daily in the work partition of my life, and given the size of our membership, laws of average make it a dead certainty that some of them are us.

As far as quality of the final printout is concerned, since the total number of image pixels stays constant throughout the process, there is zero degredation of image detail once the image is scanned....which I cannot say when one starts mucking about with image processing sofware to make constant-resolution enlargements and reductions.

As far as the printout resolution is concerned, I would dare say that between the low-end printers and mediocre paper quality used by 90% of the club membership (myself included), anything past 300 dpi is wasted effort. I absolutely stick by my statement.....if you are having difficulty figuring out how to make scale changes, try my recommendation. It may not give the degree of quality desired by those on the leading edge of the hobby bell curve, but it is guaranteed to work on the first try.

[charliec]

May I make a small point about rescaling scans - don't save the scans as .jpgs, .tif is better.

Jpeg is a lossy compression algorithm ( lose information to reduce file size ) and if you try to resize the image you may get artifacts from the interpolation algorithm. These turn up as parallel light coloured lines close to boundaries and a number of other defects. Tiff is a lossless algorithm so it produces much bigger files but retains all of the information in the file from the scanned image. You can usually resize ( within limits ) a .tif without too many artifacts appearing.

Regards,

Charlie

[Old Ranger]

Thanks for the ".tif Tip".