The picture above, of a San Francisco city block, has been framed using discarded planking from the back of a large mirror. I printed out tiled 8 1/2" x 11" sheets of typing paper, cut off the margins and taped them together, to see how the picture would look in a large size (in case I wanted to order an engineering print--see the January 4th blog post on Large Pictures on the Cheap). I like the sepia effect enough that I will probably not order the black-and-white-only engineering prints in favor of a color sepia poster-size print.
Below are instructions on how to convert an image from color to black and white in Photoshop using a channel mixer adjustment layer, so you can see how your picture will look printed out. Optionally you can add color back in for a sepia effect.
Convert Color to Black and White with Sepia
Converting your picture to black and white can give you an idea of how it would look, printed and taped to the size of the frame, in case you do decide to order an engineering print.
1) Open a color photo, crop and add the color adjustments you want.
2) On the layers palette, click the Adjustment Layer icon (the half-black, half-white circle) and choose Channel Mixer. Adjustment layers are useful because you make non-destructive changes on a separate layer.
3) Click the "Monochrome" box and then begin playing with the sliders, including the Constant, Red, Green and Blue. When you have the look you want, click OK. For a black and white engineering print, skip to #6 below to resize the image dimensions. Remember that since engineering prints are not high-resolution, professional-quality prints, a lower print resolution, especially with black and white, may be sufficient.
4) To add in sepia tones, create a new Color Balance adjustment layer.
5) For this sepia tone, I have added in mostly red, some green, and yellow.
6) Now go to Image/Image Size, or right-click the blue bar along the top of your image and go to Image Size. Unclick "Resample Image" and input the width and height you will need for your picture.
7) When the picture is the size you want, save in (jpeg) image format, and also save in PDF format. PDF allows you to print to the edges, and also makes it easy to tile multi-page prints.
8) With your picture saved in PDF format, you can print using "Tile Large Pages" under Page Scaling in Adobe Acrobat or Acrobat Reader. With all margins cut off and pages taped together, you can get an idea of how a printed poster-sized picture would look. You can then use your saved image format to order a print or poster online.