3.10. Platinum paper

Platinum printing was invented in the 1870s. Like the cyanotype, the process relied on lightsensitive iron salts. These were combined with either platinum or palladium salts and coated onto printing paper, which was usually contact-printed under ultraviolet light from a negative. After developing, the platinotype or palladiotype print contained a metal image that was prized for its tonal quality and archival stability. For half a century, platinum was at the cutting edge of photographic printing, and was used by Emerson, Evans, Strand, Stieglitz, Weston, and many others. Platinum and palladium prices rose in the 1920s and made commercial production unviable, but since the 1970s there has been renewed interest in the process often considered to be the ultimate in fine art photography.

Platinum and palladium prints are distinguishable by their tone. Both are slightly warm, although platinum has a more metallic quality and, generally, palladium is more sepia in tone, with higher contrast. Imitating these tones in Photoshop employs the same technique as the cyanotype method on page 46except that the curve's channel values are drawn from the table in step 5, below. So let's look in a little more detail at how you can take a toned photograph and work out for yourself the toning adjustments the curve should incorporate.

I wanted to apply my platinum tone to this color photograph.

The first thing to do is assess a platinum or palladium print's tone. Perhaps you will be lucky enough to own an original, or be in a position to borrow one. If not, find a reference in a book or on the Web. Scan it into Photoshop or download it. Please note, however, that you don't need to copy or reproduce the image, just measure its color. Saving it to disc would constitute copyright violation, so please respect usage of the image. With the platinum print image open in Photoshop, select the Color Sampler from the Tools palette. Adopt the Point Sample mode from the Options bar so you can click individual pixels, mark their locations, and measure their colors. Hold down the Alt/Opt key and drag the original image layer to the "Create a new layer" icon. Name the new layer "BW" and click OK. Desaturate the BW layer using Ctrl/Cmd + U. Zoom in so you can see individual pixels-to 1600%, for example-and use the Color Sampler to click pixels with three or four different tones. Avoid clicking pure blacks or whites-you need to identify a midtone, a shadow, and a highlight. Remember, the Color Sampler cursor becomes an arrow when you move over an existing marker, letting you drag and move it, or right/Ctrl-click and select Delete. Examine Photoshop's Info palette-the lower section shows the RGB values for each marker. I reach for pen and paper at this point and write down the values for each pixel. Next, hide the BW layer, and write down the RGB values for each pixelthese belong to the toned original, so have different values for each channel. You should now have a little table of "before" and "after" values. The next step is to put these values into a Curves adjustment layer, and then save it for reuse. Platinum RGB Values Marker Channel BW Toned 1 Red 204 211   Green 204 209   Blue 204 197 2 Red 122 131   Green 122 131   Blue 122 116 3 Red 69 82   Green 69 70   Blue 69 57 To test these RGB values in a curve, reveal the BW layer, click the "Create new fill or new adjustment layer" icon, and select Curves. From the Channel drop-down box, select Red and click the curve near its top. Don't drag the curve. Enter the BW layer's first Red channel value, 204, in the Input box and the corresponding value from the Toned layer. Repeat this process for the other markers' Red values, clicking the curve and keying in the readings. Do the same for the Green and Blue channels, but don't click OK. At this point it's a good idea to save your toning adjustment so you can use it again. Click on the Save button, then give your curve a suitable name and save it somewhere appropriate. When you're done, click OK to apply the curve to the present image. Applying the toning to another image is very easy. If it is a color image, first make it black and white, then add a Curves adjustment layer and use the dialog box's Load button to call up the saved curve definition. The precise tone can always be finetuned doubleclick the Curves adjustment layer and drag the curve's points, or reduce the layer's opacity percentage to moderate its effect. Making a black-and-white picture look like a platinum print is simplejust add a Curves adjustment layer. The skill lies in making your curve recreate platinum tones accurately.