Note: the following was done in Photoshop CS 3
Step 1: Turn Color into Black and White
Open the original photo in Photoshop.
Click on the New Adjustment Layer icon.
Chose Black & White from the list. This will bring up the Black & White dialog box.
Keep the Preset set to None and click OK. Many photographs of the era were not perfectly exposed so no need to make any adjustments here.
Step 2: Make the Sky Over Exposed
Usually in Civil War era photographs the sky was over exposed due to the long exposures needed in those days. This step is to lighten the sky.
Click on the New Adjustment Layer icon and click on Curves. In the Curves dialog box grab the line in the middle and drag it up until the sky is washed out.
Because only the sky should be washed out not everything, fill the Curves layer mask with black.
Make sure the layer mask is selected by clicking on it.
With black as the foreground color, click Edit > Fill. In the dialog box be sure the settings are as below and click OK.
Make white the foreground color and click on the Brush tool.
Select a medium-soft brush and paint the washed out sky back in.
Don't worry about lightening the edges of the branches, in fact it is desirable to do so.
Next copy the 3 visible layers to a new layer above in order to work on the trees.
There are two ways to do this. Holding down the Alt key (Windows) or the Option key (Mac), click on Layers in the top menu, move your mouse down to Merge Visible and click.
That can be a bit clumsy so the best way is to use the short cut keys: Shift+Ctrl+Alt+E (Windows) or Shift+Command+Option+E (Mac). You will now have a black and white layer (I named it "stamped")
In the 1860s photography was still in it's infancy and even outdoor photograph had to have long exposures. This resulted in moving people or objects often times to be blurred. In this step adds motion blur to the tree branches.
Make the stamped layer active.
Select the Quick Selection Tool. Make a rough selection of the trees. As with the sky this does not need to be prefect. In this project imperfections are good.
When the selection is satisfactory, click Alt + j or Option + j. This will copy the selection to a new layer above (I named it "trees").
Right click on the blue area of the trees layer and click on Convert to Smart Object. Smart Objects allows you to apply filters with out being destructive to the layer and allows you to go back and make adjustment to the filter if need be.
Go to Filter > Blur > Motion Blur.
I selected -8 degree for the Angel and 45 pixels for Distance but that is a matter of experimentation.
Next add a Mask to the trees layer by clicking on the Mask icon.
Use this mask to paint out some of the blurred tree limbs. I set the brush opacity to 15%. The goal is to remove most of the streaking and leave (no pun intended) most of the blur on the outer most limbs.
Step 4: Adding a Vignette
Create a layer above everything and fill it with black. Add a mask to the layer and using a soft-edged brush with white selected, paint away the center of the image. Again it does not have to be perfect, just experiment until it looks the way you want it.
Step 5: Scratches and Spots
To really age this image I found a texture online (there are lots of free ones out there). It doesn't matter if the texture you find has color or not.
Copy the texture image into a layer above everything.
On the top menu click on Image > Adjustments > Desaturate to remove any color.
Change the Blending Mode to Overlay.
The overlay blending mode gives the desired effect for everything except for the sky.
Duplicate the scratches layer by clicking Ctrl + J (Command + J).
Set the Blending Mode to Hard Light.
Click on the Mask icon to create a mask and fill it with black.
Use a soft-edged brush and paint the scratches back in the sky area.
Note: I added a mask to the first scratches layer and masked some of the scratches.
The last step I did was to add a New Adjustment Levels layer and boosted the contrast a bit.
And there you have it, a Civil War era image. View higher resolution version HERE