Image Science will be closed for the Anzac Day public holiday on Wednesday 25th of April 2018.
We help a lot of artists with art reproduction. A big part of the reproduction process for illustrators is stripping (what appears to be) a white background back to actual white.
Without doing this your background will print as a grey block - this appears messy and unfinished.
The following instructions will take you through the process of using a curve to non-destructively strip your background without erasing any parts of your image. This works with sharp and feathered edges.
Stripping a background can be done quite simply with curves and layer masks. This method of background stripping eliminates the risk of you accidentally brushing out parts of your image, it can also speed up your process. There are many methods of removing a background though this is by far the most time efficient and non-destructive.
The level of difficulty can depend on the amount of feathered edges and faint line work. If your edges are bold/sharp then this will be an easier process for you. Today I am working on artist Amy Howard’s image. Amy works with fine line pencil teamed with collage/mixed media.
This image has both hard and soft edges and mixed media, perfect for this exercise. To the right you can see the background area, although ‘white’ it appears as a grey box when printed. The image has been scanned with no adjustments at all.
Instructions as follows
1. Begin by selecting a curve adjustment layer and pull in the black and white points (without clipping of course).
*Handy tip: hold down the option key when setting your B&W points, this will allow you to set the points with precision.
2. Now add a second curve layer, this is the curve you will be using to strip the background, the first one is your global density curve.
With the second curve selected, select the hand icon in the curve box. With the curser on the white of the image, click and drag the curser up until the curve hits the top of the dialog box, this will bring the whites up. Your image will look really blown out... that’s okay, you will fix that up later.
3. Make sure the whites are white! To do this, run the curser over the white areas that you have painted, while doing this look at the ‘info’ dialog box. The numbers should be 255, if below you will need to go back into your curve and adjust the curve up until those numbers hit 255.
4. Go back to the image and find either a mid or dark tone, click on the section you have selected and drag the curser down, by doing this you are bringing detail and density back into your image. Do this until those areas look almost as they did before you brought the whites up.
If the image is looking a little too ‘hot’ or contrasty that is okay. You’re not aiming for perfection with this adjustment, just to get it looking close to the original colours/density.
5. Once you are happy with your modifications, select your layer mask on the curve layer, you won’t need to create a new layer mask as curve layers already have masks built in. Simply select it by clicking on it. Go up to the ‘edit’ menu and select fill (shift + F5). Select black.
Your image should have reverted back to how it looked before you made your ‘curve2’ modifications. You haven’t erased it, you have visually hidden it.
6. Select the brush tool. The type of brush will depend on the type of edges you have in your image. If you have feathered edges (like the ones I am working with) then use a big fluffy edged brush with minimum hardness. If your edges are sharp than use a ‘hard’ brush. You can adjust this with a slider by clicking on the brush icon that sits under the edit menu when brush tool is selected.
Have your brush set to white. You are going to paint your curve adjustments back into the image.
Handy tip; You can interchange between default black and white brush modes by hitting the ‘x’ key.
Select 'control 1' on your keyboard, this will zoom your image to ‘actual pixel’ size. Always edit your image zoomed in like this with critical edge work, it’s amazing how much you miss when editing zoomed out.
7. Begin painting around your image edges, the opacity of your brush should be 100%. Paint all around the edges. Once complete then you can zoom out and paint the larger areas that don’t affect the main part of your image.
*Please note that you will need to go back into your file after this to remove dust and scratches and do a general clean, this stripping method will remove the bulk of it though you will still need to heal/clone out those on a ‘background copy’ separate to this.
You can see in the detail image above where I have brushed around the edge of the face, you can see that it hasn’t erased any of the fine lines. This is what you’re aiming for when setting your curve. This is also a great example of image areas that are more difficult than bold/sharp edges.
When brushing the curve adjustments in, you can hit your back slash key and it will bring up a ‘quickmask’ (see image beow). This helps with precision work and so you can visualise where you are brushing so you don’t miss an area. It’s easy to miss areas when brushing white on white.
Try experimenting with brush density if you’re having trouble you can paint the curve in and out (black brush and white brush) with different densities until you are happy. Your curve really is the global adjustment; you can then go in later and fix up these areas (local adjustments).
When brushing, I find it useful to click the curve layer on and off. This will allow you to see if you have missed anything, or if you need to make adjustments to your curve settings.
That’s it! The beauty of this method is once you have completed the painting process you can reset your curve if you aren’t happy with it and begin again without having to repaint.
This method won’t clip any crucial part of your image like it would if you simply brushed your areas white without masking or used selections.
Setting the curve adjustment layers can take some time so be patient, it’s a learning curve (lol).
See below for the end result!