Print

Print


I scan my graphite sketches and love to keep the light construction lines.

My method starts and ends similar to what you do, Bruce.

-Start with the highest quality scan possible.

-Working with adjustment layers to preserve the original source image, I apply Layers>Create Adjustment Layer>Curves. Grab the white end of the spectrum and adjust in a straight line, making the lights lighter, until I start to notice loss of pale lines. From here, I can grab the curve in the middle and pull down to darken mid tones. I might need a few more points to preserve areas (keep darks from getting too dark or to darken light areas even further) but I try to keep points to a minimum because they can cause some weird effects.

-I usually do another Curve Adjustment Layer at this point and lighten even further to a step past unacceptable loss. Now I have two options: I can either cut back the opacity of this layer, or erase areas of the layer itself.)

-Here's the real trick, checking the whites of the image. Another Curve Adjustment Layer (this one temporary) will sit on top of everything else. Grab the light end of the line and move it almost ALL the way into the dark. Your image should basically turn into black and white pixels and specks as all the lightest values get pushed to the extreme end of dark.

-A Snapshot at this point is a really good idea.

-At this point I use a large eraser and erase around the image on the bottom layer (the number of times I've accidently erased the adjustment layer! Oops.) Also check the top layer against the original scan with the correction layers' visibility turned off to make sure no stray bits remain in your background. Now I switch to a smaller eraser, turn the correction layers visible again, and pick at the edges of the image. If I've done this right, the edges are fairly clean and the sketch keeps its sketchy integrity. If the piece is a pain in the ass and has a lot of light lines against smudgy paper, things can get complicated here, but not impossible.

-I make good use of the History Eraser in this process. I find that erasing part of the image and then erasing back to history can make an easier job of nice even edges than adjusting eraser size (since edge hardness does not scale with the size of the tool.) Snapshots are a good habit to develop when using Photoshop also. It's good to check your 'finished' clean up against a snapshot of your corrected but uncleaned scan to make sure you did not inadvertently erase or lighten anything you wanted to preserve.


I'll have to try your selection technique, Bruce. There are admittedly many things I do not know about Photoshop!

~Tiffany Miller Russell
www.wildlifeinpaper.com<http://www.wildlifeinpaper.com>
720-381-7879



From: SciArt-L Discussion List-for Natural Science Illustration- [mailto:[log in to unmask]] On Behalf Of Bruce Bartrug
Sent: Monday, March 10, 2014 4:35 PM
To: [log in to unmask]
Subject: Re: [SCIART] Getting white backgrounds white. Sigh.

Holly,
There are things one can do to help with white backgrounds, but I've not found one that is useful in all circumstances.

Begin with a good scan or photo, one where the white is close to the highest value.

Then when processing in Photoshop, apply a Curves layer and slide the white down to, or slightly INTO, the spike in the histogram on the white side.  If this changes the contrast in the main image, use the curves line to change that.  It helps to put a couple points up near the whitest end to prevent the white from being reduced in value when making changes elsewhere on the curve.  This will work unless there are pale colors.
Another method you should experiment with is the Select > Color Range tool.  You can use this two ways.  One is to select the white background (the background is never completely white so you'll have to use the +dropper), then either delete that or fill with white.  I'm continually amazed at the times when I've hit the delete key and it gives me a pale colored background.  Has to do with the droppers on the left, the blend mode, and the opacity, etc., so recently I've just been going to File > Clear.  Nothing else to check :).  The other way is to select the color in the image, then reverse the selection and clear.  Often, however, no matter how you do the selection with the Color Range, it will include part of the image.  If this happens, and it's only a certain part, just add to or delete from the main selection with one of the selection tools.  I usually use the Polygonal Lasso to do this.  It sometimes helps to narrow the "Fuzziness" slider on the Color Range tool, which selects a narrow range of colors.
When all else fails, take the eraser tool and carefully erase around the outside of the painting/image.  Change point size when needed and make sure the eraser is at 100%.  (Duh, been there, done that.  Once.)  Just erase out to about 50 pixels or so.  Start at one spot and move around the outside of the image in one direction.  If there's a smallish closed-in area, just erase out to where the white background is more open.  When you've finished this, use the Polygonal Lasso tool, or similar,  to make large selections out to the edge, and within the 50mpix erasures. Delete back to background color, or go File>Clear.  Do this on a large scan of the piece, as any small errors in erasure will be minimized when downsized for the web.  If this is for a client, one just needs to be very careful in the initial erasing.  A Wacom tablet helps a lot.  This is tedious, but it works.  It won't take as long as you might suspect.  Others would use the pen tool or one of the magnetic tools to do a selection, but I find the eraser easier to correct, and much easier to stop using for a few minutes to refresh my coffee :).
Hope this helps,
Bruce

On Mon, Mar 10, 2014 at 5:24 PM, Holly Butlett <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Great web site, and all looked white on my screen.  However, I would love to hear how to correct this- I have many problems with this.  Holly

Sent from my iPad

> On Mar 10, 2014, at 10:48 AM, Lynette Cook <[log in to unmask]<mailto:[log in to unmask]>> wrote:
>
> I can verify it too now: they are white. I should have thought of this first. I grabbed your vireo image, opened it in Photoshop, then took my eyedropper tool to see what value the background has. It reads 255 everywhere I check. You can't get whiter than that!
>
> Lynette
>
>> On Mar 10, 2014, at 8:41 AM, duboisworks wrote:
>>
>> Bruce:I checked out your watercolor images and where appropriate they are showing up white in the background. As to getting a white background , I use a HP scanjet G4050 and the software is Photo Studio 6 which has built in where you can choose your background color.It works very well.
>> Best
>> Ann
>
> Need to leave or subscribe to the Sciart-L listserv? Follow the instructions at
> http://www.gnsi.org/resources/reviews/gnsi-sciart-l-listserv

Need to leave or subscribe to the Sciart-L listserv? Follow the instructions at
http://www.gnsi.org/resources/reviews/gnsi-sciart-l-listserv



--
Bruce Bartrug
Nobleboro, Maine, USA
[log in to unmask]<mailto:[log in to unmask]>
www.brucebartrug.com<http://www.brucebartrug.com>

The world is a dangerous place, not because of those who do evil, but because of those who look on and do nothing.  - Albert Einstein

________________________________________________

Need to leave or subscribe to the Sciart-L listserv? Follow the instructions at
http://www.gnsi.org/resources/reviews/gnsi-sciart-l-listserv

Need to leave or subscribe to the Sciart-L listserv? Follow the instructions at
http://www.gnsi.org/resources/reviews/gnsi-sciart-l-listserv