Change the colour of a gray object to white

Question

Hi - I'm wanting to alter an image grey moulded piece of resin, to white. Hows the best way to do this?

Answer 1

Hi Dean.
I'll try to be more specific starting from the un-altered version of your picture:
Go to the channels tab.
Drag the Red channel to the New Channel icon in the bottom of the panel - this will give you a copy.
Think this way: 100% Black equals non-selected and 100% White equals selected. 50% grey equals 50% selected.
The Red channel already has a significant difference in black vs. white, enabling you to quickly tweek the difference even more.
While in the Red copy channel, hit Command+L (for Levels).
Move the black slider towards the middle of the histogram to darken the shadows until you see important information dissapear.
Then use the middle slider to tweek the background further towards black.
Stop when you feel that you are starting to remove wanted pixels in the image.
Select the Dodge/Burn tool by hitting O (as in Oxford) - you don't need the deasturation tool, so make sure you've got the right tool. You can toggle the tool by hitting Shift+O.
For the Burn tool, set it's Range to Shadows and Exposure to 50%.
Select the Dodge tool, set it's Range to Highlights and Exposure to 50%.
Now, choose fairly large soft brush.
With the Dodge tool selected, paint on the teeth - and you wil them lightening as you paint along.
If you feel the tool has a too strong effekt, lower the Exposure.
Select the Burn tool, and paint in the background areas, where it's still not black.
Keep painting suddle as you're toggling the Burn/Dodge.
When you've tweeked the image so that the edges of the teeth are almost white and you can still see a suddle transition from the teeth to the background, you've produced your basic mask.
Select the Lasso tool (hit L) and draw a selection inside teeth and fill it with white, so that everything but the grey edges is completely white.
Hit the RGB channel and return to your layers (F7).
With the background layer selected, make a new layer (Command+Option+Shift+N).
Fill it with black (Hit D then Command+Backspace).
Then hit Command+Option+4, this will load your Red copy channel. Hold down the Option key and click the Add Layer Mask icon in the Layers palette.
Click on the Layermask you've just created on the layer to make it active. You can now make the final tweeking on the mask by very, very suddle dodge/burn the edges until you see a result you like.
Finally remove some the blue colorcasting in the teeth-plaster.
Hope this explanation made it more clear to you.
Have fun.
Torben.