This writer (me-ow) uses GIMP on Ubuntu. But the same principles apply to the operation of either platform
You will need "the Application"
1a. Photoshop
or
1b. GIMP (it's free and no need pay licensing, totally legal, safe, no malware. did I mention that it is free?)
2. A photo which has either overexposed highlights or underexposed areas (or both!), for this practice
Caveat: i am not a pro. If you are a pro and don't mind sharing, please edify us all!
This technique may or may not be suited for pro work. Use at own risk
Method
1. Boot your computer up (duh). That includes turning on the power, monitor screen, peripherals, etc.
2. Run the application
3. Open the image which needs some adjustment
4. Duplicate the background layer. In Gimp you can right click in the layer name and select duplicate. In Photoshop you may need to use Layers -> Duplicate.
5.a Underexposed - set top layer blending mode to Screen.
b. If the underexposure is general, adjust the opacity until "correct" exposure is achieved. Use your eyes and taste to judge.
c. If the underexposure is regionally localized eg in the upper half of image, we must use "layer mask" - useful concept.
d. Photoshop users click on the [o] button at the bottom of Layers dialogue (mouseover to see "Add Layer Mask") . PS user may get a prompt asking for "fill" of the added mask. Select empty/transparent if slightly underexposed. Select white/full opacity if severely underexposed.
Gimp users can right click on layer itself and select "Add layer mask"
e. Using layer mask: the idea is using various painting tools like gradient, paintbrush, etc, to "paint" in or "paint" out the top layer's blending with respect to bottom layer
eg Selected transparent/black layer mask. This implies that the duplicated top layer is completely transparent having opacity zero and you will not see any of the top layer appearing. For white/filled layer mask, top layer is completely apparent, opacity 100% and top layer blends over below layers in the mode you had chosen.
e-1 )) Straightfoward painting-in using gradient (eg, top part of image is underexposed and must recover this top part, without blowing out the lower part of image due to "screen" blend burning the already properly exposed lower half of image)
Use gradient tool (hotkey G in PS, L in GIMP) drag the cursor across the layer mask to paint the part which needs recovery white. Observe if the desired part of top layer has appeared and has the blended effect on the lower layers.
If the previously correctly exposed part is now burnt, there is a chance the gradient tool is not being dragged in the correct direction.
e-2)) Dabbing using paintbrush - use paintbrush tool in transparent layer mask to selectively paint using white, in (eg faces) areas which need more brightness. User may wish to select 40-60% opacity of the tool itself, to achieve more gentle and slower paint-in.
6) Over-exposed?
Use layer blending mode of Multiply to recover. follow Steps 5(b) to (e-2) , substituting "underexposure" to "overexposure".
Not all highlights can be recovered if too blown.
Tips
1. It is possible to duplicate a layer with its mask on, and set the newly duplicated layer, to a different blending mode
2. Setting a blending mode to "overlay" can increase color saturation. (GIMP)
3. Save your work as a PSD file to stop the layers from being flattened, eg into a JPG . Export to smaller image formats as required
*** End ***
Thanks for reading, if there is anything inaccurate or plain wrong, please let me know and I will edit this post
You will need "the Application"
1a. Photoshop
or
1b. GIMP (it's free and no need pay licensing, totally legal, safe, no malware. did I mention that it is free?)
2. A photo which has either overexposed highlights or underexposed areas (or both!), for this practice
Caveat: i am not a pro. If you are a pro and don't mind sharing, please edify us all!
This technique may or may not be suited for pro work. Use at own risk
Method
1. Boot your computer up (duh). That includes turning on the power, monitor screen, peripherals, etc.
2. Run the application
3. Open the image which needs some adjustment
4. Duplicate the background layer. In Gimp you can right click in the layer name and select duplicate. In Photoshop you may need to use Layers -> Duplicate.
5.a Underexposed - set top layer blending mode to Screen.
b. If the underexposure is general, adjust the opacity until "correct" exposure is achieved. Use your eyes and taste to judge.
c. If the underexposure is regionally localized eg in the upper half of image, we must use "layer mask" - useful concept.
d. Photoshop users click on the [o] button at the bottom of Layers dialogue (mouseover to see "Add Layer Mask") . PS user may get a prompt asking for "fill" of the added mask. Select empty/transparent if slightly underexposed. Select white/full opacity if severely underexposed.
Gimp users can right click on layer itself and select "Add layer mask"
e. Using layer mask: the idea is using various painting tools like gradient, paintbrush, etc, to "paint" in or "paint" out the top layer's blending with respect to bottom layer
eg Selected transparent/black layer mask. This implies that the duplicated top layer is completely transparent having opacity zero and you will not see any of the top layer appearing. For white/filled layer mask, top layer is completely apparent, opacity 100% and top layer blends over below layers in the mode you had chosen.
e-1 )) Straightfoward painting-in using gradient (eg, top part of image is underexposed and must recover this top part, without blowing out the lower part of image due to "screen" blend burning the already properly exposed lower half of image)
Use gradient tool (hotkey G in PS, L in GIMP) drag the cursor across the layer mask to paint the part which needs recovery white. Observe if the desired part of top layer has appeared and has the blended effect on the lower layers.
If the previously correctly exposed part is now burnt, there is a chance the gradient tool is not being dragged in the correct direction.
e-2)) Dabbing using paintbrush - use paintbrush tool in transparent layer mask to selectively paint using white, in (eg faces) areas which need more brightness. User may wish to select 40-60% opacity of the tool itself, to achieve more gentle and slower paint-in.
6) Over-exposed?
Use layer blending mode of Multiply to recover. follow Steps 5(b) to (e-2) , substituting "underexposure" to "overexposure".
Not all highlights can be recovered if too blown.
Tips
1. It is possible to duplicate a layer with its mask on, and set the newly duplicated layer, to a different blending mode
2. Setting a blending mode to "overlay" can increase color saturation. (GIMP)
3. Save your work as a PSD file to stop the layers from being flattened, eg into a JPG . Export to smaller image formats as required
*** End ***
Thanks for reading, if there is anything inaccurate or plain wrong, please let me know and I will edit this post
Last edited: