NON-DESTRUCTIVE IMAGE EDITING

(AN INTRODUCTION)

This tutorial was prepared by Roy Killen and is copyright. It is part of the training materials provided for members of the Belmont 16 Ft Photographic Club and is not intended as a complete, stand-alone instructional package.

Please do not reproduce any part of this turorial without permission.

Comments and suggestions on this tutorial are welcome - they should be emailed to Roy Killen.

SOME TERMINOLOGY

When you make changes to an image in an image editing program such as Photoshop, your EDITS can be either:

ALTERATIONS - changes to the structure of the image (e.g., cropping or resizing), or

ADJUSTMENTS - changes to the appearance of the image (e.g., altering the contrast or colour balance).

This tutorial describes various ways of making ADJUSTMENTS to images.

WHAT ARE YOU TRYING TO DO?

BEFORE you make and adjustments (or alterations) to an image it is very important to try to visualise what you want as the end result (e.g., more vibrant colours, a sharper image, a monochrome version of the image, etc).

If you know what you are trying to achieve you can then think about the steps you need to take to get to that end result.

For the majority of images you will need to make several different types of adjustment and it will be important to get them in the correct sequence.

TRY THIS EXPERIMENT

Open an image in Photoshop or PS Elements.

Change the brightness of the image with Image>Adjustments>Brightness/Contrast.

Save the image and then close it.

Open the image again.

Undo the brightness adjustment.

SORRY - YOU CAN'T DO IT BECAUSE YOU MADE A DESTRUCTIVE EDIT

and you CANNOT undo destructive edits after you save and close the image.

WHAT'S WRONG WITH DESTRUCTIVE EDITING?

Well nothing - so long as you get the editing 100% correct the first time and you never want to change you mind or you never want to produce a second (different) version of the image.

CAN YOU EVER CHANGE YOUR MIND?

If you are editng an image and you decide that you want to "undo" some or all of the changes you have the following options:

UNDO the last edit you made by pressing Control+Z (Command+Z on a Mac) or by selecting "Undo" from the Edit menu. This takes you back ONE step.

STEP BACKWARDS - go back as many steps as you like by pressing Control+Alt+Z (Cmd+Alt+Z on a Mac) the required number of times. You can also select "Step Backward" from the Edit menu.

REVERT to the original version of the image and start editing again by selecting Revert from the Edit menu.

TEMPORARILY CHANGING YOUR MIND

If you are not sure whether or not you want to undo an edit or undo several edits or revert to the original image you can step back through the HISTORY STATES to remind yourself of what the image looked like earlier.

Each time you do something to an image in Photoshop that action is recorded as a "History State" in the History Palette. You can step backwards and forwards through the history states and see what the image looked like at each step without actually undoing any of the changes.

You could, for example, jump back three steps simply by selecting the history state three back from where you currently are in the History palette. (Note: The last change will appear at the bottom of the list in the history palette - the "colour balance" adjustment in the example to the right.

If you step back to a point where you want to "start again" you can then simply start your new edits and the history states that you have "stepped back over" will be removed.

The History palette looks like this:

SNAPSHOTS

At the bottom of the History palette there are three small icons.

The icon on the right is a trash can.

The icon on the left lets you create a new document based on the adjustments you have made up to the histoy state that is highlighted.

The centre icon lets you take a "Snapshot" of the document with the adjustments made up to the history state that is highlighted. This snapshot appears near the top of the History palette and is labelled "Snapshot 1" (you can change its name if you want to). You can carry on making adjustments and come back to this snapshot at any time (before you save and close the image). You can make as many snapshots as you want.

In the example to the right the top snapshot (_D3B1436.jpg) is simply the file that was originally opened - this snapshot is automatically given the file name.

The next snapshot down (Snapshot 1)was made at the "Photo Filter" step - but you can't tell this without looking at the snapshot.

The thrid snapshot down (Snaprshot 2 - after rotation) was made at the "Rotate Canvas" step and the name of the snapshot has been changed to reflect this (always a good idea).

ALL OF THE ABOVE WAYS OF UNDOING EDITS ARE FINE

SO LONG AS YOU DO NOT CLOSE THE IMAGE

BECAUSE WHEN YOU OPEN THE IMAGE AGAIN ALL THE HISTORY STATES ARE GONE.

IF YOU WANT TO BE ABLE TO UNDO EDITS ANYTIME IN THE FUTURE YOU HAVE TO MAKE NON-DESTRUCTIVE EDITS.

A SIMPLE WAY OF MAKING NON-DESTRUCTIVE EDITS

When you first open an image, duplicate the background layer, make your adjustments on the duplicate layer. Save the image as a PSD or TIFF file (complete with layers). When you open the file again the two layers will still be there. If you change you mind about the edits at any time just delete the layer on which you made the adjustments and start again.

The main problem with this approach is that you may make several adjustments on the duplicatre layer, save and re-open the image, and then find that you would like to undo just one of the adjustments. This is not possible--all you can do is delete the duplicate layer and start again.

A BETTER WAY OF MAKING NON-DESTRUCTIVE EDITS

If you want to make adjustments that are completely reversible (or adjustments that can be "fine tuned' later) you need to make each adjustment on a separate ADJUSTMENT LAYER.

Adjustment layers do not contain any image information - they simply contain instructions that alter the appearance of the layers below them.

Different image editing programs allow you to create different types of adjustment layers. For example:

TO CREATE AN ADJUSTMENT LAYER . . .

From the menu you can select Layer>New Adjustment Layer and then choose the type of adjustment layer you want (Curves in this example.)

Alternatively, you can click on the adjustment layer icon at the bottom of the layers palette and select the type of layer you want from the drop-down menu.

In Photoshop CS4 there is an even better way of adding adjustment layers - simnply click on the appropriate icon in the adjustments panel.

Whichever way you create them, you can stack the adjustment layers on top of one another to achieve the final result you want.

You can toggle an adjustment layer ON/OFF by clicking on the "eye" symbol on the appropriate layer.

Adjustments that are made with ADJUSTMENT LAYERS are non-destructive because:

(a) The adjustment layers do NOT change any of the pixel information in your image.

(b) You can remove the layer simply by dragging it to the trash can in the layers palette.

(c) You can change the adjustment by double clicking on the adjustment icon on the layer - the adjustment dialogue will lre-open and you can make the change.

(d) If you save the image as a PSD (Photoshop) or TIFF file the layers are preserved. Next time you open the image the layers are still there and you can make further adjustments to any layer if you want to.

LAYER MASKS

When you add an adjustment layer, Photoshop automatically creates a LAYER MASK on that new layer. This appears as a white rectangle next to the icon on the layer (the icon that indicates what type of adjustment layer it is).

If you click on the layer mask a border will appear around it - this means the mask has been selected and it is ready for you to paint on it.

If you paint in BLACK on a layer mask the effect of the adjustment created by that layer will be "masked" (hidden) in the area of the image where you have painted.

If you paint in GREY on a layer mask the effect of the adjustment on that layer will be partially masked (depending on the darkness of the grey) in the area of the image where you have painted.

If you paint in WHITE on a layer mask (where it was previously black or grey) the effect of the adjustment will be restored to that area of the image.

For example, if we open an image and then create a Hue/Saturation adjustment layer we will see this:

A Hue/Saturatoin adjustment could then be made to produce this image:

If the "mask" icon on the adjustment layer is selected and a BLACK brush is chosen to paint on this mask the following effect could be achieved:

Alternatively, placing a black-to-white gradient on the mask you could achieve this effect:

FINAL COMMENT

Using adjustment layers and layer masks opens up a new world of creativiity - and the best part is that all your creative experiments can be non-destructive.

For example, if I double click on the Hue/Saturation icon in the layers palette of the last example the Hue/Saturation dialogue will reopen and by moving the Hue slider I can instantly go from the previous image to this one:

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This page last updated 22nd February 2009 (RK)