ICDL Image Editing (ICDL) common mistakes
ICDL Image Editing · Understand the traps and how to avoid them.
When asked to prepare a 4 × 6 inch print at 300 ppi, the candidate creates a document 4 pixels wide by 6 pixels high, or changes the ppi value and assumes the pixel dimensions automatically become correct.
They treat ppi as a direct substitute for pixel dimensions and do not calculate that 4 × 6 inches at 300 ppi requires 1200 × 1800 pixels.
What to do instead
Use the Image Size dialog and read both pixel dimensions and document size. Calculate pixels = inches × ppi before creating or resizing, and note whether the Resample option is on.
The candidate repeatedly saves an edited photograph as JPEG after every adjustment, then wonders why edges and gradients look blocky.
JPEG is familiar and produces small files, so they assume repeated saving is harmless rather than lossy compression that discards data each time.
What to do instead
Keep a lossless working copy such as PSD, TIFF, or PNG during editing. Export a JPEG once at the end, and if a JPEG must be reused, save a new copy rather than resaving the same file repeatedly.
The candidate scans a printed photograph at 72 ppi because that is the monitor value they remember, then enlarges the scan later for printing.
They confuse screen display resolution with capture resolution and assume a low-resolution scan can be enlarged without quality loss.
What to do instead
Set the scanner to optical resolution appropriate for the final print size, commonly 300 ppi at target size or higher for small originals. Scan once at sufficient resolution and crop or downscale afterward.
The candidate accepts a camera JPEG with blown highlights or a strong colour cast and then tries to repair large clipped areas during editing.
They ignore capture settings such as exposure, white balance, and histogram review, assuming every problem can be fixed later.
What to do instead
Check the histogram and white balance before capture, shoot RAW when available, and expose to preserve highlights. Correct minor issues in editing, but avoid relying on post-processing to recover clipped detail.
The candidate creates a new document in RGB at 72 ppi for a job that will be printed in CMYK, and only changes the mode at export.
They accept the application default without checking the destination requirements, so colour mode and resolution are wrong from the start.
What to do instead
At New Document, set colour mode, resolution, dimensions, and background according to the final output. Confirm printer specifications before beginning, and convert mode only when the workflow requires it.
The candidate starts painting or pasting images directly onto the locked Background layer, then cannot move, mask, or restack individual elements.
They begin creating content immediately without planning layers, so all elements are merged into one layer from the first stroke.
What to do instead
Create and name separate layers before adding content, keep the Background layer for the base only, and use groups for related elements. Convert or duplicate the background when independent editing is needed.
The candidate removes an unwanted background with the eraser tool and later discovers that deleted edge pixels cannot be restored cleanly.
The eraser is a direct, visible tool that seems faster than masking, but it permanently destroys pixel data on that layer.
What to do instead
Use a layer mask instead of the eraser, paint black to hide and white to reveal, and refine the mask edge. Keep the original pixels intact so corrections remain non-destructive.
The candidate makes a selection while the wrong layer is active, so the adjustment affects another layer or the entire image instead of the intended area.
A selection outline does not show which layer is active, and candidates often watch the canvas rather than the Layers panel.
What to do instead
Confirm the active layer in the Layers panel before selecting or adjusting. Use an adjustment layer with a mask, or clip the adjustment to the intended layer, and verify the result by toggling visibility.
The candidate exports a logo with a transparent background as JPEG and then reports that the transparency has become a white box.
JPEG is the most familiar export format, but it does not support an alpha channel, so transparent areas are filled during export.
What to do instead
Choose a format that supports transparency, such as PNG, GIF, or WebP, or TIFF with alpha. Check the export dialog for transparency and matte options before finalising.
The candidate saves over the only layered source file with a flattened JPEG, then cannot return to separate layers for a later revision.
They use Save rather than Save As or Export, assuming one file must serve both editing and delivery purposes.
What to do instead
Keep a layered master file in PSD or TIFF and use Export or Save As to create delivery copies. Use clear version names so the editable source is never overwritten by an output file.