Photoshop - File Formats — David Barbarash

Why this matters

Every file format is a trade-off between file size, quality, editability, and compatibility. A format that excels at one usually compromises another. Working files and output files have different requirements — the working file needs editability, layer preservation, and the ability to come back and revise; the output file needs quality, appropriate file size, and compatibility with the recipient's workflow. Using the wrong format for either purpose creates problems that are expensive to fix after the fact.

Working formats

Format	Extension	When to use it
Photoshop Document	`.psd`	The primary working format for this course. Preserves all layers, layer groups, masks, adjustment layers, smart objects, channels, and paths. File sizes are large but editability is complete. This is your archive and your revision vehicle. Always keep the PSD.
Photoshop Large Document	`.psb`	Required when file dimensions exceed 30,000 pixels in any direction or the file size exceeds 2GB. You are unlikely to need this for Assignment 04 deliverables.
TIFF	`.tif`	Lossless image format that supports layers (when saved as TIFF with layers). Useful for interchange with other applications that don't read PSD. Larger than JPG, fully lossless.

Output formats

Format	Extension	Best for	Notes
JPEG	`.jpg`	Photo-quality images for digital delivery, web display, and InDesign placement	Lossy — compression discards pixel data that cannot be recovered. Save at quality 9–10 (High/Maximum) to minimize visible compression artifacts. Never re-save a JPEG repeatedly — each save adds compression damage. JPEG from PSD once, keep the PSD.
PNG	`.png`	Images requiring transparent backgrounds, line art, diagram graphics	Lossless — no quality loss regardless of how many times it is saved. Larger than JPEG for photographic content. Required for images with transparency.
PDF	`.pdf`	Flattened high-quality deliverables for printing or client sharing	Supports embedded ICC profiles and lossless compression. Use Photoshop PDF with Maximum Image Quality.
SVG	`.svg`	Not a Photoshop output format — this is a vector format from Illustrator or Rhino	Mentioned because your entourage library includes SVG files. Open them in Illustrator, rasterize at the correct size and resolution, then bring the PNG into Photoshop.

Lossy vs. lossless — the practical difference

Lossy compression (JPEG) works by discarding pixel information the human eye is least likely to notice — fine details, subtle gradations, areas of consistent color. At high quality settings this is nearly invisible. At low quality settings — or after repeated resaving — compression artifacts become visible as blocky patterns and color banding. This is a permanent quality loss; no tool can recover the discarded data.

Lossless compression (PNG, TIFF) retains all pixel data exactly. File sizes are larger, but the image is identical to the original regardless of how many times it is saved.

The practical rule: work in PSD, export to JPG or PNG once when ready to submit. Never use a JPG as a working file and never re-export JPGs repeatedly from JPG sources.

Entourage library formats

The provided entourage library contains files in mixed formats — JPG with separate alpha maps, PNG, SVG, TGA, and PSD. Each requires a different handling approach:

Format	How to use it in Photoshop
PNG with transparency	Place directly — transparency is embedded. Verify the background is fully transparent before placing (View → Show → Transparency or set the canvas to a color background temporarily to check edges).
JPG + separate alpha map	Open both files. In the alpha map (greyscale image), go to Channels, click "Load channel as selection," switch to the JPG, and apply the selection as a layer mask. See Card 10 for the masking workflow.
TGA	Open via File → Open. TGA files can carry an embedded alpha channel — check Channels panel after opening. If an alpha channel is present, load it as a selection and apply as a mask.
PSD	Open or place. Layers and masks are preserved. Check the layer structure before placing to understand how the file is organized.
SVG	Open in Illustrator, then export as a PNG at the appropriate resolution before placing in Photoshop. SVG is a vector format Photoshop cannot natively rasterize at controlled resolution.