One product shot, two very different destinations
A small ceramics studio has one high-resolution product photograph per item, captured in sRGB and saved as a 16-bit TIFF. They need: (a) marketplace listings - 2000 px on the longest side, under 2 MB each, on a white background; and (b) an A5 printed catalogue, 148 x 210 mm, printing at 300 ppi with 3 mm bleed, on coated stock. The printer has supplied a CMYK profile, and the marketplace strips embedded profiles from uploaded images. There are 60 products and one day to prepare everything.
1. Describe the preparation for the print catalogue and show the pixel dimensions you need.
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Print route:
- Trim size 148 x 210 mm plus 3 mm bleed on all sides = 154 x 216 mm document.
- At 300 ppi: 154 mm = 6.06 in x 300 = 1819 px; 216 mm = 8.50 in x 300 = 2551 px. So a 1819 x 2551 px canvas per page (plus a safe margin inside the trim for text).
- Place the image so it runs past the trim into the bleed; keep product edges and any caption inside the safe area.
- Convert to the printer's CMYK profile once, at output, using the supplied profile. Keep the RGB master untouched.
- Keep captions and the studio logo as vector/live text, not baked into the raster image.
- Export as PDF (or TIFF) at 300 ppi with bleed marks, and check the darkest shadow does not plug to solid black in CMYK.
Note that CMYK has a smaller gamut than sRGB: saturated glazes may shift, so preview the conversion before sending 60 pages.
2. Describe the preparation for the marketplace images and explain how you will stay under 2 MB without visible damage.
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Web route, per product:
- Start from the master; flatten a copy, never the master.
- Resample down so the longest side is 2000 px, using a good downsampling method (bicubic sharper or similar) - downsampling averages pixels and is safe; upsampling is not.
- Convert to sRGB and embed the profile. The marketplace strips profiles, so the pixels must already be sRGB or colours will look dull/oversaturated on other screens.
- Sharpen lightly after resizing, since downsampling softens edges; mask out the smooth background so grain does not appear.
- Export JPEG and tune quality against the 2 MB ceiling - typically quality 75-85 for a 2000 px product shot. Check the actual file size rather than assuming; a busy texture can exceed 2 MB at quality 90.
- Ensure the background is genuinely near-white (around 250-255) if the marketplace rules require white, and keep the product's own shadow.
Record the settings as a batch action/droplet so all 60 are identical.
3. Why must the RGB master be preserved, and what goes wrong if someone converts to CMYK and back to RGB for the web files?
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Every RGB-to-CMYK conversion clips colours that fall outside the CMYK gamut - vivid oranges in a glaze, for example - and that clipping is permanent. Converting back to RGB does not restore them; it simply carries the duller, clipped values into an RGB file. Round-tripping also shifts neutrals and can introduce slight casts as the profiles are applied twice.
Correct practice:
- Keep the 16-bit sRGB TIFF as the archive master and derive everything from it.
- Derive web JPEGs from the RGB master (sRGB, 8-bit, resampled).
- Derive print files from the same master, converting to CMYK once, at the end, with the printer's profile.
- If either output is ever re-done, re-derive from the master rather than editing a previously converted file.
This is also why the 16-bit master matters: repeated 8-bit JPEG edits accumulate banding and artefacts, whereas the master absorbs any number of derived outputs without degradation.