Thirty Race Photos and a Transparent Logo
You have finished a 30-image set from a charity fun run. Deliverables: a web gallery where each image must be at most 1600 px on the long edge and the whole folder must stay under 20 MB; a press pack of three images for the local paper, which asks for JPEG, sRGB, quality 90, and no smaller than 2000 px on the long edge; and a sponsor's logo overlay that must sit on a transparent background. One master file is a 45 MB 16-bit TIFF. A volunteer has already exported everything as JPEG quality 100, producing a 38 MB folder, and saved the logo overlay as a JPEG, so the logo now shows a white box around it.
1. Diagnose why the gallery folder is 38 MB and give a step-by-step plan to get under 20 MB without visible damage.
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Quality 100 is close to lossless and produces files several times larger than quality 80 with no visible benefit at web size. Thirty files at 38 MB total is about 1.27 MB each. Dropping to quality 78–82 on a 1600 px photograph typically cuts 60–75%, landing near 0.4 MB each - about 12 MB for 30 images, comfortably inside budget.
Plan:
- Work from the masters, not the existing JPEGs. Re-encoding a JPEG compounds compression artefacts.
- Resize to 1600 px on the long edge with a good downsample, then apply light screen sharpening - sharpening before resizing wastes the effect.
- Export JPEG quality 80, sRGB, progressive; use the export preview's size estimate to check the batch total before committing.
- Keep the copyright/IPTC field. Strip the embedded thumbnail and unneeded camera data if you must, but a blanket 'strip metadata' preset would remove the copyright, which is a rights problem, not a size problem.
- If it is still over, serve the gallery from a page rather than a folder, or convert to WebP.
2. Choose a file format for each of the three deliverables and justify each choice.
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Format follows destination, not habit.
- Web gallery - JPEG, quality ~80, sRGB, 1600 px. Universal support and small files. PNG would be several times larger for continuous-tone photographs.
- Press pack - JPEG, sRGB, quality 90, at least 2000 px long edge, as specified. Follow the spec even if you would prefer TIFF; a picture desk will not process an unexpected format on deadline. Send sRGB, not CMYK: most papers convert on their own RIP, and a CMYK file without their profile can print flat.
- Logo overlay - PNG-24 or TIFF with an alpha channel. JPEG has no transparency, so transparent areas are composited onto white - precisely why the logo now has a white box. If the sponsor's platform accepts SVG, supply the vector original instead.
- Archive - keep the 16-bit TIFF as the master. It is a source, not a deliverable.
Rule of thumb: transparency → PNG/TIFF; photographic tone → JPEG; intermediate editing → TIFF or PSD.
3. The paper says it uses sRGB. Explain the difference between assigning and converting a profile, and why you should not use the CMYK proof to judge the web version.
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Assign relabels the existing pixel values with a different profile - the numbers do not change, so the image's appearance shifts. Convert recalculates the pixel values so the appearance is preserved as closely as the new space allows. Convert when moving between working spaces; assign essentially never, except to correct a mis-tagged file.
For the press pack: convert from your working space into sRGB, confirm the profile is embedded, and hand over an 8-bit file. They ask for 8-bit because 16-bit JPEG does not exist - convert on the export copy and keep the 16-bit master untouched.
For colour judgement: converting a CMYK proof back to RGB and forward to CMYK again shifts saturated colour, and each round trip clips a little more. Do not judge the web version through the print file, and do not judge the print file on an uncalibrated screen. Soft-proof the CMYK file with the printer's profile and black-point compensation, and expect out-of-gamut greens and oranges to print duller than they appear on screen.