p.1 #1 · Question: What is the Most Efficient Batch Size Reduction Workflow for Images in Lightroom Classic..
I’m scanning negatives using Sony’s sixteen shot pixelshift. I convert the negatives, eliminate many and then wish to reduce the 600MB+ DNG in batch without loss of quality. Generally, with Portra 160 this means reducing the size of the image by 30-50%. What batch workflow might I use to accomplish this in Lightroom Classic, or by using plug-ins?
p.1 #2 · Question: What is the Most Efficient Batch Size Reduction Workflow for Images in Lightroom Classic..
I have no experience with this but I do like ChatGPT for giving reasonably good technical guidance if your questions or prompts are well written. I put in your post as is and it gave a description of the steps. Try it yourself and you can refine your inputs to get more specific responses. If you're willing to reduce 'quality' some, then ChatGPT gave other suggestions.
From ChatGPT:
Got it 👍 — you’re scanning film with Sony’s 16-shot pixel shift, which produces enormous 600 MB+ DNGs. After culling and converting negatives, you want to batch shrink them by ~30–50% without losing quality (so: lossless compression, not lossy).
Here’s how you can do this in Lightroom Classic and with external tools that slot neatly into your workflow:
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🔹 Lightroom Classic Only (built-in workflow)
Lightroom can’t recompress existing DNGs automatically on export, but it can batch-convert them:
1. Cull & Convert Negatives First
• Once you’ve inverted your Portra 160 scans and rejected extras, select the keepers in Library.
2. Batch Convert to Lossless DNG
• In Library → Right-click selection → Convert Photo to DNG…
• In the dialog:
• ✅ Use Lossless Compression
• ❌ Use Lossy Compression (leave unchecked)
• ❌ Embed Original Raw File (skip this, otherwise size balloons)
• (Optional) ✅ Embed Fast Load Data (speeds Lightroom preview, adds ~1–2% file size).
• Click OK. Lightroom will create smaller, compressed DNGs and replace (or sit alongside, depending on your choice).
👉 This typically cuts Sony pixel-shift DNGs by 30–50%, especially with relatively smooth-toned film scans like Portra.
👉 Quality: 100% raw-equivalent, no resolution or bit-depth loss.
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🔹 External Batch Tool (faster + more control)
Adobe DNG Converter (free) can batch-compress folders of DNGs much faster than Lightroom:
1. Download from Adobe (works standalone).
2. Point it to your folder of large pixel-shift DNGs.
3. Settings:
• Compatibility: Latest (for max compression).
• ✅ Use Lossless Compression.
• ❌ Preserve Original RAW File.
4. Output goes to a new folder (or overwrite originals if you’re comfortable).
👉 Trade-off: Same savings as Lightroom, but faster and usable outside of Lightroom (good for archiving before import).
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🔹 Plug-ins (if you want “in-Lightroom” automation)
• LR/Transporter or Photo Upload Plug-ins (by Jeffrey Friedl) can help script conversions/exports, but they don’t provide better compression than Lightroom itself.
• Really, the best plug-in-like approach is to run Adobe DNG Converter externally, then have Lightroom “synchronize folder” to update your catalog with the smaller files.
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🔹 Recommended Workflow for You
1. Import raw pixel-shift DNGs → Convert negatives, cull, edit.
2. Once you’ve identified keepers:
• Option A: In Lightroom Classic → Batch Convert to DNG with lossless compression (simple).
• Option B (faster): Outside Lightroom → Run them through Adobe DNG Converter with lossless compression → Back in Lightroom, update/sync.
3. Archive the compressed DNGs, discard the 600 MB monsters.
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✅ This gives you ~30–50% size savings, preserves full 16-bit depth and resolution, and keeps your scans fully raw/editable.
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Do you want me to write up a step-by-step Lightroom preset or collection-based workflow so that once you’ve tagged your “keepers,” you can run a single command and Lightroom automatically outputs the smaller, compressed DNGs while keeping your catalog organized?
