What scan resolution do I need to get about 8 megapixels from a 35mm negative?
Asked 7/16/2010
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2 answers
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I want to estimate what scanner resolution is needed to scan a 35mm frame and end up with roughly the same pixel count as an 8MP digital photo. I’m also trying to judge whether a scanner or scanning service will meet that need. What DPI/PPI should I look for, and how realistic are scanner manufacturers’ quoted resolution numbers?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
16y ago
2 Answers
17
You can calculate the resolution from the megapixels like this:
ppi = sqrt(mp * 1000000 * 3/2) * 25.4 / 36
Which gives you:
6 mp = 2117 ppi
7 mp = 2286 ppi
8 mp = 2444 ppi
9 mp = 2592 ppi
10 mp = 2733 ppi
11 mp = 2866 ppi
12 mp = 2993 ppi
Originally by user149. Source · Licensed CC BY-SA 4.0
user149
16y ago
0
Generated from our catalog & community — verify before relying on it.
For a 35mm frame, about 8MP works out to roughly 2440 ppi of actual optical scan resolution.
A common way to estimate it is to match the pixel dimensions of an 8MP image to the 36×24mm size of 35mm film. Using that approach:
- 6MP ≈ 2117 ppi
- 8MP ≈ 2444 ppi
- 10MP ≈ 2733 ppi
- 12MP ≈ 2993 ppi
In practice, scanner specs can be misleading. Many consumer flatbeds advertise very high numbers like 4800 dpi, but their effective resolution is often closer to about 2000–2400 dpi. Dedicated film scanners usually get much closer to their claimed optical resolution.
So if your goal is a true 8MP-equivalent scan from 35mm, look for around 2400 ppi effective resolution, not just a marketing spec. A flatbed may be borderline for this; a dedicated negative/film scanner is usually a better fit.
Also, scanning at a higher setting than the scanner’s true resolving power can still help a bit with noise when you downsize afterward, even if it doesn’t add real detail.
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