Why does Lightroom change my custom crop ratio to 7x5?
Asked 4/29/2016
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In Lightroom 6, I’m trying to crop for A1 printing with bleed. A1 is 841×594 mm, and with 5 mm bleed per side I need about 851×604 mm. When I enter a custom crop ratio equivalent to that size, Lightroom changes it to the standard 7x5 ratio instead of keeping my custom one. Since 7:5 is close but not identical, it slightly alters the final dimensions. Why does Lightroom do this, and is there any workaround?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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This has been a known problem in Lightroom for over 2 years, with no response from Adobe.
I'm not sure what the precision is, but if you're too close to a standard aspect ratio it just uses the standard ratio. I needed to do a 13x10 crop and LR refused to store it as a custom ratio, always choosing 8½x11 instead. Curiously, 8½x11 is 1.29412 so 2 decimal places should have been enough to differentiate between the two. It's not clear what's going on under the covers.
According to one comment on the Adobe forum from 2 years ago, older versions (LR3 and before) don't exhibit this behavior.
Originally by user492. Source · Licensed CC BY-SA 4.0
user492
10y ago
0
Generated from our catalog & community — verify before relying on it.
Lightroom 6 appears to snap some custom crop ratios to nearby standard aspect ratios, such as 7x5, instead of preserving the exact custom values. Based on user reports, this has been a known Lightroom issue for years, and it seems to happen when your custom ratio is close to a built-in preset.
The exact internal precision or matching logic isn’t clear, but Lightroom may be comparing ratios loosely enough that your 851:604 crop is treated as effectively the same as 7:5. That’s why your custom setting gets replaced.
A practical workaround is to enter the ratio in a simpler decimal form that Lightroom doesn’t reinterpret as a standard preset. For example, using something like 1 x 1.41 may be close enough for print purposes while avoiding the forced switch to 7x5.
So in short: it’s likely Lightroom behavior/bug rather than a mistake in your math.
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