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<blockquote data-quote="WayneF" data-source="post: 442377" data-attributes="member: 12496">If you are measuring enlargement ratio (like 1:1), it doesn't matter if you use width, height, or diagonal... so long as you compare the same dimension on subject and image.&nbsp;&nbsp; It's just about size of image on the sensor.&nbsp; If a 6mm object is a 6mm image on the sensor, then that is real life size of 1:1.&nbsp; That would be 1:1 regardless of the size of the sensor, but unfortunately, with digital, knowing sensor size is our only measuring tool.&nbsp; With film, we could simply measure it on the negative on the table.&nbsp; <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile&nbsp; &nbsp; :)" loading="lazy" data-shortname=":)" />If you are computing crop factor, diagonal perhaps has an edge if the sensor size is not 3:2 to match 35mm film. Can't really precisely compare different shapes of course, but diagonal is a good compromise.&nbsp; This can surely be argued either way.&nbsp; <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile&nbsp; &nbsp; :)" loading="lazy" data-shortname=":)" />But if sensor is 3:2 (a DSLR), matching 35 mm film, then any dimension works same as any other.</blockquote>

[QUOTE="WayneF, post: 442377, member: 12496"] If you are measuring enlargement ratio (like 1:1), it doesn't matter if you use width, height, or diagonal... so long as you compare the same dimension on subject and image. It's just about size of image on the sensor. If a 6mm object is a 6mm image on the sensor, then that is real life size of 1:1. That would be 1:1 regardless of the size of the sensor, but unfortunately, with digital, knowing sensor size is our only measuring tool. With film, we could simply measure it on the negative on the table. :) If you are computing crop factor, diagonal perhaps has an edge if the sensor size is not 3:2 to match 35mm film. Can't really precisely compare different shapes of course, but diagonal is a good compromise. This can surely be argued either way. :) But if sensor is 3:2 (a DSLR), matching 35 mm film, then any dimension works same as any other. [/QUOTE]

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