How do I do a 100% crop precisely without trial and error in LR4

Started Aug 28, 2012 | Discussions thread
richardplondon Forum Pro • Posts: 10,563
Re: How do I do a 100% crop precisely without trial and error in LR4

davidevans1 wrote:

OK thanks, please tell me how I do in in CS6, as that's another option.
Maybe it can't be done in LR4.

It is not easy to achieve a LR crop frame that has a certain exact number of original camera pixels inside it. However, if you get it roughly right (confirming this by turning on the info overlay, set to display cropped dimension) and then export, then by disabling the Resizing options in the Export dialog, a file is produced with pixel-to-pixel correspondence to your LR 1:1 view and also to suit this crop.

When it comes to cropping from Photoshop, selecting particular options in the Crop tool are no help - because those settings control what is done to transform your selected area - which you don't wnat in this case - without making sure the right quantity of the image has been selected - which is what you do want here. Your crop boundary may be quite accidental in its size, but Crop will happily process that to a given result regardless.

Say you wanted to save out an exactly 800 pixels wide area of your image, for posting online as a 1:1 and unresized sample: it is no good specifying 800 pixels wide in the Crop options. Nor is it any good selecting one or another resolution, or page size, or whatever. Say you have selected (by eye) a crop boundary that you think is roughly right - but it turns out to be 925px, or 748px, or whatever. Asking for 800px in the options, will just resample your 925, or your 748, or whatever it may be - forcibly - to a new dimension of 800 pixels. But those are 800 resampled pixels; which may have been generated from any number of original pixels.

It is IMO better to make a marquee (rectangular) selection, typing in your desired pixel dimension as an "exact size" in the tool options. Then the selection rectangle you make, will constrain itself to enclose just the right sized area of the picture (you can still move that selection around). Then Image menu / Crop will eliminate all of the picture outside this selection. You will be left with something the right size, and that has not been fiddled with in any way.


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