# Cropping 28mm to 35mm

Started 3 months ago | Discussions thread
Re: Cropping 28mm to 35mm
4

Joe Olson wrote:

People talk about cropping a image from say 28mm to 35mm in post using C1, Lightroom or whatever. I don’t understand how this works. How is the correct crop achieved. I don’t generally crop so I have no experience doing this. I have capture one and have used photoshop but I don’t see predefined choices for doing this.

Sorry if this is a stupid question but I just don’t get it.

Thank you!

What is really being said is the image is bring cropped to give the same field of view as if the picture had been taken with a 35 mm focal length in the first place. Determining the amount of cropping to achieve this is simple: it is the same ratio as the focal lengths. So in the example from 28 m to 35 mm, divide 28 by 35 to get 0.8. Multiply this times the number of pixels in each direction of the image to arrive at the number of pixels the cropped version will have. So if the full image is 3000 x 2000 pixels, you would crop it to dimensions of 3000 x 0.8 = 2400 pixels by 2000 x 0.8 = 1600 pixels. You now have the same field of view as if the picture had been taken with a 35 mm.

Dave

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