Question about downsampling.

Started May 3, 2012 | Discussions thread
crames
Regular MemberPosts: 192
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Re: Question about downsampling.
In reply to Great Bustard, May 3, 2012

Great Bustard wrote:

Let's say I have a 24 MP photo that resolves 3000 lw/ph across the frame. If I downsample the photo (by averaging pixels) to 6 MP, what will the resolution be?

I assume there's no definitive answer, but I'm thinking it will always be at least 1500 lw/ph. Is this correct? If so, how much more and under what circumstances?

Assuming the 24 MP photo is 4,000 pixels high, after downsampling it will be 2,000 pixels, so can sustain up to 2,000 lw/ph. Of the original 3,000 lw/ph, you can keep up to 2,000 lw/ph at the new size, depending on the low pass filter used. Pixel averaging isn't the best filter to use and will lose more contrast than a Lanczos or similar quality filter.

Cliff

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