Warp Sharpening

[Marpel]

I am wondering about sharpening/blurring an image as it relates to Transformations, like Warp, which may change the shape/size of an image.

From the Help details, in general, it is suggested to blur an image prior to reducing its size and sharpen an image after enlarging its size (I presume this is not just related to Warp, although it is in the Warp help).

So, a couple questions:

- If anticipating reducing an images size, should any "capture" sharpening or sharpening during raw processing be avoided until after the reduction. Doesn't make sense to me to sharpen, then blur....

- After blurring prior to reducing, is sharpening then recommended after? Or no?

- And following the two pieces of advice, using Warp to correct building "keystoning", which I do often, if as an example, a 4000 x 4000 pixel image is corrected, via Warp, and the leaning building is straightened (so only the two top Warp points are moved in towards each other), the upper image pixels are "stretched" outwards, but the image is still 4000 x 4000 pixels. Does that constitute "enlarging its size"? If so, should sharpening be applied more to the upper portions of the image (ie, using a vertical graduated mask) as the lower pixels are basically unaffected by the Warp)?

Marv

[jsachs]

In my experience, using today's high resolution cameras, as long as your warp is not too extreme, the resampling it entails does not degrade the image enough to worry about. Theoretically, where you are stretching the image, you could maybe sharpen, but it would have to be in the direction of the stretch.

In most cases, I let DxO or whatever raw converter I am using do its default noise reduction and capture sharpening and then I defer the final sharpening to the end, sometimes with a mask to limit the sharpening to certain areas and leaving others (typically the sky) unsharpened.

[Marpel]

Thanks for the explanation.