Google| Subject | Re: Lenses and sharpening |
| From | Kevin McMurtrie |
| Date | 09/14/2014 01:06 (09/13/2014 16:06) |
| Message-ID | <mcmurtrie-B0A79A.16064913092014@news.sonic.net> |
| Client | |
| Newsgroups | rec.photo.digital |
| Follows | Alfred Molon |
In article <MPG.2e7e0f5521a26e5d98cc08@news.supernews.com>, Alfred Molon <alfred_molon@yahoo.com>wrote:
Alfred MolonDefects in lenses rarely produce a Gaussian blur or haze that can be corrected with an unsharp mask. It's a complex mess with too many variables to compensate for.
Sometimes a soft lens can be very effectively compensated by some unsharp mask in post processing and you get a sharp, natural looking image.
But sometimes no matter how much sharpening you apply or what parameters you choose, you get that unnatural, "sharpened" look.
It probably depends on the unsharpness of the lens, its (spatial) frequency response or whether the sharpness is caused by the lens glass itself (i.e. lens not being sharp enough), inaccurate focus or some motion blur.
For instance I have a 70-300 lens which at the tele end generates a bit soft images, which however respond well to unsharp masking in post- processing. But that's not the case for the another lens I have (a mid- range one).
Has somebody analysed this (i.e. how to best sharpen an image, what unsharpness can be eliminated in post-processing)? Is there perhaps some web page with details?
It's better to buy a higher quality lens if you're spending lots of time on correction. Some mid-range lenses can be nearly perfect within a reduced range of aperture and focal length. Sharpness charts can help you decide what works for you. Around f/2, stabilization becomes more practical than a larger aperture for low light hand-held photography.
If you're talking about the Canon 70-300 DO IS USM, there's a magic aperture somewhere near f/6. The next step is to apply a small amount of a large diameter unsharp mask to remove the haze. Don't let the camera use small apertures. 300m at f/40 takes a picture of the fresnel lens :P
-- I will not see posts from astraweb, theremailer, dizum, or google because they host Usenet flooders.
09/13/2014-
