Hi Bart, I believe that my CS5 is set up to do bicubic for screen resizing (at least that's what I have checked in the options).
Hi Jack,
Due to the (non-)proofed preview, screen grabs are hazardous so I prefer actual resampled file comparisons, which is now possible with your crop, thanks for that. The bicubic resize preference doesn't apply to screen zooms (they are always quick and dirty), but to the default that is shown with e.g. the resize menu.
Here is a link to a 1500x1500 crop from the original.
Okay, things are getting clearer now. I've attached a (screen grab noless
) comparison of the original as background, and two zoomed in areas of a bicubic downsample, and a downsample with the V1.2.2 script to 250 pixels a side while using Down-sample plus Sharpening Amount=100, so all defaults.
What becomes obvious, is that the bicubic version is much darker(!) which adds saturation, and more jaggy/aliased which suggests sharpness (but actually are artifacts that may help in this case of organic chaotic detail). So it's not the V1.2.2 script version being much lighter, although it could turn out a bit lighter in some isolated places, due to linear light resampling to preserve color accuracy.
If that is not wanted, and one doesn't want to address that in a separate post-downsample adjustment, then one could do the resampling with some remaining gamma, by temporarily adding some gamma to the linear light converted image before actually resizing the image (or replace the colorspace conversion by a moderate gamma conversion). But I do not think that is wise, because it will produce inaccurate colors. The more correct way to deal with it may be to reduce highlight brightness before downsampling if one wants more saturated highlights.
As for sharpness, there is nothing wrong with the windowing and averaging of the resize filter that is used in the script. There are single pixel wide features where expected, and other features are just not as dark as in the bicubic version, which makes them seem wider. It is always possible to make the deconvolution more aggressive than it should be, by reducing the radius to 0.4 and increase the amount used as desired. One could also use a sharpening setting of 1 (or zero, which activates a different algorithm) instead of the default, and use a separate deconvolution plugin or Smart sharpening with a very small radius and a large amount which can simply be recorded in a PS-action.
Such tweaks could be added to a commercial version of a resampling option, with a sort of crispness control or other creative tweaker. I've mentioned a Blend-if adjustment layer before, this could be made to fit in that functionality.
Cheers,
Bart